Retrieval of Boundary Layer Precipitable Water Over the Korean Peninsula Using GK2A AMI Split-window Radiances

Low-level water vapor is a key factor in initiating and intensifying convective activity during summer over the Korean Peninsula. However, monitoring and tracking low-level water vapor remains challenging due to sparse observations over the ocean and the coarse spatial and temporal resolutions of existing observational datasets. This study aims to retrieve boundary layer precipitable water (BPW) using three infrared window channels (10.5, 11.2, and 12.3 μm) from GK2A satellite that are known to be sensitive to boundary layer precipitable water. Dry and wet absorption coefficients for each channel are first derived using simulated radiances from RTTOV using ERA5 atmospheric profiles and corresponding total precipitable water (TPW) values. These coefficients are then used to retrieve BPW values. Validation results indicate that the retrieved BPW shows good correlation with ERA5 TPW over both land and ocean, with the Pearson correlation coefficient of 0.871 and 0.872, respectively. Several case studies further demonstrate the capability of the retrieval in capturing increases in BPW prior to convective initiation, highlighting its potential value for operational forecasting.