The dependence of N₂ - N₂, O₂ - O₂, and N₂ - O₂ pairs polarizability in versus their intermolecular distance in a frame of classical Silberstein approximation was investigated. The polarizability tensor components of O₂ and N₂ dimers at the stable equilibrium configurations were calculated.

The influence of vibration-rotation interactions and anharmonicities on the polarizabilities matrix elements and scattering cross-sections of N₂ and O₂ molecules for vibrational transitions v implies v, v+1, v+2, v+3 were investigated.

The description of the narrowing effect at high pressures is demonstrated on the example of CO₂-He absorption for Q-, P-, and R-branches and for the head of the R-branch. The problem is focused on the physical meaning of this phenomenon that should be associated with the angular and translation momentum transfer to matter from the photon absorbed. The effect is described in the approximation of the single line without the conventional line mixing. A narrowing function is introduced that links the absorption in the resonance region with the one in far wings. This function enlarges the absorption of a single line approximately in two times in the resonance region at high pressures and decreases the one approximately in 20 times in far wings in comparison with the Lorentzian, independently of the type of molecule and pressures. The halfwidth of a single line is assumed to have a nonlinear pressure dependence and approaches to a saturated value at high pressures.

Different problems of atmospheric physics, astrophysics, and laser physics require acknowledge of accurate spectral line shape parameters for carbon dioxide and its main isotopic species in a wide temperature range for different vibrational bands from the mid-infrared to visible spectral region. There is no information on the coefficients of shifting by air pressure in the HITRAN-96 database. Thus, the available information is obviously insufficient, and the HITRAN database has to be expanded and supplemented with new data. In this paper we present the results calculated for the new database based on the ATC (Anderson-Tsao-Curnutte) method. The calculated coefficients of line shifting by air pressure and exponents of the temperature dependence in the range from 200 to 350 K significantly supplemented the available databases. The calculated data can be used in spectroscopy of planetary atmospheres.

This work is devoted to the water vapor spectrum analysis in the near-IR region. The water vapor spectrum was studied using intracavity laser spectrometer in 8250-9100 cm^-1 region with the spectral resolution of 0.05 cm^-1 and at temperature of 1000 K. The spectra identification was done. More than 10 vibrational bands were recorded and analyzed.

The effective operator for polarizability tensor is created ont he base of the theory of linked ordering schemes for vibration-rotational interactions in quasi-rigid molecules. The vibrational dependence of mean polarizability is presented both in polynomial form and in the form of Pade- approximants. The general results are applied for the estimation of H₂O mean polarizability in different overtones and combined tones.

The new calculation approach of water vapor rotational energy levels using symmetric top model for K_a>=J/2>>1 has proposed. The rotational spectroscopic parameters of the Pade-approximation for ground vibrational state of H₂O molecule in the frame of this model was obtained. The absorption coefficient of water vapor in a spectral range 850-920 cm^-1 was calculated for 1000 - 10000 K temperatures.

The modern method for modeling selective gas absorption to solve problems of radiative transfer in the spatially inhomogeneous atmosphere is considered. The method is based on representation of the atmospheric transmission function as a series of exponential functions. This representation not only provides for high accuracy of calculations, but also proves to be efficient when considering multiple scattering.

The accuracy of the atmospheric modeling results depends upon the accuracy both of physical processes parameterization and the physical parameter calculation. The solar radiation energetics of the atmospheric models is the main source of the atmosphere motions. The dependence of the solar radiation fluxes and flux divergence on the atmospheric, clouds and underlying surface properties is investigated. The development solar radiation calculation algorithm is based upon the two-stream delta-Eddington method with the description of the stretch form of cloud phase function by delta function. The requested by radiation algorithm parameters, that are the humidity distribution, cloud amount, cloud water content, cloud phase and mean radii of cloud particles are calculated by humidity transformation model. This model was developed earlier by Dmitrieva-Arrago (Dmitrieva-Arrago et al., 1985) and contains the microphysical algorithm modified additionally for radiation problem. The main goal of the paper is to estimate the variation of the atmospheric radiation characteristics because of the errors and uncertainty of some atmospheric and cloud parameters by numerical experiment. The cloud amount, cloud water content, specific humidity, mean radius of cloud particles, the asymmetry factor, surface albedo were varied in the limits of their possible errors of calculations or experimental uncertainty.

An estimation has been made of correlation links of cumulus cloud energy brightness fluctuations at different Cu cloud amounts within the range of 1.5-13 mcm depending on the angle between the direction to the sun and the center of the cloud field studied.

Remote sensing of atmospheric state parameters (such as temperature and mixing ratio profiles, trace gas column amounts) requires fast and accurate radiative transfer calculations. For the retrieval of a large number of species, a set of micro-windows containing single lines of the target species is generally used. However, spectral signatures of several species like CFCs are often covering large micro-windows and a forward calculation in wide spectral region must be performed to access the concentration of these species in the atmosphere using remote sensing techniques. If line-by-line calculation of the absorption cross section is used, the calculation time is important and not dedicated to operational analysis of spectral atmospheric measurements. A new retrieval algorithm has been developed at LPMA to determine vertical profiles in such conditions. In order to decrease the calculation time, pre-calculated absorption cross section look-up tables are used, allowing quick generation of absorption cross section without significant loss of accuracy. The simulation of the measurements on wide spectral region is very sensitive to instrumental characteristics like spectral variation of the instrument line shape or accurate calibration of the spectra and the corresponding modeling problems will be carefully examined.

Within the framework of the European Space Agency (ESA) SILEX project, aimed at experimentally demonstrating the feasibility of inter-satellite optical communications links, an Optical Ground Station (OGS) has been built by ESA in the premises of the Instituto de Astrofisica de Canarias (IAC, Institute of Astrophysics of the Canary Islands) Observatory of Teide, in the Tenerife island. The OGS is designed to test the optical communications payload on board the ESA's Artemis satellite and to perform ground-satellite optical communications experiments. As part of the OGS design study, an assessment of the impact of the atmosphere on the ground- satellite links was carried out. This assessment included experimental characterizations of the atmospheric effects through both measurements from stars in positions close to the Artemis one in bands comprising the SILEX wavelengths, using the IAC's Mons telescope in the Observatory of Teide, and measurements on a horizontal link with a transmitter near the IAC's Roque de los Muchachos Observatory in La Palma island, based on a laser diode similar to those to be used in SILEX, and a receiver in the Teide Observatory, almost 150 km apart, in the Tenerife island. The 830-nm wavelength horizontal measurements allowed checking the variations in the behavior of the atmospheric turbulence through the diurnal cycle. Besides the information relevant to assess the OGS performance, the horizontal-propagation experiments allowed to gather a considerable amount of propagation data on a very long path, most of it 2400 m above the sea.

Under the assumption that small-scale irradiance fluctuations are modulated by large-scale irradiance fluctuations, we developed a heuristic model of irradiance fluctuations for a propagating optical wave in a weakly inhomogeneous medium. This model takes into account the loss of spatial coherence as the optical wave propagates through atmospheric turbulence by eliminating effects of certain turbulent scale sizes that exist between two scale size, hereafter called the upper bound and the lower bound. These mid-range scale size effects are eliminated through the formal introduction of spatial frequency filters that continually adjust spatial cutoff frequencies as the optical wave propagates. By applying a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, tractable expressions are developed for the scintillation index of a Gaussian beam wave that are valid under moderate- to-strong irradiance fluctuations. Inner scale effects are taken into account by use of a modified atmospheric spectrum that exhibits a bump at large spatial frequencies. We also include the effect of a finite outer scale in addition to inner scale.

In this article, the full aperture tilt caused by the incident and returned waves of different paths is studied analytically. It is found that the variance of full aperture tilt of returned beam could be less than 10% of that of transmitted beam under some conditions, and the main reason is the asymmetrical distribution of atmospheric turbulence in different altitude. The effect of coherence of laser beams is also studied.

The results of experimental studies of angular divergence for laser beams intersecting an aero-engine jet at different angles to its axis - 90 degree(s), 45 degree(s) and 10 degree(s), are presented. The experiments were carried out on the ground with radiation wavelengths of 1.06 and 0.53 microns. Depending on conditions of the experiment, the angular divergence of radiation impacted by the jet increased 6-35 times as compared to the initial values for undisturbed beams. It has been found that the angular width of the half- micron beam is significantly (two or three times) higher than that of the one-micron beam, which does not fit in with the model of radiation scattered by typical a turbulent medium. Besides, radiation intensity angular distribution demonstrated azimuthal asymmetry correlating with physically selected spatial directions - along and across the jet stream. Based on relevant selection of spectral density for refractive index fluctuations (composition of a turbulent spectrum and additional high frequency spectral components, anisotropy in the outer scales of turbulence) analytical relationships for evaluation of the angular divergence of disturbed beams matching experimental data have been obtained.

