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大气水汽含量随海拔升高急剧减小,为准确获得水汽浓度随高度的分布,设计多波长发射水汽探测星载距离分辨差分吸收激光雷达(DIAL)。选取波长相差较小,水汽吸收截面不同的4个发射波长:其中3个吸收截面较大的波长作为信号光束,第4个吸收截面较小的波长作为参考光束,分3组对不同海拔高度处的水汽浓度进行分段探测。对4个发射波长的回波信号进行了仿真模拟,为验证其水汽探测能力,在白天和夜晚对3组波长水汽浓度探测的相对误差进行分析讨论。结果表明,在相对误差小于20%的情况下,该多发射波长星载距离分辨差分吸收激光雷达系统可以实现白天对流层(小于12 km)、夜晚平流层底以下(小于15 km)水汽浓度的探测。理论上初步证实了该多波长星载距离分辨差分吸收激光雷达能全天时精确地探测对流层水汽浓度分布。
The atmospheric water vapor content decreases drastically with the increase of altitude. In order to get accurate distribution of water vapor concentration with height, a multi-wavelength emission water vapor detection method is designed to detect the space-borne range-resolved differential absorption lidar (DIAL). Select four wavelengths with small difference in wavelength and different water vapor absorption cross sections: three of which have a larger absorption cross section as the signal beam and the fourth one with the smaller absorption cross section as the reference beam, divided into three groups at different altitudes Water vapor concentration of sub-detection. In order to verify its water vapor detection ability, the relative error of the three groups of water vapor concentration detection was analyzed and discussed in the daytime and the nighttime. The results show that the system can detect the water vapor concentration of the troposphere (less than 12 km) and the bottom of the night stratosphere (less than 15 km) when the relative error is less than 20% . In theory, this multi-wavelength satellite-based distance-resolved differential-absorption laser radar can proactively detect the tropospheric water vapor concentration accurately all day.