1. ECPC’s Forecast System
The
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. 2001a) to make routine experimental global forecasts.
These global forecasts (daily out to 7days and weekly out to 16-weeks) start
from the NCEP operational 00UTC global analysis. The GSM then forces a regional
spectral model (RSM; Juang et al. 1997; Chen et al. 1999, Roads and Chen 2000;
Roads et al. 2003b, Roads 2003) 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).
We are also beginning development of a new ensemble seasonal forecast
system, which will make use of and upgraded version of the NCEP seasonal
forecast model (Kanamitsu et al. 2003)
2. Forecast Skill Evaluations
Five
years worth of forecasts (260 forecasts) have now been used to develop a
GSM/RSM forecast climatologies, which are dependent upon season as well as lag.
Both means and standard deviations were derived in order to provide normalized
(by their respective standard deviation) anomalies. As discussed by Roads et
al. (2001a,b), Roads and Brenner (2002), Roads et al. (2003a,b); Roads (2003),
Chen et al. (2001), Chen and Roads (2003), the GSM/RSM provide skillful
forecasts of temperature, precipitation, soil moisture and fire danger indices
at long forecast ranges. Although the greatest skill occurs initially and then
decays, monthly and seasonal averages demonstrate significant skill (Reichler
and Roads 2002), which may be comparable to empirical long-range forecast
methodologies.
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 or RSM standard deviations) of 2-m surface temperature,
precipitation, soil moisture and the FWI for the 2003 MAM time frame.
Above
normal seasonal temperatures (Fig. 1)
are being forecast for much of the northern hemisphere, especially in the
tropical region, but also over Antarctica. Below normal temperatures are being
forecast for much of the southern hemisphere. Over the US, the forecast
temperatures are close to normal, with slightly above normal temperatures in
the Northwest and slightly below temperatures in the Southwest (west Texas, New
Mexico, east Arizona). These temperature forecasts are somewhat the inverse of
the precipitation forecasts described below.
Above
normal seasonal precipitation forecasts (Fig.
2) are indicated for eastern Africa, central Asia, northern Brazil. and
northern Mexico. Less than normal amounts are being forecast over southern
Brazil, Peru, and Argentina. Over the US, forecasts are indicating that the
Southwest (West Texas, New Mexico, eastern Arizona) will be above normal and
below normal precipitation will occur over the US Northwest , North Central, and Northeast.
Seasonal
soil moisture (Fig. 3) forecasts are
indicating that much of South America, Africa, and India will be below normal.
Above normal soil moisture is being forecast over central Australia and
northern Mexico. Over the US, the forecasts are consistent with the
precipitation forecasts. Above normal soil wetness is forecast over the
Southwest and southern Gulf coast states.
Below normal precipitation is being forecast in the Northwest.
The
seasonal FWI (Fig. 4) is indicating
potential fire danger over Canada, southern Brazil and Argentina, Siberia,
India and central Asia. Over the US, the Northwest, North Central, and
Northeast regions are indicating above normal fire danger, whereas the Gulf
Coast states are indicating decreased danger. The US FWI is somewhat consistent
with the precipitation and soil moisture forecasts.
References
Auad, G., A. Miller, J. Roads 2002: Ocean
Forecasts. J. Marine Res. (submitted)
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.
Chen, S. and J. Roads, 2003: Regional Spectral Model
Simulations for South America. J. Hydrometeor. (submitted)
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.
Kanamitsu, M., A. Kumar, H.-M.
H. Juang, W. Wang, F. Yang, J. Schemm, S.-Y. Hong, P. Peng, W. Chen and M. Ji,
2002a: NCEP Dynamical Seasonal Forecast System 2000. Bull. Amer. Met. Soc.,
83, 1019-1037.
Reichler, T. and J. Roads, 2002: Role of initial
and boundary conditions in seasonal predictability. Nonlinear Processes in
Geophysics (in press)
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. 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.O., S-C. Chen and F. Fujioka, 2001a:
ECPC’s Weekly to Seasonal Global Forecasts. Bull. Amer. Meteor. Soc., 82, 639-658.
Roads,
J., B. Rockel, E. Raschke, 2001b: Evaluation of ECPC’s Seasonal Forecasts Over
the BALTEX Region and Europe. Meteorologische
Zeitschrift Vol. 10 (4) p. 283-294.
Roads,
J. and S. Brenner, 2002: Global Model Seasonal Forecasts for the Mediterranean
Region. Israel Journal of Earth Sciences.
51 (1), 1-16.
Roads, J., S. -C. Chen, J. Ritchie, 2002: ECPC’s
Weekly to Seasonal U.S. Forecasts of FWI, Soil Moisture, and Precipitation.
ELLFB bulletin, Dec. 2002.
Roads, J., S.-C. Chen, M. Kanamitsu, 2003a: US
Regional Climate Simulations and Seasonal Forecasts. Journal of Geophysical
Research-Atmospheres (in press).
Roads, J., S. Chen, S. Cocke, L. Druyan, M. Fulakeza,
T. LaRow, P. Lonergan, J.-H. Qian, S. Zebiak, 2003b: The IRI/ARCs Regional
Model Intercomparison Over S. America. J. Geophys. Res. (in press).
Roads, J. 2003: Experimental Weekly to Seasonal,
Global to Regional US Precipitation Forecasts (submitted)
