The Effect of Climate Perturbations on Extratropical Cyclogenesis Along the East Coast of North America.
Large scale snow cover anomalies cause significant changes in the diabatic heating of the earth's surface. It is thought that changes in the diabatic heating can significantly alter both surface temperatures and the storm dynamics of a region. This theory was tested using the GISS 3-D GCM (General Circulation Model). The results of the GCM experiment showed that snow cover caused only a short term local decrease in the surface temperature. The results emphasized the negative feedback which limits the impact of snow cover anomalies over longer time scales. In addition, four East Coast storms were run with varying snow cover and it was found that the snow cover had little impact on the outcome of the storm's intensity and the storm's track. Other boundary conditions were varied as a comparison to snow cover such as sea surface temperatures and topography. All boundary conditions were found to have little impact on the dynamics of all four storms, although sea surface temperatures had the largest effect. The experiment was then expanded to study the impact of varying boundary conditions over much longer time scales. Storm dynamics were compared among different climate change boundary conditions for an entire winter (December-March). Possibly significant changes were found in the storm track and storm intensity of the North Atlantic as boundary conditions varied from a cold climate to a warm climate. As temperatures warmed overall storm intensity increased and the main storm track shifted north and west from an over ocean track to a more inland track. The thesis paper is divided into four chapters. The first chapter discusses modeling work done to determine the effect of anomalous snow cover on surface temperatures, which was published in the Journal of Climate. The remaining three chapters discuss the experiments involving extratropical storm dynamics along the East Coast. The second chapter gives background information on cyclogenesis along the east coast of North America, with special emphasis on explosive cyclogenesis. The chapter then goes on to explain how the experiment was set up and what modifications were necessary in the GCM to better study storm dynamics. The third chapter describes the four real world storms used in the experiment, the four model storms and the various altered boundary condition runs. The storms are described in terms of the synoptic conditions, energy and vorticity quantities. Finally, chapter four compares storm track and storm intensity along the east coast of North America for three different climates: the current climate, an Ice Age climate and a doubled CO _2 climate. The chapter concludes by describing one storm from each climate in terms of synoptic conditions, energy and vorticity quantities.
- Pub Date:
- Geophysics; Physics: Atmospheric Science