order4dThe aim of this paper is to investate a reduced-order approach for four-dimensional variational data assimilation (4D-Var), with an illustration in the context of oceanWhen you play Permutation Bet, you cover all possible permutations of the 4D number you picked. For example, if you play Permutation Bet on 1133, you cover 1133, 1313, 1331, 3131,