摘要
利用 NCEP/NCAR的 1 982～ 1 994年全球 1 2层等压面上的风场资料 ,计算了大气流场的正压分量 (即质量加权垂直平均 )和斜压分量 (即各层实际风与正压分量的差值 ) ,分析了全球冬夏季正斜压流场的分布特征 ,并从地面风场的正斜压流型角度对全球季风进行了分类。指出 :斜压流场和正压流场的季节变化都可以产生冬夏季盛行风向的反转 ,因而都能够产生季风。斜压流场反映了大气中不均匀加热 (主要是海陆热力差异 )所驱动的热力环流 ,而正压流场则主要代表动力作用所产生的环流 ,这对认识季风的性质很有意义。进一步分析表明 :亚洲热带地区、非洲、南美等典型季风区属斜压流型季风区 ,南、北半球太平洋中部的副热带地区也为季风区 ,但属正压流型季风区 ,而东亚副热带地区则属正斜压流型共同组成的混合流型季风区。
By using 1982～1994 NCEP/NCAR wind data,the atmospheric flow field is decomposited into two parts:the barotropic one, i.e. the vertical mass weighted integral,and the baroclinic one, i.e. the difference between the observed winds at a certain level and the barotropic component; The distribution feature of barotropic/baroclinic flow field in winter/summer are investigated. Monsoon is classified into three types based on the barotropic/baroclinic flow patterns at the lower troposphere. It is pointed out that the seasonal variation in the circulations of baroclinic and barotropic components are responsible for the reversal of surface winds between winter and summer, thereby for generating monsoon. The baroclinic flow field is a thermally driven circulation which is mainly caused by land sea thermal contrast, while the barotropic flow field is mostly a dynamically driven circulation. So such a decomposition is helpful for understanding the causes of monsoon. Results also show that the monsoons over tropical Asia, Africa and South America are barotropic flow pattern, while the monsoons over subtropical Pacific in the Northern and Southern hemisphere are of baroclinic flow pattern and the East Asia subtropical monsoon is of barotropic/baroclinic mixed flow pattern.
出处
《气象学报》
CSCD
北大核心
2000年第2期194-201,共8页
Acta Meteorologica Sinica
基金
国家自然科学基金会资助!( 4973 51 70 )
