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Marilyn M. Wolfson

Abstract

This report describes in detail the FLOWS (FAA-Lincoln Laboratory Operational Weather Studies) automatic weather station network which is being used in the Terminal Doppler Weather Radar program to assess the radar detectability of wind shear and to help gain an understanding of microburst forcing mechanisms. The weather stations are descended from the PROBE stations originally operated by the Bureau of Reclamation. The current instrumentation has been modified slightly but is largely the same as that originally used as is the hardware structure, but the data collection platforms are entirely new. Each station in the 30-station network transmits 1 min averages of temperature, relative humidity, barometric pressure, wind speed, wind direction and precipitation amounts, as well as peak wind speed, on a single GOES satellite channel.

Performance results from the first 3 yr (1984–86) of mesonet operations are presented. During June and July 1986 the FLOWS network was collocated with the NCAR PAM-II network near Huntsville, Alabama to measure surface data on microbursts as part of the Cooperative Huntsville Meteorological Experiment (COHMEX). A preliminary assessment of the overall performance of the two networks suggests that they performed with comparable accuracy for those meteorological characteristics most important to the detection of microbursts. While differences and discrepancies were noted, none would preclude treating PAM-II and FLOWS data together as if they were generated by a single network.

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Diana L. Klingle, David R. Smith, and Marilyn M. Wolfson

Abstract

Gust fronts produce low altitude wind shear that can be hazardous to aircraft operations, especially during takeoff and landing. Radar meteorologists have long been able to identify gust front signatures in Doppler radar data, but in order to use the radar efficiently, automatic detection of such hazards is essential.

In a study designed to accumulate statistics on the gust frontal signature in Doppler radar data, nine gust front cases were analyzed. Data were collected on those characteristics thought to be most important in developing rules for automatic gust-front detection such as gust front length and height, maximum and minimum values of reflectivity, velocity and spectrum width, and estimates of radial shear. To provide the reader with a concrete example, photographs of the Doppler radar displays of just two (in the interests of brevity) of the nine gust fronts are presented and discussed, as well as summary data for all cases. For these cases, outflows could be detected most reliably in the velocity field. Line features in the spectrum width and reflectivity fields associated with some of the gust fronts could also be identified, although somewhat less reliably than in the Doppler velocity.

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