Physical processes of summer extreme rainfall interannual variability in eastern China: Part I—observational analysis

Abstract

Extreme precipitation can have catastrophic effects in China by triggering floods, landslides, and other natural disasters. We measure extreme precipitation over eastern China by the maximum of five-day precipitation amount (Rx5day) in June, July, and August (JJA), which contributes more than 20% of the climate mean of JJA regional total precipitation. Based on the empirical orthogonal teleconnection (EOT) method, this work identifies four dominant regions of observed Rx5day interannual variability in eastern China: north-eastern China (EOT1), the southern lower reaches of the Yangtze valley (EOT2), southern China (EOT3) and the northern lower reaches of the Yangtze valley (EOT4). EOT1 extreme precipitation is related to a strong East Asian Summer Monsoon (EASM), a weak monsoon front and a northward displaced upper-tropospheric westerly jet. EOT2 and EOT4 extreme precipitation are related to an enhanced and stable monsoon front and a strong western North Pacific subtropical high (WNPSH). The WNPSH associated with EOT4 is stronger than that associated with EOT2, which pushes the monsoon front further north. EOT3 represents extreme precipitation that is related to anomalous southerlies around the western ridge of the WNPSH. The southerlies transport warm and moist air to southern China and increase precipitation there. The four key regions and the related mechanisms are not sensitive to the EOT technique, as the EOT-based extreme precipitation patterns and circulation anomalies are confirmed using Self-Organising Maps (SOMs).

Spatial-temporal variations of extreme precipitation indices and their linkage with atmospheric circulation in the middle and lower reaches of the Yangtze River

“…The precipitation in the region is highly affected by the location of WPSH as WPSH controls the precipitation belt position along the edge of the subtropical high. Meanwhile, there exhibits a high level of correlation between PRCPTOT and WPSH area (R =0.49, P<0.01), WPSH intensity (R =0.47, P<0.01), both are statistically significant, indicating that R25mm and PRCPTOT will increase significantly with the increase of WPSH area and intensity (Hu and Wang, 2021;Tian et al, 2022). There is a significant correlation (P<0.01) between the SCSHI and PRCPTOT (r=0.59, P<0.01) and R95 (r=0.46, P<0.01) (Nazari-Sharabian and Karakouzian, 2020; Zeng et al, 2019).…”

Typical Synoptic Patterns Responsible for Summer Regional Hourly Extreme Precipitation Events Over the Middle and Lower Yangtze River Basin, China

“…The regional EP in MLYRB mostly happens in summer and is largely influenced by the East Asian summer monsoon (EASM), especially the associated Meiyu front (Ding, 2004; Ding & Chan, 2005; Ng et al., 2021). Previous studies have indicated that the EP in MLYRB generally associates to the strengthened and westward‐extended western North Pacific subtropical high (WNPSH) accompanied by the intensified and eastward‐extended South Asian high (SAH) (Tang et al., 2021; F. Tian et al., 2022; Y. Tian et al., 2022; Q. Zhang et al., 2017; Y. Zhao et al., 2020).…”