Radiative transfer calculations are used to quantify the effects of physica
l and biological processes on variations in the transmission of solar radia
tion through the upper ocean. Results indicate that net irradiance at 10 cm
and 5 m can vary by 23 and 34 W m(-2), respectively, due to changes in the
chlorophyll concentration, cloud amount, and solar zenith angle (when norm
alized to a climatological surface irradiance of 200 W m(-2)). Chlorophyll
influences solar attenuation in the visible wavebands, and thus has little
effect on transmission within the uppermost meter where the quantity of nea
r-infrared energy is substantial. Beneath the top few meters, a chlorophyll
increase from 0.03 to 0.3 mg m(-3) can result in a solar Bur decrease of m
ore than 10 W m(-2). Clouds alter the spectral composition of the incident
irradiance by preferentially attenuating in the near-infrared region, and s
erve to increase solar transmission in the upper few meters as a greater po
rtion of the irradiance exists in the deep-penetrating, visible wavebands.
A 50% reduction in the incident irradiance by clouds causes a near 60% redu
ction in the radiant heating rate for the top 10 cm of the ocean. Solar zen
ith angle influences transmission during clear sky periods through changes
in sea-surface albedo. This study provides necessary information for improv
ed physically and biologically based solar transmission parameterizations t
hat will enhance upper ocean modeling efforts and sea-surface temperature p
rediction.