Simulation of water vapor multiple wavelengths lidar echo signals and error analysis

The concentration of atmospheric water vapor decreases sharply as the attitude increases. In order to obtain an accurate distribution of water vapor in atmosphere, a spaceborne range-resolved differential absorption lidar (DIAL) of multiple wavelengths emission is designed. Four wavelengths are identified with small diffeerences in wavenumbers, and with different water vapor absorption cross sections, where three wavelengths with larger cross sections are considered to be signal beams, and the last one with smaller cross section is called the reference beam. Divided into three groups, the concentrations of water vapor at different elevations can be segmentally detected. The echo signals of the four wavelengths are simulated. To verify the performance of water vapor profiles detection, the random systematic relative errors of three groups detections of DIAL from spaceborne platforms in daytime and nighttime are evaluated. The analysis shows that, under relative error less than 20%, water vapor profile measurement is possible under troposphere (less than altitude of 12 km) in daytime, and under the bottom of the stratosphere (less than altitude of 15 km) at night. It is theoretically and preliminary proved that the multiple wavelengths spaceborne range-resolved DIAL has the ability of accurate detection of water vapor concentration distributions in troposphere.