日本の梅雨期における降水量の年々変動と東アジアの500mb循環場

Abstract

In order to study relations between Baiu precipitation over Japan and large-scale circulations over East Asia, EOF (Empirical Orthogonal Function) and REOF(Varimax-Rotated EOF) analyses are applied to monthly total precipitation in June and July for a 40-year period between 1948 and 1987, and correlations between monthly mean height anomaly field and EOF and REOF components are examined.From EOF and REOF analysis, indexes of variations of Baiu precipitation are obtained; 1 'st components of EOF which are assumed to represent intensity of Baiu front around Japan, REOF components which represent variations of precipitation in objectively divided regions, and so on.From comparison between the height field and EOF and REOF components, it is shown that, in June, the intensity of Baiu precipitation is positively correlated with the height anomaly in the northern periphery of the Pacific subtropical anticyclone, and that, to the contrary, in July, it is highly correlated with middle-latitude circulations (ex. Baiu ridge or Baiu trough) instead of subtropical circulations.