UNCERTAINTY IN THE GLOBAL FORECAST SYSTEM

Journal Article · Wed Apr 15 04:00:00 EDT 2009 · Monthly Weather Review

OSTI ID:1016379

Werth, D; Garrett, A

We validated one year of Global Forecast System (GFS) predictions of surface meteorological variables (wind speed, air temperature, dewpoint temperature, air pressure) over the entire planet for forecasts extending from zero hours into the future (an analysis) to 36 hours. Approximately 12,000 surface stations world-wide were included in this analysis. Root-Mean-Square- Errors (RMSE) increased as the forecast period increased from zero to 36 hours, but the initial RMSE were almost as large as the 36 hour forecast RMSE for all variables. Typical RMSE were 3 C for air temperature, 2-3mb for sea-level pressure, 3.5 C for dewpoint temperature and 2.5 m/s for wind speed. Approximately 20-40% of the GFS errors can be attributed to a lack of resolution of local features. We attribute the large initial RMSE for the zero hour forecasts to the inability of the GFS to resolve local terrain features that often dominate local weather conditions, e.g., mountain- valley circulations and sea and land breezes. Since the horizontal resolution of the GFS (about 1{sup o} of latitude and longitude) prevents it from simulating these locally-driven circulations, its performance will not improve until model resolution increases by a factor of 10 or more (from about 100 km to less than 10 km). Since this will not happen in the near future, an alternative for the near term to improve surface weather analyses and predictions for specific points in space and time would be implementation of a high-resolution, limited-area mesoscale atmospheric prediction model in regions of interest.

• Research Organization: SRS
• Sponsoring Organization: DOE
• DOE Contract Number: AC09-08SR22470
• OSTI ID: 1016379
• Report Number(s): SRNL-STI-2009-00264
• Journal Information: Monthly Weather Review, Journal Name: Monthly Weather Review; ISSN MWREAB; ISSN 0027-0644
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AIR
FORECASTING
IMPLEMENTATION
PERFORMANCE
RESOLUTION
SEA LEVEL
SEAS
WEATHER