| Atmospheric aerosols play an important role in atmospheric physical and chemical processes, and have been shown that they have a significant impact on climate change. Consequently, study on atmospheric aerosols has been a hot research topic over the world. The challenge in quantifying aerosol direct radiative forcing and aerosol-cloud interactions arises from large spatial and temporal heterogeneity of aerosol physical and chemical properties, according to the fourth IPCC report published in2007. Lidar, one of advanced active remote sensing instruments, has been widely used in many research fields, such as Atmospheric science and Environmental science. There is no any detecting tool as lidar remote sensing, with a unique technical advantage of providing high temporal and spaitial resolution, long measured range and successive measurements. In this paper, study on atmospheric aerosols is performed based on lidar measurements, including improvments of lidar techniques, algorithm and aplications in remote sensing of the atmosphere.Characterizations of physical and properties of atmospheric aerosols over Northwest China were discussed in detail from lidar measurements, based on the field observation that was conducted at four sites by Semi-Arid Climate observatory&Laboratory (SACOL) of Lanzhou University since2007. The results also were compared with measurements of aerosols in Tsukuba, Japan by Asian dust lidar network. The study indicated that there is a large difference in vertical structure of atmospheric aerosols at those sites. Furthermore, seasonal variations of aerosols scattering ratio is the following smaller order, winter, spring, autumn and summer at SACOL, but spring, summer, autumn and winter at Tsukuba. Also, depolarization ratio at SACOL was much higher, and scattering ratio is almost four times of the result at Tsukuba.Long-range transport of dust aerosols during two severe dust storms was studied combing several ground-based and space-borne lidar systems, ground-based sun-photometer, NCEP reanalysis data, and Aura/OMI and HYSPLIT trajectory model etc. Multi-layers of dust vertical structure were observed by a lidar at Zhangye for the dust events on May2,2008, however the phenomenon didn't occur at Jingtai and SACOL. One of the reasons is that dust aerosols would not mix well at Zhangye due to closer to dust sources. A thick dust layer with～550km horizontal scale below 2km over Northwest was detected clearly by space-borne CALIPSO lidar. The results also found that there was a fast path of Asian dust long-range transported to the Arctic region for the dust events occurred on March19,2010.Several different kinds of depolarization ratios (DR), e.g., linear DR, circular DR and MPL special DR, were calculated using Mueller matrix and theory of laser remote sensing, then were verified by observation data sets measured at SACOL. The results showed that relationship between linear and MPL special DR was very complicated for complex particles like dust and cirrus, depending on their shape, aspect ratio and orientation of ice particles. Besides, aerosol volume concentration and effective radius derived from sun-photometer measurements at SACOL, was analyzed with the optical properties, such as attenuated backscattering coefficient, linear depolarization ratio and color ratio, from measurements of a dual-wavelength polarization lidar system. The results showed there are obvious interesting relations between lidar and sun-photometer observation. A new method for retrieving volume concentration and effective radius from lidar measurements was proposed based on Partial Least-Squares Regression method (PLSR). It was proved that the proposed simple retrieval method is practical and effective and could be widely used.To obtain more information of atmospheric aerosols, a powerful polarization UV lidar was developed for detecting Mie scattering, Raman scattering and laser-induced fluorescence simultaneously. Strong fluorescence signals could be observed from aerosols by the developed lidar on August29,2011in Tsukuba, Japan. Total fluorescence intensity between420nm and520nm could be a threshold value for distinguishing fluorescent aerosols from others. Also, fluorescent aerosols showed small depolarization ratio (<0.1) and color ratio (0.25-0.45), that means they were spherical fine particles. Trajectories analysis from HYSPLIT simulations interpreted that the observed aerosols could be probably attributed to bioaerosols transported from the western Pacific Ocean. It has been shown that developed lidar could effectively improve the ability of lidar remote sensing of the atmosphere.
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