南亚夏季风爆发的统计动力分析

Statistic Dynamic Analysis on the South Asian Monsoon Onset

作者对南亚(印度)夏季风爆发作了统计动力分析,即将南亚夏季风爆发前后的高低层风场看作一个整体,并以南亚夏季风爆发日为基准,作了经验正交函数(矢量)分析,得到了以下结论:偏差风场的第一模态反映了季风爆发前后大规模的风系变化,其时间系数直接体现了南亚夏季风的爆发,在爆发日前后该模态反映的偏差风系有剧烈变化,这表明季风爆发时大气环流有突变发生;第二模态反映了具有5～7天振荡周期的中纬天气尺度波系及其对低纬季风区的影响;第三模态反映了热带、副热带地区呈准双周振荡的低频扰动.

The three dimensional EOF （Empirical Orthogonal Functions） is used to study the South Asian monsoon （Indian monsoon） onset. The data are accepted based on the date of monsoon onset, from 30 days before onset to 30 days after onset. The upper and lower wind fields are considered as a whole system. The first mode of the deviation wind field shows the rapid changes of the South Asian summer monsoon circulation around the onset and time series reflect the onset of South Asian monsoon and the abrupt change of the atmospheric general circulation. The second mode depicts the mid-latitude synoptic-scale waves with 5-7 days period and the influence on monsoon region in the tropics. The third mode describes the major area of South Asian summer monsoon with quasi-biweekly oscillation.