Downward ozone transport associated with mesoscale convective storms in the central Amazon rainforest

This presentation provides an overview of a field project in the rainforest of the Brazilian Amazon region (Cuieiras Biological Reserve, 2°51' S, 54°58' W) conducted during April to July 2014. Objectives were to investigate the processes controlling the dynamics of reactive trace gases. During the wet season, only trace levels of nitrogen oxides and nitrate radicals prevailed above the 30-m forest canopy. Due to the pristine atmosphere, ozone levels typically ranged from 5 to 10 parts per billion (ppb) measured at 40 m above the surface. Such low ozone mixing ratios can be attributed to the frequent presence of clouds and precipitation and the low concentrations of ozone-precursors during the wet-season. The frequent passage of convective storms of various sizes, from local convection to well-organized mesoscale convective systems, impacted ozone levels. Ozone levels abruptly increased to a maximum of 30 ppb in response to downward transport from the mid troposphere. In this presentation, we will show how pervasive the re-distribution of ozone is in the lower tropical troposphere. We will report the relationship between magnitude of ozone transport and velocity of propagation and downdrafts of convective storms. Additionally, we will use satellite data to determine the areal extent of ozone enhancements and radar information to indicate the prevailing depth in the troposphere where ozone rich air emanates. Using the Weather Research and Forecast model with chemistry and upper air sounding data, we will estimate the regional downward transport of ozone and the corresponding surface net sink.