The results of experimental measurements of dispersion of a laser beam centroid's random wanderings for beams disturbed by a high-speed turbulent aero-engine jet stream are presented. The duration of light pulses radiated synchronously at wavelengths of (lambda) equals 1.06 and 0.53 microns did not exceed 50 ns, which made it possible to record instantaneous far-field distributions of radiation intensity. In each experimental cycle that differed from one another by geometry of experiment (beam diameter of 10 or 30 mm, different angles of beam-jet intersection) not less than 1500 frames were recorded in the computer. The range of measured values for dispersion of the laser beam wanderings depends on conditions of experiment and varies within 60 divided by 180 (mu) rad for (lambda) equals1.06 microns and within 110 divided by 300 (mu) rad for (lambda) equals0.53 microns. A certain difference in dispersion of beam wanderings in horizontal and in vertical (orthogonally to jet's axis) directions has been detected. The analytical model to calculate dispersion of laser beam's wanderings agreeable with experimental data is presented. The results of the experiment have allowed it to estimate the type of a high- frequency component of refraction index fluctuations spectrum in the jet, which supplements von Karman's spectrum for a turbulent medium.

An equation connecting the phase vortex density (wave front dislocation density) and intensity distribution of a light beam is derived. On this base a new method for calculation of the statistical characteristics of dislocations in the turbulent atmosphere is proposed. In the case of the lognormal law distribution of intensity fluctuations an integral representation of average dislocation density in terms of the correlation functions of intensity logarithm in a beam cross section is obtained.

Numerical simulation of laser beam propagation on space-to- ground and ground-to-space paths is carried out. The simulation is performed for different C_n² height profile models in dependence on atmospheric turbulence strength. Atmospheric turbulence severely degrades the performance of ground-to-satellite optical links. Using the wave to be passed from satellite to the optical ground station as the reference wave, it is studied the effectiveness of adaptive correction of laser beam propagating from the ground to satellite. Different schemes of adaptive correction are considered, namely, ideal phase conjugation, correction based on information about reference wave phase restored by mean least square procedure. The effectiveness of the correction by adaptive optics to correct wave front distortions caused by atmospheric turbulence, and possibly improving the link budgets from ground to space and vice versa is discussed. We also analyze and discuss the effect of optical scintillation on signal fade and surge.

The algorithm of wavefront phase retrieval on a pupil of an optical system using images of the same unknown source is shown. The problem is reduced to a problem of general point determination of known sets. The iterative algorithms to solve the last problem are offered. The application of the method as wavefront transmitter in an adaptive optical system is considered and illustrated by numerical simulation.

Three algorithms of dislocation localization in the wave front of a laser beam propagating in a turbulent medium are considered in the report. The precision of algorithms is assessed and statistics of dislocations is determined in different cross-sections of the path as a function of atmospheric parameters such as Fried length and the outer scale of turbulence. The preliminary results are represented characterizing adaptive control with a continuous surface mirror taken as a corrector.

In the present article the problem of Gaussian beam propagation in the turbulent atmosphere is considered on the base of numeric methods. Singular points (dislocations) development in the wavefront is analyzed. Two algorithms of dislocation detection were proposed. One of them based on the interferogram processing and can be realized in a laboratory experiment. In the second algorithm the whole wavefront is analyzed and dislocations are localized as points where cuts of the surface in 2(pi) begin. The precision of the algorithms is compared and statistics of dislocations on the path of propagation is represented.

In the paper the results of experimental researches of parameters of a laser beam passed through a convective column shaped above a zone of shining wood materials have been shown. Estimates of structural characteristics of temperature fluctuations C_(Tau )² and refractive index C_n² determined from measurements of temperature gradients at the altitude 105 cm have been presented. The root-mean-square deviations of fluctuations of the image of a divergent laser beam measured are compared with ones calculated on C_n² taking into account profile of temperature in the convective column. The spectra of fluctuations of the image and intensity of a divergent laser beam have been determined also. It is shown that the turbulent parameters in a convective column since some altitude corresponds to conditions of a free convection.

Authors investigate in numerical experiment the representation of the optical wave phase through the Karhunen-Loeve-Obukhov (KLO) functions obtained using phase correlation function calculated from experimental data. For such KLO basis the average relative error of phase expansion is 5% for 10 basis functions in the expansion series, whereas for the KLO basis calculated with the Kolmogorov structure function of phase the error of phase expansion 5% has been obtained for 78 basis functions.

Phenol and 4-chlorophenol water solutions photolysis under UV-excitation from KrCl-laser and capacitive discharge KrCl- excilamp are presented. The irradiated solutions have been investigated by spectroscopic methods. The comparison of the KrCl-excilamp and KrCl-laser irradiation effects has been realized for the first time.

The beam dynamics for equal power ray tubes and equal coherence ray tubes is investigated for the partially coherent radiation propagating in non-linear media. The Gaussian beam propagation through media with Kerr non- linearity and thermal blooming is considered on the basis of the solution of the equation for coherence function of the second order. Calculations are adduced for the two- dimensional beam. The dimension of a coherence function decreases from five down to three for this case. Consequently, the numerical solution of this equation is possible by means of the method of a separation on physical factors, widely using for a solution of the parabolic wave equation, with using the algorithm of fast Fourier transformation. The comparable analysis of the equal power and equal coherence ray tubes behavior is carried out. The same analysis is carried out for solutions of the equation for coherence function obtaining by the ray-tracing technique allowing to create effective numerical algorithms for the three dimensional problem. The technique is asymptotically exact since it gives exact solutions at limiting cases when the coherence length tends to zero or when the distribution of complex dielectric constant of medium has the parabolic form.

The task about influence optical meteorological condition (OMC) of an atmosphere on conditions of distribution of high power laser radiation (HPLR) can be considered with several, sometimes almost diametrically opposite, points of view. For example task of transmitted of laser through atmospheric path means modeling parameters of radiation, with reference to an atmospheric situation so that to avoid losses of energy, locked by the centers optical breakdown in the channel of laser beam. Hence, the generation of the plasma centers in the channel of laser beam is in this case 'parasitic' effect. In a task of use of laser radiation for posting of the lightning, generation of an extended laser spark on peak of a tower in the given direction - 'useful' effect. Certainly it is impossible to consider the second task as inversion by first. In the report the opportunity of application of results of experiments in real atmospheric path received with the decision of a task of distribution for a task of forecasting of efficiency of creation of a long laser spark in various OMC of an atmosphere is considered. The results of processing of the acoustic response from the centers optical breakdown in an atmosphere are submitted. The received dependences of the characteristics of acoustic signals (amplitude, duration) from parameters HPLR OMC are considered from the point of view of their conformity to available models of formation of an acoustic pulse. The prospects of application of supershort laser pulses in a task lightning control are discussed.

Some ways to reduce errors in measured concentrations of atmospheric trace gases by using the differential absorption lidar (DIAL) method are studied here. One requires the correction means owing to the following obvious fact. For a low concentration of an absorptive gas, the difference in signals at 'on'- and 'off'-wavelengths utilized to sound the atmosphere would be small too. So the account for different optical spectral properties of atmospheric aerosols even at closely spaced 'on'- and 'off'-wavelengths can be of great importance for such a case. This paper shows that essential changes in optical aerosol characteristics, for example, near 9 to 10 micrometers due to sulfate ions of atmospheric particles, can be a a reason, which practically precludes a concentration of a trace gas in the 'average' atmosphere from being determined to any acceptable error level. We consider here two experimental setups providing the DIAL measurements by path and sounding schemes, when reflection from a topographic target or aerosol backscatter delivers the signal to a receiver, respectively. Possible ways to correct differences in aerosol optical characteristics at 'on'- and 'off'-wavelengths are discussed. To this end, model estimations of the spectral characteristics are used. Various models are considered to compare the errors in concentrations with and without the corresponding corrections. It is shown that for a number of path measurements one would succeed in the reduction of the errors. An empirical formula to correct measurements is given.

