各层北半球环形模态异常与地面大气温度的关系研究

文中研究了不同气压层的北半球环形模态异常时,与之相应的北半球地面大气温度的变化及其月际变率特征。为衡量温度变化的程度,使用偏最小二乘回归方法定义了一个新的耦合指数。该指数定义为对地面气温距平场和北半球环形模态指数做偏最小二乘回归分析的第1主分量。分析表明,该指数可以较准确地表现出北半球环形模态异常时相应的整个温度场变化程度。通过该指数序列分析和环形模态异常时地面气温合成分析,比较了处于不同气压层面的北半球环形模态异常与地面大气温度异常的不同关系。(1)不同层面的北半球环形模态异常与同时期的地面温度关系比较:1月对流层中高层的北半球环形模态异常与1月地面温度异常关系最密切,密切程度超过其他气压层的北半球环形模态异常,与2月地面温度关系较显著的是1月平流层低层的北半球环形模态异常;(2)环形模态异常与地面气温耦合关系的月际变率分析结果:1月位于对流层中高层的北半球环形模态异常与1月地面气温耦合关系最强烈,与其他各月地面气温的耦合逐月递减,4月之后变得不明显;1月平流层低层的北半球环形模态异常除了与1月气温关系密切外,还与2、3月地面气温关系密切,4月之后不明显。

VARIABILITY OF COUPLING BETWEEN SURFACE AIR TEMPERATURES AND NORTHERN ANNULAR MODES AT VARIOUS LEVELS

This article focuses on variability of the couplings between surface air temperatures(SAT) and northern annular modes(NAM) at various levels.To measure the coupling intensity of whole SAT and NAM anomaly fields,the coupling index has been defined as the leading principal component of the Partial Least Squares Regression model of SAT anomaly,and both the composite analysis and the coupling index have been used to reveal level-by-level and monthly variability of the coupling relations between upper anomalous northern annular mode and surface air temperature in the northern hemisphere.The major results are as follows:January SAT anomalies are stronger coupled with the January NAM anomaly at the middle-upper tropospheric levels than those at the other levels,while February SAT anomalies with the January NAM anomaly at the lower stratospheric level.The January NAM anomaly at the middle-upper tropospheric levels is strongest coupled with January SAT anomaly,and the coupling intensity is successively reduced month by month and becomes trivial after April;and the January NAM at the lower stratospheric level is stronger coupled with January as well as February and March NAM anomalies,but the coupling becomes trivial after April.