Sensitivity of operational weather radars

Sensitivity, an important performance feature of meteorological radars, is a measure of how well the radar system delivers useful information from weak target echoes. Radar design parameters such as transmitter power, antenna gain, system noise power, radar wavelength, particle size distribution, hardware losses, analog to digital conversion, and signal processing techniques all affect sensitivity. The WSR-88D is known for its excellent sensitivity characteristics, and deployment of the radar network in the 1990's opened many new possibilities for observation of precursor conditions in support of forecast missions. The radar's performance also provided significant research opportunities, especially as related to the behavior of the optically clear atmosphere.

This paper explores methods of estimating radar system sensitivity and presents examples of WSR-88D performance. It also provides a discussion on system design tradeoffs related to sensitivity. The paper documents recent performance estimates and observations of radar system sensitivity resulting from the polarization technology upgrade, currently underway for the WSR-88D. The test team at the Radar Operations Center has access to data from two WSR-88D systems, spaced in close proximity, and operating at opposite ends of the allocated frequency band. This affords a unique capability to explore sensitivity and calibration performance aspects influenced by wavelength differences. The team used observational data to support theoretical analysis and the paper documents this process in detail.