GPS Dropwindsondes FRS 142 Farrell Harding Professor Ed Groth

What is a dropwindsonde? An instrument that is deployed from an aircraft over oceanic regions to determine the vertical profiles of pressure, temperature, humidity, and wind of that area GPS dropwindsondes have revolutionized hurricane track and measurement accuracy over the past decade Also called dropsondes or simply sondes

Components

Before GPS →National Center for Atmospheric Research (NCAR) created Omega- based dropwindsonde in 1970s →Next created L2D2 (Long Range Navigation Digital Dropwindsonde →L2D2 couldn’t get full global coverage Deployed sonde and parachute

Why GPS dropwindsondes? 1.OMEGA closed because of financial reasons 2.GPS could provide better accuracy for dropping sondes directly into storms 3.NCAR received new aircraft, the Gulfstream IV-SP SO… Engineers began debating the creation of new GPS-based dropwindsondes

Design Specifications for GPS-based sondes 1.The sondes must be able to operate globally at an altitude up to 24 kilometers. 2.The sondes must be able to be deployed from the aircraft at airspeeds up to 130 ms^-1. 3.The aircraft must be capable of having four sondes operating at the same time. 4.Radio Frequency transmission bandwidth must be less than 20 kHz. 5.The system must have a telemetry range of 325 kilometers. 6.The sondes must be able to descend in under 12 minutes when they are dropped from a height of 12 kilometers. 7.The sensor measurement rate must be 2 Hz. 8.The sondes must be able to last (shelf life) at least 3 years.

National Oceanic and Atmospheric Administration (NOAA) ◘NOAA uses hurricane aircraft that fly directly into storms in order to assess the structure of hurricanes ◘NOAA’s famous aircraft are the NOAA WP-3D Orion “hurricane hunters” ◘Since 1982, NOAA has been flying a new plane called the Gulfstream-IV jet, which has led to increased understanding of hurricanes Gulfstream-IV jet

AVAPS Airborne Vertical Atmosphere Profiling System  Operated by one person  Can receive and process data from four dropsondes at the same time  Simple Graphical User Interface (GUI)  Outputs real time PTH and wind for each channel as sondes are descending  Operation on aircraft with or without aircraft data systems

Modern Applications

References ★ Franklin, James & Hock, Terrence. “The NCAR GPS Dropwindsonde.” Bulletin of the American Meteorological Society. Vol. 80, No. 3, March ★ raft/welcome.html raft/welcome.html ★ ★ tml tml