Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Clifton E. Dungey, PhD


Meteorologists have encountered problems with the Velocity Azimuth Display (VAD) algorithm in the Weather Surveillance Radar - 1988 Doppler (WSR-88D) System. Under certain meteorological conditions, forecasters have observed differences between the radar's wind profiles and wind profiles from rawinsonde upper-air soundings, or wind profilers. One of the main causes of this problem is inversions in the atmosphere which cause the radar beam to subrefract or superefract, causing the VAD winds to be inaccurately reported at a particular height. This thesis used the WSR-88D Algorithm Testing and Display System (WATADS) to compare VAD winds from recorded Level 2 NEXRAD data at Vandenberg AFB, CA, with rawinsonde wind data and wind profiler data also recorded from Vandenberg. Approximately two weeks of data from each season in which low-level inversions in the atmosphere were present were used in this research. The adaptable parameters of the VAD algorithm were modified to determine if the VAD winds reported by the WSR-88D could be improved. This research discovered that only modifying the VAD range adaptable parameter resulted in any significant improvement in the VAD winds. However, no single range value could be determined to work the best in all cases. The degree to which the range value optimizes the VAD winds is seasonally dependent Overall, changing the VAD range value during low-level inversions might improve the VAD winds at one height, but will probably cause the VAD winds at another height to be unreliable.

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