IMPLEMENTATION OF A REAL-TIME PRECIPITABLE WATER CAPABILITY USING THE GLOBAL POSITIONING SYSTEM

Yehuda Bock and Peng Fang (SIO)

Link to NOAA Strategic Plan: NOAA Goal 2: Understand Climate Variability and Change to Enhance Society's Ability to Plan and Respond

NOAA Goal 3: Serve Society's Needs for Weather and Water Information

RESEARCH OBJECTIVES AND SPECIFIC PLANS TO ACHIEVE THEM

To realize the goal of estimating precise (≤ 1.5 mm RMS) integrated precipitable water (IPW) within 2 hours using two sub-networks of continuous GPS receivers distributed over the continental U.S. as a way of supplementing and improving numerical weather prediction models, i.e., short-term weather forecasting. At NOAA's Earth Systems Research Laboratory, a ground-based GPS meteorology system has been implemented, with continued scientific input, oversight and refinement from the Scripps Orbit and Permanent Array Center (SOPAC). One of the breakthroughs in the system is the ability to generate quality-controlled, hourly orbital estimates for the GPS satellites at SOPAC, using a 24-hour sliding window in hourly increments. The precision of the orbits is about 7 cm within the observed session and below 15 cm in the predicted 12-hour segment.

We have evaluated approaches to provide more robust and timely GPS satellite orbits. These include employing latest global reference frame, absolute antenna phase center model, improved tidal loading model, introducing more evenly spatial coverage of data from global GPS tracking stations, and developing redundant and more robust quality control mechanisms. We have also evaluated new methodologies to reduce the latency of derived GPS zenith delays from single-epoch instantaneously estimated zenith delay parameters.

The Co-PI (Peng Fang) interacted closely with our sponsor at NOAA (Seth Gutman and his staff) to enhance their system for GPS Meteorology. In addition, he performed special request solutions.

RESEARCH ACCOMPLISHMENTS

High quality orbits are now delivered hourly with better than 98.4% (6 interruptions over a 365 day period, most of them due to internal or external internet or centralized archive system related problems) reliability with a precision of about 7 cm, and a predictive capability of 15 cm. A redundant processing system has been implemented to improve the reliability of GPS orbit support at SOPAC for NOAA.

This research contributes to atmospheric sounding research in general, directly contributes to operational weather forecasting by NOAA in the U.S. Techniques developed for this system can support other applications in geodynamics and navigation.