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

摘要:

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Ŝ、P;最后用一元线性回归方程,将f₀计算结果Ŝ、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。

关键词:冬季北太平洋副高;面积指数;强度指数;计算方案

Abstract:

North Pacific subtropical high(H_P) 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 atmospheric circulation and regional climate anomalies.The traits of H_P are briefly described by the area and intensity indices of a closed pressure system,and the indices are used to analyze the climate and abnormal characteristics of H_P,as well as the relationship between H_P and sea surface temperature anomalies in the eastern tropical Pacific.Because H_P significantly weakens in winter,when calculating S and P indices of H_P,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 f₀ 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 (Ŝ and P) in a few extreme weak years of H_P.Finally,a simple linear regression equation is used to correct the results from Ŝ 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 H_P is appropriate.

Key words:North Pacific subtropical high in winter;area index;intensity index;calculation scheme