This project combines research related to two major airborne atmospheric chemistry studies: the recently completed Stratosphere-Troposphere Analyses of Regional Transport 2008 Experiment (START08) and the on-going High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observation (HIPPO) campaign. The START08 experiment was designed to examine the chemical structure of the extratropical upper troposphere/lower stratosphere (UT/LS) in relation to dynamical processes of a range of scales. Tracer measurements in well-defined meteorological conditions were a key component of the experimental design. The research will continue the data analysis in collaboration with others on the START08 team. In particular, this project seeks to use the unique trace gas data set from the PI's AWAS (automated whole air sampler) measurements and related measurements to examine tropospheric intrusions into the stratosphere, to evaluate mixing time scales for stratosphere-troposphere exchange, and to estimate age spectra in the UT/LS region. Further, the data will be used for comparison of chemical model simulations to satellite derived distributions and relationships in the UT/LS. The HIAPER Pole-to-Pole Observation (HIPPO) project is a multi-year research effort that focuses on understanding the global carbon cycle, on defining large-scale rates of tracer transport in the troposphere, and on understanding sources and sinks globally for carbon gases. While the emphasis of HIPPO is on carbon cycle gases, the project includes the measurement of a wider range of trace gases that complement that analysis of the major carbon cycle gases and provide additional characterization of hemispheric scale air quality and gases relevant to ozone chemistry. The PI will participate in the remaining three HIPPO global surveys and subsequent data interpretation to complete the seasonally resolved, global distributions of climate-relevant trace gases, which provides a unique benchmark of measurements for understanding emissions, transport, and as an unprecedented test for model simulations of global atmospheric chemistry.
The measurement and analysis of the suite of trace gases will add to the understanding of the relationships between greenhouse and carbon cycle gases and other climate-relevant trace gases in the atmosphere. The project also supports the development of a deployable aircraft instrument as a community resource by direct comparison to National Oceanic and Atmospheric Administration (NOAA) flasks commonly used throughout the NOAA global network. Finally, the HIPPO and START08 projects, and these measurements, will involve training of students and post-doctoral scientists, and the project will add to the development of graduate and undergraduate courses in atmospheric chemistry and environmental science.
Normal 0 false false false EN-US KO X-NONE In the recent past, the chemical composition of the atmosphere has been changing due to the influence of industrial and agricultural emissions. Furthermore, the impact of climate change is predicted to be another major influence on how the chemical composition evolves, which may further impact the pace of change. To understand and predict the impact of a changing atmospheric chemical composition, increasingly more sophisticated and complex computer models are being developed. However, to be most useful, these new chemical models must be tested against actual observations of the current chemical state of the atmosphere. The research supported under this grant provided unique measurements of a wide range of relevant trace gases over broad regions of the remote atmosphere. Measurements of a range of chemical compounds, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (CFC replacements), solvents, hydrocarbons and hydrocarbon oxidation products, and naturally occurring organic halogen compounds, were made over a several year period along transects that spanned from approximately 85N to 65S, and from the surface to near 14 km altitude. The transects were the basis of the HIPPO (HIAPER Pole-to-Pole Observations) campaign, which included many measurements taken from the NCAR/NSF Gulfstream V aircraft (See Figure 1). In particular, the measurements that were supported under this research project are being used to assess differences in the oxidation capacity of the Northern vs Southern Hemisphere, to assess the potential role of short-lived halogen containing compounds on ozone in the upper troposphere and lower stratosphere, to evaluate satellite observations of the chemical composition of the atmosphere, to test how well current models of the atmosphere represent real-life conditions, and, ultimately, to use models to better understand the processes that shape the chemistry of the atmosphere and to develop rational policies to mitigate human impact on the quality of the atmosphere. An example of the very intriguing data that have been generated is shown in Figure 2. This figure illustrates the distribution of a significant bromine containing trace gas (dibromomethane) measured in each of the 5 HIPPO campaigns. The contour curtain shows variation of high concentration (in red) and low concentration (in blue) of this compound, which is emitted by organisms in the surface ocean, as a function of latitude and altitude. The seasonal variation is driven by changes in the main atmospheric oxidant (hydroxyl radical), which has its own seasonality (high in summer, low in winter). The importance of tropical convection in mixing the atmosphere is also apparent in this figure. High concentrations of dibromomethane (and other gases in the tropical marine boundary layer) are mixed to high altitudes in the tropics along the equator. This rapid mixing has implications for moving reactive chemicals from the surface to higher in the atmosphere, where reactions can take place that impact ozone and the radiative budget of the atmosphere. In addition, measurements from another atmospheric chemistry study (START08), are being used to extend the large scale data set to include measurements over the continental US, particularly taken to study the boundary and interchange between the lower atmosphere (troposphere) and the overlying stratosphere. Data from both campaigns have been put into publicly available databases for access to interested scientists and others. The work in this project benefitted greatly from the collaborators in the START08 and HIPPO experiments.
