Speaker
Description
Mesoscale distributions of water vapour can be detected by means of the infrared limb-imaging technique. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) has been deployed onboard different aircraft and balloon platforms during measurement campaigns focusing on regions from the Arctic to the Antarctic. Here, we present airborne GLORIA observations of mesoscale water vapour distributions in the upper troposphere and lowermost stratosphere (UT/LMS) with a focus the Arctic winter and spring 2015/16. 2-dimensional vertical cross sections of water vapour derived from the observations of GLORIA onboard the German High Altitude and Long Range Research Aircraft (HALO) on 12 January 2016 resolve the mesoscale fine structure of tropopause fold over mountains and provide insight into an active mixing region. Comparisons with high-resolution deterministic forecasts by the ECMWF IFS (European Centre for Medium-Range Weather Forecasts – Integrated Forecasting System) show that the model reproduces the location, shape and depth of the tropopause fold very well. They also confirm a moist bias, which is known to be inherent to current numerical weather prediction systems and causes a systematic cold bias there. Using the GLORIA observations, the moist bias in the ECMWF IFS data is analysed for five Arctic flights. The observations confirm the that the moist bias is already present in the forecast initialisation. They furthermore suggest that the moist bias is the consequence of a model bias and a lack of water vapor observations suitable for assimilation above the tropopause. GLORIA is the airborne demonstrator for the ESA Earth Explorer 11 candidate CAIRT (Changing-Atmosphere Infra-Red Tomography explorer), which has been selected for the Phase A study. A successful mission implementation would allow global observations of water vapour in the UT and particularly the LMS, a region, where dense and continuous observations of this important species are lacking.
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