The tropospheric biennial oscillation in the East Asian monsoon region and its influence on the precipitation in China and large‐scale atmospheric circulation in East Asia

Abstract

ABSTRACT:The precipitation in China manifests a remarkable quasi-biennial signal. For interannual variability, about 70% stations over China indicate the dominance of a quasi-2-year period. The maximum precipitation variability associated with the quasi-biennial oscillation is located over the Yangtze River valley (YRV) and Huaihe River valley (HRV) as well as South China. This paper attempts to reveal the spatial-temporal evolution of the precipitation in China and related large-scale atmospheric circulation associated with the tropospheric biennial oscillation (TBO) in East Asia by using a season-dependent empirical orthogonal function (S-EOF) analysis approach.The leading two modes of the TBO of summer precipitation in China and associated large-scale circulations are examined by the S-EOF analysis and regression analyses based on the S-EOF time coefficients. The first TBO mode is characterized by an elongated band of positive precipitation anomalies along the YRV and negative precipitation anomalies over both North and South China. The second TBO mode is characterized by an elongated band of positive precipitation anomalies along the HRV and negative precipitation anomalies to the north of the Yellow River and to the south of the Yangtze River, respectively. Meanwhile, the leading modes of the TBO in East Asia may be determined by the meridional teleconnection Rossby wave pattern extending from the WNP to the midlatitudes of East Asia that is forced by the heating source fluctuation over the WNP during boreal summer. And the cold air activity, which is associated with the East Asian winter monsoon, may further influence the leading modes of the TBO through a modulation of the large-scale atmosphere circulation over East Asia during the following boreal summer.Also found is that the TBO in East Aisa depends on both the large-scale air-sea coupling over the tropical Indo-Pacific Ocean regions and the tropical-midlatitude interaction in the western North Pacific (WNP)-East Asia region. A fundamental element for the TBO in East Asia is the WNP monsoon. It is not only an important component of the TBO cycle in the tropics but also serves as a major source of the TBO signal for the subtropical East Asia. The meridional teleconnection Rossby wave train over the WNP-East Asia region acts as a conveyer belt that transports the tropical TBO signal to the midlatitudes of East Asia, and produces the TBO footprints in the large-scale circulation and precipitation in East Asia. Furthermore, the cold air activity over the East Asia during boreal summer also services as an important link in the chain events of the tropical-midlatitude interaction, with enhancing the role of the TBO modes in East Asia.

Inter‐decadal change of the middle‐upper tropospheric land–sea thermal contrast in the late 1990s and the associated Northern Hemisphere hydroclimate

“…As a consequence, summer precipitation generally increases over the subtropical East Asian (to the south of 35°N) and tropical African monsoon regions, except some scattered decreased precipitation in the Yangtze River valley of China (28°–31°N, 110°–120°E) (Figure a). The decreases/increases of summer precipitation over the Yangtze River valley/the Huanghe–Huaihe River valley indicate the enhancements in the local monsoon circulation and rainfall (Si and Ding, ; ), also providing more evidence for supporting an intensified East Asian summer monsoon since the late 1990s (Liu et al ., ; Wu et al ., ).…”

“…In the lower troposphere (Figure 4a), we note the convergence and divergence anomalies of air masses over the Eurasian-northern African (Figure 5a). The decreases/increases of summer precipitation over the Yangtze River valley/the Huanghe-Huaihe River valley indicate the enhancements in the local monsoon circulation and rainfall (Si and Ding, 2012;2013), also providing more evidence for supporting an intensified East Asian summer monsoon since the late 1990s (Liu et al, 2012;Wu et al, 2016a). The enhanced monsoon circulation and rainfall could generate anticyclonic anomalies over the adjacent arid regions that are often located to the west and north of the monsoon regions, which may be caused by the intensified descending motion in the arid region through the interaction between the Rossby wave and the mean state flow (Hoskins and Rodwell, 1995).…”

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

“…As located in a transitional zone between the largest ocean‐Pacific and the largest continent‐ Eurasian Continent, East China are dominated by large‐scale atmospheric circulations coupling with water vapour transport (Sun et al ., 2007; Si and Ding, 2012; Wang and Chen, 2012; Deng et al ., 2014). Moisture for precipitation in East China mainly originates from evapotranspiration of the Eurasian landmass, and Pacific and the Indian Ocean (IO).…”

Interannual variability of summer monsoon convective and stratiform precipitations in East Asia during 1998–2013

“…These studies pointed out that the SEAM was mainly characterized by quasi‐biennial and 4–7‐year oscillations that are associated with the variations of summer precipitation and large‐scale circulation (Ding, ; Ding et al , ). Therefore, the weakening SAM may modulate the interannual variability of precipitation in East Asia (Meehl and Arblaster, ; Huang et al , ; Ding, ; Si and Ding, ; Ding, et al , ; Huang et al , ). Studies found that the intensity of such interannual variabilities has an apparent dispersion from its mean state.…”