Geographical Variablity of the Width of the Tropical Belt

Abstract:

A number of recent studies have found evidence for a widening of the earth's tropical belt (Seidel et al). Most studies focus on the annual mean zonal mean tropical belt width. The purpose of this research, however, is to determine the longitudinal variability of the width of the tropical belt. We study how well defined the boundaries of the tropical belt are in both hemispheres as a function of longitude as well as season. The sharpness of the tropical boundaries as a function of longitude can provide information, which is otherwise hidden in the more commonly studied zonal averages. Localized widening of the tropical belt is expected to have a bigger climatic impact for a very sharp tropical boundary encompassing a drastic distinction between the climates of the tropics versus the subtropics. An improved understanding of the morphology of the tropical belt can help us determine any changes regarding these regions surrounding the edges of the tropics. By locating the subtropical tropopause break, a region where the tropopauses’ altitude drastically shifts, the boundaries of the tropical belt can be observed. By finding the gradient of the tropopause break, we can determine the sharpness of the tropical boundaries. It was found that during each hemisphere’s respective summer season the tropical belt edge over the Pacific and Atlantic oceans can display a tendency to be very fickle and thus poorly defined. For all times of the year, however, it is shown that the tropopause break in each hemisphere’s respective winter and over land has the tendency to create a well-defined and sharp tropical edge.