Two broadband radiation methods are developed to determine aerosol optical depth and the imaginary part of its refractive index. One is broadband extinction method to determine aerosol optical depth by using hourly/daily accumulated pyrheliometer data. Another is broadband solar radiation method to retrieve the aerosol imaginary part from joint pyrheliometer/paranometer data. Furthermore, aerosol optical depths over 11 meteorological observatories in China during 1980-2000, the aerosol imaginary parts and its single scattering albedoes in Beijing and Shenyang during 1993-2000 are retrieved from pyrheliometer/paranometer data by using the methods. Based on the retrieval results, the variation trends of the aerosol optical depths and its imaginary parts, the effects of Pinatubo eruption in 1991, sand-dust event and fossil fuel burning on them are empirically analyzed.
Three lidar systems are developed in Institute of Atmospheric Physics. A four-wavelength lidar is used to detect ozone, aerosol and clouds, which contains a XeCl excimer laser with output energy of about 120mJ at 308nm, a Nd:YAG laser with three operating wavelengths of 355nm, 532nm and 1064nm, and a 1m-receiver telescope. A two-wavelength mobile lidar system is used to detect aerosol in troposphere and Asian dust storm, which has a Nd:YAG laser with wavelengths of 532 and 1064nm. A 1064nm Nd:YAG lidar is used to monitor city aerosol pollution. Since January 2000 the lidar systems have been used in measuring dust storm, high cloud and ground-35km aerosol extinction coefficient profiles. Measurement results show that the aerosol optical depth between 6km and 11km has a mean value of 0.0192; the cloud optical depth between 6km and 11km ranges from 0.014 to 0.23. The aerosol extinction near above the ground changes very greatly. From measurements, the change characteristics of aerosol extinction through snow and rain course, and dust storm are analyzed. Routine city aerosol pollution monitoring result is presented. The results of measurements of ozone shows that during September-October, the maximum ozone concentration is usually in the height range from 25km to 29km, and there is usually second concentration peak in the range between 10km and 17km. The compares of lidar-detected ozone profile made during 20:40-21:35 of October 16, 2001 with balloon measurement during 15:00-16:00 of same day is given.
A backscatter Nd-YAG lidar system has been constructed in our institute, which was designed to measure and image the four- dimensional structure the aerosol and to detect wind in lower atmosphere. It contains a Nd-YAG laser with maximum repetition rate of 15 pulses per second and a 20-cm telescope with maximum field of view of 3 mrad. A fast computer controlled angular scanning system provides can make the lidar to fire at the set position and time. Data logging system provides a logarithmic amplifier of 80 dB, 8 bit A/D conversion with range resolution of 7.5 m and high pixel resolution lidar images in a graphics computer. The system allows observations of inhomogeneities in natural aerosol in boundary layer showing the spatial distribution of aerosol scattering. A model to use triple angle azimuth scan method for measuring wind velocity is developed, which agrees well with the supposed wind in numerical experiment. The lidar system is been used in observations of aerosol and wind in boundary layer during February to July of 1998 and some results are presented.
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