The depolarization-backscatter lidar reported here is developed for application in the polar stratospheric and high- tropospheric studies. That includes the following operations: detection of the stratospheric background aerosol, detection of high-altitude cirrus clouds and polar stratospheric clouds (PSC), detection of Rayleigh backscatter signal for subsequent stratospheric temperature retrieval algorithm application. The lidar is stationed in Sodankyla, Finland (67N) and intended for a 2-year operation at that site. It operates with one Nd:YAG laser with second and third harmonics conversion. The detection of the backscatter atmospheric signal is performed at the fundamental, second and the third harmonics of the laser (1 micrometer, 532 nm and 355 nm), as well as the vibrational Raman backscatter from the nitrogen pumped by the third harmonic at 387 nm. The backscatter signal at 532 nm is detected separately in (p) and (s) polarization.

A backscatter lidar for unattended, stand-alone eye-safe operation has been developed by Vaisala. The design of the CT75K lidar ceilometer takes advantage of volume-produced optics, electronics, software, and mechanics. The CT75K combines four identical optical subassemblies of the standard 7.5 km ceilometer in an array and operates them in synchronous mode. Examples of cirrus cloud and boundary layer measurements are demonstrated.

The standard meteorological instrumentation of an airport includes visibility meters enabling the tower personnel to report the ground visibility conditions to an approaching pilot. In case of ground fog the slant visibility conditions for that pilot might be much better. This is the reason for introducing a ground based lidar system that is able to determine the slant visual range. Results of a measuring campaign at Hamburg Airport show a good correlation between ground and slant visibility for a homogeneous atmosphere and a significant distinction between the two values for ground fog situations.

The ill-posed problem of aerosol size distribution determination from a small number of backscatter and extinction measurements was solved successfully with a mollifier method which is advantageous since the ill-posed part is performed on exactly given quantities, the points r where n(r) is evaluated may be freely selected. A new two- dimensional model for the troposphere is proposed.

A lidar system employing a diode laser pumped Nd:YLF laser and photon counting technique is described for use in automated cloud and aerosol measurements. A Nd:YLF laser provides 523 nm 10 (mu) J/pulse energy at 2500 Hz repetition rate. A coaxial configuration is used for transmitting laser pulse and receiving the signal with a 0.2 m Schmidt-Cassegrain telescope. An avalanche photodiode is used for back scattered photon counting in Geiger mode. This micro pulse lidar (MPL) is capable to detect subvisible cirrus and boundary layer within 10 second averaging time. Also the MPL takes back scattered signal at four different spatial resolutions of 30 m, 75 m, 150 m, and 300 m to meet various user requirements. The detected signal is processed and displayed on a personal computer. The 32 bit data processing software is running on the Window 95 platform.

Results from dual wavelength Raman lidar observations of tropical high-altitude cirrus clouds are reported. Based on 107 hours of night-time measurements cirrus clouds were present in more than 50% of the observations at latitudes between 23.5 degrees south and 23.5 degrees north and altitudes between 11 and 16 km. Volume depolarization is found to be a sensitive parameter for the detection of subvisible cloud layers. Using Mie scattering calculations estimates of the ice water content are derived.

The results of stratospheric aerosol measurements by lidar sounding over Obninsk, Russia from 1985 are presented.

Unlike filter aspiration the results both of photoelectric and lidar measurements essentially depend on the optical properties of particles. To evaluate the particle concentration on the basis of lidar sounding data, we have to utilize the proper optical model of the scatterer. The model of a spherical particle with the radially variable refractive index is proposed.

The integral solutions of lidar equation commonly in use for sounding of inhomogeneous aerosols still suffer from the fact of a priori assumed relationship between backscattering and extinction coefficients. It has necessitated the development of new integral solutions of lidar equation. Multipositional lidar techniques are based on sounding of investigated atmospheric volume from different points in space. Unlike traditional techniques, these techniques give possibility to find a posteriori relationship between measured coefficients. The simulations of the statistical errors were performed for multipositional schemes of lidar sounding. New approach appears as a result of the error calculation to be effective one for a variety of typical atmospheric scenarios.

