Convection and Tropospheric Trace Gases

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The cycle of water through the atmosphere greatly influences the airborne distribution and concentration of a number of trace chemical components. This is especially true in cases where liquid water (i.e. clouds and precipitation) is formed in the atmosphere. The dynamics of cloud formation can move trace species from one region of the atmosphere to another. Additionally, the importance of liquid phase reactions which can change species from one chemical form to another is only now being recognized and documented by atmospheric chemical research scientists. While the importance of cloud and precipitation formation processes on atmospheric chemistry has been suggested as the result of laboratory and modeling experiments, there have been very few direct field measurements to verify and quantify the significance of such processes. The direct observation of these effects is a difficult undertaking since specialized and extremely sensitive measurement equipment and methods are required. The objectives of this project are through the continuation of research initiated under NSF grant ATM-8305843 to: (1) measure the extent of convective cloud and thunderstorm induced transport of chemical species from the lower to upper troposphere; (2) measure the influence of cloud light reflection and absorption on photochemical processes; (3) measure the degree of entrainment of chemical compounds into clouds; and (4) test certain theories of photo-chemistry in the upper troposphere. This research will be carried out by equipping the National Center for Atmospheric Research Saberliner aircraft with sophisticated chemical measurement instrumentation suitable for detecting selected species in cloud and storm systems. The chemical studies will be coordinated with meteorological studies of storm formation. This project is expected to provide important information regarding physical and chemical processes which are of significance to the atmospheric sciences.