利用转动拉曼测量大气气溶胶后项散射比

利用大气的弹性散射信号与整个转动拉曼信号的比值,不需要假设任何的气溶胶的消光与后项散射比值,就可得到大气气溶胶的后项散射比.通常测量部分转动拉曼谱线之和代替全部转动拉曼谱线之和.全部的转动拉曼谱线之和是不依赖温度,但部分的转动拉曼谱线之和却是与温度有关的.因此,利用转动部分拉曼谱线之和反演大气气溶胶的后项散射比就会带来误差.模拟了随温度变化不同转动量子数的拉曼谱线之和,并且计算了由这些不同转动拉曼谱线之和反演大气气溶胶后项散射比的误差.然后文章提出了一种新的方法,不需要测量整个转动拉曼谱线之和,而只需要测量单条转动拉曼谱线及大气温度,就可以获得大气气溶胶的后项散射比.最后通过实验给出了实际测量的大气气溶胶的后项散射比的结果.

Obtaining Aerosol Backscattering Coefficient Using Pure Rotational Raman Spectrum

Atmospheric aerosol backscattering coefficient ratio can be obtained with the ratio of elastic signal to the total rotational Raman backscattering signal without assuming the ratio of aerosol extinction to backscatter. Generally, the intensity of partial rotational Raman spectrum lines instead of the total rotational Raman spectrum lines is measured. The intensity of the total rotational Raman spectrum lines is not dependent on the temperature, but the intensity of the partial rotational Raman spectrum lines is dependent on the temperature. So calculating aerosol backscattering coefficient ratio with the intensity of the partial rotational Raman spectrum lines would lead to an error. In the present paper, the change in the intensity sums of different rotational Raman spectrum lines with temperature was simulated and the errors of aerosol backscattering coefficient ratio derived from them were discussed. A new method was presented for measuring aerosol backscattering coefficient ratio, which needed not to measure the intensity of the total rotational Raman spectrum lines. Aerosol backscattering coefficient ratio could be obtained with the atmospheric temperature and a single rotational Raman spectrum line. Finally, aerosol backscattering coefficient ratio profiles of the atmosphere were acquired with the combined Raman lidar of our lab. The results show that there is no need to assume any relation between aerosol backscattering and extinction or to consider any wavelength calibration to determine the aerosol scattering coefficient.