Based on the size distribution function and concentrations of aerosol particles which were determined in the coastal zones of the southern Baltic Sea by means of the lidar method the aerosol concentrations and their gradients above the sea surface were derived. The measurements were carried out under various meteorological conditions and in various seasons of the year taking into consideration such factors as wind direction, duration and velocity and different types of sea bottoms. It was confirmed that aerosol concentrations and their gradients were relatively high in fall and winter when the winds blew from the shore. Coal burning heat production for city inhabitants during the colder months influences this phenomenon, since there is a substantial amount of pollution produced which is carried with the winds over the sea in the form of aerosols. For the winds from the open sea directions the values of concentrations and gradients were substantially lower even though the wind velocity was much greater.

In this paper a multiwavelength (355, 532, and 1064 nm) lidar sounding across a stack plume has been computer simulated. The lidar data were then inverted using four different procedures proposed by: Klett, Evans, Potter and Grabowski. Results of these inversions were dependent on both: dust particle size dispersion and mass concentration. It has been shown that Grabowski's iterative procedure retrieves a plume dust concentration profile with a reasonable accuracy and seem to be (as it does not require assumption on a backscatter- extinction ratio) advantageous to others.

We describe a new method for gas flux measurements using a combination of differential absorption lidar (DIAL) and wind videography. The wind speed was measured by an imaging method, which calculates the horizontal displacement of the plume with cross correlation techniques. High spatial and temporal resolution is achieved with histogram equalization and window filtering techniques. Simultaneous measurements of the distance, the direction of the plume and the integrated concentration were provided through the lidar measurements. Alternative methods to measure the wind speed at different heights have been used to validate precision and accuracy of the new method for different geometrical combinations. An example of SO₂ flux measurements from a paper pulp mill is presented.

Shell Research Ltd has been using an IR differential absorption LIDAR (DIAL) facility for about two years to measure the emission rates (fluxes) of VOCs from petroleum industry process units. This paper describes the measurement, flux calculation and data display procedures used. Careful system setup and tuning plus the use of appropriate calculation procedures are needed to obtain accurate measurements. The factors that affect flux measurement accuracy and detection limits under practical conditions are discussed.

A statistically significant data set of backscattering LIDAR and ground-based information has been obtained for the planetary boundary layer (PBL) of Florence (I). The summer LIDAR backscattering data at 532 and 1064 nm have been used to estimate both the size and the number concentration of the urban aerosols in the accumulation mode. This technique seems to be relatively insensitive to the aerosol composition. The time-height evolution of the PBL [mainly the stable (SL) and the mixed (ML) layers] has been plotted, together with the meteorological and ground-based pollution data for the 200 measurement days. The ground-based hourly pollution data (NOx, CO) have been compared with the hourly-averaged 1064 nm backscattering at 25 meters above the ground. A correlation, R equals 0.65, was obtained between NOx and 1064 nm backscattering during the summer period when the traffic aerosols do not grow considerably after their production. The correlation is not significant during winter, when the growth of the particles is much faster. During winter, the RH variations are more important than aerosol number variations to determine the backscattering evolution.

A feasibility study for simultaneous range resolved measurements of minor species concentration by the differential absorption lidar (DIAL) technique and wind velocity using a pulsed carbon-dioxide HCLR is addressed. The LMD heterodyne coherent laser radar (HCLR) is used to investigate the statistical properties of the distributed aerosols backscattered power and Doppler frequency shift estimation as a function of range gate. We derive a trade off between accuracy for wind velocity and species concentration. We determine an optimal pulse bandwidth accounting for pulse duration and frequency chirp to fulfill the requirements on measurement accuracies, range resolution and time resolution. We show that for accurate concentration estimations, an accumulation on a few tens shots is required. We introduce a detector array in order to improve the performances with respect to statistical distribution.

