The combined effects of the ENSO and the Arctic Oscillation on the winter climate anomalies in East Asia

Abstract

With the warm/cold phases of the El Niño and Southern Oscillation (ENSO) as a background, the impacts of monthly variation in the Arctic Oscillation (AO) on the winter climate anomalies in East Asia are studied with the NCEP/DOE Reanalysis 2 data and the Chinese station data regarding temperature and rainfall. The combined effects of ENSO and the AO indicate that the winter climate anomalies are mainly influenced by the AO in northern China and the ENSO in southern China, when an El Niño couples with a negative AO month or a La Niña couples with a positive AO month. These climate anomalies in China are consistent with the mechanisms proposed in previous studies. However, most of China presents a different pattern of climate anomalies if an El Niño couples with a positive AO month or a La Niña couples with a negative AO month, with the exception of the temperature anomalies in northern China, which are still affected dominantly by the AO. Further analysis suggests that the causes are attributed to the differences in both the stratosphere-troposphere interaction and the extratropics-tropics interaction. In the former cases, zonal symmetric circulation prevails in the winter and the extratropics-tropics interaction is weakened. Thus, the influences of the ENSO and the AO on the East Asian climate mainly present linear combination effects. On the contrary, an annular mode of atmospheric circulation is not favored in the latter cases and the extratropics-tropics interaction is strong. Hence, the combined effects of the ENSO and the AO on the winter climate in East Asia present nonlinear characteristics.ENSO, AO, winter climate in East Asia, temperature and rainfall anomalies, stratosphere-troposphere interaction Citation:Chen W, Lan X Q, Wang L, et al. The combined effects of the ENSO and the Arctic Oscillation on the winter climate anomalies in East Asia.

Combined effect of the Arctic Oscillation and the Western Pacific pattern on East Asia winter temperature

“…The EAWM is characterized by the northwesterly wind over the east coast of Eurasia caused by the pressure gradient between the Siberian High in the Eurasian continent and the Aleutian Low in the North Pacific, the East Asian trough (EAT) in mid-latitude and the polar jet stream near the south of Japan in the upper troposphere (Jhun and Lee 2004;Chen et al 2013). Variations of these characteristics affect temperature and precipitation during the boreal winter in East Asia.…”

“…Kim and Ahn (2012) and He and Wang (2013a) revealed that the autumn AO and sea surface temperature of the North Pacific affect the winter temperatures in East Asia via stationary Rossby waves. Furthermore, Chen et al (2013) examined the combined effects of the winter AO and El Niño-Southern Oscillation (ENSO) on the EAWM. They showed that when a negative AO accompanies El Niño or a positive AO accompanies La Niña, the AO strongly affects the temperature and precipitation anomalies in northern China, while ENSO affects southern China.…”

“…ENSO is an interannual phenomenon caused by the unstable interaction between the atmosphere and ocean in the tropical Pacific (Rasmusson and Wallace 1983;Chen et al 2013). The effects of ENSO on the EAWM have been studied (Zhang et al 1996;Wang et al 2000;Sakai and Kawamura 2009).…”

Variation of precipitation concentration from 1960 to 2014 in the Middle and Lower reaches of the Yangtze River Basin, China

“…The variation of precipitation pattern is a complicated progress, thus large scale circulation may be a leading factor . Previous studies had also illustrated that the abnormal precipitation or drought/flood in East Asia (especially China) was usually affected by ENSO events (Larkin, 2005;Chen et al, 2013;Shuai et al, 2013;Räsänen et al, 2015). The results of this paper have stated that in El Niño years (high ONI), the rainy season may come earlier and the precipitation may be more concentrated.…”

Interdecadal variations of the East Asian winter surface air temperature and possible causes

“…Mao et al [7] indicated that the East Asian winter SAT would be higher (lower) than the normal in association with strengthened (weakened) westerlies. Additionally, Arctic Oscillation (AO), North Pacific Oscillation, North Atlantic Oscillation (NAO) and Eurasian wave-train pattern also influence SAT [8][9][10][11][12]. In general, atmospheric circulation anomalies are intimately related to various kinds of external forcing factors.…”