MMM SEMINAR NCAR
Simulations performed by a 3D cloud-resolving model are used to study the transport of tropospheric tracers into the lowermost stratosphere via midlatitude convection. Direct transport by convection is believed to be the most likely mechanism by which short-lived chemical species can be transported from the boundary layer to the stratosphere. In previous studies of troposphere to stratosphere convective transport, the extent of irreversible transport is unclear. The tropopause location is poorly defined in the highly perturbed environment directly above an active storm. Thus, to determine the irreversibility of cross-tropopause transport, ten-hour simulations are carried out to cover the growth and decay cycles of the storm. After the decay of convection, isentropes relax to quasi-flat surfaces, allowing more confident tropopause location. At ten hours in the typical supercell simulation, at 1 km above the tropopause, the concentration of the tracer originating below 1 km has maximum of 26 percent of its original concentration. The concentration of the tracer originating in the layer between 1 and 4 km has a maximum of 23 percent of its original concentration. Increasing the altitude of the level of neutral buoyancy relative to the tropopause altitude is found to produce more transport into the stratosphere. Supercell storms produce more transport when compared with multicell storms. Using radar reflectivity as a proxy for tracer outflow will be discussed.
Monday, 31 January 2005,
3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2 Auditorium (Rm1022)