Interannual Variability of Mascarene High and Australian High and Their Influences on East Asian Summer Monsoon

Abstract

Based on the reanalysis data from NCEP/NCAR and other observational data, interannual variability of the Mascarene high (MH) and Australian high (AH) during boreal summer from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), and MH tends to be intensified with the development of the circumpolar lows in high southern latitudes. On the other hand, AH is correlated with AAO as well as El Niñ o and Southern Oscillation (ENSO), and tends to be intensified when El Niñ o occurs.Since AH, especially MH, is positively correlated with AAO, composite analysis on the difference between the positive and negative MH is performed to reveal the physical mechanism responsible for the East Asian summer monsoon anomalies associated with AAO. The result shows that, with the intensification of MH, the Somali jet, and Indian monsoon westerlies, tend to be strengthened. Accordingly, AH and the associated cross-equatorial flow, become stronger whereas the trade wind over the tropical western and middle Pacific become weaker. In association with the above changes, convective activities near the Philippine Sea are largely suppressed, as a consequence, exciting a negative convection anomaly, and a Rossby wave train from East Asia via the North Pacific to the western coast of North America (a negative Pacific-Japan pattern). Corresponding to the negative Pacific-Japan pattern, an anomalous rainfall pattern appears in East Asia.Correlation analysis between AAO and sea level pressure, 500 hPa geopotential height further indicates that AAO is a strong signal influencing the climate anomaly in both hemispheres, including East Asia. Due to the seasonal persistence, AAO and the related MH and AH in boreal spring, may provide some useful information for the East Asian summer monsoon prediction. With the intensification of MH during boreal spring through summer, the Meiyu/Baiu rainfall from the Yangtze River valley to the Japan Islands tends to increase, while less rainfall is found outside of this region. In contrast with MH, the effect of AH on summer rainfall is confined to southern China.

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

“…2a). Many studies on the variability of the location and strength of the Mascarene High (Terray et al 2003;Suzuki et al 2004;Xue et al 2004;Fischer et al 2005;Feng et al 2013;Manatsa et al 2014;Morioka et al 2015) have noted that the Mascarene High influences monsoonal flow and SST variation over the Indian Ocean. According to the large-scale environmental conditions shown here, the weakening and southward shift of the Mascarene High could be one of the favorable environmental conditions enabling the MJO onset to break the convective suppressed period of P1 over the equatorial Indian Ocean.…”

Relationship between rainfall in Korea and Antarctic Oscillation in June

“…후자의 지역은 수도권으로서 이 지역에 서의 온실효과와 연관되어 최근 강우량의 증가와 함 께 강우 강도 역시 크게 증가한 지역이다 (Choi, 2004;Chang and Kwon, 2007). (Xue et al, 2004). 머스커렌 고기압은 이전연구에서 이미 인도 여름몬순 변동의 주 요인 중의 하나임이 분석된 바 있다 (Krishnamurti and Bhalme, 1976;Ramaswamy and Pareek, 1978;Rodwell, 1997).…”

“…또한 호주 고기압은 동아시아 여름 몬순 시작시에 호주 지역에 강한 한파를 유발하여 열대서태평양으로 적도 횡단류를 강화시키며, 이는 다시 북태평양 고기압을 북쪽으로 발달시켜 결국 강 우대를 북상시키는 역할을 한다. 따라서 많은 이전 연구에서 호주 고기압이 동아시아 여름몬순 시작과 강우량의 변동에 결정적인 역할을 함이 보여졌다 (Tao et al, 1983;Xue et al, 2004). 본 연구에서도 양의 남극진동 해 동안 뉴질랜드 부근에 중심을 둔 고기 압으로부터 비교적 찬 성질을 가진 적도 횡단류가 강화되었고, 이로 인해 북태평양 고기압이 북쪽으로 좀 더 발달하였음이 분석되었다.…”

Precursory influence of the Antarctic Oscillation on the onset of Asian summer monsoon

“…Before the onset of ASM, the SCEF experiences an abrupt increase, which impels an eastward propagation of the westerly flow over the Bay of Bengal (BOB), and promotes an eastward withdrawal of the western Pacific subtropical high (WPSTH) from the SCS to the western Pacific, triggering the burst of ASM. As mentioned above, the SH subtropical high has a close relationship with the SCEF [14]. Since the pressures in the subtropics and higher latitudes in the SH have opposite variations, can the influencing factors of ASM be extended more southward to the South Pole area, i.e.…”

“…For example, following a strong AAO in boreal spring, both the MH and the AH enhance, and more summer rainfall occurs from the Yangtze River valley in China to Japan. So besides ENSO, AAO is another precursory signal for the interannual variation of summer rainfall in East Asia [14]. Among different influencing processes, the SCEF plays a key role and its interannual variability is tightly linked with the abnormal wave trains along the coast of East Asia.…”