Ozone in the boundary layer of the equatorial Atlantic Ocean

Shipboard (~ 7 m) ozone and carbon monoxide measurements made in the equatorial Atlantic Ocean, south of the intertropical convergence zone, between 5°N and 10°S and 10°—30°W in August and September of 1986 exhibited variability in excess of a factor of 2. Ozone mixing ratios ranged from < 25 to over 50 ppbv while carbon monoxide mixing ratios ranged from < 50 to over 120 ppbv along the western edge of the equatorial Atlantic in spite of the fact that the prevailing, surface winds were from the east to southeast at between 5 and 15 m/s. Ozone and carbon monoxide mixing ratios were generally lower and exhibited less variability in the eastern tropical Atlantic where a lighter, south to southeasterly wind regime predominated. Isobaric trajectory analyses indicated that the high ozone and carbon monoxide mixing ratios appear to be related to long-range transport off of the African continent. Time-series analysis of the ozone data indicates a diel cycle in ozone mixing ratios with a morning maximum and afternoon minimum.