over, the implementation of such systems in a probabilistic framework allows direct incorporation of uncertainty in forecast decisions (Murphy 1977; Krzysztofowicz et al., 1993; Applequist et al., 2002).
Potential improvements to the radar hardware and operation are building on a flexible radar scan strategy and upgrades to polarimetric capability, which will assist in expanded volume coverage, data quality control, and precipitation estimation. The networking of existing information collected by a variety of operational radar sources in addition to NEXRAD will provide redundancy and offers the potential for improved horizontal and vertical coverage, including better coverage at low levels in complex terrain and offshore. Augmentation of the existing operational radar network may be required to extend coverage to important areas not properly covered or temporarily exhibiting an enhanced threat level.
Current NEXRAD scan strategies, and some of the associated limitations, were discussed in previous chapters. Coverage diagrams in Chapter 7 illustrate the low-level coverage provided by the Sulphur Mountain NEXRAD using the current scan strategies; Paris (1997a, 1997b, 1998, 2001) treated the same topic in some detail. The Paris reports considered only the altitude of the beam axis, and because the NEXRAD beam is nearly 1.0° wide, there is some detection capability below that axis (as the diagrams in Chapter 7 demonstrate). Nevertheless, the extent of coverage at and below 6000 feet above mean sea level (MSL) is limited as long as the minimum elevation angle in the scan pattern is restricted to 0.5°.
It is obvious that use of a lower antenna elevation angle from an elevated radar site would provide greater low-level coverage in directions not obscured by intervening terrain. Brown et al. (2002), Wood et al. (2003a, 2003b), and others have noted advantages that could be obtained by using elevations below 0.5°, perhaps even slightly negative elevations, with NEXRADs at mountaintop sites. The discussion in Chapter 7 demonstrates the improvements in low-level coverage that could be achieved by operating the Sulphur Mountain NEXRAD at elevations down to 0°, or at slightly negative elevations.