冬春季北极海冰的变化特征及其与西北太平洋热带气旋活动的关系探讨

采用Hadley中心1953—2012年海冰密集度资料、NCEP/NCAR逐月再分析资料和1977—2011年日本气象厅台风资料,对冬春季北极海冰变化的主要特征进行了分析,并对冬春季北极海冰变化与西北太平洋台风活动之间的关系进行了初步探讨。结果表明,冬春季北极海冰表现为明显的年代际变化,且在1965—2004年间具有3—4 a的低频振荡周期。在20世纪60年代后期和70年代初期,海冰变化最为显著。冬春季海冰变化与西北太平洋热带气旋生成频次、强度频次的相关性在9月份明显高于其他月份,且为正相关,而与热带气旋强度等级有较显著的负相关性。冬春季北极海冰变化与夏季西太平洋副高强度、副高面积均有很好的负相关关系。冬春季海冰面积偏多(少)时,夏季北美东部、冰岛附近地区、北太平洋以及中低纬度大部地区500 h Pa高度场为负(正)距平分布。冬春季北极海冰面积异常对北半球大气环流的持续性影响,在随后到来的台风盛期有较明显的体现。

Characteristics of winter-spring Arctic sea-ice and its relationship with tropical cyclone in the Northwest Pacific

The spatial and temporal characteristics of Arctic sea ice are studied using the monthly data for sea-ice concentration from the Hadley Center, NCEP/NCAR reanalysis data and best-track data from the Regional Specialized Meteorological Center (Tokyo) Typhoon Center of the Japan Meteorological Agency from 1977 to 2011. The relationship between the winter-spring sea-ice variation and tropical cyclone in the Northwest Pacific is discussed. It is found that the variation of winter-spring sea ice in the Arctic has obvious decadal changes and oscillated with a period of 3—4 years from 1965 to 2004. There were significant changes in sea ice in the late 1960s and early 1970s. The connection between sea-ice anomalies and tropical cyclone is more marked in September than in other months. There is a positive correlation between winter-spring sea ice and tropical-cyclone strength. There is a strong negative correlation between winter-spring sea ice and the Western Pacific Subtropical High. When there is more (less) winter-spring sea ice than average, the summer 500hPa geopotential height is lower (higher) than usual in eastern North American, Iceland, the North Pacific and medium-low latitudes. A persistent relevance between winter-spring sea ice and the northern-hemisphere atmospheric circulation is recognized in the following typhoon season.