Effect of Horizontal Nonuniformity of Diabatic Heating on Tropical Cyclone Intensity and Structure

The effect of the horizontal variation of diabatic heating on the tropical cyclone intensity and structure is studied in this paper. According to the potential vorticity (PV) equation in axis-symmetric cylindrical coordinates, PV disturbance caused by the radial difference of diabatic heating is positive (negative) inside (outside) the maximum heating radius, implying that the radial nonuniformity of diabatic heating should contribute positively to the intensity of a tropical cyclone while negatively to its size. A primitive equation model is then used to get some quantitative ideas on the problem. Results show that the modeled tropical cyclone weakens by about 20% but is larger in size if the effect of horizontal variety of convective heating is excluded in thermodynamic and dynamic equations. The PV disturbance originated from the horizontal nonuniformity of diabatic heating is positive inside the maximum heating radius and negative outside, in consistent with the PV equation analyses. The maximum disturbance (both negative and positive) appears around the maximum heating level and their magnitude is comparable to that generated by vertical variance of heating. It is concluded that the effect of the horizontal heat nonuniformity on the intensity and structure of TC cannot be neglected.