GPSWVAPOR

Near Real-Time GPS Water Vapor Data Availability

1 January 2005 - 11 March 2005

Lead Scientist: Seth Gutman

Observatory: SGP

Near Real-time GPS Water Vapor Data from DOE ARM Sites in Oklahoma and Kansas Support NOAA Weather Forecast Research The Department of Energy’s Atmospheric Radiation Measurement facility in the Southern Great Plains of the United States hosts the worlds’ largest concentrations of Global Positioning System (GPS) receivers dedicated to atmospheric research. Since 1993, the facilities and resources of the SGP CART Site have been used by NOAA’s Forecast Systems Laboratory (FSL), other government agencies, and universities to develop ground-based GPS water vapor observing systems and perform data intercomparisons to assess their characteristics and evaluate their suitability for climate research and observing system (primarily radiosonde and satellite) calibration and validation. In addition to their use in research and climate studies, GPS water vapor measurements have proven to be extremely useful in improving short-range weather forecasts accuracy over the coterminous United States. GPS observations from over 300 stations (including 30 ARM SGP sites) are now assimilated into NOAA numerical weather prediction models every hour with consistently positive impact on 3-h weather forecasts. In addition to their use in weather models, regional weather forecasters at National Weather Service Forecast Offices and Centers use GPS water vapor data to provide situational awareness under rapidly changing conditions, verify other moisture observations, and validate weather model predictions. One application of GPS that shows great promise was developed by FSL for the NWS Storm Prediction Center (SPC) in Norman Oklahoma. In this application, 1-h, 2-h, and 3-h changes in IPW at each site are displayed to provide SPC forecasters with current information about moisture convergence zones and where thunderstorms are most likely to first break out. Operational implementation of this technique requires highly reliable observations that are available with minimal latency. GPS and surface data from SuomiNet GPS receivers at some of the ARM Extended Facilities in Oklahoma and Kansas were arriving too late to be used to test and evaluate this new regional forecasting tool. At the request of FSL, the ARM program evaluated the feasibility of upgrading the communications at these sites to provide data in near real-time for operational forecasting and agreed to do so before the start of the severe storm season in 2005. FSL and SPC extend their gratitude to the ARM program for their assistance in this effort. Contact Information Name: Seth Gutman Tel: (303)497-7031 Seth.Gutman@noaa.gov