Principal Investigator Raymond Plumb
We evaluate transport characteristics of two- and three-dimensional chemical transport models of the stratosphere by comparing their simulations of the mean age of stratospheric air and the propagation of periodic oscillations in tracer mixing ratio at the tropical tropopause into the stratosphere to inferences from in situ and satellite observations of CO2, SF6, and water vapor. The models, participants in the recent NASA "Models and Measurements" study, display a wide range of performance. However, most of the models underestimate mean age throughout the stratosphere, some by factors of two or more, and most have at least one of several unrealistic features in their mean age contour shapes. Model-to-model variation in the photochemically active species N2O, NOy, and Cly is correlated with variation in mean age in the lower stratosphere. We conclude that transport inaccuracies contribute uncertainty to the simulation of important chemical species in the lower stratosphere.