Roles of Synoptic to Quasi-Biweekly Disturbances in Generating the Summer 2003 Heavy Rainfall in East China

Abstract

During the mei-yu season of the summer of 2003, the Yangtze and Huai River basin (YHRB) encountered anomalously heavy rainfall, and the northern YHRB (nYHRB) suffered a severe flood because of five continuous extreme rainfall events. A spectral analysis of daily rainfall data over YHRB reveals two dominant frequency modes: one peak on day 14 and the other on day 4 (i.e., the quasi-biweekly and synoptic-scale mode, respectively). Results indicate that the two scales of disturbances contributed southwesterly and northeasterly anomalies, respectively, to the mei-yu frontal convergence over the southern YHRB (sYHRB) at the peak wet phase. An analysis of bandpass-filtered circulations shows that the lower and upper regions of the troposphere were fully coupled at the quasi-biweekly scale, and a lower-level cyclonic anomaly over sYHRB was phase locked with an anticyclonic anomaly over the Philippines. At the synoptic scale, the strong northeasterly components of an anticyclonic anomaly with a deep cold and dry layer helped generate the heavy rainfall over sYHRB. Results also indicate the passages of five synoptic-scale disturbances during the nYHRB rainfall. Like the sYHRB rainfall, these disturbances originated from the periodical generations of cyclonic and anticyclonic anomalies at the downstream of the Tibetan Plateau. The nYHRB rainfalls were generated as these disturbances moved northeastward under the influence of monsoonal flows and higher-latitude eastward-propagating Rossby wave trains. It is concluded that the sYHRB heavy rainfall resulted from the superposition of quasi-biweekly and synoptic-scale disturbances, whereas the intermittent passages of five synoptic-scale disturbances led to the flooding rainfall over nYHRB.

Simultaneous modulations of precipitation and temperature extremes in Southern parts of China by the boreal summer intraseasonal oscillation

“…For instance, both Lu et al (2014) and Zhu et al (2003) revealed that floods in the Yangtze River Basin during 1998 were in tandem with the active phase of 30-60-day BSISO. Liu et al (2014) emphasized the great contribution of the quasi-biweekly agent to heavy rainfall in the Yangtze-Huai River Valley during 2003. Studies based on specific cases can't fully address influences of the BSISO on precipitation extremes in China.…”

Influence of boreal summer intraseasonal oscillation on rainfall extremes in southern China

“…Previous flooding case studies found that the unusually persistent episodes of wet condition in southern China were related to convective phases of boreal summer intraseasonal oscillation (BSISO) (Yang and Li, ; Zhu et al , ; Mao and Wu, ; Gao et al , ; Liu et al , ; Li et al , ). The BSISO has been identified as the dominant source of short‐term climate variability and extremes in Asia (e.g.…”

Different characteristics of the quasi-biweekly oscillation over the South China Sea in two boreal summer stages

“…In other ways, it was documented that the QBWO could influence the active/broken cycles of Indian summer monsoon (Krishnamurti and Ardanuy 1980;Yasunari 1981;Goswami et al 2003) and South China Sea (SCS) summer monsoon (Chen et al 2000;Chan et al 2002;Mao and Chan 2005;Zhou and Miller 2005). Some studies also indicated that the QBWO was closely related to the rainfall in the Yangtze and Huai River basin of China in boreal summer (Yang et al 2010;Liu et al 2014). Besides, the QBWO could impact the track of the tropical cyclone.…”