Volume scan strategies for the WSR-74C in support of Space Launch

The Eastern Range's (ER) Weather Surveillance Radar, model 74C (WSR-74C), at Patrick Air Force Base (PAFB), Florida provides the 45th Weather Squadron (45 WS) with dedicated weather radar coverage in the Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS) area. Radar reflectivity data is critical for the evaluation of lightning launch-commit criteria during launch countdowns, for special forecasts for ground processing activities, and for daily warnings of adverse weather required to protect personnel and physical resources on the ER and KSC. Three-dimensional observations of the reflectivity structure of convectively generated clouds are used to evaluate the potential for lightning and severe weather.

The scan strategy calls for a volumetric scan every 2.5 minutes, accomplished by a scan rate of about 6 revolutions per minute (rpm) and consisting of 12 elevation angles. The sequence of scan angles can be selected according to several different criteria. These include contiguous beam coverage at low elevation angles, designed for detailed mapping of precipitation and thunderstorms at ranges beyond 60 nautical miles (nm) or uniform spacing of beams with gaps at moderate elevation angles, designed for optimal observations of precipitation and thunderstorms at ranges within 60 nm. Given the importance of natural and rocket triggered lightning to the 45 WS, scan strategies based on “floating” 0°C to -20°C temperature levels may be useful. These temperature levels could be derived from monthly climatological temperature heights, or could be updated on a day-to-day basis based on local rawinsonde observations. The optimal scan strategy depends on the vertical and horizontal scales of targets of interest and on the interpolation scheme used for display and analysis of the data. An analysis of scan strategies to best meet the different ER requirements is presented and discussed.