Jc. Ohlmann et Da. Siegel, Ocean radiant heating. Part II: Parameterizing solar radiation transmission through the upper ocean, J PHYS OCEA, 30(8), 2000, pp. 1849-1865
Accurate determination of sea surface temperature (SST) is critical to the
success of coupled ocean-atmosphere models and the understanding of global
climate. To accurately predict SST. both the quantity of solar radiation in
cident at the sea surface and its divergence, or transmission, within the w
ater column must be known. Net irradiance profiles modeled with a radiative
transfer model are used to develop an empirical solar transmission paramet
erization that depends on upper ocean chlorophyll concentration, cloud amou
nt, and solar zenith angle. These factors explain nearly all of the variati
ons in solar transmission. The parameterization is developed by expressing
each of the modeled irradiance profiles as a sum of four exponential terms.
The tit parameters are then written as linear combinations of chlorophyll
concentration and cloud amount under cloudy skies, and chlorophyll concentr
ation and solar zenith angle during clear-sky periods. Model validation giv
es a climatological rms error profile that is less than 4 W m(-2) throughou
t the water column (when normalized to a surface irradiance of 200 W m(-2))
. Compared with existing solar transmission parameterizations this is a sig
nificant improvement in model skill. The two-equation solar transmission pa
rameterization is incorporated into the TOGA COARE hulk flux model to quant
ify its effects on SST and subsequent rates of air-sea heat exchange during
a low wind, high insolation period. The improved solar transmission parame
terization gives a mean 12 W m(-2) reduction in the quantity of solar radia
tion attenuated within the top few meters of the ocean compared with the tr
ansmission parameterization originally used. This results in instantaneous
differences in SST and the net air-sea hear flux that often reach 0.2 degre
es C and 5 W m(-2), respectively.