Hemispherical mean monthly abnormal geopotential height fields are divided into hemispherical homogeneous and inhomogeneous parts,and corresponding homogeneous anomaly index ξand inhomogeneous anomaly index ηconstructed.The time lag correlation analyses of ξand ηshow that the duration of ξ in Northern(Southern) hemisphere is significant,and it can persist for 1 year(3 years) in January(July) respectively.The persistence of η is not obvious and the duration generally less than 1 month;the stronger perisistence occurs in stratosphere in northern summer with the longest being 4 months.