Investigation of cirrus cloud structure by airborne water-vapor DIAL measurements during the HALO Techno-Mission

Abstract

During the first campaign of the new German research aircraft HALO, measurements with the differential absorption lidar (DIAL) WALES from the DLR Oberpfaffenhofen were performed. Comparisons with collocated in-situ measurements on board the DLR’s Falcon20-E5, performing synchronous flights below HALO, were used to validate the DIAL measurements. Furthermore they justified the use of ECMWF analysis temperature to calculate the relative humidity from DIAL measurements of the absolute humidity, as they showed, that the main variability of the relative humidity results from the water vapour fluctuations and not from temperature fluctuation. Thus for the first time studies of the absolute and relative humidity within a fully developed cirrus cloud could be performed.