Measuring FORUM sensitivity to surface emissivity using observed atmospheric data

FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) is a satellite mission selected in 2019 as the ninth ESA (European Space Agency) Earth Explorer mission. FORUM will provide interferometric measurements in the spectral interval encompassing the Far-InfraRed (FIR) part of the spectrum, responsible for about 50% of the outgoing longwave flux lost by our planet into space. While more accurate measurements of the Top Of the Atmosphere (TOA) resolved spectrum in the FIR are necessary for reducing uncertainty in climate models, existing instruments are insufficient. The observations will also improve the knowledge of several atmospheric variables, such as water vapor in the upper troposphere - lower stratosphere region, ice cloud properties and especially surface emissivity in the FIR, the focus of this seminar. In particular, I will present the results of our recent study of FORUM sensitivity in measuring surface emissivity in both clear and cloudy sky conditions, focusing on different aspects of the computational pipeline. Of particular interest are procedures for the injection of data from the ERA5 database, that is the fifth generation ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis for the global climate and weather, and Bayesian techniques for deriving a-priori estimates from the MODIS (Moderate Resolution Imaging Spectroradiometer) database. Finally, I will conclude by discussing extensions of the current surface emissivity database to IASI-NG (Infrared Atmospheric Sounding Interferometer New Generation) frequency range.