Department Seminar: Michael Prather
Title: Atmospheric Chemistry & Transport – A Wrinkle or two in Space-Time
Abstract: When scientific or policy-relevant questions involve atmospheric chemistry, one often hears "nonlinear" or "complex" being invoked pejoratively to avoid having to deal with the complexity. Even some of one's peers in climate science find the chemistry of greenhouse gases to be primitive, lacking robust answers, and thus distasteful. First, let us admit that atmospheric chemistry is complex and nonlinear. By involving reactions of two species, the Taylor expansion of the chemical tendency equations–where differentiable–includes 2nd order terms (x2, y2 or xy). The transport and radiation components couple across species, the atmosphere, and other ocean/land reservoirs. There is actually much joy and discovery in a science of this complexity. In this seminar, I select a set of problems worked on by colleagues and myself over the last four decades. These include: multiple solutions in stratospheric chemistry; ozone depletion; our developing understanding of methane; chemical feedbacks, eigenvalue decomposition, and indirect greenhouse gases; numerical methods for tracer transport; seeing the tail wag the dog; and, finally, measuring the rich chemical heterogeneity that is tropospheric chemistry. I hope to convince you that pursuit of the oddities, the strange, barely noticeable traces of nonlinearity and other weird behavior provides rewarding scientific insights. Most of these 'eureka' moments are just personal, but some can change the way others think about our planet.