The relationship of turbulence and nitrogen oxides within and above a tropical forest canopy

Nitric oxide, nitrogen dioxide, ozone, and sulfur dioxide mixing ratios were measured above an Amazon rainforest canopy, 60 kilometers north-northwest of the city Manaus. The prevailing wind direction was from the east, thus atmospheric conditions at the site were mostly clean. Wind speed and wind direction data for the same time period were also measured to assess the impact of air turbulence on gas levels above the canopy. Emissions of nitric oxide from Manaus and soils influenced nitrogen oxides and ozone levels observed above the canopy. On days that canopy venting occurred, nitrogen oxides mixing ratios above the canopy increased to a daily maxima of about 0.5 parts per billion, whereas ozone mixing ratios reached 10 parts per billion. On days when emissions from Manaus dominated air chemistry above the canopy, nitrogen oxides mixing ratios attained values between 2 to 5 parts per billion and ozone mixing ratios peaked at values up to 30 parts per billion. The strength of turbulent mixing played a critical role in the temporal variation of nitrogen oxides signals observed in both natural and polluted conditions.