Line Shape Parameters in Support of Remote Sensing of Earth's and Planetary Atmospheres

该项目涉及开发一个理论模型，以计算满足遥感领域需要的地球和行星大气中气体的压力加宽半宽度和压力引起的谱线移位及其与温度的关系。半宽仍然是用于减少遥感数据的光谱参数和用于计算温室气体辐射强迫的逐行模型的主要误差来源。由于许多不同气体的数千个转动振动跃迁都需要数据，因此需要一个基于物理的计算有效的理论模型来正确确定谱线形状参数。半经典复数Robert-Bonamy形式主义是该理论方法的基础。为了使结果适用于所有跃迁，不仅是强线，分子间势必须展开到非常高的阶数，分子动力学必须使用哈密顿方程。对于近红外和可见光光谱区的跃迁，需要更好的波函数和能量，因为经典的有效哈密顿确定被打破了。人们正在探索使用从头算能量和波函数来确定还原的矩阵元素，作为解决该问题的一种手段。目前正在研究碰撞诱导参数的振动态、旋转态和温度依赖性。由于星载光谱仪的改进，线形模型需要改进。虽然Voigt模型构成了线形的基础，但在这项工作中必须并正在考虑对Dicke变窄和速度相关性的修正，以及它们之间的相关性。由此产生的数据将大大改善线形参数及其温度相关性，通过减少模型中使用的半宽度和其他线形参数的不确定性，帮助研究人员对地球和其他行星的热平衡进行浓度和温度分布的反演和辐射传输研究。这项工作将提高对光谱遥感结果的信心，并能够更好地确定温室气体的辐射强迫。对地球能量平衡的理解的改善将有助于做出更明智的政策决定。这些数据将通过HITRAN、HITEMP、GEISA和IUPAC(水蒸气)数据库和首席调查员网站分发。一名博士后学者和几名本科生将在这个项目上工作，学习他们在课堂上学不到的技能。与当地一所高中正在进行的合作允许本科生定期访问学校，谈论他们的工作，目的是激发高中生对科学的兴趣。

This project involves development of a theoretical model to calculate pressure-broadened half-widths and pressure-induced line shifts and their temperature dependences for gases in the terrestrial and planetary atmospheres that meets the needs of the remote sensing community. 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. Because data are needed for many thousands of ro-vibrational transitions of many different gases a computationally efficient theoretical model, based on physics, is desired that can correctly determine the line shape parameters. The semi-classical Complex Robert-Bonamy formalism is the basis of the theoretical approach. For results to be good for all transitions, not only strong lines, the intermolecular potentials must be expanded to very high order and the molecular dynamics must use Hamilton's equations. For transitions in the near infrared and visible spectral regions better wavefunctions and energies are needed, since the classic effective Hamiltonian determination breaks down. The use of ab initio energies and wavefunctions in the determination of the reduced matrix elements is being explored as a means to remedy the problem. The vibrational state, rotational state, and temperature dependence of the collision-induced parameters are being investigated. Because of the improvement in space borne spectrometers, line shape models need to be improved. While the Voigt model forms the basis for line shape, corrections for Dicke narrowing and speed dependence, and their correlation, must be and are being considered in this work.The resulting data will provide greatly improved line shape parameters and their temperature dependence, aiding researchers doing concentration and temperature profile retrievals and radiative transfer studies of the heat balance of Earth and other planets by reducing the uncertainty of the half-widths and other line shape parameters used in their models. This work will improve confidence in spectroscopic remote sensing results and allow a better determination of the radiative forcing of greenhouse gases. The improvement in understanding the energy balance of the Earth will help make more informed policy decisions. The data will be distributed via the HITRAN, HITEMP, GEISA, and IUPAC (for water vapor) databases and the principal investigator's web site. A postdoctoral scholar and several undergraduate students will work on this project, learning skills that they would not get in a classroom setting. An ongoing collaboration with a local high school allows undergraduate students to routinely visit the school to talk about their work with the aim of creating interest in science among the high schoolers.