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The wave activity flux representing the energy propagation direction of planetary Rossby wave generally originates from a large wave source area. This study investigates the interdecadal variability and formation mechanism of Rossby wave source over the Tibetan Plateau (TP-RWS) and its impact on the atmospheric circulation and precipitation pattern in East Asia based on the ERA-20C reanalysis dataset in summer (June–July–August) during 1900 to 2010. Results show that the region with the maximum variabilities of Rossby wave source (RWS) in the past 110 years appears over the Tibetan Plateau (TP) during boreal summer, and the TP-RWS shows prominent characteristics of interdecadal oscillation. Secondly, the TP-RWS is mainly composed of the vortex stretching term (RWS-S1) and the absolute vorticity advection term (RWS-S2). The interdecadal TP-RWS is a synergistic result of the snow cover over northwestern TP associated with the RWS-S1, and the deep convection over southeastern TP associated with the RWS-S2. Furthermore, the interdecadal TP-RWS can lead to an alternatively positive and negative pattern of geopotential height anomalies from the northwestern TP to the North Pacific, which has a great climate effect on the precipitation in Huang-huai River Basin, South Korea and Japan Island. Under the guidance of the anomalous cyclonic circulation in East Asia, the prevailing southerly and easterly winds occur over the West Pacific and the Huang-huai River Basin, which lead to the water vapor convergence and upward movement at middle and lower troposphere. [ABSTRACT FROM AUTHOR]

This study investigated the impacts of Tibetan Plateau vertical heating (TPVH) on the Asian summer monsoon (ASM) on the interdecadal scale since the beginning of the 20th century. The ASM, corresponding to TPVH, generally enhances on the interdecadal scale. In the upper troposphere, the upper‐level westerly and easterly jet streams shift northwards in Asia, with two meridional "southern low and northern high" wave‐like patterns dominating in East Asia and India, respectively. In the lower troposphere, the summer monsoonal airflow and convergence zone migrate northwards in Asia, and two meridional "southern high and northern low" patterns appear in East Asia and India, respectively. Thus, TPVH can strengthen the baroclinicity over northern East Asia and northern India, but weaken it over southern East Asia and southern India. Moreover, two anomalous meridional circulation cells are identified in East Asia and India, with ascending branches in their northern parts and descending branches in their southern parts. Eventually, the ASM strengthens, leading to a southern dry and northern wet pattern in East Asia and India. [ABSTRACT FROM AUTHOR]

In the peak-summer of 2022, the Yangtze–Huaihe River Basin (YHRB) in China experienced its most extreme heatwaves since 1961. Notably, a rare heatwave also occurred in the YHRB in 2013. However, the Tibetan Plateau (TP) exhibited different thermal conditions during those two years. Observational analysis indicates that the 2013 and 2022 heatwaves were closely related to the local anomalous high pressure. The synergistic effects of the East Asian subtropical jet (EASJ), South Asian high (SAH), western Pacific subtropical high (WPSH), and divergence of moisture, supported the formation and maintenance of the high pressure. Compared to 2013, under the synergistic control of these intensified circulation systems in 2022, which led a broader descending motion and stronger heatwaves prevailed over the YHRB. Also, the surface air temperature of TP reached its highest value in 2022, whereas it was not distinctly anomalous in 2013. Corresponding to the TP thermal anomaly, an abnormal high pressure appeared throughout the troposphere over the northern YHRB. The TP heating contributed to the northward strengthening of the SAH and EASJ, which enhanced the anomalous westerly winds to the north of the anticyclone. Moreover, the WPSH extends westward during strong TP heating years. With the cooperation of high pressure and moisture, there was an anomalous meridional circulation pattern with ascending motion in North China and descending motion in the YHRB, accompanied by reduced cloud cover and increased insolation in the YHRB, leading to further intensification of local heatwaves in 2022. This study demonstrates the significant role of TP thermal anomaly in YHRB heatwaves. • The YHRB experienced severe heatwaves in 2022 and 2013, with the TP exhibited different thermal conditions. • The synergistic control of SAH, EASJ, WPSH and moisture divergence makes 2022 YHRB heatwaves more extreme compared to 2013. • The 2022 TP thermal anomaly affects the key atmospheric circulation, causing stronger downdrafts and heatwaves than 2013. [ABSTRACT FROM AUTHOR]

In this study, the precipitation recycling ratio (ρ) on the Tibetan Plateau (TP) was calculated based on the improved two-dimensional precipitation recycling model, and the contribution of internal and external cycling precipitation to the changes in total precipitation in the plateau was quantified. From 1979 to 2018, the annual average ρ of the TP was approximately 12.2%, with the highest being 26.3% in summer, approximately 9% in spring and autumn, and only 4.3% in winter. Moreover, ρ tended to increase, and such an increasing trend was more noticeable in summer. Spatially, ρ showed an up-climbing tendency over most areas of the TP, among which the central and eastern regions had more notable success as the recycling process over most areas of the TP strengthened. However, ρ in some western regions showed a weak decreasing trend, indicating that the recycling process was weakened. As the external cycling precipitation (P o) contributed by advection moisture was much greater than the internal recycling precipitation (P w) contributed by evapotranspiration, the changes in TP total precipitation were mainly dominated by P o changes. Quantitatively, the TP annual precipitation showed a significant increasing trend in the nearly 40 year period, to which the increase in P o contributed 68.4% and the increase in P w contributed approximately 31.6%. • The precipitation recycling ratio of the Tibet Plateau was about 12.2%/a, and has an increasing trend from 1979 to 2018. • The recycling precipitation increasing more notable in central and eastern regions of Tibet Plateau. • 31.6% of the increase precipitation in Tibet Plateau was contributed by recycling precipitation. [ABSTRACT FROM AUTHOR]