东亚-北太平洋副热带海气耦合模态及其对降水的影响

利用53年的NCEP/NCAR再分析资料和英国气象局Hadley气候预测和研究中心的海表面温度资料,使用SVD方法研究了东亚-北太平洋地区表层海温(SST)异常与大气环流异常间的主要耦合模态.分析结果表明,中纬度北太平洋地区存在两种主要的海-气耦合模态,第一模态是海温异常分布的纬向型,第二模态主要表现为经向海温差异分布.两种空间耦合模态共同反映出中纬度北太平洋地区大气和海洋的异常中心有很强的局地耦合性.在第一模态的正(负)异常年,东亚-北太平洋地区主要为负(正)的降水异常,在第二模态的正(负)异常年,东亚和北太平洋的大部分地区出现降水正(负)异常,北美西岸及以西的部分区域出现降水的负(正)异常.两个模态所对应的降水差异显示,海气耦合模态的循环变化有利于形成我国降水分布南北差异的改变.

THE AIR-SEA COUPLED MODE IN EAST ASIA-SUBTROPICAL NORTH PACIFIC AND ITS IMPACT ON RAINFALL

53-year National Centers for Environmental Prediction/National Center for Atmospheric Research (USA) reanalysis data and sea surface temperature data of the Hadley Center, United Kingdom Meteorological Office, are used in singular value decomposition (SVD) analyses to investigate the leading coupled modes between the sea surface temperature anomalies (SSTA) and the atmospheric circulation anomalies in the East Asia-subtropical North Pacific region. Results show that there are two leading coupled modes between the atmosphere and ocean, particularly in the mid-latitude North Pacific region. For the first mode, the SSTA is a pattern with zonal distribution. For the second mode, the SSTA is of meridional distribution. Two air-sea coupling modes exist in the mid-latitude North Pacific; the first is a zonal pattern of SSTA and the second a meridional one. The two spatial coupling modes reflect, jointly, that local coupling is strong in the anomalous atmospheric and oceanic centers in the East Asia-North Pacific region. Further analysis suggests that years of positive (negative) SST anomalies with the first mode are associated with years of negative (positive) precipitation anomalies in the East Asia-North Pacific region; years of positive (negative) SST anomalies with the second mode are accompanied with years of positive (negative) precipitation anomalies in most of the East Asia-North Pacific region and negative (positive) precipitation anomalies in the west coast of North America and part of area to the west. The difference of precipitation anomalies corresponding to the two modes shows that the cycle of coupled modes is favorable to pattern changes in the north-south difference of precipitation in China.