Extended Abstract (376K)6B.2
Important considerations toward developing site-specific scanning strategies for WSR-88Ds
Randy M. Steadham, NOAA/Radar Operations Center, Norman, OK; and R. A. Brown
The lowest elevation angle scanned by all radars in the Weather Surveillance Radar–1988 Doppler (WSR-88D) network is 0.5 deg. Forecasters who use WSR-88Ds—especially those radars located on mountaintops—find that the radars can partially or completely overshoot shallow hazardous weather phenomena (such as microbursts, tornadoes, and shallow heavy precipitation systems). It has been proposed that the elevation angles at appropriate WSR-88D sites be lowered to better detect such weather conditions. Simulations using fine-resolution terrain height data show that coverage of low-altitude phenomena from mountaintop sites would be greatly enhanced by using negative elevation angles. The simulations also show that radars on flat terrain would improve their coverage if the lowest elevation angle were set at 0.2 deg.
There are several factors that must be considered when designing optimum site-specific scanning strategies. Among them are the height of the surrounding terrain relative to the radar height, whether radar coverage can be improved by lowering elevation angles (taking into account the extent of nearby blocking terrain), and radar characteristics such as the wave form, pulse repetition frequency, number of samples, and antenna rotation rate. From a practical standpoint, there is the need to develop only a few sets of lower elevation angles for all of the affected radar sites. Current thinking is that one of three sets of lower angles would be added to one clear-air and one precipitation scanning strategy. For example, for a flatland radar, an additional angle of 0.2 deg would be added. For mountaintop radars, there would be two choices: (1) -0.8, -0.4, and 0.0 deg and (2) -0.4 and 0.0 deg, depending on the height of the radar above the surrounding terrain. Preliminary plans are under consideration for field tests to be conducted at a few flatland and mountaintop WSR-88D sites, but ultimate implementation of the tests depends on the availability of funding.
Session 6B, Radar IIPS and Applications, Part I
Wednesday, 23 January 2008, 8:30 AM-10:00 AM, 207
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