Relationship between the East-Asian Cold Anomalies in Winter of 2010/11 and Blocking

Abstract

An anomalous cold-weather period occurred during January 2011 in East Asia, and this study investigates the event by focusing on the blocking phenomena formed at Northeastern Asia. The area of cold weather is determined to represent the characteristic features of abnormal cold temperature. The 2010/11 winter is divided into three periods P1, P2 (cold period), and P3. For the cold area (30-50 o N, 115-135 o E) the corresponding cold period P2 is determined to be 39 days from 23 December 2010 through 30 January 2011. During P1 and P3 temperature anomalies from the climatological mean are small with large standard deviation compared to those of P2, which has large negative anomaly and small standard deviation. The period P2 is dominated by blocking, which was determined by distributions of 500-hPa geopo-tential height and potential temperature on the 2 PVU surface. Correlation-coefficient analyses show that during P2 the temperature in the cold area is related with pressure of Northeastern Asia, while the temperature during P1 and P3 is related with pressure of Northwest of Korea. Also, during P1 and P3 the temperature pattern shows eastward propagation, but during P2, a stationary pattern. All the observations imply that, during the cold period P2, the temperature in the cold area is related with blocking in Northeastern Asia. During P1 and P3 temperature pattern is related with 500-hPa geopotential height in Siberia, and this relationship is also observed in the climatological mean state. Key words: East-Asian winter temperature, cold temperature anomaly, cold period, blocking 1. 서 론 Choi et al. (2013)은 2010/11년 겨울의 동아시아 한 랭 아노말리 특성 연구에서, 2011년 1월은 그 한달 전 인 12월과 한달 뒤인 2월에 평년과 유사한 기온 분포 를 보이는 것과 달리 거의 한달 이상 이례적인 추위 가 지속되었다는 것을 보고하였다. 추위가 지속되었 던 2011년 1월 동안 시베리아 고기압과 알류샨 저기 압이 모두 발달하였고, 지위고도의 아노말리 분포는 지상에서 성층권 고도까지 순압성을 보이며 알류샨 저기압이 성층권에 이르기까지 같은 지역에 발달해 있어 공간적으로 규모가 대단히 큰 현상이었다. 500 hPa 지위고도 자료를 이용한 행성파 분석에서는, 1월 에 파수 1, 2, 3의 장파가 많이 나타났으며, 중위도대 (30-50 o N)에서는 그 위상이 정체되어 있는 반면 고위 도대(50-70 o N)에서는 급격한 위상변화를 보여 12월, 2 월과는 다르게 나타났다.