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In the context of global warming, the extreme summer precipitation over the Tibetan Plateau (TP) has changed significantly. In this study, the summer (June–August) extreme precipitation on the TP was classified into three spatial types by applying the K-means clustering method to the Third Pole Region long time-series high-resolution (1/30°) precipitation dataset (TPHiPr, 1979–2020). The characteristics of the circulation anomalies and precursors corresponding to the extreme precipitation on the TP in summer during 1979–2020 were investigated. The results showed that the summer extreme precipitation of the TP can be categorized into northwestern (NW), southeastern (SE), and southern Himalayan (HS) types based on extreme precipitation thresholds. The NW and SE types are mainly influenced by anomalous signals in the mid-to-high latitude regions upstream of them, whereas the HS type is controlled by the localized subtropical anomalous circulation. On the 8th day before the onset of the NW type, an anomalous cyclone was observed in the western Atlantic Ocean (60°W, 50°N), which triggered the west-to-east quasi-latitudinal propagation of Rossby waves. On the onset day of the NW type, the upper troposphere showed positive-negative-positive geopotential height anomalies along the latitudinal 40°N from the Caspian Sea, the western part of Xinjiang, to the northeastern TP. Moisture entered from the Arabian Sea along the southeastern edge of the anomalous cyclone on the southwestern TP and converged in the northwestern TP. Compared to the NW type, the precursors of the SE type appeared at higher latitudes and were more intense. On the 8th day before the onset of the SE type, an anomalous cyclone occurred near Greenland (60°W, 70°N) and excited Rossby waves propagating southeastward. On the onset day of the SE type, the upper troposphere showed negative-positive-negative geopotential height anomalies across Eurasia from the Ural Mountains and the Iranian Plateau to the northern TP in the northwest-southeast direction and entered the southeastern TP from the Bay of Bengal along the southeastern edge of the anomalous cyclone in the southern TP. On the 6th day before the onset of the HS type, the anomalously high pressure in the middle and lower layers of the low-latitude region extended westward, and a significant anticyclonic anomalous circulation occurred on the southern TP on the onset day of the HS type, enabling the delivery of moisture from the Bay of Bengal to the southern foothills of the Himalayas. Additionally, an anomalous cyclone perched in the northeastern TP at a geopotential height of 200 hPa strengthened westerly winds in the southern TP and contributed to the maintenance of the anticyclonic system on the southern TP. [ABSTRACT FROM AUTHOR]

ABSTRACT On the basis of the daily precipitation records of 442 meteorological stations throughout Northeast Asia ( NEA) from 1961 to 2009, this study investigates spatiotemporal changes in summer extreme precipitation ( SEP) and the relationship between SEP and East Asia summer monsoon ( EASM) in NEA. The results show that the spatial patterns of the trends in SEP indices are similar, with obvious clustering, except for the consecutive dry days ( CDD) index. Stations exhibiting increasing trends are mainly located in Eastern China ( EC) and the western part of Western Japan ( WJ). Stations with decreasing trends are mostly distributed in Northern China ( NC) and the southern region of Eastern Japan ( EJ). The spatial patterns of the correlations between the EASM index EASMI and the SEP indices are similar, except for the CDD index. Stations that show decreasing trends mostly exhibit positive correlations between SEP indices and the EASMI, and vice versa. The spatial patterns of trends (increasing trends in EC, decreasing trends in NC and Northeast China) in SEP indices between 1961 and 2009 have a correlation with a weakening EASM. This study demonstrates that the mechanism dominating the mean state change of the EASM also applies to SEP. A strong mid-latitude cyclone could result in a regional SEP (R99p occurred in more than 20 stations over a subregion in 1 day) in EC and Japan in weak EASM years, and could result in a regional SEP in NC in strong EASM years. [ABSTRACT FROM AUTHOR]