Long-term behavior of cloud systems in TOGA COARE and their interactions with radiative and surface processes. Part III: Effects on the energy budgetand SST
Xq. Wu et Mw. Moncrieff, Long-term behavior of cloud systems in TOGA COARE and their interactions with radiative and surface processes. Part III: Effects on the energy budgetand SST, J ATMOS SCI, 58(9), 2001, pp. 1155-1168
Most atmospheric general circulation models (GCMs) and coupled atmosphere-o
cean GCMs are unable to get the tropical energy budgets at the top of the a
tmosphere and the surface to simultaneously agree with observations. This a
spect is investigated using a cloud-resolving model (CRM) that treats cloud
-scale dynamics explicitly, a single-column model (SCM) of the National Cen
ter for Atmospheric Research (NCAR) Community Climate Model that parameteri
zes convection and clouds, and observations made during Tropical Oceans and
Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE
). The same large-scale forcing and radiation parameterizations were used i
n both modeling approaches. We showed that the time-averaged top-of-atmosph
ere and surface energy budgets agree simultaneously with observations in a
30-day (5 December 1992-3 January 1993) cloud-resolving simulation of tropi
cal cloud systems. The 30-day time-averaged energy budgets obtained from th
e CRM are within the observational accuracy of 10 W m(-2), while the corres
ponding quantities derived from the SCM have large biases. The physical exp
lanation for this difference is that the CRM realization explicitly represe
nts cumulus convection, including its mesoscale organization, and produces
vertical and horizontal distributions of cloud condensate (ice and liquid w
ater) that interact much more realistically with radiation than do paramete
rized clouds in the SCM.
The accuracy of the CRM-derived surface fluxes is also tested by using the
fluxes to force a one-dimensional (1D) ocean model. The 1D model, together
with the surface forcing from the CRM and the prescribed advection of tempe
rature and salinity, simulates the long-term evolution and diurnal variatio
n of the sea surface temperature. This suggests that the atmosphere-ocean c
oupling requires accurate representation of cloud-scale and mesoscale proce
sses.