Cold Surge Pathways in East Asia and Their Tropical Impacts

Abstract

Cold surges occurrence is one of the robust features of winter monsoon in East Asia characterized by equatorward outbreaks of cold air from the high latitudes. Beside greatly affecting weather variability across the Far East, cold surges are of importance for Southeast Asian countries because they can propagate far to the tropics and excite convective activities. However, the tropical responses highly depend on the downstream pathways of the surges. To better understand how cold surges influence tropical weather, we investigate 160 cold surges identified using a quantitative approach during 40 winters from 1979/80 to 2018/19, and then classify them into several groups based on their prominent pathways. At the mid-latitudes, we find two groups: one for surges that show clear equatorward propagation of cold air to lower latitudes; and the other for surges that turn eastward and bring cold air to the North Pacific. These groups arise due to the strength difference of the Siberian High expansion controlled by cold air blocking near the Tibetan Plateau. The tropical impact is evident in the former group. We perform further classification on this group and find four types of surges based on their pathways in the low latitudes: 1) South China Sea (SCS) surges, 2) Philippines Sea (PHS) surges, 3) both SCS and PHS surges, and 4) blocked surges. They exhibit distinct precipitation signatures over the Maritime Continent, which are driven by interactions between the surges and the pre-existing synoptic conditions over the tropics, particularly the Madden-Julian Oscillation (MJO).

Synoptic conditions and potential causes of the extreme heavy rainfall event of January 2009 over Mindanao Island, Philippines

“…(b) The meridional wind anomaly along 15°N and between 122.5° and 130°E should exceed one standard deviation of the climatological (1981-2010) meridional wind anomaly along the same region. This definition is adopted from Abdillah et al (2021) who referred to these types of cold surges as the Philippine Sea type. (c) The daily rainfall in any of the four stations located to the north and eastern Mindanao Island (Lumbia airport, Butuan City, Hinatuan, and Surigao City) should exceed the 99th percentile rainfall of all January from 1979 to 2017.…”

Two Types of the East Asian Cold Surge and Their Impacts on El Niño

“…Figure 1a shows the leading EOF mode (EOF1) of surface meridional wind in the western tropical Pacific in winter. EOF1 explains 52.91% of the total variance, with two centers of maximum variance right on the area where CSs frequently occur (Abdillah et al., 2021; Chan & Li, 2004; Compo et al., 1999). The principal component is highly correlated with the Niño3.4 index (Figure 1c).…”

“…The CS appears near 40°N in northern China in association with intensification of the Siberian High (Wu and Chan, 1997; Yokoi & Matsumoto, 2008), and moves equatorward into the tropics along the East Asia coast over a period of 2–15 days (Ooi et al., 2011; Yokoi & Matsumoto, 2008; Yu et al., 2003). The CS not only leads to severe weather disasters in East Asia via advecting tremendous cold air from high latitudes (Abdillah et al., 2021; Chan & Li, 2004; Pang & Lu, 2019), but also exerts a considerable influence on the climate of the tropical Pacific (Chan & Li, 2004; Ding & Krishnamurti, 1987; Li, 1990).…”

Combined analysis of early pressure observation data and historical daily weather documents for winter climate reconstruction in Japan

“…3(c)-(d)). The southward expansion of the Siberian High was assumed to have contributed significantly to the southward intrusion of cold air outbreaks in East Asia (Song and Wu, 2017;Abdillah et al, 2021).…”