Comparative evaluation of GPM IMERG V07 early, late and final run products compared to IMERG V06 in Sichuan Province, China

Satellite precipitation products (SPPs) provide an effective means of obtaining precipitation data over large areas and even on a global scale. The Integrated Multi-satellite Retrievals for the Global Precipitation Measurement (IMERG) is a key high-resolution source of precipitation data in the GPM era. In July 2023, IMERG algorithms were upgraded to Version 07 (V07). However, a comprehensive evaluation of V07 products-Early Run (ER), Late Run (LR), and Final Run (FR)-remains outstanding. This study selected daily precipitation data from 723 stations in Sichuan, China, spanning from October 2014 to September 2021, to evaluate the improvements and limitations of V07_ER, V07_LR, and V07_FR relative to the previous V06 version. The results indicate the following: (1) IMERG V07 addresses the spatial inversion accuracy issues of the V06 version, with the estimated heavy precipitation areas aligning more closely with the measured precipitation fields; (2) Compared to V06, IMERG V07 demonstrates better detection capabilities in the Sichuan Basin (Zone A) and the Western Sichuan Plateau (Zone C), but the ability to capture precipitation in the Basin-Plateau Transitional Zone (Zone B), with complex topography, remains limited; (3) IMERG V07 shows better alignment with the observed monthly average precipitation process; (4) IMERG V07 enhances the observational sensitivity to daily-scale precipitation events across various seasons, with particular improvements in detecting heavy rainfall events (> 50 mm/d). The precipitation days estimated by V07_LR and V07_FR closely align with ground-based measurements, demonstrating improved accuracy in capturing intense precipitation. Overall, IMERG V07 shows significant advancements over V06, offering better temporal and spatial consistency with surface precipitation observations.