全球热带风暴时空分布特点

The statistical characteristics of the spatio-temporal distribution for global tropical storms

对全球三大洋热带风暴的统计分析表明 ,全球热带风暴在时空分布上具有明显的统计特性 .各海域热带风暴都具有季节集中性 .在太平洋和印度洋 ,风暴发生频繁的时间在地理位置上有沿逆时针移动的分布 .全球风暴总数在 8月、9月份明显偏多 ,在 4月、5月份明显偏少 .北半球风暴扩展范围和分布密度大于南半球 ,并以东北太平洋和西北太平洋风暴分布密度为最大 .各海域热带风暴发生频数在统计长度(3 3a)内都表现年际和 1 0年际“振荡” ,不同程度地存在 2～ 3a ,6～ 7a ,1 1～ 1 2a及2 1～ 2 3a的重复性变化 .较强的风暴 ,往往寿命也较长 .在月份之间比较 ,风暴在多发月份 ,一般平均寿命较长 ,强度也较大 ;而在年度之间比较 ,风暴在多发年度 ,平均寿命却往往较短 ,强度也较小 .风暴在大尺度环境中较好地沿反气旋路径向高纬度运动 .

Statistical analysis to the global tropical storms shows that there are some significant statistical characteristics in the their spatio temporal distribution.In every oceanic area,the storm occurring frequency is of seasonal concentration,with the peaks of frequency of the tropical storms corresponding to the peaks of SST.In the Pacific Ocean and the Indian Ocean,the areas of the storm dense months go geographically counter clockwise a year.The total occurrence frequency of the global tropical storms is the highest in August and September,and the lowest in April and May.The occurring density and extending extent of storms are larger in the northern hemisphere than in the southern one.The largest density is located in the North East and West Pacific Ocean.The storm occurring frequency in each oceanic area is of interannual and decadal oscillation,existing distinctly the repeating change of two to three years,six to seven years,eleven to twelve years and twenty one to twenty two years.It is quite often that the stronger the storms,the longer the life spans of the storms.Among months,the stronger and longer lasting storms occur more often in the months with higher storm frequency than in the months with lower storm frequency,yet, among years,the stronger and longer lasting storms usually occur in the years with less storms.In the large scale background,the storm moves along the anticyclonic path.