The atmospheric environmental situation over the urban area of a large city is determined by a complex combination of anthropogenic pollution and meteorological factors. The efficient way to provide three-dimensional mapping of gaseous pollutants over wide areas is utilization of lidar systems employing tunable narrowband transmitters. The paper presented describes activity of RRC 'Kurchatov Institute' in the field of lidar atmospheric monitoring. The project 'mobile remote sensing system based on tunable laser transmitter for environmental monitoring' is developed under financial support of International Scientific and Technology Center (Moscow). The objective of the project is design, construction and field testing of a DIAL-technique system. The lidar transmitter consists of an excimer laser pumping dye laser, BBO crystal frequency doubler, and scanning flat mirror. Sulfur dioxide and atomic mercury have been selected as pollutants for field tests of the lidar system under development. A recent large increase in Moscow traffic stimulated taking into consideration also the remote sensing of lower troposphere ozone because of the photochemical smog problem. The status of the project is briefly discussed. The current activity includes also collecting of environmental data relevant to lidar remote sensing. Main attention is paid to pollutant concentration levels over Moscow city and Moscow district areas.

Optical parametric oscillators (OPOs) are powerful solid-state sources of broadly tunable coherent radiation. Since the recent improvement of intense pump sources and the availability of high quality nonlinear optical materials OPOs can routinely be operated in the UV, VIS and IR spectral range with conversion efficiencies exceeding 30%. Therefore OPOs offer a great potential for lidar measurements and, due to their solid-state character, in particular for airborne lidar applications. We are currently investigating OPOs for an airborne differential absorption lidar (DIAL) system for water vapor monitoring. Any detailed understanding of the role of water vapor in the global climate system requires precise measurements in the atmosphere with high temporal and spatial resolution. The DIAL technique applied in the near infrared spectral range is generally considered to be appropriate for this purpose. In order to accurately determine atmospheric gas concentrations by means of the DIAL technique tunability and spectral properties of the lidar transmitter are very important. The stringent requirements can be achieved with an OPO by employing the technique of injection seeding with radiation from a dye laser or from a diode laser. At the same time, the diode laser is an ideal tool for the spectroscopic analysis of the absorption lines.

We have developed conceptual designs for multi-purpose lidar transmitters using common assumptions and analysis to estimate transmitter efficiency and weight in a space based, long life configuration. We examined five basic transmitters, each using diode array excitation of the active laser medium. These approaches were evaluated for application in four different measurements: cloud and aerosol scattering, water vapor sensing, ozone measurement, and wind velocity measurement using incoherent or 'edge' techniques. We projected the mass of each of these systems subject to the constraint of input power limited to 200 W total for the lidar source, as appropriate for smaller satellites. The mass of a single purpose sensor source is projected at 30 kgms to 40 kgms, while multi-purpose transmitters weight in the range of 70 kgms to 80 kgms. Operating pulse pair rates are driven strongly by the application nd the transmitter laser choice, with ozone being the most stressing application, providing the lowest PRF, approximately 7 Hz for on-line/off-line pulse pairs in the best case. We evaluate the risks.

With the remote airborne measurement of three dimensional wind field it is possible to observe a wide area in a relatively short period of time. On the other hand the knowledge of the exact velocity and orientation of the aircraft is mandatory. Any small deviation in these parameters will cause a systematic error in the estimated wind field. The conical scanning airborne cw carbon-dioxide Doppler lidar ADOLAR has been designed to gain experience concerning the correction of the inertial reference system on board the aircraft using the ground return as a reference and for testing different signal processing algorithms. Besides this the instrument can also be used for the measurement of small scale wind phenomena e.g. valley wind or flow around a hill. The lidar was used at two campaigns in 1994 and 1996 onboard the DLR research aircraft Falcon F20. The missions covered measurements overland where the ground return was used to calibrate several parameters of the lidar and the aircraft reference system as well as measurements over the North Sea and the Baltic Sea at regions with a lower aerosol density.

