激光掩星探测大气温压反演方法的仿真分析

Simulation Analysis of Inversion Method of Atmospheric Temperature and Pressure for Laser Occultation

针对激光掩星探测对流层中上层到平流层下层高度范围内大气温度和压强的反演方法,进行了研究和仿真分析。选择对温度不敏感而对压强敏感的吸收线,利用吸收系数与吸收截面和压强的关系,通过迭代方式求解得到压强。选择弱吸收峰附近的吸收线,利用吸收系数与压强和温度的关系,根据反演得到的压强值通过迭代方式求解得到温度。为减小大气中其他气体吸收以及大气散射等消光因素对反演结果的影响,仿真过程采用差分波长的方法,在氧气A吸收带内,选取合适的吸收线,利用激光掩星差分透过率数据由Abel积分反变换反演得到各个激光轨迹切点高度处的差分吸收系数廓线,然后利用差分吸收系数反演各个切点高度处的压强和温度。仿真结果显示:压强反演误差主要受差分吸收系数反演误差的影响,随高度下降呈不断增大的趋势,最大误差约为6%;根据反演得到的压强值对温度进行反演,温度反演误差主要受压强和差分吸收系数反演误差的影响;两种影响部分抵消,最大温度反演误差在5 km高度附近约为1.5 K。建立误差模型进行分析,对反演误差中出现的一些变化趋势和影响因素进行解释。在去除差分吸收系数反演误差的条件下,对压强和温度进行1次循环求解,得到压强最大反演误差约为0.3%,温度最大反演误差约为1 K,将该条件下温度和压强的反演误差与有差分吸收系数反演误差时的反演误差进行对比,证实了减小差分吸收系数反演误差的重要性。

The inversion method of temperature and pressure from the upper and middle troposphere to the lower stratosphere is studied and simulated.An absorption line is selected,which is not sensitive to temperature but sensitive to pressure,and the relationship among the absorption cross section,pressure and the absorption coefficient is used to determine the pressure by using the iterative method.An absorption line is selected near the weak absorption peak and the relationship among the absorption coefficient,pressure and temperature is used according to the retrieved pressure value to determine the temperature by using the iterative method. In order to reduce theinfluence of other absorption and scattering factors on the inversion results,the simulation process adopts the methodof differential wavelength. In the oxygen absorption band,the appropriate absorption line is selected,and the profileof the differential absorption coefficient at the tangent altitude of each laser track is obtained by retrieving thesimulated data of the laser occultation differential transmittance from the Abel integral inverse transformation,andthen the pressure and temperature at each tangent altitude are retrieved using the differential absorption coefficient.The simulation results show that the inversion error of pressure is primarily affected by the inversion error of thedifferential absorption coefficient,which increases with altitude decreasing,and the maximum error is approximately6%;the inversion error of temperature is affected at the same time by the inversion error of pressure and thedifferential absorption coefficient;the two influences are partially offset,and the maximum error is 1. 5 K near analtitude of 5 km. Through analysis of the error model,some change trends and influence factors in the inversionerror are explained. Under the condition of eliminating the inversion error of the differential absorption coefficient,the pressure and temperature are solved once in a cycle,the maximum inversion error of pressure is approximately0. 3%,and the temperature is approximately 1 K. The comparison between this inversion error and the inversionerror of the differential absorption coefficient highlights the importance of reducing the latter.