Analysis of microburst observability with Doppler radar through comparison of radar and surface wind sensor data
Summary
As part of the FAA Terminal Weather Doppler Weather Radar (TDWR) measurement program in Huntsville, AL and Denver, CO during 1986 and 1987, respectively, the ability of a single Doppler weather radar to observe microburst outflow signatures (i.e., show identifiable radial velocity patterns) was assessed by comparing radar-observed microbursts with those identified by joint use of both radar and data from a mesoscale network (mesonet) of surface meteorological stations (Clark, 1988; DiStefano, 1988). Observability by radar must be considered together with pattern recognition algorithm performance for observable microbursts (Campbell et al., 1988) in order to fully assess the potential effectiveness of an automated microburst detection system which relies on data from a single Doppler radar. The comparison of radar and surface sensor data presented here investigates the possibility that some outflows may not be observable by radar due to: (1) low SNR (signal-to-noise ratio), (2) very shallow outflows for which the radar beam is scanning too high above the surface, (3) blockage of the beam, and/or (4) asymmetry in the surface outflow causing the radar to significantly underestimate the magnitude of the surface wind shear (Eilts and Doviak, 1987; GAO, 1987). Also addressed is the possibility that microbursts are not observed by the mesonet surface sensors because the spacing between stations is too great, or because the microburst outflow does not reach the surface due to a dense layer of cold air at the surface.