Summary
This report evaluates the capability of Airport Surveillance Radars (ASRs) for the detection of low altitude wind shear associated with the outflows of dry microbursts. It describes results of simulations of dry microburst observations by an ASR. These simulations incorporated weather and clutter data collected by the FL-2 pencil-beam Doppler weather radar at Denver Stapleton Airport in 1988 and 1989 and clutter data collected by the FL-3 ASR-9 emulation radar at Hunstville, Alabama. The impact of signal strength, overhanging precipitation, and ground clutter on both observability and algorithmic performance are assessed. Principal results of study are the following: 1. Overhanging precipitation and weak signal strength do not, by themselves, prohibit detection of dry outflows; however, occurence of false alarms and biases in velocity estimates indicate that improvements in the dual beam estimator that was evaluated would be required for reliable detection of these events. 2. Ground clutter tends to obscure dry outflow in regions where the difference between median effective clutter reflectivity and weather reflectivity exceeds 17-20 dB. A method for predicting the percentage of missed microburst detections due to ground clutter is used to estimate overall microburst detection probabilities for a "dry" environment such as Denver. Using measured clutter from an experimental ASR in Hunstville, AL, overall microburst detection probability is 83 percent. Using simulated Denver clutter, overall detection probability is 91 percent.