Quantifying the Convective Transport of Air to the Lower Stratosphere with an Observationally-Constrained Model

Cross-tropopause convection provides a means of rapidly and irreversibly transporting lower tropospheric air and water into the LS. While the signature of convective hydration has been shown to be significant, likely due to the sublimation of ice, the signature of convective influence in other trace species is often difficult to observe and quantify. However, even if the contribution of tropospheric air mixed into the LS in the extra-tropics is small, its chemical impact may be significant because boundary layer air has a much different chemical composition than that of the free troposphere, and convection can transport air from the surface to stratospheric altitudes on a time scale of hours, thereby preserving the concentrations of short-lived chemical constituents. Here, we attempt to quantify convective airmass transport independent of hydration, using trace species data acquired during multiple NASA airborne campaigns and a 1-D mixing model.

The Observationally-Constrained Atmospheric Mixing Model (OCAMM) relies solely on a suite of simultaneous in situ observations of trace species – including methane, ozone, carbon dioxide and carbon monoxide – to provide a vertically resolved, quantitative account of the contribution from a set of predefined transport pathways, including convection, to the composition of the LS. Critically, in situ data can capture and resolve both the spatial extent of convective outflow, as well as synoptic scale processes such as quasi-isentropic transport associated with the North American Monsoon Anticyclone. As such, OCAMM provides an independent and complementary perspective on the interactions between stratospheric dynamics, cross-tropopause convection, and airmass composition of the LS.