Mesoscale Observing System Simulation Experiment (OSSE) to Evaluate the Potential Impact from a Geostationary Hyperspectral Infrared Sounder

Abstract

Herein, the impact of a hyperspectral infrared sounder on a geostationary satellite (GeoHSS) in a regional numerical weather prediction system is investigated during the Baiu seasons in 2017, 2018, and 2020, including events of heavy rainfall. The reanalysis-based observing system simulation experiment (OSSE) technique uses ERA5 as the pseudo-truth atmospheric profile. Temperature and relative humidity pseudo-observations are generated using one-dimensional variational retrieval scheme based on the spectral characteristics of the GeoHSS. Verification against radiosondes shows improvements at various altitudes and forecast times (FTs). Although wind pseudo-observations are not assimilated, winds are also impacted through assimilation cycles and forecasts. Furthermore, the precipitation forecasts show an improving trend with a notable impact to extend the forecasts' lead time. Case studies show impacts on precipitation primarily during longer FTs, accompanied by improved prediction of depressions on the Baiu front and upper-level troughs. These are due to large-scale impacts from the pseudo-observations with a comprehensive coverage over clear-sky areas, propagating to precipitation areas through the assimilation cycle and forecasts. However, the prediction of an event of small-scale localized heavy rainfall is insufficient even at short forecast ranges due to a limited spatial resolution. Experiments show that extracting information in the lower atmosphere is critical and that the impact on upper-level environments is sensitive to using observations in cloudy areas.