We present measurements of water vapor using a differential absorption lidar (DIAL) system mounted downward looking on board a meteorological research aircraft. Flight tracks flown in 1.5 - 3 km above ground show the height and entrainment structure of the atmospheric boundary layer top. Cross sections of water vapor can be used to study for example land- sea interactions or the structure of thermals in a convective boundary layer. Applying spectral and autocorrelation analyses across horizontal DIAL water vapor series gives insight into the turbulent structure of the atmosphere. Vertical fluxes of humidity at the top of the boundary layer can be estimated from the DIAL variance water vapor profiles using a set of empirically derived equations. Such measurements are of high climatological interest, since they enable us to evaluate and monitor evaporation and biosphere-atmosphere exchange processes.

We show some examples of real and simulated return signals of airborne and space-based LIDARs. These return signals from cirrus and water clouds demonstrate the contributions from the different orders of multiple scattering. For a space-based LIDAR even for subvisible cirrus clouds the contribution from multiple scattering is substantial, for water clouds it is absolutely dominant. For an airborne LIDAR multiple scattering is much less important. The simulations have been done using variance reduction Monte Carlo methods allowing for controlling the variance. The variance reduction methods of these Monte Carlo methods are based on scattering splitting, extinction splitting, exponential transform, and local estimates. Our program for the calculation of multiply scattered LIDAR returns has been tested successfully in several international contests. It reproduces real LIDAR returns obtained from the space-based LITE (NASA) and from the airborne ALEX (DLR) equally well. We propose a very efficient and a very generally applicable procedure for the retrieval of microphysical parameters from such multiply scattered LIDAR returns. This procedure is based on the combination of a comparison of the measured signal with simulated signals and a uniform grid or random search procedure for minimization. As a by-product this retrieval technique allows for a sensitivity analysis of the dependence of the signals on variations of parameters. We apply the retrieval method to obtain the variable extinction coefficient of a cirrus cloud from the real LIDAR returns of the airborne lidar ALEX and the space- based lidar LITE.

Long-term surveillance of coastal zones like the German Bight with airborne laser fluorosensors have shown the capability of active remote sensing to investigate various oceanic parameters, such as dissolved organic matter (gelbstoff) or chlorophyll in algae. Recently the feasibility of a spaceborne laser fluorosensor for large-scale monitoring of water-column parameters has met increasing interest. Complementary to passive remote sensing instruments, like SeaWifs or OCTS, active remote sensing promises to provide a powerful tool for detection of substances which are otherwise hardly detectable, using inherent molecular fluorescence at specific wavelengths. The feasibility of such measurements using platforms at altitudes of up to 800 km is studied. This would allow the instrument to be operated as an attachment to atmospheric lidars. A simulation of radiative transfer in a cloudless and horizontally stratified atmosphere is presented, with particular emphasis on wavelengths which are relevant for hydrographic measurements. Results of this simulation are presented, especially the geometrical aspects of radiative transfer through the atmosphere, optimization of lidar parameters and effects of dispersion.

Comparison between theoretical previsions on the backscattered signals and experimental ones have indicated some disagreements which led to a revision of the optical receiver system of the carbon-dioxide laser dial equipment. A new telescope has been set up as well as an optical system designed to control routinely the alignment, and, the overlapping among the telescope optical axis and the laser beams.

