A methodology to define uncertainties associated with ocean surface
heat flux calculations has been developed and applied to a global climatology
that utilizes a summary of the Comprehensive Ocean-Atmosphere Data Set
surface observations. Systematic and random uncertainties in the net oceanic
heat flux and each of its four components at individual grid points and
for zonal averages have been estimated for each calendar month and for
the annual mean. The most important uncertainties of the 2° x 2°
grid cell values of each of the heat fluxes are described. Annual mean
net shortwave flux random uncertainties associated with errors in estimating
cloud cover in the Tropics yield total uncertainties that are greater than
25 W m-2. In the northern latitudes, where the large number
of observations substantially reduces the influence of these random errors,
the systematic uncertainties in the utilized parameterization are largely
responsible for total uncertainties in the shortwave fluxes, which usually
remain greater than 10 W m-2. Systematic uncertainties dominate
in the zonal means because spatial averaging has led to a further reduction
of the random errors. The situation for the annual mean latent heat flux
is somewhat different in that even for gridpoint values, the contributions
of the systematic uncertainties tend to be larger than those of the random
uncertainties at most latitudes. Latent heat flux uncertainties are greater
than 20 W m-2 nearly everywhere south of 40°N and in excess
of 30 W m-2 over broad areas of the subtropics, even those with
large numbers of observations. Resulting zonal mean latent heat uncertainties
are largest (~30 W m-2) in the middle latitudes and subtropics
and smallest (~ 10-25 W m-2) near the equator and over the northernmost
regions. Preliminary comparison of zonal average fluxes suggests that most
atmospheric general circulation models produce excessively large ocean
surface fluxes of net solar heating and evaporative cooling when forced
with realistic sea surface temperatures. It is expected that the method
introduced here will be refined to produce increasingly reliable estimates
of uncertainties in surface flux atlases derived from ship observations.