季风指数及其年际变化II·南海夏季风分量动能强度指数及其年际变化

计算了各年南海夏季风建立前后流场的场相似度、场比幅、季风分量动能强度指数和突变度。指出按变差度最大或相似度绝对值最小及其变化最陡以及比幅最小,可客观定量地定出季风来临的预兆日期,在大多年份该日期比用天气气候学方法得到的季风来临(爆发)日期要早些,且两者有较好正相关。绝大多数年份季风建立时有环流突变发生,但也有少数年份呈调和变化或二次突变。季风分量动能强度指数能够反映各年南海夏季风建立后的强度。最后分析指出,南海850 hPa夏季风的前兆日期,突变度和强度指数都有明显的年际和年代际变化。

Monsoon Index and Its Inter-annual Variability Part II: The Kinetic Energy Index and Its Inter-annual Variability in South China Sea Summer Monsoon Region

We calculated the field similarity,field amplitude ratio,the onset day,the kinetic energy intensity of monsoon component and the degree of abruptness for every year in South China Sea summer monsoon region.The "presage day" of summer monsoon in South China Sea region for each year can be determined by the similarity and amplitude ratio.There are minimum of the absolute value of similarity,maximum of the similarity variability and minimum of the kinetic energy of flow field at the "presage day".For most years the "presage day" is a slightly earlier than the "onset day" determined by the conventional synoptic-climatological method.The onset of summer monsoon in South China Sea region is characterized by the abrupt change of flow field in most years,but a few years characterized by harmonic change(no abrupt transition).The kinetic energy intensity index reflects the intensity of monsoon after onset in South China Sea region. The "presage day" and the kinetic energy intensity index and the abruptness undergo pronounced inter-annual and inter-decadal variability.