EdGCM climate model provides an interface to the NASA GISS-II global climate model. The purpose of this simulation is to use the EdGCM modeling software to evaluate the effects of future changes in greenhouse gas concentration on the parameters for tropical cyclone formation.
The model used by EdGCM operates at a grid spacing of eight degrees latitude and ten degrees longitude. This grid spacing is much too coarse to model actual tropical cyclones, which have much higher wave numbers than can be resolved at this grid spacing However, the model simulation may be of use in evaluating the parameters that are considered favorable for the formation and development of tropical cyclones.
A number of parameters are of interest in evaluating the formation of Atlantic tropical cyclones. For example, one useful parameter is sea surface temperatures in the Atlantic basin. Warmer sea surface temperatures are favorable for tropical cyclones. Also of interest is the mid-level relative humidity over the Atlantic. Higher mid-level relative humidity is also favorable for tropical cyclone development. Vertical wind shear is unfavorable for the development of tropical cyclones and is another parameter investigated in this study. Gray (1987) suggests that strong hurricanes in the Atlantic basin are related to rainfall in the Sahel region of Africa, and is another parameter studied in the simulations.
A variety of scenarios for greenhouse gas concentration in the atmosphere are evaluated extrapolating current trends through 2050 with various modifications for increases or decreases in current trends. Future concentrations of greenhouse gases in the atmosphere are subject to many factors, many of which cannot accurately be predicted. Therefore it is useful to simulate a variety of scenarios to determine the range of possible effects of greenhouse gas concentration increases on tropical cyclone formation parameters.