ESA-Univ. READING - Water vapour CCI+ Phase 2 (Resp. G. ZAPPA)

Extreme precipitation events due to extra-tropical cyclones (ETCs) are one of the key meteorological hazards posed by climate change. These events result from the combined action of intense cyclone-associated surface winds and high atmospheric moisture, with the latter expected to increase close to Clausius-Clapeyron under climate change.  However, climate models still suffer from some systematic biases in the simulation of the precipitation associated to ETC and a systematic assessment of whether the moisture environment plays a role in these precipitation biases is currently lacking. This proposal aims to fill this gap by using the TCWV data (CDR2) from the WV-CCI to assess the ability of both the ERA5 reanalysis and the state-of-the-art CMIP6 climate models to represent the ETC-associated water vapour, its sensitivity to surface temperature anomalies, and its role for ETC-associated precipitation extremes. This will be achieved by identifying extra-tropical cyclones in both ERA5 and in the CMIP6 climate models, and by composing observed and simulated water vapour, precipitation and sea surface temperature at the cyclones’ locations. This database will serve to assess the biases in the simulated moisture environment and in the scaling relationships between precipitation, TCWV and SSTs. Overall, these results will increase our understanding of whether the ERA5 reanalysis is suitable to determine the climatology and trends in the water vapour of ETCs, and explore possible causes of systematic biases in the CMIP6 models’ simulation of precipitation extremes.