Weather Support to Deicing Decision Making (WSDDM): A Winter Weather Nowcasting System

This paper describes a winter weather nowcasting system called Weather Support to Deicing Decision Making (WSDDM), designed to provide airline, airport, and air traffic users with winter weather information relevant to their operations. The information is provided on an easy to use graphical display and characterizes airport icing conditions for nonmeteorologists. The system has been developed and refined over a series of winter-long airport demonstrations at Denver’s Stapleton International Airport, Chicago’s O’Hare International Airport, and New York’s LaGuardia Airport. The WSDDM system utilizes commercially available weather information in the form of Next Generation Weather Radar WSR-88D radar reflectivity data depicted as color coded images on a window of the display and Aviation Routine Weather Report (METAR) surface weather reports from Automated Surface Observating System stations and observers. METAR information includes wind speed and direction, air temperature, and precipitation type/rate, which are routinely updated on an hourly basis or more frequently if conditions are changing. Recent studies have shown that the liquid equivalent snowfall rate is the most important factor in determining the holdover time of a deicing fluid. However, the current operational snowfall intensity reported in METARs is based on visibility, which has been shown to give misleading information on liquid equivalent rates in many cases due to the wide variation in density and shape of snow. The particular hazard has been identified ashigh visibility–high snowfallconditions. The WSDDM system addresses this potentially hazardous condition through the deployment of snow gauges at an airport. These snow gauges report real-time estimates of the liquid equivalent snowfall rate once every minute to WSDDM users. The WSDDM system also provides 30-min nowcasts of liquid equivalent snowfall rate through the use of a real-time calibration of radar reflectivity and snow gauge snowfall rate. This paper discusses the development of the system, including the development of new wind shields for snow gauges to improve catch efficiency, as well as the development of the above mentioned real-time method to convert radar reflectivity to snowfall rate on the ground using snow gauges. In addition, we discuss results from a user evaluation of the system, as well as results from an efficiency and safety benefits study of the system.