Search

The Tibetan Plateau (TP), known as the "Asian water tower," provides freshwater resources for hundreds of millions of people in Asia. Most of the Asian rivers, such as the Yangtze, the Jinsha, the Salween and the Brahmaputra, are generated from southeastern part of the TP (SETP). In order to explore the influences of atmospheric circulation on the precipitation over the SETP, self‐organizing mapping (SOM) was utilized to identify the weather regimes (WRs) and related precipitation over the SETP and its surrounding areas. The daily scale of large‐scale circulation via ERA5 were classified into nine WRs by the SOM. There are two favourable regimes (rainy WRs) and three adverse ones (rainless WRs) for the SETP precipitation among these WRs, respectively. Furthermore, water vapour transport of the WRs and the relevant effects of ENSO are investigated. The droughts and floods of SETP are determined by the interannual variations of occurred frequency of the WRs. In particular, the SETP is flooded in the years with frequent occurrence of the rainy WRs and vice versa. The occurrence of WRs is closely related to the phase state of ENSO. The 9th WR (SOM9) and the 4th WR (SOM4) are separately occurred more frequently in the El Niño and the La Niña years. Regulation of ENSO on the SETP precipitation are effective through its influences on the state of atmospheric circulation, that is, frequency of various WRs. It implies that the occurred frequency of WRs is modulated by the climate systems and results in the interannual variations of precipitation over the SETP. [ABSTRACT FROM AUTHOR]

Extreme precipitation events (EPEs) often bring disastrous consequences, such as floods, urban waterlogging and landslides. Understanding the effects of weather systems on EPEs can help improve the accuracy of weather forecasts. The Tibetan Plateau vortex (TPV) is a mesoscale weather system that is active near the surface of the Tibetan Plateau (TP). Though the crucial role of TPVs on the TP precipitation has been widely known, the influence of TPVs on EPEs is not yet clear. In this study, the quantitative impacts of TPVs on the EPEs over the TP and its surrounding areas are investigated based on the TPV datasets from the ECMWF Reanalysis v5 (ERA5) and four precipitation datasets from the ERA5, NOAA Climate Prediction Center (CPC), Integrated Multi-satllitE Retrievals for the Global Precipitation Measurement (GPM) Mission (IMERG) and in-situ rain gauges. The results show that the TPVs have remarkable positive contribution to the EPEs over the TP and its adjacent regions for all four precipitation datasets. The TPVs induce more than half of the daily EPEs over the central TP, while the number of days influenced by TPVs only accounts for <20% of the total days over this region. A higher frequency of EPEs is identified over the central TP, and a higher ratio of the TPVs tends to be associated with EPEs after they move out of the TP. The EPEs tend to occur near the center and the southeastern quadrant of TPVs. For the TPVs associated with EPEs (EPE-TPVs) and those having no relation to EPEs (NEPE-TPVs), the structure of TPVs and related large-scale circulation are significantly different at the upper- and lower-level of the troposphere. The EPE-TPVs tend to be larger, stronger, thicker, and move farther than the NEPE-TPVs. The TPVs inducing EPEs usually consist of some specific synoptic components, including the southwest monsoon current along the southern side of TPVs, the shear line near the surface of the TP, and the South Asia high in the upper-troposphere. EPE-TPVs related atmospheric circulations and the climatology of circulations are analyzed in detail to provide a better understanding for forecast service. • The contributions of Tibetan Plateau vortices (TPVs) to extreme precipitation events (EPEs) over the Tibetan Plateau and its vicinity are consistent by using different precipitation datasets. • The TPVs contribute to more EPEs with more intense EPEs threshold. • The TPVs associated with EPEs (EPE-TPVs) are relatively larger, stronger, thicker and longer-lived than those having no connection to EPEs (NEPE-TPVs). • The South Asian high is under the western (eastern) mode for EPE-TPVs (NEPE-TPVs). [ABSTRACT FROM AUTHOR]