Eigenvectors for representing the 500 mb geopotential surface over the Northern Hemisphere

Abstract A set of empirical orthogonal functions is produced which enable the large‐scale features of the 500 mb topography over the Northern Hemisphere to be represented with near optimal efficiency. The more important functions are described. Some of the properties of the coefficients of these functions which best represent the 500 mb charts for each day of the years 1965 to 1967 are summarized. The question of the number of functions required to obtain the most satisfactory representation of the 500 mb fields is discussed.