Ozone and aerosol distributions over the Amazon Basin during the wet season

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Abstract
Measurements of ozone (O3) and aerosols were made over the tropical rain forest of Brazil during the wet season in April–May 1987 as part of the NASA Global Tropospheric Experiment to study the Amazon boundary layer. Remote and in situ measurements of O3 and aerosols were made from aircraft on flights over Brazil in the vicinity of Manaus and between Manaus and Belem. Ozonesonde data were also obtained near Manaus. Ozone mixing ratios of 3 produced from biomass burning or photochemistry. These values are lower than those found during the 1985 dry season by 6–8 ppbv. These low O3 mixing ratios indicate a strong removal process near the surface during the wet season. The region from the mixed layer top to 3 km in altitude had a slowly increasing O3 profile from 12 to 20 ppbv. On long‐range flights between Manaus and Belem, no significant difference was found in the distribution of O3 above the mixed layer between the inland tropical rain forest and the marine conditions near the coast. Within the mixed layer, there was a definite trend to lower O3 levels above the forest compared to over the ocean. This reflects the marked difference in the sinks for O3 over these two regions. The rate of growth of the mixed layer over the rain forest in the wet season was found to be ∼9 cm s−1, which is within the 7–10 cm s−1 range found for the dry season. There was no evidence of the trade wind inversion that was seen during the dry season, and due to frequent precipitation, the background aerosol loading was lower in the wet season than in the dry season.