¥Not
really an extension – given 3 modes, most often space, time, climate variable, choose one as ÔvariableÕ, one as ÔobservationÕ, ignore the third, and do PCA. 6 possibilities.
¥S-mode
most usual: space = variables, time = observations.
¥T-mode,
not uncommon: time = variables, space = observations.