Ozone measurements in the troposphere of an Amazonian rain forest environment

Ozone concentration profiles from the ground to above the stratospheric peak have been obtained, for the first time, in an equatorial rain forest environment near Manaus (3°S 60°W). We have described in detail the average ozone profile in the troposphere, the observed variations, and a major biomass‐burning event that occurred near the end of the experiment. The average ozone mixing ratio at 1000 mbar was 13 parts per billion by volume (ppbv), increasing to 45 ppbv at 500 mbar. From 500 mbar upward, in the free troposphere, the mixing ratio stays roughly constant. The peak O 3 concentration occurs at 20 mbar (26.6 km) reaching 4.4×10 12 molecules cm −3 . The values in the troposphere are much lower than results from the low‐latitude Atlantic coast. The average gradient below 1000 m in Manaus is twice as large. The diurnal variation is strongest near the surface, decreasing upward. Close to the surface the ozone gradient is largest in the early morning, decreasing toward noon. A significant pollution (burning) event, near the end of the experiment, was responsible for large changes in ozone concentrations, which increased first in the lower troposphere but eventually reached the free troposphere as well.