Ducting conditions for electromagnetic wave propagation in tropical disturbances from GPS dropsonde data

Abstract

In this thesis, more than 13000 vertical profiles from GPS-enabled dropsondes, recorded from 1996 through 2010, were analyzed to determine the characteristics of electromagnetic and electro-optical ducting in the boundary layer, an environmental condition that significantly affects the propagation of radio waves. A radio wave propagation duct is formed when there are significant gradients in the humidity and temperature profiles of the atmosphere. In this study, the frequency of occurrence and the characteristics (height, depth, and strength) of a duct are identified using the temperature and humidity profiles measured by dropsondes. The identified ducts are separated based on duct types occurring in the lower troposphere: surface ducts, surface-based ducts, and elevated ducts. We further separate the duct occurrence based on the location relative to their respective storms. Based on the number of soundings in different types of tropical disturbances, we chose to further analyze duct conditions in hurricanes and tropical storms. The results suggest frequent occurrence of ducting, especially elevated ducts. This result is consistent with previous research of a similar nature. However, no preference of ducting was identified in any quadrant of the storm.