Satellite remote sensing of ocean color is a powerful tool for large-scale investigations on water properties. In particular, ocean color is directly connected to the pigment concentration. This latter, in turn, is related to the presence of phytoplankton which plays a major role in the biogenic flux of carbon dioxide in the oceans. Thanks to this process, oceans represent an important sink for atmospheric carbon dioxide, thus influencing the climate equilibrium. This explains the renewed interest in space missions and oceanographic researches focused on ocean color. In this paper we review the Sea-viewing Wide Field- of-view Sensor (SeaWiFS), carried by the OrbView-2 satellite, and we compare its imagery with the measurements performed by the ENEA Lidar Fluorosensor (ELF). In particular, lidar measurements can be very useful for calibrating the satellite imagery of chlorophyll-a in a region where seasonal and spatial distributions of phytoplankton require further investigations. Actually, the present imagery processing algorithms are not exempt from uncertainties, especially because the water-leaving radiance must be separated from the atmospheric radiance, which typically represents about 80% of the 'at sensor' radiance. Moreover, such algorithms nowadays are tuned for biota very different from that of the Souther Ocean.

A new method of inclusion of refraction in the radiative transfer equation (RTE) for the atmosphere-ocean spherical system (AOS) is proposed. It is based on deformation of the spherical coordinate system according to spatial distribution of refraction index of light. It is shown that in the coordinate system deformed thus, the differential and integral operators of the RTE take a simpler form free of refraction members and corresponding to rectilinear propagation of light if the refraction is taken into account. Reflection, transmission and refraction of light at the interface in the AOS model is defined by optical parameters of an elementary volume of medium in the RTE. These parameters are introduced with the use of notions of the generalized functions theory and the Fermat principle. They are defined in Sobolev-Shvarz sense and expressed through the linear continuos functionals.

The problem of improving the resolution of NOAA AVHRR images, which is no higher than 1 X 1 km²/pixel, is solved. The a priori information invoked for solution of this problem includes the assumption that the initial video data, first, have the higher (subpixel) resolution as compared to the AVHRR data. In addition, it is assumed that the recorded images are formed by a scanning spot with a fixed, but unknown, pupil function. A salient feature of the proposed approach is adaptive reconstruction of a 'spreading-smoothing' operator, which is, in its turn, the convolution of two point-spread functions (PSF), on describing the instrumental function of the scanner pupil and another simulating the interpolation method used for reconstruction of the missing values of radio brightness of the subpixel raster. Some examples of the improved resolution of real images are presented.

Within the framework of resource-ecological monitoring of the Earth's surface, the problem of recognition of cloud types from NOAA AVHRR data is considered. Based on the statistical approach, a nonparametric algorithm is developed for recognition of stochastic fields, as well as the procedure for estimation of informative indicators from the condition of minimum estimated recognition error. The conditional probability models of recognized images are reconstructed from learning samples selected by an experienced operator. Classification of the types of cloud fields is exemplified by the NOAA satellite data.

The lidar signal component caused by a scattering of the first two orders is described in detail within the framework of the theory of laser sensing taking into account a multiple scattering in the small-angle approximation. Simple formulas are obtained determining a double scattering signal with consideration for lidar geometrical parameters for the media with a strongly extended scattering phase function. The role of diffraction and geometrical optics components of the scattering phase function in a doubly scattered signal is investigated. Estimations are obtained of an accuracy of a considered approximation depending on the field-of-view angle of the receiver at different optical thickness of the scattering layer.

This work continues development of simplified approaches to study the transformation of polarized light produced by a narrow linearly polarized beam propagating through a multiply scattering medium with highly forward-peaked phase function. This work presents a relatively simple fast technique to evaluate the near-forward degree of linear polarization due to incident beam that is suitable for the case of scattering in media containing large soft scatters, such as the sea water and biological media. Two scalar equations of the approximate analytical vector theory are used to obtain two leading elements of the propagation matrix and through its ratio the linear polarization degree. To solve these equations it is employed the multicomponent approximation which includes the small-angle approximation and approximate asymptotic approach earlier developed. A simplifying approach to solve by using the small-angle approximation the equation that defines small-angle scattering of purely linear polarized part of radiation in a medium with large soft scatters is proposed. Examples of calculations made for the case of light scattering in a water suspension of milk with use of experimental phase function are presented.

This paper presents the methodology to process data of combined experiments using a Sun/sky scanning radiometer and a multi-frequency aerosol lidar. An algorithm is proposed to retrieve the optical properties of altitude-inhomogeneous aerosol layer reflecting both the vertical changes of atmospheric aerosol detected by lidars and the integral aerosol properties measured by ground-based Sun/sky radiometers.

A problem on introduction of additional a prior assumptions to construct a closed set of lidar equations at several wavelengths and on their solutions to estimate microphysical parameters of atmospheric aerosols by multi-frequency laser sounding data is discussed. Some regression relations between spectral values of aerosol backscatter and extinction coefficients in the visible and near-IR are used as the assumptions. The regressions are constructed by model considerations. The optical atmospheric aerosol model of the World Meterological Organization is taken as a basic one. The constructed regressions enable one to evaluate the solvability of, generally, ill-conditioned lidar equations and the errors in the solutions as well as to make some estimations with respect to the determination of aerosol microstructural parameters. This work has been directed towards the design of procedures and algorithms to process laser sounding data gathered routinely by lidar setups of the Institute of Physics, Belarus National Academy of Sciences, Minsk, Republic of Belarus within the frame of a number of International and National research and development programs.

On the basis of processing and analysis of the sounding data of tropical cyclones in the Norther Atlantic of 1998 and 1999 made by the microwave radiometer SSM/1 on board the USA DMSP satellites an analysis was made of the microwave radiometric determination of the surface wind field characteristics in the vicinity of a cyclone with the use of the radiation-wind models available. A semiempirical method is proposed for determining the characteristics of the tropical cyclone central zone, the effective dimensions of the hurricane wind zone and maximum wind velocities in their number, based on the key characteristics of the system 'ocean-atmosphere' revealed by the authors at different wavelengths.

For a long time fluorescence techniques have provided interesting information in oceanography. Lidar (LIght Detection And Ranging) has been used to have fast profiling tools over several meters especially in high dynamic water masses. While fluosensors provide the fluorescence response to a well defined excitation in a small volume, remote sensing operates over several meters and their power to excite fluorescence at a range R depends on optical properties of the medium during the light propagation. In order to study the influence of the propagation properties of the aquatic medium on spectra from fluorescence Lidar a new ranging concept was realized. The presented study is focused on the bistatic design of Lidar combined with a spectral analysis of the backscattered signal for tomoscopic applications. The data were obtained with a frequency doubled Nd:YAG ((lambda) equals 532 nm) and a gated angular resolved detection. While the time base of the system can be compared to ranging by other on-axis Lidar, the spatial dimension of the signal brings complementary information of the light flux distribution as a function of the angle of incidence. The bistatic configuration of this Lidar permits geometrical ranging by a set of detection channels, detecting simultaneously the spectrum (532 nm - 720 nm) with the same system time base. The analysis of fluorescence by the bistatic angular resolved detection is focused on the temporal aspects of fluorescence in near field data of this Lidar. First sea trials with this Lidar have shown the potential for the investigation of fluorescence profiles even in very turbid estuaries.

Sum frequency generators of Er³⁺:CaF₂ ((lambda) equals 2.76 micrometers ), Er³⁺:YAG ((lambda) equals 2.94 micrometers ), and cw CO₂ lasers with ZnGeP₂ single crystals has been developed to enlarge the possibilities of spectroscopic systems based on CO₂ lasers. The generated spectra overlapped the ranges from 2.0 to 2.4 micrometers , which coincide with the two main atmosphere transparence windows. The energy efficiency of sum frequency generation is about 3% at phase-matching angle of 52 degree(s). The results of numerical simulation of the high-altitude profiles definition of atmospheric meteorological parameters by differential absorption lidar system working in eye-safe spectrum range at 2 micrometers has shown, that errors of the temperature and humidity profiles restoring have reasonable values in all altitude range 0 - 2 km.

