Global Atmospheric Chemistry: Uncertainties and Errors; Modes and Parametric Models

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Research will be continued on the basic properties of chemistry-transport models (CTMs), focusing on: (1) correction of the numerical error in CTMs due to grid resolution, and (2) chemical mode studies that include the derivation of a stratosphere-troposphere coupled chemistry mode and the formulation of a simplified (parametric) model having the same modes as the CTM. A new approach for calculating the numerical errors associated with grid resolution will be developed and tested. The results will be broadly applicable to all CTMs, and will not only characterize the resolution errors but may also be used to help correct them. The existence of global chemical modes in CTMs will be used as a fundamental diagnostic of the models. The tropospheric chemical mode that describes decadal perturbations to methane will be coupled, for the first time in a CTM, with the century-long stratospheric mode involving nitrous oxide and ozone. Global chemical modes will be used to develop reduced-dimension parametric models using sensitivity calculations with a CTM. A reduced-dimension Jacobian will be calculated that completely defines the parametric model and can be compared with the modes of the full CTM.Broader impacts range from improving the atmospheric chemistry/composition elements in Earth system models to providing more accurate scientific input on global change. The quantification of even one component of uncertainty in projecting atmospheric composition should benefit Earth system models and their policy applications. This project will also help prepare undergraduate students, doctoral students, and post-docs working in atmospheric chemistry with the mathematical skills needed to diagnose and analyze complex Earth system models.