Evaluation of ERA5 precipitation over the eastern periphery of the Tibetan plateau from the perspective of regional rainfall events

Abstract

The eastern periphery of the Tibetan Plateau (EPTP), which connects the Tibetan Plateau in the west and the Sichuan Basin in the east, is a typical area with steep terrain. The performance of the ERA5 reanalysis data in revealing the regional rainfall events (RREs) over the EPTP was evaluated by conducting a comparison with the rain-gauge data. The results showed that the ERA5 precipitation could capture the general spatiotemporal features of the evolution of the observed RREs with spatial correlation coefficients greater than 0.8, but obvious bias still existed. The rainfall frequency was generally greater and the rainfall intensity was weaker in the ERA5 precipitation from the Tibetan Plateau to the Sichuan Basin, with the rainfall amount being smaller over the EPTP and Sichuan Basin and larger over the eastern Tibetan Plateau. ERA5 precipitation tended to start earlier and end later relative to the RREs in the gauge data. During the RREs, the distribution of the precipitation intensity in ERA5 was weaker and more uniform than that of the gauge records, and the spatial ranges were larger, which responded well to the higher rainfall frequency but weaker intensity in ERA5 when compared with the gauge data. These findings remind us that attention should be paid when using reanalysis precipitation, especially over complex terrain such as that of the EPTP. Moreover, the incorrect timing of the ERA5 precipitation and the underestimation of the precipitation intensity indicated that problems still exist in the state-of-the-art model system.