Reply on RC1

Abstract

The tropospheric water vapour data record generated within the ESA Climate Change Initiative "Water Vapour" project (ESA TCWV-COMBI) is used to evaluate the interannual variability of global climate models (CMIP6 framework under AMIP scenarios) and reanalysis (ECMWF ERA5). The study focuses on the tropical belt, with a separation of oceanic and continental situations. The intercomparison is performed according to the probability density function (PDF) of the total column water vapour (TCWV) defined yearly from the daily scale, as well as the evolution of the large-scale overturning circulation. The observational diagnostic relies on the decomposition of the tropical atmosphere into percentile of the PDF and into dynamical regimes defined from the atmospheric vertical velocity. Large variations are observed in the patterns among the data records, especially over tropical-land, while oceanic situations show more similarities in both interannual variations and percentile extremes. The signatures of El Nino/La Nina events, driven by the sea surface temperatures, are obvious over the oceans. Differences also occur over land for both trends (a strong moistening is observed in the ESA TCWV-COMBI data record which is absent of CMIP6 models and ERA5) and extremes years. The discrepancies are probably associated with the scene selection applied in the data process. Other sources of differences, linked to the models and their parametrizations, are highlighted.