Enhancing Lower-Tropospheric Atmospheric Profiles Over Land Using Ground-Based Observations in Geostationary Satellite-Based Infrared Retrievals

Accurate retrieval of temperature and humidity profiles in the lower troposphere over land is crucial for improving weather forecasts and climate analyses. However, conventional retrieval methods using satellite infrared measurements suffer from limited accuracy near the surface due to insufficient sensitivity and errors in background profiles. This study develops a retrieval scheme for the Advanced Meteorological Imager (AMI) onboard the second geostationary satellite of Korea, with a particular focus on improving the accuracy of profiles in the lower troposphere over land. The retrieval is based on the optimal estimation method, with key advancements introduced in both the state vector and background fields. Specifically, near-surface observations, including 2-m temperature and humidity, from the automated surface observing system (ASOS) were incorporated to adjust the lower boundary of the background profile derived from the local data assimilation and prediction system (LDAPS) forecast. Additionally, to further improve retrievals near the surface, the state vector was extended to include surface skin temperature and surface emissivity for AMI infrared channels, enabling simultaneous retrieval of these variables and atmospheric profiles. Experiments conducted for the summer and winter of 2022 show that the proposed method significantly improves retrieval accuracy, particularly during summer. Based on radiosonde validation, the new retrieval method reduces the root-mean-square error (RMSE) relative to the LDAPS forecast by approximately 29% for temperature and 21% for humidity below 850 hPa, whereas the conventional LDAPS-only method achieves reductions of about 5% and 1%, respectively. These results highlight the potential of integrating real-time ground-based observations with the retrieval system based on geostationary satellite data to produce more accurate lower tropospheric profiles over land, leading to increased reliability of satellite-based products.