The return of a spaceborne lidar system contains essential contributions form multiple scattering. Hence, methods for the retrieval of cloud parameters from such returns must be based on equations which take into account such multiple scattering. The more precisely this is done the more complicated these equations will be and the less changes are to be able to retrieve the parameters. At least this is true for retrieval procedures which are based on solving integro- differential equations. Hence, in such a case it is necessary to use simplified equations to describe such returns. Such simplified equations may be equations which introduce a correction term into the classical (single scattering) lidar equation or which take into account one or two orders of multiple scattering only or which have the for of some sophisticated exponential series including knowledge of depolarization. Of course, it is necessary to check the validity of such approximative multiple scattering lidar equations. We show simulations of lidar returns from different clouds. These simulations are obtained by variance reduction Monte Carlo methods which are based on an exact multiple scattering lidar equation obtained within the framework of a stochastic model from the transport of polarized light through the atmosphere. These simulations demonstrate the great importance of the contributions from multiple scattering to the return signal, the diffusion of the laser beam in the cloud seen from the receiver, the difficulty of determining the type and the location of the particles contributing to the return, and the need of careful analysis of returns of spaceborne lidar systems. We show simulations of such returns from clouds of aerosols (randomly oriented oblate and prolate spheroids) and a sensitivity analysis for such returns from water clouds with varying extinction coefficient and droplet size distribution. The simulations and the sensitivity analysis clearly show that the validity of retrieval procedures based on approximative multiple scattering lidar equations has to be examined with care.

Possibility of sounding of the clear-air turbulence by airplane coherent Doppler lidar is analyzed based on the numerical simulation. It is shown that the accuracy of estimation of the strength of turbulence from the lidar data depends on the intensity of turbulence, the signal-to-noise ratio, and number of sounding pulses. The conditions are determined for which detecting of the clear-air turbulence zones with the coherent Doppler lidar is possible.

At present there are half a score of satellite ocean color sensors being in operation or prepared for launch; they offer strong possibilities of providing data on spatial and temporal variability of various characteristics of atmosphere and ocean, primarily of the optical ones. As of now, data from the satellite scanner SeaWiFS (Sea-viewing Wide Field-of-view Sensor) are in most common use; they have been available since September 1997. The possibilities and problems of retrieval of optical characteristics of atmospheric aerosol, cloudiness, and sea water from SeaWiFS data are considered. The algorithms developed in the P.P. Shirshov Institute of Oceanology Russian Academy of Sciences are presented as well as some results of their validation by data of field measurements. The examples of spatial distributions and seasonal changeability of aerosol optical thickness and seawater optical characteristics derived from SeaWiFS data are given.

A comparison of statistical characteristics of large arrays of the experimental and model spectra of the brightness coefficients (BC) for upwelling radiation from water was made. A practically total identity of the characteristics is shown. A conditions of applications of the regression model well-known in oceanology and limnology are defined. Concentrations of the individual optically active components (OAC) can be determined with the adequate accuracy in particular cases only. A comparative analysis of two representations of data obtained under the remote sensing of water objects was carried out: the OAC and the optical state of water ecosystem (OSWE) representations. The behavior of model spectra in the space of optical states (SOS) is analyzed. The layout geometry of SOS was studied and the interpretation of some region of the space in the frame of the conventional hydrochemical and hydrobiological terms was performed. It was shown that the information content of the brightness coefficients for water objects is determined by integral status of ecosystem.

The heavy metal concentrations in water media (sea, lake, etc.), phytoplankton, natural indicators have been estimated by optical spectral method. The obtained results are evident on efficiency of this noncontact, nonreagent, express optical method. It can be adopted for remote monitoring of aqueous media and assessment of purification system efficiency.

One of the main problems in retrieval of microstructure of aerosol in atmospheric column is connected with derivation of the single scattered radiance. In the present work, the ways to solve (or avoid) this problem for aureole measurements using spectral aerosol extinction data are considered. Aerosol optical thickness (AOT) in visible and near-IR is determined mostly by submicron aerosol fraction (except for the situations with extremely high coarse aerosol loading, like a dust storm). This fraction is also predominant in side scattering. So, it may be supposed that the single scattering phase function out of aureole region can be derived from the spectral AOT by means of inversion and following Mie calculations for retrieved submicron aerosol. For rough estimations, it is sufficient to calculate the Angstrom exponent and take the phase function for the corresponding power law distribution. Analysis of the model and derived from the experimental data size spectra showed that inversion of the spectral extinction allows to recover the phase function in the angular range 20 - 150 deg. with accuracy, comparable with the measurement accuracy. The phase function obtained gives the information needed for the account of multiple scattering in the aureole region. The asymmetry of clear sky radiance due to multiple scattering is much less than for single scattering. Numerical simulations showed that aerosol size spectra, retrieved from measured and single scattered aureole radiance, differ only in the region of small particles (less than wavelength). Thus, the aerosol size distribution can be obtained as a combination of the results of the inversion of AOT (submicron fraction) and aureole brightness (coarse fraction). The limits of applicability of the approaches proposed are discussed. The examples of the results obtained for different model and experimental size distributions are given.

Light scattering by ice crystals of cirrus clouds is described by the geometric optics approximation with a good accuracy. This approximation is realized numerically with various ray-tracing codes. However, a majority of authors apply the ray-tracing codes not to the electromagnetic field but to its quadratic quantities, for example, to the Stokes parameters. Though this approach simplifies essentially calculation algorithms, the wave effects like diffraction and interference turn to be ignored. In this paper, ray- tracing is applied directly to the electro-magnetic field yielding the Jones matrix of the scattered field. As a result, two scattering (Mueller) matrices appear called the pure and mixed Mueller matrices. Here, the pure Mueller matrix is obtained via the Jones matrix by means of a simple transformation and the mixed one is a sum of the field quadratic quantities. A problem appears: which of the matrices is measured at lidar sounding of cirrus clouds?

The main optical characteristics of light scattering by mixed-phase clouds (the phase scattering function, the scattering, absorption and extinction efficiencies) were investigated. A theoretical study using a particle size spectrum of a mixed-phase cloud microstructure under the assumption of its spatial homogeneity is presented. The calculations of optical characteristics for the droplets of the mixed-phase cloud were made with the Mie theory and for the crystalline fraction the calculation methods connected with the geometrical optics and diffraction were used. For the mixed-phase cloud particle size spectrum the expressions were used that connect the ratio of droplets liquid water content to the crystals ice content (t) with the ratio of scattering coefficients for these fractions (q) for mixed- phase clouds. This made it possible to use the known expressions for calculations of the t values depending on the cloud layer temperature T to calculate the dependence of q on T.. The parameter q determines unambiguously basic optical characteristics for a mixed-phase cloud medium. It depends on the parameters of a particle size spectrum for water droplet and ice crystal fractions of a mixed-phase cloud and significantly depends on the incident radiation wavelength.

Further progress in plankton ecology is connected with the development of methods for organism observation in their natural habitats. Investigation of processes and phenomena taking place in microvolumes of the water environment is becoming more and more topical. Possibilities, advantages and limitations of holography applied to zooplanktonic studies in Lake Baikal are estimated in the paper. Peculiarities of the Lake Baikal zooplankter holographing are studied in laboratory experiments. The endemic pelagic crustacean Macrohectopus branickii (Amphipoda) was one of the objects studied. Images of the crustacean body fragments (5 - 40 micrometers and more) allowed us to estimate the resolution of holographic methods for different distances from the hologram plane. The resulting holograms reveal the interior of hard chitin structures (spines and other body parts). It is possible to count and to size the less hard structures (e.g., setae). A lot of biological particles are transparent or semitransparent and holographic image of such particle differs from the opaque particle image. Peculiarities of holographic images of these particles are discussed in the paper. As a result, we proposed method for evaluation of the particle optical features (refractive index and absorption factor), in addition to its geometrical parameters. The additional information can provide more precise identification of particle type. Method is based on analysis of intensity distributions in various cross- sections of holographic image. The above technique has been applied to experimental measurements of the refractive index of water drops in the air, latex spheres in various liquids, air bubbles in water. The accuracy of measurements was about 10% for the particles of 100 micrometers in diameter. Results of holographing of biological microparticles are presented as well.

The scientific clause is devoted to complex examinations of optical properties of micro crystals of alkali-halides simulative an atmospheric salt aerosol. In laboratory requirements the interactions in system 'micro crystals of salts - gas phase' were explored at superimposition of high- energy fields. Thus the scale of radiation and cold air plasma was utilized ultraviolet, X-ray. Is shown, that the presence of high-energy fields gives in interaction of micro crystals and gas phase. At interaction the chemical composition, structure and optical properties of salt particles changes. The scientific clause is devoted to study of optical properties of salt particles mainly in infrared range of a spectrum. The purpose of operation is the study of transformation of salt micro crystals and its communications with optical parameters.

