THE DEPENDENCE OF THE HADLEY CIRCULATION ON THE THERMAL RELAXATION-TIME

Analytic and numerical solutions are found for the nonlinear Hadley ci rculation problem with respect to the dependence of the strength and t he extent of the Hadley circulation on the thermal relaxation time. Th e dependence on the thermal relaxation time is a crucial parameter to investigate since the simplifications used in previous studies assumed a large thermal relaxation time, to justify the geostrophic assumptio n, but in the presence of moist convection, thermal relaxation may be fast in the convection regions. In this study, a primitive equation mo del is used to investigate the effect of different latitudinal distrib ution of thermal relaxation time on the extent of the circulation cell s, the zonal wind, the temperature distribution, and the strength of t he meridional circulations. It is found that the extent of the Hadley circulation is insensitive to the value of the thermal relaxation time tau, while the strength of the circulation is very sensitive to tau ( but in a way that is predictable based on the 1/tau scaling).