Sensitivity of an Axi-Symmetric Tropical Cyclone Model to Two External Parameters

Abstract

Article History: Received: 18 Oct. 2018 Accepted: 17 Dec. 2018 More realistic simulation of hazards caused by Tropical Cyclones (TCs) requires knowledge of the mechanisms that formulate tropical cyclone. Here, sensitivity of an idealized framework has been tested to investigate role of two external parameters in vertical entropy flux. The first parameter controls the ratio of width of eyewall and downdraft regions to radius of maximum wind and the second parameter controls radial decay of wind velocity between two regions. This numerical model used conservation principles, assumed axisymmetry and steadiness to model TC vortex, and let ventilation be occurred via the path-ways of downdrafts outside eyewall and eddy fluxes directly into eyewall. To test this framework, Tropical Cyclone Haiyan (TCH, formed over the Western part of Pacific Ocean on 3 November 2013) has been selected. Two kinds of datasets including Joint Typhoon Warning Centers (JTWC) Best Track data of Japan Meteorology Agency and Global Forecast System Analysis (GFS-ANL) data have been used. The model has been run for 60 different configurations, based on change of the two external parameters and size of two random do-mains. The sensitivity of the modeled convective entropy flux to the applied changes has been examined via two different aspects of investigation. In the first aspect, terms of the reference equation of convective entropy flux have been considered and their responses to the changes have been studies. While in the second aspect, values of the convective entropy flux at TCH peak activity time (PAT), before and after that have been inspected. Results, obtained from the first aspect, obviously indicate that the increase of the first external parameter increases the all terms of the referred equation, while increase of the second external parameter influenced the terms differently. Also enlarging the domains’ size does not impress the results similarly. Outcomes of the second aspect reveal that the implemented changes non-uniformly impact the values of the modeled convective entropy flux in the three considered times.