It is known, that the majority of alkali-haloids crystals can long be stored in usual requirements, not changing the properties. But under certain conditions surface of crystals and ambient air begin to interact. The alkali-haloids crystals enter a composition of atmospheric salt aerosols. Therefore it is important to know, under what requirements their reactivity in relation to an environmental gas phase changes. In sectional operation is shown, that the reactivity of system 'salt particle - air' changes at action of high-energy radiations. Therefore results of laboratory experiment can be useful at revealing mechanisms of transformation of salt aerosols in requirements of a meteorological atmosphere.

Results of measurements of ground level ozone concentration in an atmosphere of Ulan-Ude and at southern coast of Lake Baikal in October, 1998, in January, May, July, 1999 are given. Seasonal variations of ground level ozone concentration in Ulan-Ude are received for the first time. The high hourly average values of ozone in summer period are revealed. Formation and distribution of gas impurities in a coastal zone of Lake Baikal in summer period of observation is connected with photochemical and local circulating processes. The low values of ozone concentration are the reason of prevalence of processes of formation NO₂ above processes photolysis. High values of NO₂ concentration at southeast coast of Lake Baikal are caused by action of anthropogenous sources.

The measuring of spectrums of model particles of alkali- haloids salts can be one of blocks in a complex of indicator examinations at estimation of a radio ecological state of an atmosphere. By laboratory examinations of system 'alkali- haloids micro crystals - air' is shown, that the processes of interaction with a gas phase simulate processes reference for a salt aerosol in a meteorological atmosphere. The action at system was carried out by high-energy radiations (ultraviolet, X-ray, scale). As a result of superimposition of fields of high-energy actions in the specified system the composite physicochemical processes are initiated which give in change of a composition, structures and series of properties of salt particles. The presence of high-energy fields should render influence on the performances of a salt aerosol. On the other hand, the occurrence of similar changes in a salt aerosol can serve indication of high- energy fields in a meteorological atmosphere.

The results of comprehensive field experiment are presented. The objective of the experiment is lidar technique development for control of pollutant dispersion from pulse source. Experiment was carried out in steppe region, underlying surface was covered with sparse vegetation. Charge exploded at the altitude of 10 m stand for source of pollutant. Lidar was used to trace the cloud of explosion products. The ratio of backscatter signal from the cloud to aerosol background signal was recorded along with the time and coordinates of sounded points. Ultrasonic meteorological station and sodar 25 - 30 meters distant from explosion location were used to measure air temperature, vertical and horizontal components of wind velocity and its direction, total energy of turbulent motions, tangential turbulent friction stress and vertical turbulent heat flow. Experimental data were compared with the results of numerical modeling of pollutant spatial distribution performed on the basis of Gaussian statistical model. Numerical results were primarily in satisfactory agreement with experimental data.

The results of investigations carried out during several months in different seasons are presented. Measurements were performed with an acoustic (ultrasonic) meteorological complex. In addition to the standard meteorological parameters, we measured such turbulence parameters, as the turbulent kinetic energy, momentum and heat fluxes, wind and temperature scales including the Monin-Obukhov length, etc., and also their statistical characteristics. Classes of atmospheric stability were determined in the course of measurements. The results obtained are compared with the data of conventional measurements at the meteorological station. The behavior of the measured parameters is studied depending on the general atmospheric state.

The results of continuous measurements of methane concentrations (CH₄) in air samples taken near the ground and in the atmospheric depth (column) in Obninsk in 1998 - 2001 are given. The air samples were taken in town so the measurement results were affected by not only natural but also by anthropogenic sources. Under a temperature inversion in the atmospheric boundary layer the concentrations of CH₄ found were significantly higher than its typical values. This is caused by anthropogenic CH₄ accumulation in air near the ground due to the absence of vertical mixing at a temperature inversion. Seasonal variations of methane in the boundary layer were determined over CH₄ minimal concentrations. A height- averaged concentration of methane in the atmospheric column was determined over the solar radiation spectra in the absorption band of CH₄ with the center at 3.3 micrometers . A comparison of the results shows that methane concentration near the ground exceeds its height-averaged concentration in the atmospheric column by about 0.15 ppm.

The data of long-term (1980 - 2000) continuous spectroscopic measurements of total water vapor content in the column of the continental atmosphere (the Issyk Kul station, the center of Eurasia) are given. The amplitudes and phases of water vapor seasonal variations have been defined, their long-term values and seasonal differences of the gas content variability are given for the observation site depending on the atmospheric temperature. A year-to-year variability of atmospheric total water vapor content is stated under a linear approximation that corresponds to an annual increase of its content by 0.015 g./cm². With the help of the spectral analysis of the data the main periodic components of water vapor variability were revealed with the periods of 6, 12, 35, 51 and 110 months. Their connection is shown with the temperature seasonal variations (periods of 6 and 12 months), with the El Nino phenomenon global consequences (a 51 month period) and with powerful volcanic eruptions (periods of 35, 51 and 110 months). An empirical statistical model was constructed for the atmospheric water vapor variability, that describes its mean monthly contents with an error of +/- 13%.

In the paper are discussed a research and numerical study of abnormal temperature near a source of warm water on the bottom of the lake Baikal (geothermal vent). The speeds of currents are designed at presence of a difference of water's temperature. The impact of the source spreads up to 2 km distance.

The analyzed results of calibrating data for chlorophyll 'a' concentration of the SeaWiFS satellite color scanner, being contained in the special purpose satellite of NASA - 'OrbView-2' (formerly - SeaStar) by data of field measurements on the surface of Peter the Great Bay are presented. It is shown that for the waters with the different chlorophyll 'a' content it would be more expedient to enter their calibration equations with the use of which can obtain the chlorophyll 'a' concentration fields more or less approximate to the real values from SeaWiFS.

The analyzed results of calibrating data for chlorophyll 'a' concentration of the SeaWiFS satellite color scanner, being contained in the special purpose satellite of NASA - 'OrbView-2' (formerly - SeaStar) by data of field measurements data on the surface of the north-western part of the Sea of Japan.

The comparative research of the chlorophyll contents for a number of arboreous plants has been carried out using traditional spectrophotometric and fluorescent laser techniques. Seasonal changes are analyzed in the net chlorophyll content during the sprint-summer period for coniferous and deciduous wood plants. The changes in the chlorophyll contents due to needles and leaves fading are observed. The experimental results are obtained using the spectrophotometric and lidar techniques to study the seasonal dynamics of chlorophyll and pigment complex destruction in the course of needles and leaves fading. Analysis has shown that the results obtained different methods are identical.

Geoinformation modeling system structure for assessment of the environmental impact of atmospheric pollution on forest- swamp ecosystems of West Siberia is considered. Complex approach to the assessment of man-caused impact based on the combination of sanitary-hygienic and landscape-geochemical approaches is reported. Methodical problems of analysis of atmosphere pollution impact on vegetable biosystems using geoinformation systems and remote sensing data are developed. Landscape structure of oil production territories in southern part of West Siberia are determined on base of processing of space images from spaceborn Resource-O. Particularities of atmosphere pollution zones modeling caused by gas burning in torches in territories of oil fields are considered. For instance, a pollution zones were revealed modeling of contaminants dispersal in atmosphere by standard model. Polluted landscapes areas are calculated depending on oil production volume. It is shown calculated data is well approximated by polynomial models.

In this paper the interrelation between geomagnetic pulsations and variations in frequency Doppler shift f_d of the ionosphere-reflected radio signal is under investigation. The experiment on simultaneous recording of f_d variations and geomagnetic pulsations was organized at high latitude station in Norilsk (geomagnetic latitude and longitude 64.2 degree(s) N, 160.4 degree(s) E, L equals 5.3) during February - April of 1995 - 98. Thirty cases of simultaneous recording of duration from 10 min to two hour were analyzed: 6 cases of simultaneous recording of variations fd and regular geomagnetic pulsations Pc5; and 25 cases of recording of f_d variations and irregular pulsations Pi2. On the basis of experimental results, the following conclusions have been drawn: (1) Hydromagnetic waves in the range of regular Pc5 pulsations, when interacting with the ionospheric F2 layer, make the main contribution to short- period f_d variations. The possible mechanism of fd variations are oscillations of electron density, associated with distribution of a hydromagnetic wave in an ionosphere. (2) There exists an unquestionable interrelation between fd variations of the sporadic E layer-reflected radio signal and irregular Pi2 pulsations, but for some reasons it is traced poorly.

