Large‐scale synoptic atmospheric moisture circulation patterns associated with variability of daily precipitation overEast China

Abstract

This study identifies the variability of large-scale atmospheric patterns (LSMPs) and atmospheric moisture circulation patterns associated with the variability of daily precipitation over East China using the self-organizing maps (SOM) method. The spatiotemporal characteristics of the occurrence and intensity of daily precipitation were linked with the variabilities of LSMPs.Results show that the synoptic moisture transport over East China in both dry season and rainy season can be classified into eight patterns, and the occurrence frequency and primary occurring months of the eight patterns are varied. In the dry season, the wetter pattern (the drier pattern) exhibits a significant decreasing (increasing) trend with a slope of −0.23 (0.63)% year −1 at the confidence level of 0.95 during 1979-2018. The LSMPs corresponding to each atmospheric moisture circulation pattern, including the composite mean values of vertically integrated water vapour transport fields, 500 hPa geopotential height (Z500) anomalies and sea surface temperature anomalies (SSTA) in surrounding oceans, indicate that the primary oceanic moisture source of the dry season is western North Pacific (WNP), while that of the rainy season is WNP and the Indian Ocean. The location and intensity variabilities of subtropical high affect the transport and amount of water vapour along with its western flank to arrive in East China. SSTA has an influential link with the regional circulations and convection activity, and thus plays an important role in affecting water vapour transport.

Variation of Hourly Extreme Precipitation in the Three Gorges Reservoir Region, China, from the Observation Record

“…The decrease in sea-land temperature difference caused by the abnormal warming of the Western Pacific Warm Pool (WPWP) Index was one of the important driving factors of the transition of summer extreme precipitation in eastern China around 1990 [18]. Summer extreme precipitation is statistically significantly correlated with the western North Pacific subtropical high (WPSH) and positive anomalies of 500 hPa geopotential heights [19]. With the ridge of the western Pacific subtropical high typically staying around the northeastern quadrant of the South China Sea, persistent extreme precipitation events that are induced by the typical East Asia/Pacific conditions will be more likely to occur in the Yangtze River Valley [19].…”

“…Summer extreme precipitation is statistically significantly correlated with the western North Pacific subtropical high (WPSH) and positive anomalies of 500 hPa geopotential heights [19]. With the ridge of the western Pacific subtropical high typically staying around the northeastern quadrant of the South China Sea, persistent extreme precipitation events that are induced by the typical East Asia/Pacific conditions will be more likely to occur in the Yangtze River Valley [19].…”

Advancing Cloud Classification Over the Tibetan Plateau: A New Algorithm Reveals Seasonal and Diurnal Variations

“…As the highest and largest plateau on Earth, the Tibetan Plateau (TP) markedly shapes local climate, influences large‐scale atmospheric circulation, and impacts the hydrological cycle through thermal and mechanical forcing (Bao et al., 2019; D. Chen et al., 2016; Gao et al., 2003; Lai et al., 2024; Y. Li et al., 2006; Manabe & Broccoli, 1990; X. Wang et al., 2020; Y. Wang et al., 2020; Yanai et al., 1992). Home to the highest mountain range on Earth, the TP acts as a natural laboratory for studying cloud formation and microphysical properties, while also impeding the influx of tropical water vapor.…”