System Requirements for Phased Array Weather Radar

Preamble This is the final report to Lockheed Martin on the requirements for a phased array weather radar. Discussed herein are those meteorological requirements that need to be met by weather radars having either reflector type antennas or active phased array elements. These requirements impact the design of the antenna, the transmitter-receiver, and signal processor. Justifications for these meteorological requirements (presented in this report) are based, for the most part, upon meteorological considerations, but sometimes practical limitations of the radar dictate what can be done. Because microwaves penetrate cloud and rain, they are in an unchallenged position to remotely survey the atmosphere. The Doppler radar is the only remote sensing instrument that can detect tracers of wind to reveal a storm's internal structure and the hazardous phenomena harbored therein. The recent inclusion of polarimetric capability to research Doppler weather radars has added a new dimension to radar observations by providing information that can be used to considerably improve the estimation of rainfall, as well as allow for the classification of precipitation type. Thus, included in this report is discussion on the requirements for polarimetric radar. The unique capabilities of the polarimetric Doppler radar make this the instrument of choice to survey weather. 1. INTRODUCTION Weather observations have been part of radar technology since its very beginning. Although military applications have driven this technology and are often credited with its inception, first radar-like instruments were made in the 1920s to remotely probe the ionosphere. Today a similar technology is used to produce vertical profiles of winds throughout the troposphere (to over 15 km above ground). These wind profiling radars operate in the UHF (e.g., 400 MHz) and VHF (e.g., 50 MHz) bands and serve mainly the research community. Nonetheless, specialized applications exist to monitor conditions at launch or landing of space vehicles, and there is even a small experimental network of profiling radars in the central USA.