Analysis of Atmosphere-Ocean Interactions over South China Sea and its Relationship with Northeast Asian Precipitation Variability during Summer

Abstract

This study investigates the changes in the atmosphere-ocean interactions over the South China Sea (SCS) by analyzing their variables in the period of 1979~2011 during the boreal summer (June-July-August). It is found that a simultaneous correlation coefficient between sea surface temperature (SST) and precipitation over SCS during summer is significantly changed before and after the late-1990s. That is, the variation of precipitation over SCS is negatively (positively) correlated with the SST variations before (after) the late-1990s. Our further correlation analysis indicates that the atmospheric forcing of the SST is dominant before the late-1990s accompanying with wind-evaporation feedback and cloud-radiation feedback. After the late-1990s, in contrast, the SST forcing of the atmosphere through the latent heat flux from the ocean to the atmosphere is dominant. It is found that the change in the relationship of atmosphere-ocean interactions over SCS are associated with the changes in the relationship with Northeast Asian summer precipitation. In particular, a simultaneous correlation coefficient between the precipitation over SCS and Northeast Asia becomes stronger during after the late-1990s than before the late-1990s. We argue that the increase of the SST forcing of the atmosphere over SCS may lead a direct relationship of precipitation variations between SCS and Northeast Asia after the late-1990s. 1. 서 론 서태평양과 인도양사이에 위치하는 남중국해는 남 동아시아에서 가장 큰 연해이다. 남중국해는 분지형 태로 평균수심은 1800 m이고 중앙 분지에서 최대수 심은 5400 m에 이른다(Twigt et al., 2007). 남중국해 는 남동아시아 몬순 시스템에 영향을 받으며, 남중국 해 주변 지역의 바람 분포에 의하여 다양한 표층 순 환이 발생하는 것으로 알려져 있다(Wyrtki, 1961; Shaw and Chao, 1994; Chu et al., 1999; Hu et al., 2000; Liu et al., 2001a, b; Centurioni et al., 2009). 여름철 남중국해 지역에서는 남서풍이 주풍을 이루며, 시계 방향의 표층 순환이 우세하게 나타나는데 이러한 흐 름은 베트남 연안에서 용승현상을 유발시켜 표층 수 온을 차갑게 유지시킨다. 특히 이 지역에서 표층의 순 열속은 표층 수온 변동에 주요한 요인이며(Liu et al., 2001b; Qu, 2001), 단파복사와 잠열 또한 표층 수온의 증가 및 감소에 주요한 요인으로