A Numerical Study on Influences of Hurricane Gloria (1985) on the Environment

Abstract

The influence of Hurricane Gloria (1985) on the environment is investigated by comparing hurricane model integrations either including or excluding the hurricane in the initial condition. Results for three cases of Gloria at different states of development are presented. The hurricane's cumulative influence is identified as the differences between the hurricane and nonhurricane integrations. Throughout the integration period, area with sea level pressure differences exceeding 1 hPa in magnitude expanded in each of the three cases and was centered at the hurricane location. The influence radius of the storm, which was determined from the sea level pressure difference field, eventually reached approximately 1500 km in all cases. Comparisons of the sea level pressure differences among three cases showed that the expansion rate differed for each case but was only weakly related to the intensity or intensity change of the particular storm. The comparisons of the wind and temperature fields from the hurricane and nonhurricane integrations indicated that the areas extent of the hurricane's influence was much larger at the upper layer than at the lower layer. A stronger anticyclonic circulation and relatively warmer temperatures developed at the upper layer in the hurricane integration compared to the nonhurricane fields. These upper-layer changes extended over an area comparable in size with the sea level pressure differences. These general features were identified in all three cases. At the lower layer, the differences between the hurricane and nonhurricane wind and temperature fields showed the impact of hurricane on the passage of a cold front over the eastern United States. Apparently, the hurricane's cyclonic circulation at the lower layer affected the movement of the front approaching from the west. The frontal passage was delayed north of the storm in the hurricane integration because of the reduction in the eastward component of the wind. To the south of the hurricane, the westerly winds were enhanced to accelerate the front movement. There were related changes in the fields of precipitation and the low-level temperature; for example, southwest of the hurricane, there was a reduction in the accumulated frontal precipitation in the hurricane integration because of the faster frontal movement.