Wet chemical surface ozone measurements during POLARSTERN cruise ANT-I/2 (PS01) in 1983

On the outward journey, European air masses, loaded by photochemically produced ozone, may have partly influenced the measurements in clean air. As simultaneously measured low concentrations of Krypton-85 (which only has anthropogenic sources) show, the high ozone mixing ratios at 0-5°N cannot be explained by photochemical formation, but must be of natural origin. On the return journey, the ITCZ was at 6°S and was weak. This explains the very low ozone values of only 4 ppb at times, caused by the photolysis of ozone.