The Relationship Between Anomalous Presummer Extreme Rainfall Over South China and Synoptic Disturbances

Abstract

A spectral analysis of daily rainfall data has been performed to investigate extreme rainfall events in south China during the presummer rainy seasons between 1998 and 2015 (excluding 1999, 2006, 2011, and 2014). The results reveal a dominant frequency mode at the synoptic scale with pronounced positive rainfall anomalies. By analyzing the synoptic‐scale bandpass‐filtered anomalous circulations, 24 extreme rainfall episodes (defined as those with a daily rainfall amount in the top 5%) are categorized into “cyclone” (15) and “trough” (8) types, with the remaining events as an “anticyclone” type, according to the primary anomalous weather system contributing to each extreme rainfall episode. The 15 cyclone‐type episodes are further separated into (11) lower‐ and (4) upper‐tropospheric migratory anomalies. An analysis of their anomalous fields shows that both types could be traced back to the generation of cyclonic anomalies downstream of the Tibetan Plateau, except for two episodes of lower‐tropospheric migratory anomalies originating over the South China Sea. However, a lower‐tropospheric cyclonic anomaly appears during all phases in the former type, but only in the wettest phase in the latter type, with its peak disturbance occurring immediately beneath an upper‐level warm anomaly. The production of extreme rainfall in the trough‐type episodes is closely related to a deep trough anomaly extending from an intense cyclonic anomaly over north China, which in turn could be traced back to a midlatitude Rossby wave train passing by the Tibetan Plateau. The results have important implications for understanding the origin, structure, and evolution of synoptic disturbances associated with the presummer extreme rainfall in south China.

Statistical Characteristics of Pre-summer Rainfall over South China and Associated Synoptic Conditions

“…8d-f) can be traced back to the migratory cyclonic anomalies originated near the southeastern margin of the Tibetan Plateau a few days earlier (Li et al 2014;Huang et al 2018), or are closely related to a deep trough anomaly extending from an intense cyclonic anomaly over north China, which in turn could be traced back to a midlatitude Rossby wave train passing the Tibetan Plateau (Huang et al 2018).…”

Spatiotemporal Characteristics and Associated Synoptic Patterns of Extremely Persistent Heavy Rainfall in Southern China

“…The release will cause a strong negative pressure change at surface, and the wind generated by the pressure change forces the ultra‐low‐level jet to be further strengthened (Gao & Sun, 1984), which is an important mechanism for producing continuous and strong precipitation. The observation and analysis of most PHR events can determine the back‐building/quasistationary (BB) and training line/adjoining stratiform (TL/AS) characteristics (Ding & Liu, 2001; Huang et al., 2018; Luo et al., 2013; Schumacher, 2009; Schumacher & Johnson, 2009; Schumacher & Peters, 2017; Xu et al., 2012), and the quasistationary characteristics are obvious, closely related to the cold pool and associated outflows mainly induced by rain evaporation, which acts as an importance feedback effect for local rainfall with long‐duration (Liu et al. 2018; Wang et al., 2014; M. Wu & Luo, 2016).…”

Dominant variation modes associated with Yangtze–Huai River Basin summer heavy rainfall events

“…Meanwhile, they indicated that southern YHRB (sYHRB) heavy rainfall resulted from the superposition of quasi-biweekly (10-20-day) and synoptic-timescale disturbances. Following this work, Huang, Luo, and Zhang (2018) also revealed the important contribution of synoptic disturbances to the pre-summer extreme rainfall over South China. Therefore, synoptic-timescale modes should be given equal attention in heavy rainfall studies.…”