Extratropical extended-range precursors near the tropopause preceding persistent strong precipitation in South China: a
- PDF / 9,092,903 Bytes
- 18 Pages / 595.276 x 790.866 pts Page_size
- 89 Downloads / 170 Views
Extratropical extended‑range precursors near the tropopause preceding persistent strong precipitation in South China: a climatology Liang Zhao1 · Haiwen Liu2 · Yamin Hu3 · Huhua Cheng4 · Ziniu Xiao1 Received: 4 December 2019 / Accepted: 19 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The pre-summer rainy season (PSRS; April–June) is the period of most frequent strong precipitation in South China (SC). Persistent strong precipitation events (PSPEs) can cause greater loss of life and property than short-lived strong precipitation. This paper investigates extended-range signals near the tropopause preceding two persistent positive climatological intraseasonal oscillations (PPCISOs) in precipitation corresponding to two climatological PSPEs in SC during the PSRS, using the CISO analysis of isentropic potential vorticity (IPV). It is found that precursor signals can be better seen in IPV CISOs than in unfiltered IPV. The first rainfall PPCISO is caused by an eastward propagation of high-IPV CISOs along the dynamical tropopause originating from the Arctic region and west of the Tibetan Plateau. The second is the most persistent (13 days). Its high-IPV CISOs originate over the Arctic region and the tropical monsoon region, respectively, 20 or more days prior to the rainfall CISO peak. The west of the Tibetan Plateau and the northern region of the East Asian westerly jet near the tropopause are two transit points where extratropical high-IPV CISOs strengthen and then change their propagation direction. The southward high-IPV CISOs and the northward positive IPV CISO caused by the monsoon begin to interact about 10 days prior to rainfall peak. Since then, the interaction leads a narrow meridional positive PV channel on the inclined 345 K isentropic surface. A specific CISO pattern, characterized by an elongated high-IPV CISO isolated by three negative IPV CISOs (the South Asian, the Okhotsk and the western Pacific subtropical highs), is responsible for the long duration of the second rainfall PPCISO. Keywords Climatological intraseasonal oscillations · Persistent rainfall · Pre-summer rainy season in South China · Isentropic potential vorticity · Extended range · Interaction between the stratosphere and the troposphere · Monsoon
1 Introduction
* Liang Zhao [email protected] * Ziniu Xiao [email protected] 1
LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, No. 40 Hua Yan Li, ChaoYang District, Beijing 100029, China
2
Department of Aviation Meteorology, Civil Aviation University of China, Tianjin 300300, China
3
Guangdong Climate Center, Guangdong Province, Guangzhou 510080, China
4
63729 Troops, Taiyuan 030027, China
The period from April to June is usually the main rainy season, called the pre-summer rainy season (PSRS), over South China (SC) (Ding 1992, 2004). The rainfall over SC during the PSRS accounts for 44% (721 mm) of the total annual rainfall (1652 mm), whereas rainfall during July, August, and September (JAS) accounts for 35% (5
Data Loading...
