夏季副热带涡旋活动的气候学研究

A CLIMATOLOGICAL INVESTIGATION OF THE ACTIVITY OF SUMMER SUBTROPICAL VORTICES

引入新的涡旋识别方法,在全球副热带选取西北太平洋、东北太平洋、西北大西洋、东北大西洋和澳洲及其附近南太平洋5个涡旋活动代表性区域,用1985—2002年夏季ECMWF40年再分析资料统计,再用同期NCEP40年再分析资料对比,研究了副热带涡旋的气候学问题。结果表明:(1)两种再分析资料得到的涡旋空间分布型在5个区域都有较好的一致性,其中西北太平洋区域两种资料的相关性最好。(2)NCEP再分析资料得到的涡旋频数和强度都明显弱于ERA40计算结果,这主要是由于两种再分析资料的模式分辨率不同而造成的。(3)5个区域的涡旋活动主要分布在近海和海陆交界处,向陆地和内海方向减少。(4)西北太平洋有两个涡旋活动的高值中心:一个位于中国南海,另一个位于菲律宾东侧向北分布至中国黄海的西太平洋近海海域,为5个研究区域中面积最大。(5)西北大西洋的涡旋活动主要分布在从巴拿马地区向西侧太平洋延伸的纬度带内。(6)东北太平洋和东北大西洋的涡旋活动分布型相似,都位于5°—20°N的纬度带内,由海陆交界处伸向海洋。(7)澳洲及其附近南太平洋区域的涡旋活动不如其余4个区域强,主要分布在赤道一侧的近海区域。(8)除西北太平洋和西北大西洋区域外,其余两种再分析资料得到的3个区域涡旋活动年际变化有较大差异。(9)在西北太平洋和西北大西洋区域,涡旋活动的频繁程度没有表现出长期趋势,但具有清楚的阶段性特征,且两个区域的年际变化并不相同。(10)西北太平洋区域从20世纪80年代中期以来,涡旋个体强度呈增强趋势,这个增强的趋势在全球副热带地区最为明显。西北大西洋在90年代中期以前,涡旋强度有显著增强的趋势,而之后减弱。

By utilizing a new vortex detection method and the ECMWF 40 years re-analysis data from 1985 to 2002, the climatology of summer vortices is investigated in five subtropical regions, which are the western North Pacific, the eastern North Pacific, the western North Atlantic, the eastern North Atlantic and the Australia near ocean. After that, results are validated by NCEP/NCAR re-analysis data. It was shown that： （1） The spatial distributions of ERA40 vortices activities （VAC） were well consistent with those of NCEP re-analysis （NRA） vortex activity in all regions, especially in the western North Pacific. （2） Because of different model resolution, the NRA vortices＇ number （intensity） were clearly less （weaker） than ERA40 vortices＇. （3） Vortices mainly cruised in coasts and the adjacent seas, from where to the land or to the open sea vortex activities are decreased gradually. （4） There were two active centers in the western North Pacific. one was located in South China Sea; and the other, as the largest area of five regions, spread from the east side of Philippines to Japan. （5） Over the western North Atlantic, most vortices occurred in the Panama area and its west-side offshore. （6） The vortex distributions were similar between the eastern North Pacific and the eastern North Atlantic, both spreading from the coast to the west-side sea in 5°- 20°N zone. （7） In the Australia near ocean, vortices are not as active as those in the other four regions, and mostly take place in the equator-side of near ocean areas. （8） Aside from the western North Pacific and the western North Atlantic, the VAC annual variations in other three regions were different between ERA40 and NRA. （9） The VAC annual variation could be separated into several distinct stages in the western North Pacific and the western North Atlantic. （10） Since the mid 1980＇s, the mean vortex intensity was getting increased in the western North Pacific, which was most significant in the subtropical areas on a global basis. In the western North Atlantic, there was a decreasing （increasing） trend of the mean vortex intensity before （after） the mid 1990＇s.