The Aerosol Optical Characteristics In Representative Regions Over China

By recalling and analyzing the establishment, progress and actuality of the CMA Aerosol Remote Sensing Network (CARSNET), the indoor and field calibration methods of CE318 sunphotometer are explored and compared the calibration results of the two methods in 2007. Based on integrating sphere radiation calibration method, an experiment is carried out for the calibration of the sky scattering radiation channels at eight different wave bands of CE318 sunphotometer. Langley calibration method and standard instrument relative calibration method are used to calibrate sun direct radiation channels at different wave bands of CE318 sunphotometer. The results of this experiment show that the calibration results of sky scattering radiation channels at 670 nm, 870 nm, 1020 nm and the original calibration of the same instrument are fundamentally equal with the discrepancy less than 6%. It has higher reliability. Unfortunately the result of the wave band of 440 nm is higher than the original calibration, and departure range is about 18.9%. Based on the calibration results, it can be concluded that there are good feasibility and reliability in using integrating sphere for calibrating the sky scattering radiation channels. However there is a little difference between the calibration results and the original calibration. Considering the fact using conditions and measurement for long periods outdoors, it might lead to aging filters, or maybe there are some aerosol particles falling on the filters which are inside the sensor head, even because the filters run very long time, and made the filters broken. Generally speaking, the calibration results of the sun direct radiation channels are slightly larger than the original calibration. The results show that the filters of some channels are aging, so it is necessary to replace them to ensure observation precision. In addition, the comparisons between the Langley method and standard instrument relative calibration method are made. From the comparison results, the Langley method requires good weather condition on the day of calibration, including good sun, no clouds and stable atmosphere, and the standard instrument relative calibration method requires very accurate standard instrument. Because the standard instrument relative calibration method is more advantageous than the Langley method from the comparing results, the present study employs the standard instrument relative calibration method to calibrate the CE318 sunphotometer in the CARSNET of China Meteorological Administration to guarantee the precision of the observation data. Comparing the aerosol optical depth (AOD) derived by the CMA and AERONET, there are good coefficients between them. Therefore, the reliability and veracity of the AOD derived by CMA can be insured.Data of CE318 sunphotometer in 2006 and 2007 for Lin'an, Shangdianzi and Longfengshan, which are regional background sites, are used to analysis the temporal and spatial distribution of AOD and ?ngstr?m parameters in the characteristic region over china. The results as follows: the AOD for Lin'an is larger than the Shangdianzi's and Longfengshan's. The mean monthly of AOD oscillates with two apices. The diversity among four seasons is not notable. And the fine aerosol particles take a great part; For Shangdianzi the mean monthly of AOD oscillates with single apex. The diversity among four seasons is notable. And the aerosol particles are almost coarse; For Longfengshan the diversity among four seasons is notable. And the largest is in spring. The scale of aerosol particles is between the Lin'an and Shangdianzi.These stations are influenced by dust storm badly. Shangdianzi station is influenced by storm most largely. AOD is up and down frequently, while the dust storm happening. When the stronger dust storm happens, the AOD at 440nm is larger than the mean seasonally of AOD in Spring, about 2.3 times; Longfengshan station is also influenced by dust storm largely in 2006. The AOD becomes large while dust storm happens. However, this does not happen in 2007. For the special geographical location of Lin'an station, it is influenced feebly by dust storm. Comparing the AOD for the three sites during dust storm in 2006 and 2007, it can be concluded that Shangdianzi station is most largely influenced by dust storm, Longfengshan station is more largely, and Lin'an station is most feebly in 2006; and Shangdianzi station is also most largely influenced by dust storm in 2007, while Longfengshan and Lin'an stations are feebly influenced.Comparing AOD at 550 nm derived by using the MODIS remote sensing data and AOD derived by the CMA, it can be concluded that the error is accepted. The linear coefficients between AOD and aerosol chemical composition are very small. It suggests that there is not only linear relationship between them. There are many facts effecting AOD, as well Size Spectrum, shape of particles and water vapor in the air. These are deserved to make farther study.