Atmospheric Model Experiments - Six atmosphere-only integrations
initialized on 1 January, 1979 are integrated through 1997. These
integrations differ only in small perturbations to the initial conditions.
All AGCM integrations used the same prescribed daily SSTs. These
analyses of observed SSTs were produced using an ocean data assimilation
system (Rosati et. al., 1994) driven by the GFDL modular ocean model (MOM2).
The atmospheric model used in this study is a "full physics" global
spectral GCM (AGCM) which, for the most part, incorporates the physical
parameterizations described in Stern and Miyakoda (1995).
For this study, some of the key features of the physics include a relaxed
Arakawa-Schubert (RAS) type cumulus convective parameterization, the addition
of a full diurnal cycle in the radiation scheme and an interactive, diagnostic
cloud prediction scheme.The AGCM resolution was T42L18 (triangular truncation
at wave number 42 with 18 vertical sigma levels). More details regarding
the basic spectral GCM can be found in Gordon and Stern (1982).
Coupled Model Experiments - Six member ensembles of coupled ocean-atmosphere
GCM forecasts were produced starting with 1 January and 1 July of each
year from 1979 thorugh 1997. Each forecast was integrated for one
year. Intial conditions for the ocean are produced by the GFDL ocean data
assimilation system using the MOM2 ocean model, forced by observed wind
stresses, to assimilate observed SSTs and sub-surface thermal data (Rosati
et al., 1994). Atmospheric initial conditions for these coupled integrations
were taken from each of the six long AGCM run solutions at the appropriate
1 January or 1 July starting date.
The ocean model is MOM2 using a nearly global grid with ralistic bottom
topography and horizontal resolution of 1 deg longitude by 1 deg latitude,
except within the equatorial band of 10N-10S, where the meridional resolution
is 1/3deg. the vertical resolution is 15 unequally spaced levels
with most of the levels in the upper ocean above 500m. Physical parameterizations
include penetration of solar insolation to the ocean subsurface, Pacanowski-Philander
vertical mixing, and constant horizontal mixing coefficients (see Pacanowski,
1995, for more details).
References:
Gordon, C. T., and W. F. Stern, 1982: A description of the GFDL global spectral model. Monthly Weather Review, 110(7), 625-644.
Pacanowski, R.C., 1995: MOM 2 documentation, user's guide and reference manual. GFDL Ocean Group Tech. Rep. 3, 232 pp.
Rosati, A., R. Gudgel, and K. Miyakoda, 1994: Decadal analysis produced from an ocean data assimilation system. Monthly Weather Review, 123(7), 2206-2228.
Stern, W., and K. Miyakoda, 1995: Feasibility of seasonal forecasts inferred from multiple GCM simulations. Journal of Climate, 8(5), 1071-1085.