The present paper is devoted to the description of two distinct multiparametric lidar system presently under development. The first system is based on a Nd:YAG laser pumping a dye laser equipped with a dual wavelength device. The second lidar system is based on two optical parametric oscillator (OPO) lasers pumped by a Nd:YAG laser operating at a pulse repetition rate of 100 Hz. OPO lasers represent a new design for coherent radiation sources continuously tunable in the UV -- near IR range (up to 2 micrometer). This allows us to perform differential absorption lidar (DIAL) measurements in a spectral region where most of atmospheric pollutants display absorption lines. The selection of the wavelengths to be used for DIAL measurements is a non trivial task. In particular, a method to select the optimal (lambda) _ON and (lambda) _OFF has been developed and applied to several molecular gases. Both systems have been designed to carry out simultaneous measurements of atmospheric aerosols, water vapor profiles, temperature and density profiles, atmospheric transmissivity, and atmospheric pollutants concentration.

A compact carbon-dioxide laser source has been developed at the ENEA remote sensing laboratory, with the aim of emitting two alternate wavelengths in rapid succession along the same line for use in lidar/DIAL applications. The solutions adopted in the new design successfully overcome many of the problems previously encountered running a lidar test site. The overlapped emission of two different wavelengths beams from a single cavity is a major improvement on the traditional systems which relied on two separate laser sources operating on different lines. Additional upgrading of the receiver apparatus and of the acquisition electronics have led to further improvements in the performance of the complete lidar system. The new design system represents a significant step towards the development of a compact fully mobile lidar.

Laser remote sensing technique using coherent lidar systems are being widely used for wind measurements. Laser wind measurements use the Doppler shift of backscattered radiation to determine the wind speed. To measure the small Doppler shifts accurately heterodyne detection is used. This technique requires an energetic, low divergence, narrow linewidth laser transmitter to maintain a high degree of coherence. For measurements from ground, air, or space platform, a reliable, all solid-state laser transmitter in the eye-safe region with appreciable energy/pulse is required. This paper reports development and performance of a diode-pumped solid-state amplifiers at 2-micrometer. Q-switched, 400-ns pulses with output energy of 700 mJ at 2-micrometer, representing an optical-to-optical efficiency of 2%, was achieved from five diode-pumped Ho:TM:YLF laser amplifiers at room-temperature.

Diode-pumped solid-state pulsed coherent laser radar systems have recently been developed at Coherent Technologies, Inc., for the remote measurement of atmospheric wind fields. Flash- lamp pumped systems have been utilized since 1990 for obtaining wind field measurements. These flash-lamp pumped lidar systems have been applied to wind profiling, aircraft wake vortex measurements, airport wind shear and gust front monitoring, and military cargo air drops and many other applications. The diode-pumped coherent lidar systems currently available are capable of near turnkey operation. The Tm:YAG laser transceivers operate at 2.02 microns with output pulse energies of 1 t 10 mJ with PRFs of 1,000 to 100 Hz respectively. Range resolution of 30 - 75 m are typical. A real-time lidar signal processor has also been developed for collecting and analyzing laser radar (lidar) data. The signal processor is based on a commercial PC architecture and offers a real-time data acquisition, analysis, display, recording and playback environment. Wind measurements and overall system performance results are presented. Wind measurement performance, for a variety of applications, are presented using the flashlamp and diode pumped coherent lidars including measured wind profiles from ground and on aircraft, wake vortex tracking results, and example flows over mountain terrain.

We present the first broadly tunable KNbO₃ OPO in tracking-free configuration (TFC), pumped by a flashlamp- pumped Ti:Sapphire laser. Tuning the pump laser from 733 to 841 nm yielded to an OPO tuning range from 908 nm to 1402 nm for the signal, and 2103 to 3803 nm for the idler. This range was limited by the mirror coatings, and continuous tuning should be achievable up to and beyond 400 nm. Threshold was as low as 15 MW/cm² and efficiencies up to 10% have been observed without AR-coatings on the crystal.

Atmospheric NO and NO₂ distribution in urban area near the capital city of Japan were measured by an all solid-state differential absorption lidar (DIAL). These were measured over 15 hours in December 1996. According to the wind speed, the concentration show temporal variation in a NO₂ case. NO_x analyzer data shows a similar behavior to the result measured by the lidar.

