최근 동아시아 몬순 변동성과 북반구 대기 대순환과의 상관성 연구

Abstract

본 연구에서는 동아시아 몬순 변동성과 북반구 대기 대순환과의 상관성을 알아보기 위하여 1970년부터 2009년까지의 겨울철 우리나라의 평균 기온과 북극진동, 시베리아 고기압, 알류산 저기압과의 관계에 대하여 조사하였다. 전체 기간 동안에는 모든 대기 순환 지수들이 우리나라의 겨울철 평균 기온과 유의한 상관성을 지니고 있었으나 1980년대 중반에 우리나라의 겨울철에 발생한 기후 체계 변동 이후 북극진동은 우리나라와 매우 밀접한 상관성을 지니게 되었고 시베리아 고기압과 알류산 저기압은 그 관계가 약화되는 현상이 나타났다. 그 원인을 1980년대 중반 이후의 북극진동 위상에 따른 해면 기압 구조의 대칭성 증가로 나타내었으며 북극진동의 대칭성 증가는 하층 바람장과 500hPa 지위고도장의 구조적인 변화를 가져왔다. 이러한 변화로 인해서 우리나라의 겨울철 기온 변동과 북극진동과의 상관성은 1980년대 중반 이전에 비해서 이후에 증가한 것으로 보인다. 이와 같은 대기 순환장의 변화가 동아시아 지역의 기후 변동성에는 어떠한 영향을 주었는지 알아보기 위하여 동아시아 지역의 기후를 나타내는 동아시아 몬순과의 관계를 조사하였다. 겨울철과 여름철의 동아시아 몬순의 세기는 동아시아 겨울철 몬순 지수와 동아시아 여름철 몬순 지수로 나타낼 수 있다. 동아시아 몬순 지수들은 다양한 방법으로 정의되며 다양한 동아시아 몬순 지수들 사이의 관계에서 동아시아 몬순의 예측성을 반영하는 동아시아 몬순 지수들 사이의 Spreadability가 시간에 따라 변화하는 것을 알 수 있었다. Spreadability의 변화 원인을 알아보기 위하여 동아시아 몬순 지수의 정의에 이용한 배경장에 따라 몇 가지의 집단으로 나누었고 그 중 가장 큰 변화를 보인 해면기압을 이용한 집단의 지수들을 중점적으로 살펴보았다. 이 집단의 Spreadability의 변화는 대기 순환장 중 특히 알류산 저기압의 변동과 매우 밀접한 관계를 가지고 있는 것으로 드러났다. 알류산 저기압은 웜풀 지역의 해수면 온도 그리고 시베리아 고기압과 관련성을 갖고 있는 것으로 나타났는데 알류산 저기압의 세기가 약하고 웜풀 지역의 해수면 온도과 밀접한 상관성을 지니면 동아시아 몬순의 Spreadability는 높은 값을 나타냈고 반면 알류산 저기압의 세기가 강하고 시베리아 고기압과 밀접한 상관성을 지니면 동아시아 몬순의 Spreadability는 작은 값을 갖는 것을 알 수 있었다. 이러한 Spreadability의 변화는 동아시아 지역의 기후를 설명하는 정도의 변화를 가져오는데 Spreadability가 클 때는 동아시아 지역의 기후를 잘 설명하지 못하고 예측성이 약화되며 Spreadability가 작을 때는 동아시아 지역의 기후를 잘 설명하고 예측성이 강화된다. |This study investigates the relationship between the Korean temperature and the atmospheric circulation such as Arctic Oscillation, Siberian High and Aleutian Low during the winter (December-January) for the period of 1970-2009. It is found that all indices to represent aforementioned circulations are significantly correlated with Korean winter temperature for the period of 1970-2009 with changing on the low-frequency timescales. There are marked contrasts in such relationship before and after the mid-1980s when a significant regime shift of Korean winter temperature occurred. While Korean winter temperature has a close relationship with Arctic Oscillation after the mid-1980s, its relationship with Siberian High and Aleutian Low is weakened. The composite analysis between a positive and negative phase of Arctic Oscillation before and after the mid-1980s is conducted to examine a recent strengthening of Arctic Oscillation-Korean winter temperature relationship. Our further analysis indicates that the structural changes of low-level wind and the geopotential height at 500hPa between the two phases of Arctic Oscillation are more effective to influence Korean winter temperature after the mid-1980s. This may induce a close relationship between the Korean winter temperature variability and Arctic Oscillation after the mid-1980s compared to before the mid-1980s. In order to look at how the recent changes of atmospheric circulation influences on the East Asian climate variability, we also examine the variability of East Asian monsoon index to measure the East Asian monsoon intensity during the boreal winter and summer. It is found that the spreadability among East Asian monsoon indices, reflecting the predictability of East Asian monsoon, changes on the low-frequency timescales and it is closely associated with the changes of atmospheric circulation in the midlatitude, in particular, the variability of Aleutian low pressure. To understand such characteristics, we investigate the relationships between the East Asian monsoon indices, in particular, the indices based on sea level pressure and the atmospheric circulations. When the intensity of Aleutian Low pressure is weak and correlated with the sea surface temperature over the warm pool region, the East Asian winter monsoon indices have a large spreadability. On the other hand, when Aleutian Low intensity is strengthened and correlated with the Siberian High, the East Asian winter monsoon indices have a small spreadability. Our analysis also indicates that the atmospheric circulation over the Northern Hemisphere, which is associated with the variations of Aleutian low pressure, significantly changes from before the late 1980s to after the late 1980s.; This study investigates the relationship between the Korean temperature and the atmospheric circulation such as Arctic Oscillation, Siberian High and Aleutian Low during the winter (December-January) for the period of 1970-2009. It is found that all indices to represent aforementioned circulations are significantly correlated with Korean winter temperature for the period of 1970-2009 with changing on the low-frequency timescales. There are marked contrasts in such relationship before and after the mid-1980s when a significant regime shift of Korean winter temperature occurred. While Korean winter temperature has a close relationship with Arctic Oscillation after the mid-1980s, its relationship with Siberian High and Aleutian Low is weakened. The composite analysis between a positive and negative phase of Arctic Oscillation before and after the mid-1980s is conducted to examine a recent strengthening of Arctic Oscillation-Korean winter temperature relationship. Our further analysis indicates that the structural changes of low-level wind and the geopotential height at 500hPa between the two phases of Arctic Oscillation are more effective to influence Korean winter temperature after the mid-1980s. This may induce a close relationship between the Korean winter temperature variability and Arctic Oscillation after the mid-1980s compared to before the mid-1980s. In order to look at how the recent changes of atmospheric circulation influences on the East Asian climate variability, we also examine the variability of East Asian monsoon index to measure the East Asian monsoon intensity during the boreal winter and summer. It is found that the spreadability among East Asian monsoon indices, reflecting the predictability of East Asian monsoon, changes on the low-frequency timescales and it is closely associated with the changes of atmospheric circulation in the midlatitude, in particular, the variability of Aleutian low pressure. To understand such characteristics, we investigate the relationships between the East Asian monsoon indices, in particular, the indices based on sea level pressure and the atmospheric circulations. When the intensity of Aleutian Low pressure is weak and correlated with the sea surface temperature over the warm pool region, the East Asian winter monsoon indices have a large spreadability. On the other hand, when Aleutian Low intensity is strengthened and correlated with the Siberian High, the East Asian winter monsoon indices have a small spreadability. Our analysis also indicates that the atmospheric circulation over the Northern Hemisphere, which is associated with the variations of Aleutian low pressure, significantly changes from before the late 1980s to after the late 1980s.