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Recent years have witnessed contrasting trends in summer total rainfall (STR) over the Tibetan Plateau (TP), with an increase in the northern and a decrease in the southern TP. This study identifies four significant centers of rainfall trends: eastern TP ("region A"), Qiangtang Plateau ("B"), Qaidam Basin ("C"), and the northern foothills of the Himalayas ("D"). Heavy rainfall dominates STR trends in regions A and D, accounting for 55.6% and 52.0%, respectively. In region B, moderate and light rainfall contribute almost equally, accounting for 37.3% and 44.8% of the STR trend, respectively. Region C is primarily influenced by light rainfall, explaining 71.2% of the STR trend. Notably, the contributions of different rainfall intensities to STR in each region vary annually, with region A experiencing more heavy rainfall, region B having moderate dominance but less light rainfall, and region C and D showing reduced and increased light rainfall contributions, respectively. Mechanistically, the strengthening of the upper-level westerly jet and the South Asian High, coupled with changes in moisture transport and convective available potential energy, collectively cause variations in rainfall intensity, characterizing the spatial heterogeneity in STR in the TP. [ABSTRACT FROM AUTHOR]

We investigated the effect of increased spring (April–May) dust aerosol over the Arabian Peninsula (AP) on the subseasonal-to-seasonal (S2S) variability of the Asian summer monsoon (ASM) using MERRA-2 re-analysis data (1980–2018). Result shows that abundant AP spring dust leads to more dust covering the AP and Pakistan northwestern India (PNWI) during May–June, causing a cooler land surface and a warmer lower and middle atmosphere with enhanced local atmospheric stability. However, the warmer atmosphere increases the meridional temperature gradient, boosting moisture transport from the Arabian Sea to PNWI, causing increased convective potential energy in PNWI region. As season advances, the accumulated convection potential energy eventually breaks through the local stability, via the elevated heat pump (EHP) effect, increasing precipitation over PNWI. In July and August, cloud radiation-circulation feedback further enhances the warming of the upper troposphere, strengthening precipitation in PNWI. Dynamical adjustments of large-scale circulations induced by the feedback strongly modulate ASM precipitation. Over southern and central China, precipitation is reduced, in conjunction with a contraction of South Asian High, and the development of an anomalous east-to-west oriented upper-level wavetrain in July. In August, the upper level wavetrain undergoes strong wave-mean flow interaction, culminating in the development of an anticyclonic center with drought conditions over northeast China, Korea and Japan. Over the Indian subcontinent, increased precipitation in PNWI plays an important role in initiating the EHP feedback leading to increased precipitation over the Indian subcontinent, and in modulating the jetstream-wave interaction in downstream East Asian regions in July–August. [ABSTRACT FROM AUTHOR]

We investigated the intraseasonal relationship between the atmospheric heat source over Tibetan Plateau (TP) and summer rainfall in eastern China. A quasi-biweekly oscillation (QBWO) is the common dominant periodicity over both the TP and eastern China. Crucially, the TP heat source QBWO leads rainfall QBWO over its downstream region by 2–8 days. The QBWO over the TP shows a significant eastward propagation. Phase composite further identified the specific propagation pathway: TP QBWO first propagates eastward to central China, southward to southern China, and then northeastward to the lower reaches of the Yangtze River with a zigzag propagating pathway. Mechanistically, the eastward propagation of the upper level divergence caused by the movement of the 200 hPa jet core and south Asian high contributes to the eastward propagation of the rainfall QBWO. Simultaneously, the eastward (westward) shift in the western north Pacific subtropical high causes deepening (flattening) of the monsoon trough and the occurrence of an anomalous cyclone (anticyclone) over the western north Pacific. An anomalous anticyclonic (cyclonic) circulation around the TP appears with the wet-to-dry (dry-to-wet) phase transition of the TP QBWO. Together, they play a crucial part in the southward (northeastward) movement of the QBWO. Further dynamic analysis indicates that the horizontal moisture advection acts on the whole eastward-propagating process of the QBWO, whereas the horizontal vorticity advection is only significant when QBWO is over the TP. This study shows that the fluctuations in TP heat source are important indicators in extended forecasts of summer rainfall in eastern China. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau Vortex (TPV) is mainly divided into east moving (E-TPV), northeast moving (NE-TPV) and so on according to its moving path after moving off the Tibetan Plateau (TP). Based on the database of TPV from 1979 to 2018, this paper mainly makes statistical analysis on the NE-TPV in summer. According to its moving-off position, NE-TPV is subdivided into westward vortex (denoted as NE I -TPV) and eastward vortex (denoted as NE II -TPV). In terms of source, structure, circulation, moving speed, life history and influence on precipitation, the characteristics of two types of NE-TPVs were analyzed and compared with E-TPV to reveal the activity characteristics of the NE-TPVs and the similarities and differences between them. The results show that: (1) The NE I -TPV is mainly generated in the northwest of the TP, while the NE II -TPV and E-TPV are generated in the whole TP. There are mainly three centers of vortex sources: west, middle and east. The eastern sources of TPV with different paths differ greatly in north-south location and concentration. The eastern source of NE I -TPV is northward and concentrated, while the E-TPV is southward and dispersed, and NE II -TPV is between the former two. (2) The intensity of NE II -TPV is stronger than that of NE I -TPV before moving off, and the ascending motion of these two is located near the vortex center. After moving off, the relative vorticity and vertical velocity of both of them weakened significantly, and the maximum upward movement of NE I -TPV moved to the northeast of the vortex, while the NE II -TPV is similar to E-TPV, and its rising region is located in the southeast of the vortex. (3) The moving direction before moving off and moving-off position of TPV is mainly affected by the 200 hPa westerly fluctuations, while after moving off, the moving direction is mainly affected by 500 hPa troughs and ridges. Among them, the Hetao High-Pressure Ridge is particularly important in blocking NE-TPV. (4) Besides the influence of altitude difference, the moving speed of TPV is closely related to its moving direction, so the TPV moving eastward move faster. (5) NE II -TPV and E-TPV have longer mean life history than NE I -TPV, meanwhile, they often result in a wider range of precipitation and a higher proportion of rainstorms. The precipitation of NE I -TPV is mainly located in the Hexi Corridor. While the precipitation of NE II -TPV is mainly located in the eastern part of Northwest China. • According to its moving-off position, the northeast moving Tibetan Plateau Vortex (NE-TPV) is subdivided into westward vortex (denoted as NE I -TPV) and eastward vortex (denoted as NE II -TPV). • It is found that TPV mainly has three sources, which are located in the west, the middle and the east of the TP. The eastern source of TPVs with different paths is quite different. • After moving off the TP, the maximum ascending motion of NE I -TPV is located in the northeast side of the vortex, while that of NE II -TPV is located in the southeast side of the vortex, just like the E-TPV. • On the one hand, the moving speed of TPV is affected by the altitude difference. On the other hand, it is also related to the moving direction. [ABSTRACT FROM AUTHOR]