The analysis and evaluation of rainfall events of different durations in the Tibetan Plateau

The Tibetan Plateau, known as the 'Asian Water Tower,' has drawn significant attention to its hydrological cycle and associated atmospheric dynamics. The Qiang-tang Plateau, located in the northern part of the Tibetan Plateau's  endorheic basin (hereinafter referred to as the plateau), experiences notable climate and water cycle variations. The spatial characteristics of its precipitation determine the spatial patterns of hydrological elements and ecological environments in the Qiang-tang Plateau. However, its harsh environment and challenging conditions for station establishment have resulted in a severe scarcity of precipitation observation data. Presently, mainstream reanalysis products consistently overestimate precipitation levels on the plateau and fail to accurately simulate daily precipitation variations. To address this, utilizing data from 206 tipping-bucket rain gauges deployed across the plateau from 2017 to 2020, the study investigates rainfall events of different durations: short-term (1-3 hours), medium-term (4-6 hours), and long-term (7 hours or more).

The research reveals that the precipitation intensity at plateau sites is generally low, with short-term rainfall events being predominant. However, the contribution of short-term rainfall events increases spatially from the southeast edge to the inland of the plateau. Notably, the Qiang-tang Plateau exhibits a significantly higher proportion of short-term precipitation compared to other regions on the plateau. Furthermore, based on a newly established mountainous precipitation transect, it was discovered that as one ascends from the Gangdisi Mountains to the Qiang-tang Plateau, the contribution of short-term rainfall to the total precipitation significantly increases with elevation. Additionally, an analysis of mainstream reanalysis products (ERA5, MERRA2) and high-resolution model simulation data (HAR2) for different duration rainfall events indicates that reanalysis products consistently underestimate the contribution of short-term precipitation while overestimating long-term precipitation. HAR2 outperforms ERA5 specifically in the Qiang-tang Plateau and the northeast part of the plateau, whereas MERRA2 fails to capture the spatial heterogeneity of different duration rainfall events. Although reanalysis products can capture the diurnal peak of short-term precipitation, they tend to prematurely estimate the diurnal peak of long-term precipitation.