Comparative analysis of horizontal water vapor flux estimates based on SSMIS and ERA5 reanalysis data

Abstract

Water vapor, as a greenhouse gas, plays a vital role in shaping the Earth's climate. Understanding how water vapor participates in energy and matter transfer over time and space is essential for assessing water resources and forecasting hazardous meteorological events. Reanalysis data provides the most comprehensive assessments of the state and dynamics of the atmosphere. However, discrepancies in estimates across reanalysis schemes indicate problems related to imperfect parameterization of physical processes, inadequate description of the underlying surface in numerical models, and errors in the diverse data being assimilated. Furthermore, reanalysis calculations are resource-intensive and not always suitable for practical (particularly operational) applications in Earth remote sensing (ERS). The Space Research Institute of the Russian Academy of Sciences is developing a satellite radiothermovision approach that allows for the reconstruction of atmospheric dynamic characteristics (in particular, horizontal water vapor fluxes) directly from satellite observations by microwave radiometers. This paper compares horizontal water vapor fluxes based on ERA5 reanalysis and satellite radiothermovision data from SSMIS. The comparison covers all SSMIS observation points for 2013–2020. This study yielded maps of the mean residuals of the zonal and meridional components of vertically integrated horizontal water vapor fluxes from satellite data and reanalysis, the root-mean-square (RMS) spread of these residuals, and the correlation coefficient between the ERA5 and SSMIS fluxes.