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) 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).
2.
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. 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 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
initial state and boundary conditions
3. Global
seasonal GSM forecasts and US monthly RSM forecasts
Fig.s 1,2,3,4 show the GSM and RSM seasonal normalized (by GSM
standard deviation) anomaly forecasts 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 and
standard deviations, 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.
Below normal seasonal
temperatures (Fig. 1) are being
forecast for most southern US states, the tropical eastern Pacific, tropical
eastern Atlantic, Siberia, the Southern Indian ocean, and the southern Pacific
coast of Australia. Above normal temperatures are being forecast for the
subtropical Pacific, the NH Atlantic, eastern Africa, the southern polar
oceans, and the western tropical Pacific.
Above normal seasonal
precipitation forecasts (Fig. 2)
include the subtropical western Pacific, the tropical Atlantic and the tropical
eastern Pacific, western Canada and the Middle East. Below normal precipitation
is being forecast for the subtropical South Pacific, the subtropical North
Atlantic, equatorial and Southern Africa, eastern Canada and along the Asian
coast. The US is forecast to have normal precipitation, except for the wet
areas over the west and the dry regions over the northeast.
Soil moisture (Fig. 3) forecasts are indicating that
most of the land regions may be dry, with perhaps the major exception being the
Asian region. Over the US the forecasts are close to climatology, except for
perhaps the Rocky Mountains, where the RSM is known to have a precipitation
bias.
The seasonal FWI (Fig. 4) is forecast to be below normal
over Mexico and Asia and above normal over Northeast Brazil, equatorial and
South Africa, Alaska and Siberia. Over the US, southern California,
southeastern Arizona, and Montana are above normal, whereas below normal or
normal FWI is forecast for other areas.
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., J.
Roads, A. Miller, Ritchie, 2001: Seasonal Forecasts of the Tropical and
Extratropical Pacific Ocean. ELLFB bulletin, Mar. 2001.
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., J. Roads, M. Kanamitsu, 2001: 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, Jun. 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)
