ABI Water Vapor Radiance Assimilation in a Regional NWP Model by Accounting for the Surface Impact

Abstract

AbstractThere are a growing number of advanced imagers for geostationary meteorological satellites, which can provide water vapor radiance observations with high temporal and spatial resolutions. To assess the impact of those imagers, radiance assimilation experiments were conducted with the Advanced Baseline imager (ABI) on board the Geostationary Operational Environmental Satellite‐16. The radiances from the three water vapor absorption bands of Geostationary Operational Environmental Satellite‐16 ABI were assimilated through the National Oceanic and Atmospheric Administration Gridpoint Statistical Interpolation data assimilation system in a regional numerical weather prediction (NWP) model. The forecast impacts for Hurricane Irma (2017) and Hurricane Harvey (2017) have been studied and analyzed in this work. Due to complicated surface situations (emissivity, terrain height, etc.) over land, the infrared (IR) radiance assimilation is still limited; thus, handling surface effects in radiance assimilation needs to be considered. By analyzing the Jacobian function of skin temperature in the ABI radiance assimilation process, it is shown that assimilating water vapor IR radiances over high elevation surfaces or in dry regions is problematic even where the bands are mostly sensitive to the upper level of the atmosphere such as Band 8 (6.19 μm). Additional quality control steps using skin temperature Jacobians to eliminate the contamination from the surface impact are developed and added for ABI radiance assimilation. The results show that ABI radiance assimilation with quality controls is able to improve tropical cyclone forecasts. The methodology used in this study can be applied to the assimilation of IR radiances from other geostationary satellites or polar‐orbiting satellites.