Minzheng Duan

Impact of vertical stratification of inherent optical properties on radiative transfer in a plane-parallel turbid medium

The atmosphere is often divided into several homogeneous layers in simulations of radiative transfer in plane-parallel media. This artificial stratification introduces discontinuities in the vertical distribution of the inherent optical properties at boundaries between layers, which result in discontinuous radiances and irradiances at layer interfaces, which lead to errors in the radiative transfer simulations. To investigate the effect of the vertical discontinuity of the atmosphere on radiative transfer simulations, a simple two layer model with only aerosols and molecules and no gas absorption is used. The results show that errors larger than 10% for radiances and several percent for irradiances could be introduced if the atmosphere is not layered properly.

Comparative analysis of the multi-type atmospheric aerosol lidar ratios

For lidar probing technique, the lidar ratio is one of key factors which impact the precision of lidar detection. Lidar ratio depends on not only incident laser wavelength but also aerosol size distribution and complex refractive index, and its value is between 0 and 90sr. However, lidar ratio was simply suggested as a fixed value of 50 sr for a long time, which means that the atmospheric aerosol size distribution and chemical compositions do not change with temporal and special variableness. In order to improve the detection precision of lidar extinction profile, it is necessary to study the changes of lidar ratio. For the measurements with an upward-looking monostatic lidar system, due to the change of the relative humidity along the measurement path, the lidar ratio may differ considerably from an assumed constant range-independent value. One of the objectives of this study is to quantify this variability for different aerosol types by numerical methods, and we will give out multi-type aerosol lidar ratios, such as continental clean, continental average, continental polluted, urban, desert, maritime clean maritime polluted and maritime tropic et al. The results will provide valuable references for the lidar development and the derivation of atmospheric aerosol extinction profile.