From September 25 to 27, 1998, a strong geomagnetic storm occurred, during which the planetary index of geomagnetic activity Kp was as high as approximately 8.5, and Dst was approximately -207 nT. During the concerned storm, the Irkutsk Incoherent Scatter Radar measured height-time variations of electron density, electron and ion temperatures and plasma drift line-of-sight velocities. An interpretation of the measurements involved comparing them with results of calculations in terms of a numerical model of the ionosphere and plasmasphere. It was shown that the measured variations of such ionospheric parameters as the electron density, electron and ion temperatures, as well as ion fluxes along the geomagnetic field are reasonably accurately reproduced in model calculations. Furthermore, the ionospheric response to the magnetic storm under consideration was controlled mainly by a disturbance in the composition of the neutral atmosphere. The enhancement of the horizontal wind left the ionospheric response essentially unaffected as a consequence of what occurred in the morning hours when the ion production sources were insufficiently intense.

Reconnection of magnetic field lines is a very important coupling mechanism in space for configurations with considerable skew in the magnetic field. In a magnetospheric context such configurations occur at the dayside magnetopause and in the magnetotail. Thus, reconnection couples phenomena prevailing in the solar wind with ionospheric phenomena. We report on the most important signatures of reconnection. Recent developments of reconnection theory are presented. Reconnection phenomena in the tail are briefly discussed.

Many ionospheric and magnetospheric phenomena, e.g., the northern lights, require the existence of accelerated particle populations. One possible explanation for the development of such particles is an electric field directed along magnetic field lines. The main aim of this paper is to investigate the physical mechanisms leading to an electric potential difference along the Jo flux tube with special emphasis on the processes acting in the outer ionosphere of Jupiter. As a starting point, we assume a pressure perturbation at the position of Ιo and follow the evolution of this pressure perturbation from To towards Jupiter. Initially, the pressure pulse produces two slow mode waves propagating along the Ιo flux tube. These slow mode waves are converted into slow shocks traveling towards Jupiter, and are accompanied by a supersonic flow behind the shock front. The crucial point is now that due to the propagation into a more narrow flux tube, the flow velocity behind the shock increases, in particular fast near the surface of Jupiter. Such a strong plasma flow generates an electric potential difference along the magnetic field. We estimate this potential difference using well-known techniques of kinetic theory. It turns out that the strength of the potential drop is directly proportional to the flow energy of ions. Thus, the very heavy ion populations in the Ιo torus plasma provide an appropriate environment in order to generate an electric potential difference of the order of 1 kV. Therefore, the pressure pulse mechanism can contribute to the explanation of aurora and planetary radio emissions together with the generally accepted Alfven wings model.

To study magnetosphere-ionosphere interactions, appropriate considerations on the solar wind, the bow shock, the magnetosheath, and the outer ionosphere are of importance. In this study, we concentrate on the analysis of an inclined fast shock including upstream and downstream pressure anisotropy and apply it to conditions at the Earth's bow shock. It is the main goal of this work to perform a parameter study of the magnetic field strength and plasma parameters downstream of an inclined fast shock as functions of upstream parameters and downstream pressure anisotropy. For closing the set of equations we use two threshold conditions of plasma instabilities as additional equations to bound the range of the pressure anisotropy, i.e., the criterion of the fire-hose instability and the criterion of the mirror instability. We found that the pressure anisotropy in the solar wind has a small influence on the changes of the relevant physical quantities across the shock wave. We further show that the variations of the plasma and field parameters are strongly influenced by the upstream Alfven Mach number and the angle between the normal vector of the discontinuity and the upstream magnetic field.

During periods of southward interplanetary field and basically constant dynamic pressure, the magnetopause can move earthward due to the so-called phenomenon of magnetopause erosion. In this study, we present several erosion events monitored at geostationary orbit by the GOES spacecrafts underlying WIND measurements in the solar wind. We selected a number of events using 4 years of WIND observations (1996-1999). Specific selection criteria are based on obtaining a progressively decreasing IMF B_z negative, to have various levels of erosion, with and without dynamic pressure changes and of different durations in time. To figure out the erosion effect on geostationary orbit, we have to compare the measured depression in the geostationary magnetic field strength with the magnetic field strength on the well known May 11, 1999, the day the solar wind almost disappeared.

The plasma sheet is considered as a thin electrically conducting layer with a prescribe flow across the magnetic field lines at the equatorial plane of the magnetotail. Electric field resulting from the geomagnetic field diffusion into the solar wind is also added to the model. This gives a defined electric potential distribution at the flanks of the plasma sheet. The calculated electric potential from the plasma sheet and from the diffusive magnetopause is projected to the ionosphere along the magnetic field lines. At the ionospheric level they map to an oval strip at the polar cap boundary. Electric potential in the regions of the ionosphere both poleward and equatorward of this region is obtained by numerical solving of the problem of electric conductivity in the ionosphere. The patterns of electric potential contours in the ionosphere are similar to that known from observations. The positive and negative peaks of electric potential located at dawn and dusk sides of the polar oval correspond to the same peaks in the far plasma sheet at distance of about 150 R_E. The influence of the flow in the plasma sheet and other parameters of the model on the electric potential distribution in the ionosphere is discussed. The total potential drop across the polar cap is equal to 100 kV that exceed observed value. A conclusion is made that resistance to the field-aligned currents in the tail lobes should be taken into account.

Variations of plasma pressure in a magnetic flux tube can produce MHD waves evolving into shocks. In the case of low plasma beta, the plasma pressure pulses in the magnetic flux tube generates MHD slow shocks propagating along the tube. In the case of converging magnetic field lines, like in a dipole magnetic field, the cross section of a magnetic flux tube decreases enormously with increasing magnetic field strength. In such a case, the propagation of MHD waves along the magnetic flux tubes is rather different from that in the case of uniform magnetic field. The propagation of MHD slow shocks is studied numerically using an ideal MHD equations in an approximation suitable for a thin magnetic flux tube. In this approximation, the total pressure (sum of magnetic and plasma pressures), is a known function of the distance along the tube. Numerical method used for calculations is based on a conservative finite difference numerical scheme in material coordinates. The result obtained in the numerical study show that the intensity of the slow shock increases very much while the shock is propagating along the narrowing magnetic flux tube towards a region of a strong magnetic field.

Magnetospheric boundary (magnetopause) flowed by solar wind plasma is considered to be a thin layer with constant thickness and curvature radius. The plasma parameters and the magnetic field are assumed to obey the ideal incompressible magnetohydrodynamics. A Fourier analysis is used to calculate small perturbations of the magnetic field and plasma parameters near the magnetopause in a linear approximation. The instability growth rate is obtained as a function of the magnetopause thickness, curvature radius, velocity and magnetic field vectors given on the both sides of the magnetopause. The resulting instability is a combination of interchange and Kelvin-Helmholtz instabilities of the magnetospheric boundary. For a fixed plasma velocity, the instability is the strongest in a case of antiparallel magnetic fields at the magnetopause. The instability decreases if the magnetosheath magnetic field deviates from the direction antiparallel to the geomagnetic field. Instability growth rate is an increasing function of plasma velocity component perpendicular to the magnetic field. On the other hand, plasma flow along the magnetic field diminishes the instability growth rate. For zero plasma velocity, the instability growth rate is positive only within a relatively small angle interval for the deviation of the magnetosheath magnetic field from the antigeomagnetic direction. This angle interval depends on the curvature radius and inner structure of the magnetopause.

In March and August/September 1995, February 1996, and in March-April 1998, observations of the inhomogeneous structure of the high-latitude ionosphere were carried out at Norilsk (geomagnetic latitude and longitude are 64.2 and 160.4, and L equals 5.3). Small-scale irregularities (with the lifetime of several seconds, and the spatial scale less than 5-7 km), and medium-size wave irregularities (with the period of 10 - 50 min, and the horizontal size of tens and hundreds of kilometers) of the ionospheric F layer were investigated under different geophysical conditions. A total of 300 hours of observations was recorded, including 250 reflections from the F2 layer, and the other reflections from the sporadic E layer.

