Study of the stable components in extended-range forecasting for the coming 1030 days during the snow storm event in January 2008

Abstract

In this paper we extract components in extended-range forecast for the coming 10-30 days by the Butterworth Band-pass filter using the NCEP/NCAR reanalysis daily data of geopotential height from 1978 to 2007 and from January 6th to February 4th, and at the same time extract the basic function of climate state by empirical orthogonal function (EOF). And we use the same way to deal with the daily data of geopotential height during the snow storm event in January 2008 by the Butterworth Band-pass Filter. We use the contribution rate to explain the variance of EOF and the elements which influence this weather process in a period of 1030 days. Stable components in extended-range forecast for the coming 1030 days can be divided into two parts according to the contribution rate analysis: climatic stable components and abnormal stable components. Results show that climatic stable components are in the subject status during the snow storm event in January 2008 while abnormal stable components are equivalent to a disturbed value superimposed on climatic stable components. The influence of abnormal stable components cannot be neglected, and they can play quite a significant role. The circulation patterns of abnormal stable components correspond well to anomalies in Pacific region. These conclusions deepen our understanding of 1030 days components and provide a new way to think and solve the problem of extended range forecast for the coming 1030 days.