The NCAR GPS Dropwindsonde

The National Center for Atmospheric Research (NCAR), in a joint effort with the National Oceanic and Atmospheric Administration (NOAA) and the German Aerospace Research Establishment, has developed a dropwindsonde based on the Global Positioning System (GPS) satellite navigation. The NCAR GPS dropwindsonde represents a major advance in both accuracy and resolution for atmospheric measurements over data-sparse oceanic areas of the globe, providing wind accuracies of 0.5-2.0 m s^-1 with a vertical resolution of ∼5 m. One important advance over previous generations of sondes is the ability to measure surface (10 m) winds. The new dropwindsonde has already been used extensively in one major international research field experiment (Fronts and Atlantic Storm Track Experiment), in operational and research hurricane flights from NOAA's National Weather Service and Hurricane Research Division, during NCAR's SNOWBAND experiment, and in recent CALJET and NORPEX El Niño experiments. The sonde has been deployed from a number of different aircraft, including NOAA's WP-3Ds and new Gulfstream IV jet, the Air Force C-130s, NCAR's Electra, and a leased Lear-36. This paper describes the characteristics of the new dropwindsonde and its associated aircraft data system, details the accuracy of its measurements, and presents examples from its initial applications.