Edwin Gerber, Professor, New York University
Trace gases in the stratosphere impact surface climate. Seemingly small changes in stratospheric water vapor, on the order of one part per million as observed in the year 2000, impact surface temperature by as much as a tenth of a degree. Chemistry climate model simulations of stratospheric ozone also depend critically on the transport of ozone and ozone depleting substances. Biases in transport are a leading source of uncertainty in the recovery of stratospheric ozone.
In this talk, I'll show that observations of trace gases provide an opportunity to improve our ability to characterize and understand the circulation of the stratosphere. In particular, recent work enabled a measurement based estimate of the overturning circulation of the stratosphere, a first order climatological quantity that has been a challenge for atmospheric reanalyses. This suggests that incorporation of trace gas measurements into reanalyses could improve their ability to capture the dynamics of the stratosphere. Then I'll focus on the challenge trace transport presents to numerical climate prediction. A benchmark test of atmospheric model cores reveals the sensitivity of the circulation and tracer transport to numerics and resolution. State-of-the-art cores developed by GFDL and NCAR do not capture a consistent representation of stratospheric transport.