ECPC's June 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

ECPC's Forecast System As previously discussed by Roads et al. (2001a), the Scripps Experimental Climate Prediction Center (ECPC) currently 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. 1999). 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. 2000, 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, 1997) 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. 2001) and corresponding ocean forecasts are shown in Auad et al. (2000).

Forecast Skill Evaluations 2 years worth of forecasts (104 forecasts) have been used to develop a GSM forecast climatology dependent upon season as well as lag. As discussed by Roads et al. (2001b,c, d) 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 (see Reichler et al. 2001), which may be comparable to empirical long-range forecast methodologies. Similar evaluation efforts are underway for the regional forecasts, which currently use the GSM to start the forecasts.

Global seasonal GSM forecasts and US monthly RSM forecasts Figs. 1,2,3,4 show the GSM seasonal anomaly forecast for 06/2001-09/2001 along with the corresponding RSM monthly anomaly forecast for 06/2001 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 an effect on the RSM anomalies discussed below. We are still trying to develop a more suitable RSM climatology for the RSM simulations.

Above normal seasonal temperatures (Fig. 1) are now being forecast for most areas in the Northern Hemisphere. Europe, Northwest Canada and parts of the Sahel are exceptions. Lower temperatures are forecast over South America, Australia and most of the Southern Hemisphere. Lower temperatures are being forecast for most of the US during June by the RSM.

GSM seasonal precipitation forecasts (Fig. 2) indicate potentially below normal precipitation tropical ocean regions, especially over the eastern Tropical Pacific, and Atlantic. Above normal precipitation is being forecast over the Indian Ocean, the regions associated with the Asian monsoon, and many southern ocean regions. During June, below normal precipitation is forecast for North Central and Western US land regions. Above normal regions are forecast for parts of the US West, South, and Great Lakes region.

Soil moisture (Fig. 3) forecasts are somewhat coincident with the global and US precipitation 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 central Russia, the Congo, parts of Brazil, and the US, especially the US West. June RSM forecasts indicate wet regions in the US Central to Eastern regions and dry regions in the Northwest, southern Canada and Gulf of California Mexican regions.

The seasonal FWI (Fig. 4) is forecast to be above normal in central Russia, Middle East, Sahel, and the US West. Above normal FWI is now being forecast over parts of the West, especially Nevada, Idaho, Montana during June. This dryness extends to California and Oregon during the subsequent summer season.

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/. Additional forecast ranges, variables, and regions are displayed at http://ecpc.ucsd.edu/m2s/m2sECPCforecasts.html/. All forecasts and new experimental fire danger (USFS fire danger indices), land surface, and ocean predictions (seasonal to Decadal) are linked from http://ecpc.ucsd.edu/predictions/.

References:

Anderson, B.T., J. O. Roads, S. -C. Chen, and H-M.H.Juang, 2000: Regional Simulation of the Low-level Monsoon Winds Over the Gulf of California and Southwest United States. JGR-Atmospheres, 105 (D14) 17,955-17969.

Auad, G., J. Roads, A. Miller, Ritchie, 2000: Seasonal Forecasts of the Tropical and Extratropical Pacific Ocean. ELLFB bulletin, Dec. 2000.

Auad, G., J.O. Roads, A. Miller, and D. Cayan, 2001: An ocean model response to NCEP, COADS and FSU surface flux fields. Journal of Geophys. Res (in press).

Chen, S. -C., J.O. Roads, H. -M. H. Juang, M. Kanamitsu, Global to regional simulation of California's wintertime precipitation. Journal of 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. Bulletin Amer. Meteor. Soc., 78, 2125-2143.

Kalnay, E. et al., 1996: The NMC/NCAR reanalysis project, Bulletin. Amer. Meteor. Soc., 77, 437- 471.

Reichler, T., J. Roads, M. Kanamitsu, 2001: Role of initial and boundary conditions in seasonal predictability. Nonlinear Processes in Geophysics (to be submitted)

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.O., S. -C. Chen, M. Kanamitsu, and H. Juang, 1999: Surface Water Characteristics in the NCEP Global Spectral Model and Reanalysis, J. Geophys. Res. 104, 19307-19327.

Roads, J.O. and S-C. Chen, 2000: Surface Water and Energy Budgets in the NCEP Regional Spectral Model. JGR-Atmospheres. 105 (D24) p. 29, 539.

Roads, J., S. -C. Chen, J. Ritchie, 2001a: ECPC's Weekly to Seasonal U.S. Forecasts of FWI, Soil Moisture, and Precipitation. ELLFB bulletin, Mar. 2001.

Roads, J.O., S-C. Chen and F. Fujioka, 2001b: ECPC's Weekly to Seasonal Global Forecasts. Bull. Amer. Meteor. Soc., April, Vol. 82, No. 4, p. 639-658.

Roads, J., B. Rockel, E. Raschke, 2001c: Evaluation of ECPC's Seasonal Forecasts Over the BALTEX Region and Europe. Meteorologische Zeitschrift. (in press).

Roads, J. and S. Brenner, 2001d: Global Model Seasonal Forecasts for the Mediterranean Region. Israel Journal of Earth Sciences (in press).

Fig. 1 Temperature (C) anomalies: (upper) 06/2001-09/2001 GSM forecast anomalies: (lower), Jun. RSM forecast anomaly.

Fig. 2 Precipitation (mm/day) anomalies: (upper) 06/2001-09/2001 GSM forecast anomalies: (lower), Jun. RSM forecast anomaly.

Fig. 3 Soil Moisture anomalies: (upper) 06/2001-09/2001 GSM forecast anomalies: (lower), Jun. RSM forecast anomaly.

Fig. 4 FWI anomalies: (upper) 06/2001-09/2001 GSM forecast anomalies: (lower), Jun. RSM forecast anomaly.