Report 3: The Effect of Horizontal Resolution on
Ocean Surface Heat Fluxes in the ECMWF Model
Gleckler, Peter J.and Karl E. Taylor
August 1992, 29 pp.
Annual mean ocean surface energy fluxes have been studied as a function
of horizontal resolution in the ECMWF model (cycle 33) and compared with
Oberhuber's COADS (1959-1979) based empirical estimates. The model has
been run at resolutions of T21, T42, T63 and T106 for 15 months with prescribed
monthly varying climatological SST and sea ice. The T42 simulation was
extended to 2 years, which enabled us to determine that many differences
between the resolution runs were significant and could not be explained
by the fact that individual realizations of an ensemble of years can be
expected to give different estimates of the annual mean climate state.
In addition to systematic differences between the modeled and the observed
fluxes, the simulated fields of surface shortwave and longwave radiation
showed much more spatial variability than the observed estimates. This
may be attributable more to deficiencies in the observations than to errors
in the model. The modeled latent and sensible heat fields were in better
agreement with observations.The primary conclusion concerning the dependence of ocean surface fluxes
on resolution is that the T21 simulation differed significantly from the
higher resolution runs, especially in the tropics. Although the differences
among the three higher resolution simulations were generally small over
most of the world ocean, there were local areas with large differences.
It appears, therefore, that in relation to ocean surface heat fluxes, a
resolution greater than T42 may not be justified for climate model simulations,
although the locally large differences found between the higher resolution
runs suggest that convergence has not been achieved even at T106. (pdf
file)
UCRL-MI-123395