The original purpose of EOFs was to reduce the large number of variables of the
original data to a few variables, but without compromising much of the explained
variance. Lately, however, EOF analysis has been used to extract individual modes of
variability such as rainfall, (A. Hannachi,2004)
known as teleconnections (Angstr¨om 1935; Bjerknes 1969; Wallace and Gutzler 1981,
etc.). EOFs are presented in section 2.