Jp1j.14 Differences between Explicit and Approximated Radar Ray Paths Due to the Vertical Gradient of Refractivity

The United States operational WSR-88D Doppler radar radar network (NEXRAD) is becoming increasingly important for improving the real time detection and warning of hazardous weather (Alberty et al. 1991; Crum et al. 1998; Serafin and Wilson 2000). It is viewed as an essential observing system for initializing nonhydrostatic, storm-resolving (i.e., horizontal grid spacing of order 1 km) numerical weather prediction (NWP) models (e.g., Lilly, 1990; Droegemeier, 1990, 1997). Attempts to demonstrate such capability began early in the past decade (e.g., Sun et al., 1991), and subsequent efforts have been notably successful (e.g., Gao et al. 1998; Weygandt et al. 2002a,b; Crook and Sun 2002; Xue et al. 2003; Brewster et al. 2003; Gao et al. 2004, Hu et al. 2005a,b).