Daily Numerical Weather Prediction with the Global
University of Wisconsin Hybrid q-h Model
Todd Schaack, Tom Zapotocny, Allen Lenzen, Don Johnson
University of Wisconsin - Madison
The University of Wisconsin (UW) global hybrid isentropic-eta (q-h) model has been developed as part of an effort to demonstrate the feasibility of hybrid models for weather and medium-range prediction. This development has proceeded through a hierarchy of models from preliminary channel models to the full fledge global climate and NWP models in use today. Model development has entailed studies of a wide variety of numerics employing both Eulerian and semi-Lagrangian numerics and different algorithms for boundary layer and dry and moist convective parameterizations. The robust climate simulation capabilities of the UW θ-η model have been documented in a 14 year climate simulation and compared against results from the NCEP reanalysis project.
In this talk, a summary of the capability of the UW q-h global model to simulate day-to-day weather events is examined. The results of seven day forecasts produced daily at 0000 UTC are evaluated by presenting the mean forecast error for extended length time periods as well as daily time series of anomaly correlation and root mean square error. The impacts of horizontal resolution and three different physical parameterizations (CCM3, CCM3/MCRAS, GFS) on mid-latitude NWP are also discussed. The forecast experiments cover a time period of four and a half years and use initial conditions and verifying analyses from the NCEP Global Data Assimilation System/Forecast System (GDAS/GFS).
The results will show that the UW q-h model produces daily mean forecasts of standard synoptic fields, which are comparable in accuracy with forecast fields by the NCEP GFS. The 500 hPa geopotential height anomaly correlations and RMS errors are also comparable to the GFS when averaged over extended length time periods even though the UW q-h model forecasts were run at reduced horizontal and vertical resolution relative to the GFS. As an example, the results show a virtual tie for the NH 500 hPa geopotential height anomaly correlations, and slightly better SH anomaly correlations for the UW q-h model over the period of this study. These results covering four and one half years of daily global forecasts serve to demonstrate the feasibility of employing hybrid isentropic coordinate models for NWP.