Modelling the Synoptic Scale Relationship between Eddy Heat Flux

A simple statistical-dynamical model relating synoptic scale changes in the meridional temperature gradient to changes in the meridional eddy sensible heat flux is developed. The model solution is compared with observations relating the flux to the stability parameter for the two layer model which, assuming the variance of the critical shear in the two layer model is negligible, is equivalent to the meridional temperature gradient. The comparison suggests that a diabatic time scale of about one day is appropriate for perturbations due to changes in the flux, and that roughly one half of the variance of the temperature gradient can be ascribed to processes with time scales much less than the synoptic time scale. The possibility that variations in the critical shear are important is discussed. Feedback of the temperature gradient on the flux is added to the model. Three model parameters emerge which, if properly tuned, could yield significantly better results than the model without feedback. Although this provides supporting evidence for the presence of feedback, other more justifiable mechanisms yield similar results. Thesis Supervisor: Peter Hunter Stone Professor of Meteorology Title: