ECPC's Mar. 2001 Atmospheric Forecasts
contributed by J. Roads, S. Chen, J. Ritchie
Experimental Climate Prediction Center Scripps Institution of Oceanography UCSD, 0224 La Jolla, CA 92093
1. ECPC's Global to Regional Atmospheric Forecast System
As previously discussed by Roads et al. (2000a), the Scripps Experimental Climate Prediction Center (ECPC) uses the reanalysis I version (Kalnay et al. 1996) of the National Centers for Environmental Prediction's (NCEP's) medium range forecast (MRF) model or global spectral model (GSM; Roads et al. 1999a). These global forecasts (4xdaily-7 days and weekly to 12-weeks) start from the NCEP operational 00UTC global analysis. The GSM then forces a regional spectral model (RSM; Juang and Kanamitsu, 1994; Juang et al. 1997; Chen et al. 1999, Anderson et al. 1999, Roads and Chen 2000) in order to gain increased spatial resolution (50-25 km resolution) at shorter time scales (4xdaily-7 days and weekly to 4-weeks) for several selected regions (US, CA, SW, Brazil). At even smaller space (2-km resolution) and time scales (8xdaily to 2 days) either the NCEP analysis or GSM forces a corresponding nonhydrostatic mesoscale spectral model (MSM; Juang 1999) for the Hawaiian Islands. All atmospheric models are based upon the same physics used in the GSM and can, in principle, be updated as the GSM is updated. Output products from the atmospheric models include a fire weather index (FWI, see Roads et al. 1997) and associated variables such as 2m-temperature, relative humidity and 10m-windspeed as well as precipitation and soil moisture. The global atmospheric model is now forcing an ocean model (Auad et al. 1999), and corresponding ocean forecasts are shown in Auad et al. (2000)
2. Preliminary Forecast Skill Evaluations
Two years worth of forecasts (104 forecasts) have been used to develop a GSM forecast climatology dependent upon season as well as lag. This ensemble of forecasts has also been used to evaluate forecast skill. As discussed by Roads et al. (2001a,b,c) and Chen et al. (2001), the GSM provides skillful forecasts of temperature, precipitation, soil moisture and a fire weather index at long forecast ranges. Although the greatest skill occurs initially and then decays toward zero, daily, weekly or monthly forecast skill does not ever reach zero and forecasts averaged into monthly and seasonal averages demonstrate significant skill, which may be comparable to other long-range forecast methodologies. Similar evaluation efforts are underway for the regional forecasts, which currently use the GSM to start the forecasts and the GSM climatology to derive regional anomalies.
3. Global seasonal GSM forecasts and US monthly RSM forecasts
Fig. 1, Fig. 2, Fig. 3 and Fig. 4 show the GSM seasonal anomaly forecast for 03/2001-06/2001along with the corresponding RSM monthly anomaly forecast for 03/2001 of 2-m surface temperature, precipitation, soil moisture and the FWI. It should be noted that both the GSM and the RSM use the same GSM climatology to calculate the anomalies, which may have a deleterious effect on the RSM anomalies discussed below. We are still trying to develop a more suitable RSM climatology for the RSM simulations.
Below normal seasonal temperatures (Fig. 1) continue to be forecast for most areas in the Northern Hemisphere: Iran, Afghanistan and equatorial Africa are notable exception. Higher temperatures are forecast over South America, especially Argentina. Over the US, even lower temperatures are being forecast for the first month by the RSM especially over the Rocky Mountains. The low RSM temperatures over the US NW are partially due to the use of a lower elevation GSM climatology. An RSM climatology is now being produced to reduce this bias.
GSM seasonal precipitation forecasts (Fig. 2) are starting to indicate increased rainfall in many land regions. Tropical ocean regions, especially the western Tropical Pacific, Indian Ocean and North Atlantic are forecat to be below normal. Over the US, precipitation is forecast to increase in the southern part and remain below normal in the northern part during March.
Soil moisture (Fig. 3) forecasts are generally coincident with the global and US precipitation and temperature predictions, which reflects the influence of precipitation on soil moisture as well as potential feedbacks by the soil moisture on precipitation and temperature. Dry areas are being forecast for Iran and Afghanistan, southern China, central Africa, northern Argentina, northeast Australia and the northern US. Note that over much of the southern US, increased precipitation is forecast, although the soil moisture is still forecast to remain below normal in Florida.
The FWI (Fig. 4) is forecast to increase in northwestern America, Iran, Afghanistan, and north equatorial Africa, which is somewhat coincident with the soil moisture and precipitation forecasts. Except for eastern Montana, fire danger is forecast to be low here over much of the US. Again, the fire weather index only expresses anomalous weather characteristics associated with relative humidity, wind speed, and to some extent, temperature.
Other experimental GSM and RSM forecast fields (wind speed, relative humidity) and additional forecast months) can be found at http://ecpc.ucsd.edu/projects/ellfb/. Other forecast ranges and other regions can be found at http://ecpc.ucsd.edu/m2s/m2s ECPC forecasts.html/.
Anderson, B.T., J. O. Roads, S. -C. Chen, and H. -M. Huang, 1999: Regional Modeling of the Low-level Monsoon Winds Over the Gulf of California and Southwest United States: Simulation and Validation, (in press).
Auad, G., J. Roads, A. Miller, D. Cayan, W. White, 1999: Comparison of wind stresses and surface heat fluxes from the COADS, FSU and NCEP data sets. (submitted)
Auad, G., J. Roads, A. Miller, Ritchie, 2000: ECPC's Dec. 2000 Ocean Forecasts. ELLFB, Dec. 2000.
Chen, S. -C., J.O. Roads, H. -M. H. Juang, M. Kanamitsu, Global to regional simulation of California's wintertime precipitation. J. Geophys. Res., 104(24), 31517-31532, 1999.
Chen, S-C. J. O. Roads, and M. Wu, 2001: ECPC's Asia forecasts. Journal of Terrestrial-Atmosphere-Oceanography (in press).
Juang, H. -M. H., and M. Kanamitsu, 1994: The NMC nested regional spectral model. Mon. Wea. Rev., 122, 3-26.
Juang, H. -M. H., S. -Y. Hong and M. Kanamitsu, 1997: The NCEP regional spectral model: an update. Bull. Am. Meteor. Soc., 78, 2125-2143.
Kalnay, E. et al., 1996: The NMC/NCAR reanalysis project, Bull. Am. Meteor. Soc., 77, 437- 471, 1996.
Roads, J.O., S. -C. Chen, F. M. Fujioka, H. Juang, and M. Kanamitsu. 1997 Global to Regional Fire Weather Forecasts. Int. Forest Fire News, 33-37.
Roads, J., S. Chen, M. Kanamitsu, H. Juang, Surface water characteristics in NCEP global spectral model reanalysis. J. Geophys. Res., 104, 19307-19327, 1999a.
Roads, J., S. -C. Chen, J. Ritchie, 2000a: ECPC's Weekly to Seasonal U.S. Forecasts of FWI, Soil Moisture, and Precipitation. ELLFB, Dec. 2000.
Roads, J. and S. Chen, 2000b: Surface Water and Energy Budgets in the NCEP Regional Spectral Model. J. Geophys. Res. (in press)
Roads, J.O., S-C. Chen and F. Fujioka, 2001a: ECPC's Weekly to Seasonal Global Forecasts. Bull. Am. Meteor. Soc. (in press).
Roads, J., B. Rockel, E. Raschke, 2001b: Evaluation of ECPC's Seasonal Forecasts Over the BALTEX Region and Europe. Meteorologische Zeitschrift. (in press).
Roads, J. and S. Brenner, 2001c: Global Model Seasonal Forecasts for the Mediterranean Region. Israel Journal of Earth Sciences (in press)
Fig. 1 Temperature (C) anomalies: (upper) 03/2001-06/2001 GSM forecast anomalies: (lower), Mar. RSM forecast anomaly.
Fig. 2 Precipitation (mm/day) anomalies: (upper) 03/2001-06/2001 GSM forecast anomalies: (lower) Mar. RSM forecast anomalies.
Fig. 3 Soil Moisture anomalies: (upper) 03/2001-06/2001 GSM forecast anomalies: (lower) Mar. RSM forecast anomalies.
Fig. 4 FWI anomalies: (upper) 03/2001-06/2001 GSM forecast anomalies: (lower) Mar. RSM forecast anomalies.