J5.4
Vertical transport enhances ozone levels in the tropical atmospheric boundary layer
Jeffrey M. Sigler, Yale University, New Haven, CT; and J. D. Fuentes, M. Garstang, and X. Lee
Under stable nocturnal conditions, surface-level ozone is typically scarce. However, here we report unusual increases in nocturnal surface-level ozone recorded at a pasture site in the Amazon basin, Brazil during January and February 1999. We attribute these increases to downward transport of ozone during convective activity, and utilize micrometeorological data and atmospheric thermodynamic knowledge to support this contention. In particular, the increases in surface-level ozone are highly correlated with decreases in equivalent potential temperature, suggesting vertical transport of cool, dry air from above cloud base. Two months of observations indicate that this vertical transport is present whenever convective precipitating systems influence the region, day or night, and can abruptly produce surface ozone increases by as much as 17 ppb. Moreover, vertical convective transport of ozone augmented the average diurnal trend of ozone at the site by 10-15%. Our current understanding of convective transport to surface-level ozone concentrations is incomplete. Studies such as this one are a first step toward formulating modeling systems to quantify this vertical transport process.
Joint Session 5, Atmospheric Chemistry (Joint with the Fourth Symp. Urban Environment, 12th Joint Conf. on the Applications of Air Pollution Meteorology with A&WMA, and 25th Conf. Agricultural & Forest Meterology; Cosponsored by the AMS STAC Committee on Atmospheric Chemistry)
Thursday, 23 May 2002, 1:30 PM-4:59 PM
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