The purpose of the given work is comparison of data, received on IS radar in Irkutsk with international ionospheric model IRI-95 for determination of the model accuracy in Siberian sector of the Earth. In the work results of comparison of electron and ion temperatures and electron density, measured during years 1998 and 2000 in a range of heights from 200 up to 700 km with data of model are submitted.

A technique is proposed for reconstructing of parameters space distributions of electronic concentration in ionosphere, based on a parametrization of the solution of system of integral equations connecting measured delays of navigational satellites signals to distribution of electronic concentration along beams 'navigational satellite - receiver' for a network of two-frequency receivers GPS. Results obtained are compared with Millstone-Hill incoherent scatter radar data.

The peculiarities of the arrangement of Irkutsk incoherent scatter radar are those, that the direct measurements of signals from a range of heights lower 160 km, are impossible owing to reflections from an earthly surface. However at the analysis of experimental results the information on dynamics of particles density in the ionosphere E-layer, located usually at height 100 - 120 km is frequently necessary. A method is offered for indirect estimation of concentration in the given area on the basis of Faraday effect, which is used on the radar for determination of electron density.

MF radar observations of mesospheric backscatter were carried out during summer - winter 1999 in Tumanny (69.0 degree(s)N, 35.7 degree(s)E) using PGI radar of the vertical sounding. The measurements indicated the presence of strong radar returns from altitudes between about 74 and 99 km. Usually, the reflection region looks like as 2 or 3 distinct layers, which are located at heights 74 - 82, 82 - 89 and 89 - 99 km. The features of MF waves backscattered from a height range of 82 - 89 km are very similar to VHF radar measurements of Polar Mesospheric Summer Echoes (PMSE). A distinctive feature of these measurements is a registration of sharp gradients of the electron density at the heights where the backscattered waves amplitudes were more intensive. An analysis of the digital ionograms obtained in Loparskaya (68.6 degree(s)N, 33.3 degree(s)E) have shown that the intensive sporadic E-layers are observed during the strong MF radar returns from the mesopause region.

The Irkutsk Incoherent Scatter (IS) radar is a unique facility in Russia, designed for geophysical and radio- probing investigations of the upper atmosphere. The range of problems tackled using the radar is quite extensive. Having a high potential and investigative capability, the radar represents an extremely sophisticated engineering facility. A maximum possible knowledge of all performance data of this instrument is necessary for conducting accurate measurements of space environment parameters and for scientific experiments. Of particular interest in this regard is the radar's antenna system. The spatial distribution of the radiation power (directional pattern) of the antenna system is as yet imperfectly understood. Because of the complexity and the unconventional nature of the antenna design, a mathematical simulation and calculation of the directional pattern involves a highly cumbersome task, and the reliability of such calculations is low. The overall worldwide practice shows that the most powerful tool for obtaining the directional pattern characteristics is to measure the variations of the noise power level when various cosmic radio sources traverse the beam. The advancement of digital technology in the present state of the art makes it possible to record large amounts of information needed to construct an accurate spatial distribution of the power received and radiated by the antenna. Results, thus obtained, are useful for correctly selecting the IS radar operation modes.

Based on minimizing the standard deviation between the echo signal and its model representation, we developed an algorithm for determining parameters of two interfering signals. A numerical simulation was used to assess the validity of the algorithm in the presence of noise. As a result of the simulation, it was possible to reveal the main factors influencing the errors of determining the parameters of interfering signals. The resolving power of the method was estimated. It is shown that the form of the emitted pulse has a substantial influence on the method's resolution.

Adaptive regional total electron content space distribution model, based on the data of the IGS (International GPS Service for Geophysics) international network of GPS- stations is proposed in the article. The method of the spherical harmonic analysis with the selection of the spectrum of approximating harmonic with the greatest contribution was applied at creation of the model. The method essence consists in a such spherical harmonics series spectrum selection when the harmonics, with orthogonal projection exceeding an input data errors level appropriate number of times, are used in an approximating function. The comparative estimation of results obtained by the least squares process and throug offered method has executed. The usage of the least squares process when solving the problem of the spherical harmonics analysis at reconstructing the space distribution of the total electronic contents because of the poor conditionality of normal equations system, results in considerable errors of approximating strongly dependent on selected the length of series. The selection of the spherical harmonics series spectrum with the greatest contribution allows to regularize the normal equations system solution and to increase its accuracy and stability. The model can be used to increase the accuracy of detecting satellite radionavigation system users in a relative navigation mode, at ionospheric monitoring etc.

New method for wave propagation description in multi-scale random media is suggested. The method uses double Fourier transform of the observed wave field both in coordinates of receivers and those of the moving source (satellite). It is shown, that the suggested approach is consistent with known partial solutions: geometrical optics method and Born approximation in areas of their applicability. The method under consideration is valid in the case of strong fluctuation, caused by large-scale focusing inhomogeneities and in the same time describes backscattering effects. Characteristic for wave propagation in small-scale random media.

In this paper, based on the macroscopic approach, for a one- dimensional model of high-frequency radio wave backscattering from small-scale ionospheric irregularities, formulas have been obtained for quadrature components of the received signal having regard to the regular electron density component. Results of this study can be used in theoretical analyses of incoherent-scatter signal processing techniques and in mathematical simulations of the backscatter phenomenon for the one-position mode of measurements.

Obtaining information about the state of the sea surface using HF radars has been the subject of intense investigations during the past several decades. Most theoretical investigations made to date have adopted, as the incident wave, a plane wave with a certain wave vector. In real conditions, however, with the finite beam width, the ionosphere-reflected beam of waves of a finite width is usually incident on the scattering sea surface, which must be taken into account when investigating the form of the spectrum and processing it by extracting information about the sea surface. This paper investigates the scattering of fluctuating ionospheric radio waves from the sea surface within limits of the geometrical optics by taking into consideration the finiteness of the beam of the receive and transmit antennas. A numerical simulation is used to investigate the influence of the finiteness of the beam width, the time of coherent integration, and ionospheric irregularities on the structure of the spectrum of the received signal of the overt-the-horizon sea surface radar.

The paper aims to study the effect of gravity wave propagation on atmospheric trace gas distributions in the upper mesosphere and lower thermosphere. A two-dimensional, time-dependent, nonlinear photochemical-dynamical coupling gravity wave model is made. Important photochemical reactions in middle atmosphere are considered in this model. The model includes diabetic process produced by photochemistry and the dynamical effect of gravity wave on atmospheric chemical species. The pseudospectral method is used in the horizontal direction and the finite difference approximations are used in vertical direction z and time t. FICE method is used to solve the model. The results of the simulation by using the model show that the gravity wave propagation can induce large change of the mean profiles of oxygen compound and hydrogen compound in mesopause region. The effect of gravity waves on the distributions of the atmospheric species in night is greater than that in daytime.

The problem of researching the ozone layer of Earth's atmosphere is uncovered in the article. The data on preliminary research and prospects for exploiting the system - adaptive models based on achievements of neuroinformatics for predicting contents of ozone in a stratosphere and troposphere are described. The results of last satellite researches of an Antarctic ozone hole are represented and interpreted.

The data analysis of the refractive index (RI) on the frequency 10 GHz shows the RI fluctuation character may give the short forecasting of geo- and troposphere catastrophes. The data set has more than four years of continuous observations. The mechanisms of the earthquake focal point forming are proposed. It is also discussed the possible infrasound source in the atmosphere.

We present and analyze the data of daily observations of ground-level near-noon ultraviolet (UV) radiation of the Sun in the wavelength range 295 - 345 nm at Irkutsk (East Siberia, 52 degree(s)N, 104 degree(s)E) for 1998 - 2000. The study revealed an asymmetry of the seasonal variation of UV radiation with respect to the summer solstice, and its dependence on the wavelength in the spectral range under consideration. Irregular variations of ground-level UV radiation, typical of the region, were identified, which depend on the season, and on the selected spectral range. The detected features of the irregular variations are interpreted in terms of the existence of a pronounced annual variation in total ozone content, the variation (during different seasons) of the proportion of the contribution to the attenuation of UV radiation from the Rayleigh and aerosol scattering, the absorption by ozone, and of the specific climatic weather regime in East Siberia.

