Improved Water Vapour retrieval from AMSU-B/MHS in polarregions

Abstract. Exact monitoring of water vapour in the Arctic on long time scales is essential for predicting Arctic weather and understanding climate trends, as well as addressing its influence in the positive feedback loop contributing to Arctic Amplification. However, this is challenged by the sparseness of in-situ measurements and the problems that standard remote-sensing retrieval methods for water vapour have in Arctic conditions. Here, we present advances in a retrieval algorithm for vertically integrated water vapour (total water vapour, TWV) in polar regions from data of satellite-based microwave humidity sounders: (1) In addition to AMSU-B, we can now also use data from the successor instrument MHS; (2) artifacts caused by high cloud ice content in convective clouds are filtered out. Comparison to in-situ measurements using radiosondes during the N-ICE2015 campaign show overall good performance of the updated algorithm. Combining TWV data from the present algorithm with those retrieved from microwave imagers like AMSR-E and AMSR2 makes a continuous record of TWV since the year 2000 possible, with nearly complete and year-round coverage of the Arctic.