Two aircraft, the National Research Council of Canada (NRCC) Convair 580 (CV580) and NRCC DHC-6 Twin Otter, along with the Yarmouth and Digby Ferries, a ground site near Yarmouth and coordination with satellite overpasses (AVHRR and LANDSAT) provided an exceptionally well rounded compliment of observing platforms to meet the project objectives for the radiation, aerosols and cloud experiment (RACE) (refer to http://www.on.doe.ca/armp/RACE/RACE.html for a complete list of instrumentation and investigators involved). The general flight plans involved upwind measurements of a selected target by the CV580 lidar, followed by coincident flights allowing the Twin Otter to perform in-situ measurements while the Convair used a variety of remote sensors from above. The CV580 then descended to perform in-situ measurements including size segregated samples through the use of a micro-orifice uniform deposit impactor (MOUDI). This paper focuses on the airborne lidar results during RACE and in particular introduces two case studies comparing the lidar with a MOUDI impactor and ASASP particle probe using Mie theory.

By LIDAR and CCD camera analysis the geometrical evolution of a vortex phase contrail (descent rate V_d equals 2.7 m/s, vortex separation D equals 47 m, vertical extension (sigma) _z equals 140 m after 77 s) is analyzed. The contrail of a four-engine aircraft is showing a diffuse central wake phenomenon. From coincident in situ measurements all relevant meteorological parameters are characterized. Ambient humidity had been close to ice saturation. From this a non-exhaust formation of ice can be excluded. Also the mechanism of non- entrainment of exhaust into the vortices is excluded of being responsible for the observed early onset of the central wake (870 m behind aircraft). The central wake onset originates from early detrainment starting after a 3/4 roll-up period of the vortex. Baroclinic and shear forces do not contribute to the detrainment (imaginary Brunt-Vaisala-frequency N² equals negative 3 multiplied by 10^-5 s^-2, shear dS/dz equals negative 0.01 s^-1, bulk Richardson number R_i, equals N²/(dS/dz)² equals negative 0.3). Ambient turbulence had been fully developed with an inertial range and locally isotropic turbulence for wavenumbers k-equals 0.004 - 0.1 radian/m. The eddy dissipation rate (epsilon) equals 7.4 plus or minus 0.5 multiplied by 10^-5 m²s^-3 exceeds the values found over the North Atlantic flight corridor at cruising altitude by a factor of 1000. Turbulence was identified as the dominating detrainment mechanism.

A complex of theoretical and experimental investigations and numerical modeling for working out of effective methods and means of atmosphere monitoring on the basis of their spatial selectivity improvement and stability-against-background- radiation (SABR) rising has been executed. Designing principles of the SABR atmospheric-optical-information- processing (AOIP) systems have been formulated. They are based on: (1) an introduced spatial-angular-efficiency criterion; (2) the results of investigations and developments of wide- dynamic-range and wide-range-of-tolerable-background-radiation VIS&NIR optical receivers; (3) forming of specifications for electro-optical means parameters on the basis of stability- against-background radiation analysis of receiving signals processing algorithms used.

A compact differential absorption LIDAR (DIAL) system was developed for monitoring spatial distribution of NO₂ concentration in relatively short range. The DIAL system was composed of a LD pumped Nd:YLF laser and an optical parametric oscillator (OPO) as light source. A telescope, filters, a photo tube and photomultiplier were used to detect backscattered signals. A digital oscilloscope was used as a data accumulator. A personal computer and a pulse generator were used to control the DIAL system. The output energy of OPO was 40 (mu) J and its bandwidth was 5 cm^-1. Using this compact DIAL system, the spatial distribution of NO₂ concentration around a hollow tube connected to a 2% NO₂ gas bottle was measured. The maximum concentration value was 0.6% and the NO₂ concentration peak placed at 30 m away from DIAL system. This result was in good agreement with the geometrical set up of the hollow tube.