The lower polar ionosphere research are carried out by the modified measuring complex of the observatory Tumanny (69.0 degree(s)N, 35.7 degree(s)E) since 1999. It were performed an analysis of the dynamical processes caused by the neutral gas motion, preliminary investigation of statistical and spectral characteristics of the backscattered waves and, furthermore, variations of the electron density were calculated. The areas, where the electron density irregularities with scales more than 100 m at heights from 70 till 99 km were groped, were detected by the spaced sensors measurements of the backscattered waves. During the solar eclipse of 1999 August 11 for the short time the increased radioecho intensity was observed at the heights near the mesopause.

The paper describes scientific methodology of developing complex nonlinear dynamic models which form the basis of a new scientific trend called Stikhioniks and are an efficient tool to device atmosphere models. The model is aimed to develop complexly organized hierarchical non-equilibrium adaptive systems with a wide range of connections and elements and is a new step as related to the now dominant mechanical-statistical paradigm.

The response of the atmosphere to a harmonic source of a vertical impulse moving along the Earth surface is investigated. It is shown that a small amplitude source can result in two appreciable nonlinear effects: flow formation and changing of an atmosphere temperature. The flow is an especially considerable effect. An ion-neutral friction is not taken into account; therefore, the effects obtained can be a little bit overstated. At increasing of the source amplitude, at the heights 100 - 200 km some irregular oscillations arise due to wave disintegration into disturbances of smaller scales. The scales of these disturbances are of the one order with the grid steps; therefore, it is possible to study them only with a finer grid.

Peculiarity of nature and climate changes in middle latitudes of the Northern Hemisphere and in Siberia is that the temporal variability of meteorological quantities here has a wide range and their spatial variability has a complicated zone structure. Therefore, regional monitoring of modern nature and climate changes in Siberia is of scientific interest from the viewpoint of the global changes observed. Another Siberian peculiarity is associated with the fact that there are many unique objects that have global importance both as natural complexes (boreal forests, water- bog systems, Baikal lake, etc.) And as technogenic objects (oil and gas production, coal mining, metallurgy, transport, etc.). Therefore monitoring and modeling of regional nature and climate changes in Siberia have great practical importance, which is underestimated now, for industrial development of Siberia. Taking into account the above peculiarities and tendencies on investigation of global and regional environmental and climate changes, the multidisciplinary project on Climate and Ecological Monitoring of Siberia (CEMS) was accepted to the research and development program Sibir' since 1993. To realize this project, the Climate and Ecological Observatory was established in Tomsk at the Institute for Optical Monitoring (IOM) SB RAS. At the present time the stations (the basic and background ones) of this observatory are in a progress and theory and instruments for monitoring are being developed as well. In this paper we discuss some results obtained in the framework of CEMS project that were partially published in the monographs, in scientific journals, and will be published in the Proceedings of the 8th Joint International Symposium on Atmospheric and Ocean Optics and Atmosphere Physics. This review has a purpose not only to discuss the obtained regularities but also to formulate scientific and technical tasks for further investigations into the regional changes of technogenic, natural, and climate systems.

Time series of the surface air temperature for Tomsk and Irkutsk over a period of 1881-1995 were investigated using wavelet transformations. In both time series the oscillation structures of the scales of 3 - 7; 8 - 12; 13 - 24; 28 - 40; 50 - 64 years were found out. Simultaneously, we analyzed the series of the South Oscillation Index (SOI), the geomagnetic planetary index Ap, the Wolf numbers W, the critical frequencies of the F2 layer of the ionosphere f_oF2. We also performed a correlation analysis both of the series of the considered values and the periodicities of various scales. The significant correlation for the series taking on the value of 0.69 is observed only between the surface temperature series. A significant anticorrelation was found between the temperature oscillations and the SOI in the scales of the order of 22 years. A positive correlation occurred for the temperature and Ap in the scale of 30 years, and for the temperature and W over a period of 22 years.

In this study, one-dimensional spatial distributions of the total liquid water content Q in the extended cloud layers are statistically analyzed. The distributions were derived from the ground measurements of the brightness temperatures of the atmosphere T_B((lambda) ) at wavelengths (lambda) equals 0.8 and 2.3 cm which were carried out during winter monsoon at the northern Taiwan coast. The duration of continuous microwave observations of unbroken clouds ranged from 14 to 225 h. The values of Q were retrieved from the increments of the brightness temperature of the cloud atmosphere relative to the clear one taking into account air temperature and humidity. The 'frozen turbulence' hypothesis was applied to determine spatial distributions of Q. Spatial frequencies of Q variations were found using data on wind speed and direction at the cloud level. The spectral analysis was performed to estimate scale-invariant regimes. The regimes are defined by the scales where spectra follow the power law E(x) approximately exp (-(beta) x). The lower limit of the scales was restricted by an antenna field of view at the cloud level and was about 400 m. The upper limit was a function of the observation duration and the used averaging method and ranged from 40 to 400 km. The results of four case studies are presented. In all cases, the scale-invariant regimes were clearly revealed. Two types of spectra were found: (1) scale-invariant spectra covering the whole scale range analyzed, and (2) spectra with two scale-invariant ranges with (beta) > 2.5 at lower scales and (beta) < 1.5 at upper scales.

Amplitude-phase characteristics (APCs) of surface air temperature (SAT) annual cycle (SAT) are analyzed. From meteorological observations from the XX century and meteorological reanalyses for its second half it is found that alongside with the well-known negative correlation of SAT AC amplitude T_s,1 with annual mean SAT T_s,m a peculiarity in the North Pacific exists where T_s,1 and T_s,m are positively intercorrelated. In contrast, SAT AC phase characteristics show more regional behavior. In particular southward of the characteristic annual mean position of the snow-ice boundary (SIB) SAT AC is harmonized under climate warming while northward it is deharmonized. In the Far East (southward about 50 degree(s)N) SAT AC shifts as a whole with its extrema occurring earlier with increasing annual mean SAT. From the energy-balance climate considerations these tendencies of change of the SAT AC APCs in the middle and high latitudes are associated to the influence of the albedo-SAT feedback due to the SIB movement and in the Far East - to the interannual cloudiness variability. Tendencies of change for SAT AC related to the SIB movement are simulated reasonably well by the climate model of intermediate complexity in the experiments with greenhouse gases atmospheric loading. In contrast, the tendencies resulting from the cloudiness variability are not reproduced by this model.

The methods and means of the system-evolutionary analysis of mesoclimate state ensemble in multidimensional phase space of meteorological variables provide new opportunities for estimation of features of climate changes. The method of graphic climate representation includes procedures of processing of meteorological data, calculation of the estimation characteristics and construction of meteorological portraits. The techniques of the analysis use procedures of identification of particular areas in state space for long-term intervals, determination of the variability characteristics of the state ensembles. The characteristics of interdecadal and long-term variability of Siberian mesoclimate were obtained. The features of changes in relations between surface processes and atmospheric climate processes, variation of periodicity and violation of climate rhythm synchronism at the transition stages, tendencies to temperature and precipitations growth during cold period and an increase in the duration of warm periods are revealed.

An analysis of time series of meteorological parameters has shown that long-term time intervals (stages and steps) with almost uniform climate regime do exist. These stages and steps are due to existence of steady periods in basic climate-forming factors - atmospheric circulation, solar activity and other astronomical and geophysical factors. New concepts of climatic regime norm for stage and general climatic norm are introduced. A method for revealing climatic stages and steps and determining climatic norms is proposed based on integral estimation functions of radiative, thermal, water and other regimes of a climate process. Time intervals with relatively constant climate are determined for 16 weather stations of West Siberia on the basis on the analysis of secular series of cumulative sum of annual air temperatures and annual precipitations.

Thunderstorm activity variations relative to the onset of > 10 MeV proton flow rise and in the periods of galactic cosmic ray decreases (Forbush-effects) are studied by the superposed epoch technique. Thunderstorm activity is estimated by VLF-noise level registered in Yakutsk. In summer day and winter night hours the decrease of the VLF- noise level up to minimum is observed on the third day after the proton burst and then the increase - on the forth-fifth day. With respect to the onset of Forbush-decreases one can distinguish two phases of the effect: during the first phase the decrease of the VLF-noise amplitude occurs on the 0, -1 day, and during the second one the increase takes place on the +1, 2 day with the excess of the initial undisturbed level. The obtained results allow to connect the considered reasons and to imagine the thunderstorm activity variations in common sequence. The simultaneous consideration of effects shows that the decrease of the VLF- noise level is caused by the burst of protons and the increase of the noise level during subsequent days is caused by GCR Forbush-decreases.