Changes in Transport from the Northern Hemisphere Midlatitude Surface

Abstract:

Understanding future changes in transport from the Northern Hemisphere (NH) midlatitude surface, a source of major greenhouse gases, ozone depleting substances, tropospheric ozone and aerosols, is central to understanding and predicting tropospheric air quality, stratospheric ozone depletion, and changes in the earth's radiative balance. Here we present an analysis of transport from the NH midlatitude surface using idealized age tracers that probe different aspects of the transport circulation, as simulated in integrations of the Goddard Earth Observing System Chemistry Climate Model and the NCAR Community Climate System Model subject to present-day and future greenhouse gases and ozone depleting substances. Implications for the seasonal and interannual variability as well as long-term changes in a range of chemical constituents, including carbon monoxide, are made and interpreted in terms of shifts in the location and strength of tropical convection and changes in isentropic transport out of the NH midlatitude surface layer. Intermodel differences in the variability and long-term trends in transport are interpreted in terms of intermodel differences in large-scale dynamics.