ANNUAL AND INTERANNUAL VARIATIONS OF EARTH-EMITTED RADIATION BASED ONA 10-YEAR DATA SET - COMMENT

Bess et al. [1992] have stated that empirical orthogonal functions com puted from spherical harmonics amplitudes and transformed into grid po int space are identical to empirical orthogonal functions (EOF) of gri d point data derived from the transformed amplitudes if and only if an equal area grid is used. It will be shown that this does not hold in general and that there is always a one-to-one correspondence between E OF's in spherical harmonics or grid point representation. The equal ar ea grid is only a special case of a more general approach. A simple ex ample is given to illustrate the results of the mathematics.