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

The effect of the horizontal variation of diabatic heating on the tropicalcyclone 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 differenceof diabatic heating is positive (negative) inside (outside) the maximum heating radius, implyingthat the radial nonuniformity of diabatic heating should contribute positively to the intensity of atropical cyclone while negatively to its size. A primitive equation model is then used to get somequantitative ideas on the problem. Results show that the modeled tropical cyclone weakens by about20% but is larger in size if the effect of horizontal variety of convective heating is excluded inthermodynamic and dynamic equations. The PV disturbance originated from the horizontal nonuniformityof diabatic heating is positive inside the maximum heating radius and negative outside, inconsistent 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 byvertical variance of heating. It is concluded that the effect of the horizontal heat nonuniformityon the intensity and structure of TC cannot be neglected.