Intrusions of tropospheric air can have a significant effect on the concentrations of radiatively active trace gases in the extratropical lower stratosphere and thus on the global energy balance. This project will analyze the transport of tropical upper tropospheric air into the extratropical lower stratosphere using in situ observations and model simulations. It will use data collected by the National Center for Atmospheric Research (NCAR)/National Science Foundation (NSF) Gulfstream V (GV) aircraft during the Stratosphere-Troposphere Analyses of Regional Transport 2008 (START08) field program to study transport in the upper troposphere and lower stratosphere (UT/LS) and its impact on atmospheric composition. The research will characterize the composition, frequency, location, and magnitude of tropospheric intrusions during the START08 period. The methods to be applied include trajectory analysis, trace species analysis, and correlations between multiple trace species to establish source air mass and mixing properties. Dynamical systems methods will be used to study the detailed structure of irreversible transport events and map their occurrence. The START08 data will also be used to evaluate the performance of NCAR Whole Atmosphere Community Climate Model (WACCM) simulations of chemistry and transport.
This research will advance our scientific understanding of dynamical, chemical, and radiative processes in the UT/LS, which has the potential to improve model simulations of anthropogenic climate change. Analysis of the START08 data will also advance the development of the GV aircraft as a high-capability observing system. This project will also contribute to the development of human resources in science by training graduate students for research careers and preparing undergraduate students for future graduate study or technical careers.
The Earth's temperature is primarily regulated by greenhouse gases, such as carbon dioxide and water vapor, in the layer from about 3 to 10 miles above the Earth's surface. This project analyzed measurements of those gases and other atmospheric properties made in 2008 with a National Science Foundation research aircraft operated by the National Center for Atmospheric Research in Boulder, CO. The measurements made by the aircraft, and other types of meteorological data collected by NOAA and NASA, were used to study the atmospheric processes that regulate those greenhouse gases and to evaluate the ability of current computer models to correctly simulate those processes. The research aircraft made the first detailed observations of thunderstorms penetrating into the stratosphere in a region near the jet stream where the boundary between the lower atmosphere and the ozone-rich stratosphere can be folded over. Using data from the national weather radar network, we were able observe this type of convection over a much longer period than the aircraft flights and calculate its impact on the lower stratosphere. The aircraft data were used to evaluate a global model that simulates the chemistry and physics of the Earth's atmosphere. Because of the great complexity of the atmosphere, current global atmospheric models are not able to simulate all of the important processes in complete detail. Instead, they use simplifications and approximations, which introduces uncertainties in the model results. Our analysis of the aircraft data shows that current models do a very good job of representing the greenhouse gases in the region where the aircraft flew. The aircraft data were also used to evaluate a regional weather forecasting model. The aircraft data show that these models are able to simulate with good accuracy the transport of pollutants by thunderstorms from near the Earth's surface deep into the atmosphere. This study has improved our understanding of a critical part of the Earth's atmosphere and increased our confidence in using computer models to predict how the atmosphere and climate will change due to human activities.
