冬季北太平洋副高面积和强度指数的一个计算方案

A calculation scheme of the area and intensity indices on North Pacific subtropical high in winter

月(季)平均海平面气压场中的北太平洋副高(H P)是北半球的永久性大气活动中心,它与大气环流及区域气候异常关系密切。利用闭合气压系统面积指数S、强度指数P简要描述H P性状,并用它们分析H P气候及异常特征,以及H P与热带东太平洋海表温度异常等关系。因冬季H P明显减弱,在计算H P的S、P指数序列时,难以找出适于整个分析时段的、环流意义明晰的特征等压线。针对该问题,本文给出一个计算方案,先选择一个值较高的f0,用它计算多数年份环流指数S、P;再选择一个值较低的^f0,计算少数H P极端偏弱年份的环流指数^S、^P;最后用一元线性回归方程,将^f0计算结果^S、^P订正至f0计算结果 S、P,得到S、P的完整序列。应用结果表明,由此求得的H P该完整序列是适当的。

North Pacific subtropical high（Hp） in monthly and seasonal mean sea level pressure fields is a permanent atmosphere activity center in the Northern Hemisphere, which is closely related to the at- mospheric circulation and regional climate anomalies. The traits of Hp are briefly described by the area and intensity indices of a closed pressure system, and the indices are used to analyze the climate and ab- normal characteristics of Hp, as well as the relationship between Hp and sea surface temperature anoma- lies in the eastern tropical Pacific. Because Hp significantly weakens in winter, when calculating S and P indices of np,it is difficult to find a typical isobar, which can clearly describe the circulation features throughout the analysis period. To solve this problem, a calculation scheme is proposed. Firstly, a higher fo is choosed and used to calculate the circulation indices （S and P） in most years. Then a lower f0 is selected to calculate the circulation indices （S and P） in a few extreme weak years of Hp. Finally, a simple linear regression equation is used to correct the results from S and P indices to S and P indices and the complete sequences of the S and P indices are obtained. The application results show that the obtained complete sequence of Hp is appropriate.