Alexander, M. A., and J. D. Scott, 1995: Atlas of Climatology and Variability in the GFDL R30S14 GCM. U.S. Government Printing Office, 121 pp.


An atlas of the Geophysical Fluid Dynamics Laboratory (GFDL) Rhomboidal 30 with 14 Sigma Levels (R30S14) general circulation model (GCM) is made available in order to facilitate the intercomparison of the climate and variability of the model with observations and other modeling studies. Our goal is to reveal some of the model's strengths and weaknesses, providing a benchmark for future experiments with the GFDL model.

The R30S14 version of the GFDL GCM is a global, spectral, primitive equation model. There are 14 unequally spaced sigma levels in the vertical (from 0.9967 to 0.015) and a rhomboidal truncation at wave number 30, yielding a horizontal grid spacing of approximately 3.75° of longitude and 2.225° of latitude. The model has seasonally varying insolation, sea surface temperature (SST) and sea ice, but the values are fixed for each day. The SSTs and sea ice vary according to long-term observed climatologies and the same cycle is repeated for each year in this 17 year integration. The spectral representation of the orography has been improved by smoothing out some of the artificial ripples in the field that are generated by the spectral transformation. This model also features gravity wave drag and predicted clouds. Stratiform clouds form and large scale precipitation begins when the relative humidity exceeds 100%. Subgrid scale precipitation is parameterized by moist convective adjustment. The surface temperature over land is calculated assuming there is no heat storage in the ground. Soil moisture is predicted using the bucket method, in which the ground can absorb up to 15 cm of rainfall before runoff begins (Manabe, 1969). Standard bulk aerodynamic formula are used to calculate the surface wind stress and sensible and latent heat fluxes using a constant transfer coefficient of 1x10-3 over the oceans and 3x10-3 over land. More details on the GFDL GCM can be found in Goron and Stern (1982), Manabe and Hahn (1981) and Lau (1981).