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A full description of the ModelE version of the Goddard Institute for Space Studies (GISS) atmospheric
general circulation model (GCM) and results are presented for present-day climate simulations (ca. 1979).
This version is a complete rewrite of previous models incorporating numerous improvements in basic
physics, the stratospheric circulation, and forcing fields. Notable changes include the following: the model
top is now above the stratopause, the number of vertical layers has increased, a new cloud microphysical
scheme is used, vegetation biophysics now incorporates a sensitivity to humidity, atmospheric turbulence is
calculated over the whole column, and new land snow and lake schemes are introduced. The performance
of the model using three configurations with different horizontal and vertical resolutions is compared to
quality-controlled in situ data, remotely sensed and reanalysis products. Overall, significant improvements
over previous models are seen, particularly in upper-atmosphere temperatures and winds, cloud heights,
precipitation, and sea level pressure. Data–model comparisons continue, however, to highlight persistent
problems in the marine stratocumulus regions.