In our contribution water vapor and aerosol measurements with a new modular two wavelength Rayleigh Raman lidar instrument are described. A comparison of the data with radiosonde data are shown and the results discussed. The new mobile aerosol Raman lidar (MARL) is able to measure aerosol backscatter and extinction coefficient as well as depolarization in the altitude range 5 to 50 km. The system is operational since July 1996 and participated at the ALBATROSS (atmospheric chemistry and lidar studies above the Atlantic Ocean related to ozone and other trace gases in the tropo and stratosphere) campaign aboard the German research vessel Polarstern on a cruise from Bremerhaven, Germany to Punta Quilla, Argentina in October/November 1996. Key parts of the lidar system include a frequency doubled and tripled Nd:YAG laser, a large receiving telescope mirror (1.15 m diameter) and a sophisticated polychromator. The system's power aperture product is more than 9 Wm² on each wavelength (532 nm and 355 nm). The instrument is installed in a standard 20 ft ISO container and is operational in polar as well as tropical environments wherever a supply with electrical power is available.

Statistical methods give an opportunity to measure the main drift velocity of aerosol inhomogeneities. Using one of these methods for velocity measurement of moving inhomogeneities with different velocities is described. Some extreme values are obtained. Each extreme value corresponds to separate inhomogeneity and defines its velocity.

We present the results of a detailed lidar study on urban aerosols performed in summer 1996 in Lyon. Mie calculations have been performed to determine the optical backscattering and extinction coefficients of the real size distribution obtained by sampling, and then used for lidar measurements. The solid particles have been sampled using cut-off filters. Size distribution and composition, determined by scanning electronic microcopy (SEM) and x-ray microanalysis, reveal two main modes at 0.1 and 0.9 micrometer, the composition of which is soot for the first one and 60% soot - 40% silica for the second. The combined SEM and lidar techniques allowed to obtain the first quantitative lidar profiles of urban aerosols. Potential and limitations of the method are critically discussed.

The use of coherent Doppler lidar for measuring atmospheric wind fields attracts considerable interest. A number of computer programs have been developed to simulate atmospheric return signals and extract wind speed information from it. We present a new software toolbox based on LabVIEW, differing from previous ones not only by a brilliant graphical user interface but also by stochastic return signal simulation, sophisticated heterodyne front end modelling and the choice among several frequency estimators.

In the paper some polarization investigations of objects and phenomena in the planetary boundary layer of the atmosphere are presented. The observations described were performed by a ground-based lidar over the region of Sofia city where various industrial enterprises exist along with a heavy transport and aerial communications. The changes in the optical characteristics of fog and snow depending on the changes in the microphysical characteristics of the respective objects caused by the meteorological situation changes. The dynamics of the cloud system formation during a warm front advection is observed. The lidar data give possibility of following the base of two of the clouds layers along with the changes in their polarization characteristics. Differences between the optical properties of the aerosol near the clouds base and top are established. The depolarization coefficient changes depending on the penetration depth allows the phase composition of the cloud layers to be determined.

Excimer lasers in conjunction with Raman shifting techniques have commonly been used to get a multi-wavelength laser source for sounding of tropospheric and stratospheric ozone by differential absorption lidar (DIAL) systems. Stimulated vibrational Raman scattering in high-pressure gases as H₂ and D₂ has generally been used for shifting the output of high power excimer lasers to different wavelengths. In this paper it is shown that the stimulated rotational Raman scattering (SRRS) can also be efficiently employed to get laser radiation at the wavelengths required for DIAL measurements. In particular the first rotational Stokes generated by stimulated Raman scattering in H₂, pumped by a XeCl excimer laser at 308 nm, is at 314 nm, and the wavelength pair 308 nm/314 nm may be quite suitable for DIAL measurements of stratospheric ozone. The experimental conditions to optimize the Raman conversion to the first rotational Stokes are found in this paper, demonstrating that energy conversion efficiencies as high as 38% are obtainable with circularly polarized pump radiation.