摘要
季风环流可以分解为经向环流和纬向环流。使用NCEP和ECMWF再分析资料,计算亚洲季风区的经向动量环流和纬向动量环流强度的季节内和年际变化,结果表明:对于南亚夏季风和东南亚-西太平洋夏季风,其各自的经向环流和纬向环流的季节内变化和年际变化存在着相当的联系,尤其东南亚-西太平洋夏季风。但南亚夏季风的经向环流和纬向环流的年际变化在不同月份有着不同的关系。对于东亚夏季风,经向环流和纬向环流变化之间的相关在季节内尺度上是线性独立的,而在年际尺度上存在一定的联系。作者指出:这种大尺度上的联系是通过科里奥利力发生作用,并且受热源调节的。同时局地的对流和辐射相互作用则在某种程度上削弱这种联系,导致在不同月份相关程度有所不同。从各季风系统的经向环流之间或纬向环流之间的线性相关看,南亚夏季风,东亚夏季风和东南亚-西太平洋夏季风是相互独立的系统。计算表明,Webster-Yang和Wang-Fan分别提出的南亚夏季风指数在描述纬向环流年际变化上较好,而在经向上勉强令人满意。Wang-Fan提出的描述东南亚-西太平洋夏季风指数,则较好地表示了该区域的经向和纬向环流的年际变化。Goswami提出的季风Hadley环流指数,以及郭其蕴、施能等提出的东亚夏季风指数则较好地描述了相应区域的经向环流圈年际变化,却无法描述相应的纬向环流圈的年际变化。通过计算还表明,NCEP再分析资料和ECMWF再分析资料在1968年以前的南亚季风区和东亚季风区存在着较大的差异。用NCEP再分析资料计算东亚季风区和南亚季风区经向动量环流圈的变率在20世纪60年代较ECMWF的偏大。用NCEP再分析资料计算施能等定义的东亚季风区指数,也较使用ECMWF再分析资料、UCAR的DS010.1及CRU的北半球海平面气压资料计算的偏大。
The monsoon circulation can be decomposed into the zonal circulation and the meridional circulation. The results obtained by use of both NCEP reanalysis data and ECMWF reanalysis data show that the zonal circulation correlates well with the meridional circulation on intraseasonal and interannual timescales for the South Asian and the Southeast Asian-western Pacific summer monsoon, but poorly on intraseasonal timescales and partly on interannual timescales for the East Asian summer monsoon. It＇s suggested that the connection between the zonal circulation and the meridional circulation is accounted for Coriolis force, but regulated by heat source and impaired by the interaction of local convection and radiation. The correlates with the zonal circulations or the meridional circulations over the above three regions are insignificant on interannual timescales. The indices for the South Asian summer monsoon designed separately by Webster et al. and Wang et al. are good indictors of the interannual variation of the zonal circulation, but barely satisfactory of the meridional circulation. The index for the Southeast Asian-western Pacific summer monsoon devised by Wang et al. characterizes both the zonal circulation and the meridional circulation well. The monsoon Hadley circulation index suggested by Goswami and the East Asian summer monsoon index devised by Guo Qi yun and Shi Neng et al. depicts the interannual variation of the meridional circulation in corre sponding region satisfactorily, but fails in the situation of the zonal circulation. There＇re great discrepancies in the East Asia and the South Asia between NCEP reanalysis data and ECMWF reanalysis data before 1968. The variability of meridional momentum circulation in the two regions before 1968 is much larger in NCEP reanalysis data than in ECMWF reanalysis data. The same situation also occurs for the East Asian monsoon index defined by Shi Neng et al. , which is much larger in NCEP reanalysis data than in ECMWF reanalysis data, DS010.1 of UCAR and the Northern Hemisphere sea-level pressure dataset of CRU.
出处
《气候与环境研究》
CSCD
北大核心
2005年第3期323-332,共10页
Climatic and Environmental Research
基金
国家自然科学基金资助项目40233027
关键词
季风
季风指数
动量环流
经圈环流
纬圈环流
monsoon, monsoon index, momentum circulation, zonal circulation, meridional circulation
