Variability in the East Asian Monsoon: a review

Abstract

ABSTRACT:This study presents reviews of recent research on the structure and the multiscale variability in the East Asian monsoon. The boreal summer and winter seasons in the East Asian monsoon region exhibit significant intraseasonal, interannual and interdecadal variabilities. The interannual intensity of the East Asian summer monsoon (EASM) is mainly associated with the position of the centre of the Bonin High, which may be distinguished from the North Pacific anticyclone. The frequencies of heavy rainfall events and associated rainfall amounts increase, and extreme heavy rainfall is higher in August than in July, due to changes that occurred in the August rainfall-El Niño-Southern Oscillation (ENSO) relationship around the mid-1970s. This intraseasonal variability in EASM plays a more important role in the explanations of the interannual variability and climate change than does the annual mean. The interannual variability in the East Asian winter monsoon (EAWM) depends on the behaviour of the Siberian High (SH), Aleutian Low and the subtropical westerly jet stream. An EAWM index that takes into account the meridional shear of a 300 hPa zonal wind is a good indicator to represent the intensity of the EAWM. The Arctic Oscillation has a close relationship with the EAWM intensity on the decadal time scale. Distinct sub-seasonal variability is characterized with northward propagation and is observed in the interdecadal change in the monsoonal intraseasonal oscillation (ISO)-ENSO relationship. The preceding winter ENSO influenced the early summer northward propagating ISO (NPISO) activity before the late 1970s, whereas a strong NPISO-ENSO relationship appeared during the later summer after the late 1970s. The NPISO-ENSO relationship is robust owing to a tropical atmospheric bridge process involving the Walker Circulation and Rossby Wave propagation.

Dominance of climate warming effects on recent drying trends over wet monsoon regions

“…We computed the daily PET and PET /P and then estimated their annual mean values at individual weather sites. Due to the decadal variation in eastern Asian monsoon circulation (Ding et al, 2008;Ha et al, 2012), the entire analysis period is divided into two subperiods (1961-1983 and 1984-2010) by applying three change-point methods to the temporal variations in PET /P (Pettitt, 1980;Lund and Reeves, 2002;Beaulieu et al, 2012, see Sect. S2 of Supplement for details).…”

The Inclusion of Forest Hydrological Services in the Sustainable Development Strategy of South Korea

“…In fact, such conditions have resulted in relatively frequent floods and droughts in South Korea [32,34]. The severity of floods and droughts is highly variable, as the EASM exhibits a substantial interannual variability in intensity [35]. Eighteen droughts have occurred over the last 100 years, with severe droughts occurring in seven-year cycles since 1994 (Table 1).…”

“…The observed changes are predicted to intensify until at least 2100, along with an increase in the occurrence and severity of In recent decades, changes in the climate of South Korea have been observed, namely an above-global-average increase in surface temperature, and a substantial increase in the frequency and intensity of heavy rainfall events [36][37][38]. From 1954 to 1999, surface temperature increased at a rate of 0.23 • C per decade, and from 2001 to 2010, at a rate of 0.5 • C per decade [35]. Choi et al (2008) [39] reported that, in the region of the Lake Soyang watershed, the precipitation of extremely wet days increased by 61 to 80 mm per decade over the period from 1973 to 2007.…”

A Mechanism of the Interdecadal Changes of the Global Low-Frequency Oscillation

“…One has a period of 30-90 days, and is often referred to as the intraseasonal oscillation (ISO); the other has a period of 10-20 days, and is often referred to as the quasi-biweekly oscillation (QBWO) [4][5][6][7]. The studies on both the mechanism and the climatic impacts of the ISO and QBWO have been hot topics since the early 1970s [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”