Date of Award

January 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Atmospheric Sciences

First Advisor

Gretchen Mullendore

Abstract

Convective hazards such as lightning, hail, and turbulence are known to be

dangerous to aviation. In order to limit aviation accidents associated with convection, the Federal Aviation Administration (FAA) has several avoidance policies in place. Though these policies have been solely based on research performed in the midlatitude, continental United States (U.S.), U.S. aviation operations in the tropics still abide by the FAA avoidance policies. In this study, a limited three year climatology of tropical convection is created using both ground-based and satellite-based radar in the Guam region in order to analyze the frequency of several storm types and to gain a sense of which storm types could most commonly influence aviation. Storm types that are classified are shallow stratiform, isolated, mesoscale convective systems, and tropical cyclones. The results of the climatology indicate that storm type most frequently present near Guam are isolated. In addition, the frequency of storms with higher echo top heights increase during the summer months, suggesting that aviation operations would be most influenced by convection during the summer. The percentage of time that the area coverage of storms exceeds the FAA avoidance policy for thunderstorm coverage also increases during the summer months. Using the Weather Research and Forecast (WRF) model, convection on August 5-6 2005 is simulated to determine the strength and extent of turbulence caused by convectively induced gravity waves. Turbulence is estimated using the Ellrod Index and indicates that Moderate-Severe turbulence is present from 10-20 km, with the greatest concentration of Moderate-Severe turbulence at 14 km throughout the entire simulation period. Further investigation of the Ellrod Index shows a dependency of turbulence strength and extent on the horizontal model resolution. The results from the model simulations are then compared to the avoidance policies set by the FAA to determine if these policies are representative of tropical convection hazards.

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