在反演大气气溶胶后向散射系数时,为了消除激光雷达系统常数,通常在对流层顶附近假设一个气溶胶后向散射系数的边界值。但当激光雷达的有效探测高度达不到对流层顶时,边界值的确定变得十分困难。从米氏散射激光雷达方程出发,得到了边界值与激光雷达距离平方校正回波信号之间的等式关系,并将该关系作为判据,利用迭代法在低层大气中找到一个比较准确的后向散射系数的边界值。将该方法应用于实际激光雷达回波信号反演中,得到低层大气中气溶胶后向散射系数廓线,并与在对流层顶选取边界值反演得到气溶胶后向散射系数廓线进行比较。结果表明,利用提出的方法在低层大气中确定的后向散射系数边界值,可以较好地反演出低层大气中气溶胶后向散射系数廓线。

In the procedure of retrieving aerosol backscatter coefficient,the boundary value of aerosol backscatter coefficient is always assumed around the troposphere to eliminate the lidar constant. When the range of the lidar detection cannot reach the tropopause,it is very difficult to determine the boundary value. A relationship between boundary value and range square corrected signal is derived from elastic scattering lidar equation. Using this relationship as a criterion,a boundary value can be determined in the lower troposphere with iteration algorithm. A profile of aerosol backscatter coefficient ,which is retrieved with the boundary value determined using a new method introduced in this paper,is compared with the one retrieved with the boundary value assumed around the troposphere. The comparison shows that these two profiles seem to be consistent with each other well. The profile of aerosol backscatter coefficient can be retrieved with the boundary value determined using the new method in the lower troposphere.