At-sea demonstration of the SPS-48E radar weather extraction capability

The SPS-48E is a S-band, long range, air defense, volume scanning radar onboard US Navy aircraft carriers and large deck amphibious ships. It operates with multiple pencil beams in a rotating phased-array antenna that scans electronically in elevation, and completes a volume scan in 4 seconds. A Weather Extractor Computer (WEC) and a Weather Data Interface Card (WDIC) have been developed for the SPS-48E that provide Doppler data at the lowest three elevation scans and reflectivity data at all elevation scans in Universal Format (UF). In early 2006, a prototype WEC and WDIC were successfully tested by the US Navy using a land-based SPS-48E, and then later deployed onboard the USS PELELIU for an at-sea demonstration.

This paper demonstrates nowcasting products derived from archived SPS-48E UF data obtained during the USS PELELIU's encounter with hazardous weather near Hawaii on February 22, 2006. The commanding officer of the PELELIU used the SPS-48E weather radar data to guide operational maneuvers around the storm cells that day. The UF data files contained 22-elevation volumes scans with an azimuthal resolution of 1 degree and a range resolution of 0.915 km, executed at a frequency of 5 minutes for 22 hours. The maximum range for reflectivity (radial velocity) data was 275 (52) km. The data products were produced from the UF data after undergoing quality control for radial velocity aliasing, clutter and artifacts. Basic products such as single-elevation displays of reflectivity and radial velocity, and vertical profiles of Velocity Azimuth Display winds were produced. Also, the Naval Research Laboratory (NRL) UF data decoder and three-dimensional reflectivity mosaic system software were adapted to handle a radar coordinate origin that corresponds to the ship's geographical location at the start of each volume scan. Composite reflectivity data from the mosaic grid, covering 6.7 degrees latitude by 7.1 degrees longitude, were used by the NCAR TITAN storm identification and extrapolation system to successfully nowcast the storm cell movement out to 60 minutes. These products demonstrate the readiness of NRL to process SPS-48E data and extract valuable weather information that would be available in real-time on Navy nowcasting systems and serve to support tactical decision making. In the near future, these SPS-48E data and the adapted software will also be applied to a variational radar data assimilation system under development for the Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model.

COAMPS is a registered trademark of the Naval Research Laboratory.