The interplay between ocean photochemistry and surface boundary-layer
physics is explored in a range of analytical and numerical process mod
els. For simple systems, key attributes of the photochemical distribut
ion-diurnal cycle, surface concentration, and the bulk concentration d
ifference across the ''mixed layer'' - can be expressed in terms of a
small number of physical (vertical diffusivity) and photochemical (tur
nover timescale and production depth scale) scaling factors. A coupled
, 1-D photochemical/physical model is used to examine the more general
case with finite mixing rates, variable photochemical production and
evolving boundary layer depth. Finite boundary layer mixing rates act
to increase both the diurnal cycle and mean concentration at the surfa
ce. The diurnal cycle and mean surface concentration are further ampli
fied by coupling between photochemistry and diurnal physics. The daily
heating/cooling cycle of the upper ocean can lead to a significant re
duction in mixing and boundary-layer depth during the day when photoch
emical production is at a maximum. Accounting for these effects result
s in additional surface trapping of photochemically produced species a
nd significant enhancements of the surface diurnal cycle and daily mea
n. The implications of our model results for field data interpretation
and global air-sea flux calculations are also discussed.