New science for the WSR-88D: validating the dual polarization upgrade

The current NEXRAD WSR-88D transmits pulsed electromagnetic waves in a horizontal only, or single polarization, transmission mode. From a high level perspective, horizontal polarization provides information on water content, velocity, and turbulence, which are derived from the three base moments, reflectivity, velocity, and spectrum width. The scientific community has shown that additional information can be derived from transmitting simultaneously two pulses with orthogonal polarizations, also known as dual polarization (dual pol). Through three dual pol variables: differential reflectivity, correlation coefficient, and differential phase, dual polarization provides additional hydrometeor information such as drop size, hydrometeor phase homogeneity, and rain rate, The NEXRAD tri-agencies (DOC, DOD, DOT) determined that adding dual pol to the WSR-88D will improve the mission of the network of weather radars that covers our nation. L3 Communications and Baron Services were contracted to design and implement the dual pol hardware and software upgrades. Since the mission of the Radar Operations Center (ROC) is to manage the life-cycle support of the network of weather radars, we must ensure that all upgrades to the WSR-88D, including the implementation of the dual pol upgrade, maintain the operational standards of data quality and adhere to previous statistical WSR-88D system requirements. This paper outlines the ROC's disciplined, systems engineering approach for validating the implementation of the WSR-88D dual pol upgrade. It will include the methods used to verify the conformity to previous statistical requirements of the base moments and the approach for evaluating the dual pol variables.