Druyan, L. M., K.Shah, K-W.Lo, J. Marengo and G. Russell,
1995: Impacts of model improvements on general circulation model sensitivity
to sea-surface temperature forcing. International Journal of Climatology,
15, 1061-1086.
The sensitivity of the 4° x 5° resolution general circulation
model of the Goddard Institute for Space Studies to some basic changes
in model formulation was studied by comparing parallel simulations forced
by global sea-surface temperature of June-August 1987 and 1988. The new
modelling schemes were substituted for the control model's parameterizations
of moist convection, planetary boundary layer, ground hydrology, and cloud
optical thickness in a series of sensitivity experiments. In addition,
linear and quadratic upstream schemes for advecting tracers were tried
in place of second-order differencing. Elimination of the vertical mixing
of horizontal momentum by moist convection was also tested. Impacts of
the new modelling schemes on simulated circulation, temperature, and precipitation
rates were inferred from pairs of simulations made by model versions that
differed with respect to a single change. No discernible positive impacts
were found for the new ground hydrology scheme or for changes in the determination
of cloud optical thickness. Profiles of zonal wind speeds and lower tropospheric
circulation patterns, both in the tropics, were more realistic when the
vertical mixing of horizontal momentum was included. Major improvements
in modelling the interannual variability of the planetary circulation,
mid-tropospheric temperature, and precipitation can be attributed to the
salutary effects of the new moist convection, new planetary boundary layer,
and the quadratic upstream scheme for advecting tracers.