2002 Annual

Thursday, 17 January 2002: 9:30 AM
Freezing Drizzle (FZDZ) Identification from the Automated Surface Observing System (ASOS):  Status of the ASOS Multi-sensor FZDZ Algorithm
Allan C. Ramsay, SAIC, Sterling, VA
Poster PDF (255.7 kB)
The FAA and the aviation industry have identified freezing precipitation as the most important precipitation type for aviation safety.   Surface observations of freezing drizzle are vital for aircraft deicing opeations, and can also provide significant inputs to in-flight icing forecasts.  Over 600 locations in the United States are now capable of providing automated observations of freezing rain, using the Rosemount 872C3 icing detector on the Automated Surface Observing System (ASOS).  While the ASOS is highly effective in reporting freezing rain, it does not currently report freezing drizzle.  Since the mid 1990's, the National Weather Service (NWS) has sponsored an ASOS Product Improvement Initiative intended to enhance the system's capabilities to identify and report freezing drizzle.  This paper will present results of the most recent field evaluation of a multi-sensor ASOS freezing-drizzle algorithm, conducted over the last winter season (2000-2001).  The paper will briefly describe the algorithm; present comparisons of the potential automated reports with manual observations;  quantify the hours of freezing drizzle that would have been reported had the algorithm been implemented in the ASOS, and include a detailed case study of an icing event which illustrates the performance of the algorithm.  The presentation will conclude with the current implementation status of the algorithm in the Automated Surface Observing System.

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