The Characteristic Feature of Medium Scale Distubances in the Atmosphere (II)

Abstract

The stability of medium scale disturbances is discussed taking into account the latitudinal variation of the perturbations. In connection with this problem, we introduce three parameters, i.e., the Richardson number R_i and the Rossby numbers R_x and R_y in the longitudinal and latitudinal directions respectively. Theoretical consideration shows that according to R_iR_x²_??_R_y² (1- R_i) the baroclinic or shearing instability predominates and it is also shown that the growth rate of disturbances in the latter case is larger than that in the former case. Numerical experiments are also performed in two cases where R_i≈2 and R_i≈1/2 in the lower atmosphere. The case where R_i≈1/2 presents the similar situation with the rapid cyclogenesis of medium scale disturbances along the surface front.