A complete dynamical ozone budget measured in the tropical marine boundary layer during PASE

Ocean uptake of ozone was observed to be fairly slow (mean deposition velocity of 0.024 ± 0.014 cm s−1) accounting for a diurnally averaged loss rate that was ∼30% as large as the net photochemical destruction. From the measurement of deposition velocity an ozone reactivity of ∼50 s−1 in seawater is inferred. Due to the unprecedented measurement accuracy of the dynamical budget terms, unobserved photochemistry was able to be deduced, leading to the conclusion that 3.9 ± 3.0 ppt (parts per trillion by volume) of NO is present on average in the daytime tropical marine boundary layer, broadly consistent with several previous studies in similar environments.

It is estimated, however, that each ppt of BrO hypothetically present would counter each ppt of NO above the requisite 3.9 ppt needed for budget closure. The long-term budget of ozone is further analyzed in the buffer layer, between the boundary layer and free troposphere, and used to derive an entrainment velocity across the trade wind inversion of 0.51 ± 0.38 cm s−1.