Examining the Distributions of Ozone, Water Vapor, and Chemical Tracers from the CONTRAST Campaign

The goal of the Convective Transport of Active Species in the Tropics (CONTRAST) campaign was to investigate the impact of deep convection and convective transport on the atmospheric composition over the Tropical Western Pacific (Pan et al. 2015). This campaign provides high-resolution, in-situ measurements from the marine boundary layer near the surface to the upper troposphere (Pan et al. 2015). A bimodal distribution of ozone concentration was previously observed by Pan et al. (2015), where one mode was around 20 ppbv and the other around 60 ppbv. Only the mode around 20 ppbv was observed when relative humidity (RH) was restricted to between 45% and 100%. Using data from the CONTRAST campaign, this study will analyze the distributions of water vapor, ozone, and chemical tracers.

Preliminary analysis shows a maximum ozone concentration of 60 ppbv observed around 150 hPa for “clear-sky” conditions. The maximum ozone concentration at 150 hPa for “in-cloud” conditions is observed around 20 ppbv, about 40 ppbv lower than the maximum for “clear-sky” conditions. The two ozone modes observed by Pan et al. (2015) are clearly seen when RH is restricted to below 20%. The 20 ppbv mode is mainly observed between 200 hPa and 400 hPa, while the 60 ppbv mode is mainly observed above 400 hPa. The two modes are still observed when RH is restricted to between 20% and 40%, but is not as distinct as when RH is restricted to below 20%. When RH is restricted to between 40% and 60%, 60% and 80%, 80% and 100%, and greater than 100%, the 60 ppbv mode is no longer observed. These results indicate that ozone has a stronger relationship with RH than with the presence of clouds.

Larger concentrations of water vapor and carbon monoxide (CO) are observed near the surface, while larger concentrations of ozone are observed at pressures lower than 200 hPa. Larger concentrations of CH₃CN and HCN (biomass burning tracers) are observed in the mid-tropopause (between 400 hPa and 800 hPa). Analyzing vertical velocity values show updrafts greater than 0.1 ms^-1 and larger updraft frequencies are found between ozone concentrations of 10 ppbv and 100 ppbv and CO concentrations of 60 ppbv and 140 ppbv. Average RH values greater than 80% are observed between ozone concentrations of 10 ppbv and 50 ppbv and CO concentrations between 60 ppbv and 180 ppbv. An area of higher potential temperature (greater than 340 K) is observed between ozone concentrations of 10 ppbv and 70 ppbv and between CO concentrations of 80 ppbv and 120 ppbv. More analysis of water vapor, chemical tracers, vertical velocity, and potential temperature will be done to identify relationships between the chemical tracers.