1. 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) 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
and corresponding ocean forecasts are discussed in Auad et al. (2002).
2. Forecast Skill Evaluations
4 years worth of forecasts (208 forecasts) have been
used to develop a GSM forecast climatology dependent upon season as well as
lag. Both means and standard deviations were derived in order to provide
normalized (by the standard deviation) anomalies. 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,
daily, weekly or monthly forecast skill does not ever reach zero and forecasts
averaged into monthly and seasonal averages demonstrate significant skill (see
Reichler and Roads 2002), which may be comparable to empirical long-range
forecast methodologies. Similar evaluation efforts are underway for the
regional forecasts, which currently use the GSM initial state and boundary conditions,
as well as the GSM climatology.
3. Global seasonal GSM forecasts and US
monthly RSM forecasts
Fig.s 1,2,3,4 show the GSM and RSM seasonal forecast anomalies
normalized (by GSM standard deviations) of 2-m surface temperature,
precipitation, soil moisture and the FWI for June-Aug. 2002.
Above normal seasonal temperatures (Fig. 1) are now being forecast for
California, Northeast Brazil, Central Africa, Northern Europe and Greenland,
central Africa, Asia and the central Pacific, South Atlantic and Indian ocean.
Below normal temperatures are being forecast for the North Atlantic and
Southern Indian ocean and Argentina as well as the eastern portion of the US.
Above normal seasonal precipitation forecasts (Fig. 2)
include the eastern US, Central Pacific, southern Europe, central Asia, and
Siberia. Below normal precipitation is being forecast for the western US,
Venezuela, western equatorial Africa, Russia, and the maritime continent.
Soil moisture (Fig.
3) forecasts are indicating that the western US, most of Africa,
northern Europe, Australia, Southeast Asia and Venezuela will be dry. Wet
regions include the Amazon, Peru, eastern US, and Siberia will be wet. Some,
but not all of the dry regions, should be ameliorated by increased
precipitation.
The seasonal FWI (Fig. 4) strongly corresponds to the soil moisture variations with
increased danger over most of the western US, Canada, Venezuela, Central
Africa, northern Europe, and China. Decreased danger is expected over the
eastern US, Amazon, South Africa, and southern Europe.
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/m2s_ECPC_forecasts.html/.
All forecasts and new experimental fire danger (USFS fire danger indices), land
surface, and ocean predictions (seasonal to decadal) can be 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., A. Miller, J. Roads 2001: Ocean
Forecasts. JGR (submitted)
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. 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, 12, 377-400.
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, Bull. Am.
Meteor. Soc., 77, 437- 471.
Reichler, T. and J. Roads, 2002:
Role of initial and boundary conditions in seasonal predictability. Nonlinear
Processes in Geophysics (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, Dec. 2001.
Roads,
J.O., S-C. Chen and F. Fujioka, 2001b:
ECPC’s Weekly to Seasonal Global Forecasts. Bull. Amer. Meteor. Soc., 82, 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)
