Variations in Optical Scattering and Backscattering by Organic and Inorganic Particulates in Chinese Lakes of Taihu, Chaohu and Dianchi

This study presents an investigation of the scattering and backscattering properties of the particulates in three Chinese inland lakes(the Taihu Lake, the Chaohu Lake and the Dianchi Lake) based on in situ measurements taken at 119 sites. We modeled the particulate scattering spectra using a wavelength-dependent power-law function, finding that the power-law exponents in the Taihu Lake and the Chaohu Lake differ from those in the Dianchi Lake but are similar to the values in the U.S. coastal waters. In contrast to the open ocean, the backscattering properties in the three lakes can not be determined only from chlorophyll-a concentration. The backscattering ratio spectra exhibit a wavelength dependence feature in all three lakes, generally decreasing with the increasing wavelength. Analysis results of the correlations between the backscattering ratio and the individual water quality parameters clearly show that there are distinctive relations among the three lakes, attributed primarily to different compositions of optically active materials in the three lakes. Analysis of the mass-specific scattering and backscattering coefficients shows that the coefficients at wavelength 532 nm in the Taihu Lake and Chaohu Lake are similar, but they are apparently different from those in the Dianchi Lake. Lastly, Model I multiple linear regressions were adopted to partition the mass-specific cross-sections for scattering and backscattering into organic and inorganic cross-sections to further interpret the scattering and backscattering properties. The relative contribution of organic and inorganic particulates to scattering and backscattering is clearly different among the three lakes. The scattering and backscattering properties of the particulates in the three inland lakes vary significantly based on our collected data. The results indicated that the existing semi-analytical water quality retrieval models of the Taihu Lake can not be applied perfectly to the Chaohu Lake and the Dianchi Lake.

The observations on Polar Stratospheric Clouds at Zhongshan Station，Antarctica

lidar system (694 nm) was used to measure the stratospheric aerosol layer at Zhongshan Station (69°22'S, 76°22'E ) in 1993. A total of 53 sets of lidar data presented in this paper were obtained over a period of 224 days between March 27 and November 5, 1993. The average vertical profiles of stratospheric aerosol backscattering ratio and the integrated backscatter coefficient over the 12 km～30 km altitude range were reversed from the return signal of lidar. The results of observations show that the stratospheric aerosol content more noticeably enhanced in 1993 than that in 1990 due to Mt. Pinatubo eruption in Philippines in June of 1991. Polar Stratospheric Clouds (PSCs) were observed from late May until early August. The vertical profiles of stratospheric aerosol backscattering ratio at Antarctica in 1993 show a clear double-layer structure. One layer is at an altitude of about 12 km,the other is at an altitude of about 25 km. The upper layer is varied with season.