Comparison of Airborne Water Vapor Lidar Observations with ECMWF Analyses and first Assimilation Experiments

Abstract

Water vapor is the most important greenhouse gas and controls cloud formation and the evolution of weather systems. As its tropospheric concentration may rapidly vary over four orders of magnitude, accurate monitoring of water vapor, especially in the upper troposphere and lower stratosphere (UT/LS) and in remote areas remain important scientific and logistical issues. Between 2002-2005 the DLR Falcon research aircraft performed a couple of long-range transfer flights to various remote campaign destinations in Oklahoma, Brazil and Australia, carrying the water vapor Differential Absorption Lidar (DIAL) in nadir looking arrangement. The large dynamical range of tropospheric water vapour is impressively demonstrated. Large gradients in the H₂O and backscatter fields dominate the scene and in general can qualitatively be reproduced by mesoscale simulations and even to a large extent by ECMWF analyses.