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The Tibetan Plateau vortices (TPVs) are mesoscale weather systems active at the near-surface of the Tibetan Plateau (TP), which are one of the major precipitation-producing systems over the TP and its surrounding areas. TPVs mainly occur in the warm season from May to September. In this paper, we investigated the interdecadal change of TPVs in the warm seasons of 1979–2020 with the six widely used reanalysis datasets. A significant change of the TPVs frequency appears around the mid-1990s, associated with less TPVs during 1979–1995 and more TPVs during 1996–2020, which is constant among the multiple reanalysis datasets. The abrupt change of TPVs is caused by a transition of the Atlantic Multi-decadal Oscillation (AMO) from a cold phase to a warm phase in the mid-1990s. The shift of AMO leads to a silk-road pattern-like wave train and a spatially asymmetric change of tropospheric temperature. It modifies the intensity of the subtropical westerly jet and the TP heating, leading to the interdecadal change of TPV activities. [ABSTRACT FROM AUTHOR]

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]

FLake has been one of the most extensively used lake models in many studies for lake thermal structure simulations. However, due to the scarcity of lake temperature observations, its applicability and performance on lakes over the Tibetan Plateau are still poorly investigated, especially in small- to medium-sized lakes. In this study, based on water profile observations in Dagze Co, a medium-sized lake on the central Tibetan Plateau, the sensitivity of lake thermal features to three key parameters in FLake was investigated. The performance of FLake in reproducing the lake thermal features was evaluated and improved by optimizing these key parameters. The results showed that the FLake model with default parameter settings can generally reproduce the thermal features of Dagze Co, but there are still significant deviations compared to observation. The sensitive experiments demonstrated that the thermal structure of the lake obviously responds to the change in the water extinction coefficient (Kd), friction velocity (u*), and ice albedo ( α i c e ). Based on previous studies and sensitive experiments, the three key parameters were set to the optimized value, which substantially improved the performance of FLake. The values of bias and RMSE of simulated lake surface water temperature decreased from 3.08 °C and 3.62 °C to 2.0 °C and 2.48 °C after parameter optimization. The integration of a simple salinity scheme further improved the ability of FLake to reproduce the observed thermal features of Dagze Co. These results will improve our understanding of thermal processes in lakes on the Tibetan Plateau, as well as the applicability of lake models. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau vortex (TPV) is a major rain-producing system over the Tibetan Plateau (TP) in summer. The vertical structure of TPV is critical in understanding the generation and development of TPV. In this paper, the ERA-Interim reanalysis data and an objective TPV detection and vertical tracing method are used to investigate the vertical structure of TPV in boreal summer (June–August). Most TPVs are shallow, with only 1/5 of them can reach 400 hPa. Among the TPVs that move off the TP, more than half are deep vortices. The tilting direction of TPV is related to its baroclinic structure. In general, TPVs tilt to the direction of the cold air from low to high isobaric levels, and the tilting direction depends on the relative positions of the warm pool and the cold air intruding into TPV. Deep TPVs inside the TP and those moving off the TP have different vertical structures. On the plateau, TPVs have convergence at the low levels (400–500 hPa) and divergence at the high levels (above 400 hPa), which can cause updrafts in the vortex and a tropical cyclone-like structure. For the TPVs moving off the TP, the updrafts are significantly weak due to the relatively low low-level convergence and the relatively low high-level divergence. These TPVs almost have positive vertical vorticity and present an extratropical cyclone-like structure. The vertical thickness of TPV is important in determining whether the TPV could move off the TP. The results show that the deep TPVs are more likely to move out than the shallow ones. Therefore, the vertical structure is a better predictor on the movement of TPV than its other properties. [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]