2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/121547A systematic mathematical methodology for derivation of boundary layer expansions is presented. An explicit calculation of boundary layer sizes is given and proved to be coordinates system independent. It relies on asymptotic properties of symbols of operators. Several examples, including the quasigeostrophic model, are discussed.Analysis of PDEsMathematical Physics35Q30text