Multi-Scale Evaluation of ERA5 Air Temperature and Precipitation Data over the Poyang Lake Basin of China

Reanalysis datasets, such as ERA5, are essential for climate research, offering comprehensive spatiotemporal coverage. However, their accuracy needs thorough evaluation for effective regional application, particularly in areas with complex topography like the Poyang Lake Basin (PLB), China's largest freshwater lake. This study evaluated ERA5's accuracy in simulating near-surface air temperature and precipitation in the PLB, using data from 24 meteorological stations. Key metrics, such as the correlation coefficient (R), root mean square error (RMSE), and mean absolute error (MAE) were applied across daily, monthly, seasonal, and annual scales. The results show that ERA5 performs well for daily mean temperature, with daily R values above 0.98 and RMSEs ranging from 0.95 degrees C to 3.11 degrees C. Its highest accuracy was in February and March, with R values exceeding 0.95, and seasonal trends were best captured in spring and autumn (R > 0.99). However, ERA5's performance for precipitation was less accurate, with daily R values between 0.578 and 0.687 and RMSEs between 8.58 mm and 11.10 mm. ERA5 consistently overestimated precipitation, particularly during 1980-2003. These findings highlight ERA5's strengths in temperature modeling and its limitations in precipitation, providing insights for identifying climate events and improving climate simulation in the PLB.