Validation of ERA5-Land and NCEP/NCAR Reanalysis-Based Precipitation Data over the Sichuan-Yunnan Region Using Satellite Observations

This study evaluates the applicability of ERA5-Land and NCEP/NCAR reanalysis precipitation data in the Sichuan-Yunnan region by comparing them with GPM-IMERG satellite observations from 1998 to 2023. The analysis focuses on seasonal variations in precipitation across Sichuan-Yunnan Region and its surrounding areas. Results indicate that both datasets effectively capture the seasonal precipitation patterns observed in IMERG, with precipitation peaking in summer, followed by autumn and spring, and reaching its lowest levels in winter. On average, summer precipitation is approximately seven times higher than in winter. Over the full study period (19982023), both datasets tend to overestimate precipitation compared to satellite observations. However, from 2010 to 2023, ERA5-Land exhibited smaller biases than NCEP/NCAR, whereas from 1998 to 2010, their biases were relatively similar. In terms of spatial distribution, ERA5-Land generally overestimates precipitation, particularly in the western Hengduan Mountains and in parts of Sichuan and Yunnan, where summer and autumn precipitation exceed 1000 mm. Meanwhile, NCEP/NCAR consistently identifies a high-precipitation center (peaking at around 500 mm) in Sichuan Province, with significant precipitation extending eastward into Sichuan and western Yunnan. During winter and spring, this high-precipitation center shifts further east, reaching southern Yunnan. Notably, in summer and autumn, NCEP/NCAR underestimates precipitation by approximately 650 mm in areas west of Sichuan and east of Yunnan.