7月青藏高原大气热源空间型及其与东亚大气环流和降水的相关研究
THE MAIN SPATIAL HEATING PATTERNS OVER THE TIBETAN PLATEAU IN JULY AND THE CORRESPONDING DISTRIBUTIONS OF CIRCULATION AND PRECIPITATION OVER EASTERN ASIA
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摘要: 对1958～1999年的7月份NCEP/NCAR再分析资料中青藏高原区域大气热源强度(整层气柱的总非绝热加热率)做旋转经验正交函数分析,结果表明该区域内大气热源强度的空间分布特征复杂,各地差异显著.前4个REOF型的加热中心位于高原东北部、高原西南部、克什米尔地区以及高原东南部地区上空.小波分析还表明各空间型都有2～4a的变化周期.文中计算了前4个RPC与东亚中、低空纬向风(U)、经向风(V)、纬向水汽通量(Qu)、经向水汽通量(Qv)的相关系数,并用这些相关系数构造矢量,进而分析其流场和水汽通量散度场,发现高原不同区域的大气加热异常所对应的东亚大气环流形势及降水也大不相同,由此表明,在研究高原加热对中国气候的影响时,应注意加热的空间分布特征.Abstract: Based on the 1958-1999 monthly averaged NCEP/NCAR reanalysis data,the REOF analysis is applied to get the main spatial modes of normalized atmospheric heating source over the Tibetan Plateau (TP) in July.Results show that the four leading modes locate over the northeast TP,southwest TP,Kashmir and southeast TP respectively,and the cumulative variances are no more than one third of the total.It denotes that the heating source distribution is very complicated over the TP in July.In other words,it is difficult to depict heating spatial distribution with few modes.By using wavelet analysis,2-4 years variation period is identified in these modes.Moreover,correlation coefficients between each RPC and tonal wind U,meridional wind V,tonal moisture flux,meridional moisture flux,and precipitation rate over East Asia are calculated to construct correlation fields.Results show that different heating modes over the TP correspond to different circulation,vapor flux as well as precipitation patterns.Precipitation over North China (or Kashmir) is negatively (or positively) correlated with REOFl.Similarly,notable negative (or positive) correlation can be found between the rainfall over south part of Southwest China,South China,and Philippine (or Japan) and the REOF3.Due to high localization of diabatic heating over the TP,it is not enough to study the influence of TP thermal forcing on the climate with an area-averaged heating index.
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Keywords:
- Tibetan Plateau /
- Atmospheric heating source /
- Circulation /
- recipitation
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