LATITUDINAL VARIATION OF MEASURED O-3 PHOTOLYSIS FREQUENCIES J(O1D) AND PRIMARY OH PRODUCTION-RATES OVER THE ATLANTIC-OCEAN BETWEEN 50-DEGREES-N AND 30-DEGREES-S

The latitudinal variation of the photolysis frequency of ozone to O(1D) atoms, J(O1D), was measured using a filter radiometer during the cruise ANT VII/1 of the research vessel Polarstern in September/October 1988. The J(O1D) noon values exhibited a maximum of 3.6 x 10(-5) s-1 (2pi sr) at the equator and decreased strongly towards higher latitudes. J(O1D) reached highest values for clean marine background air with low aerosol load and almost cloudless sky. The J(O1D) data, measured under these conditions and a temperature of 295 K, can be expressed by: J(O1D) = exp{-8.02 - 8.8 x 10(-3) S + 3.4 x 10(-6)S2} (s-1) where S represents the product of the overhead ozone column (DU) and the secant of the solar zenith angle. The meridional profile of the primary OH radical production rate P(OH) was calculated from the J(O1D) measurements and simultaneously recorded O3 and H2O mixing ratios. While the latitudinal distribution of J(O1D) and water vapour was nearly symmetric to the equator, high tropospheric ozone levels up to 40 ppb were observed in the Southern Hemisphere, SH, resulting in higher P(OH) in the SH.