Line Shape Parameters and Their Temperature Dependence for Molecules of Importance in Earth's Atmosphere

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The Principal Investigator (PI) plans to develop a theoretical framework to calculate pressure-broadened half-widths and pressure-induced line shifts for trace gases in the terrestrial atmosphere. The half-width remains the major source of error in the spectral parameters used for reducing remote sensing data and in line-by-line models used to calculate radiative forcing from greenhouse gases. The inclusion of the line shift in profile retrievals also reduces the error in the procedure. For applications to the Earth's atmosphere, data are needed for thousands of ro-vibrational transitions. Hence a theoretical model is needed that is computationally efficient and capable of determining gamma and delta within the needs of the spectroscopic and remote sensing communities. In this work the temperature dependence of the half-width and the line shift will be investigated. The vibrational state, rotational state, and temperature dependence of these collision-induced parameters will be investigated.Broader impacts include education of a postdoctoral student and three undergraduate students in the research project. The work will also provide resources for research and education. All the results of the calculations will be made available online (http://faculty.uml.edu/Robert_Gamache). The line shape information for atmospheric molecules will be incorporated into the HITRAN molecular absorption parameter database for use by the community. The contributions beyond science and engineering are that the results will be used by the remote sensing community and will allow them more confidence in their data. These results will allow a better understanding about planet Earth, its energy balance, how the concentration of ozone and other gases are changing with time, and how climate is evolving. This knowledge will allow for better regulation and stewardship of the planet's interacting systems and will allow better presentations of the information to the citizens of the United States and the world.