Assimilation of MetOp-C AMSU-A Data Using the ARMS as an Observation Operator in the YH4DVAR System

The Advanced Radiative Transfer Modeling System (ARMS) is a fast satellite observation operator and is integrated into the four-dimensional variational data assimilation (4DVAR) system of the Yinhe (YH) global forecast model. This study investigates the impacts of assimilating satellite data from Meteorological Operational Satellite-C (MetOp-C) and the onboard Advanced Microwave Sounding Unit-A (AMSU-A) on the YH4DVAR performance. A comprehensive month-long statistical analysis from global data, complemented by a case study of Typhoon Hinnamnor, is undertaken to evaluate the impacts of AMSU-A under clear-sky conditions on model results. It is found that (1) the ARMS can achieve a comparable accuracy to the Radiative Transfer for the Television and Infrared Operational Satellite Operational Vertical Sounder version 11.2 (RTTOV v11.2) model in simulating satellite brightness temperatures, with only a 0.5% discrepancy in data retention after quality control; (2) incorporating the ARMS as a forward operator in the YH4DVAR system enhances the accuracy of tropical 850-hPa temperature and 500-hPa geopotential height forecasts; and (3) compared with RTTOV, the ARMS improves the intensity forecast for Typhoon Hinnamnor, reducing the average wind speed error by approximately 2% and the average pressure error by approximately 1%. Owing to its precision, stability, and computational efficiency, the ARMS is now an alternative observational operator to YH4DVAR and has great prospects in satellite data assimilation.