Profiling tropospheric water vapour with a coherent infrared differential absorption lidar: a sensitivity analysis

In the last decade the precision of coherent Doppler differential absorption lidar (DIAL) has been greatly improved in near and middle infra-red domains for measuring greenhouse gases such as CO 2 , CH 4 and winds. The National Institute of Information and Communications Technology (NICT, Japan) has developed and is operating a CO 2 and wind measuring ground-based coherent DIAL at 2.05 μm (4878 cm -1 ). The application of this technology from space is now considered. In this analysis we study the use of the NICT DIAL for profiling tropospheric water vapour from space. We present the methodology to select the spectral lines and summarized the results of the selected lines between 4000 and 7000 cm -1 . The choice of the frequency offset, the pulse energy and repetition frequency are discussed. Retrieval simulations from the line at 4580 cm -1 (2.18 μm) suitable for the boundary layer and the stronger one at 5621 cm -1 (1.78 μm) for sounding the boundary layer and the middle troposphere, are shown.