The effect of synoptic-scale wave breaking on cross tropopause transport and trace gas distribution
Final Report Abstract
Within this project the factors, which lead to the formation and maintenance of the tropopause inversion layer (TIL) during baroclinic life cycles were investigated to further address the relation between these processes and cross tropopause exchange. For this purpose a channel version of the COSMO model was used and modified by including artificial tracers to quantify changes of various thermodynamical as well as transport properties during the evolution of the baroclinic wave. The first set of simulations was performed by including only dry adiabatic processes into the model simulations. These simulations led to the first unexpected result, which indicated a persistent effect of inertia-gravity waves (IGW) on the TIL. The excitation of such waves by the jet stream introduces a persistent effect by generating Kelvin-Helmholtz instabilities which provide conditions favourable for wave breaking to allow for a persistent effect on the static stability at the tropopause. Alternatively wave capture may further introduce a persistent modification of the stability. Building upon these simulations diabatic effects were subsequently included to study the effect on the tropopause and TIL development as well as the effect on tracer exchange across the tropopause. Notably, the study constitutes the first consistent simulation of the diabatic processes during a baroclinic wave breaking event, which modifies the thermal structure of the tropopause region. The results highlight particularly the role of moisture and phase transition as well as water vapor during the different phases of the baroclinic evolution. Water vapor enhances the speed of the baroclinic evolution in total compared to the dry adiabatic simulation. In addition phase transitions and latent heat release are crucial for the initial phase of the TIL strengthening by accelerating the vertical uplift and convergence of the vertical wind. Later on the formation of ice clouds and the strengthening of the vertical water vapor gradient take over and are essential for the maintenance of the TIL. The results are very similar for LC1 and LC2 cases. The effect of these processes on exchange of tracers has been separated from the sensitivity study for the TIL-relevant processes and is subject of a follow-up publication based on the diabatic life cycle experiments. The results indicate a relation between static stability and tropospheric layer thickness above the tropopause. The relevant study, which includes Lagrangian analyses of the cross tropopause exchange and the Eulerian frame work already lead to two papers, which addressed the relations of phase transitions and cloud formations in combination with air mass transport at the inversion layer and at the top of convective clouds.
Publications
- Can inertia-gravity waves persistently alter the tropopause inversion layer, Geophyiscal Research Letters, 41, 7822-7829
Kunkel, D., Hoor, P., Wirth, V.
(See online at https://doi.org/10.1002/2014GL061970) - The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS), Atmos. Chem. Phys., 15, 6467-6486
Frey, W., Schofield, R., Hoor, P., Kunkel, D., Ravegnani, F., Ulanovsky, A., Viciani, S., D'Amato, F., and Lane, T. P.
(See online at https://doi.org/10.5194/acp-15-6467-2015) - Airborne observation of mixing across the entrainment zone during PARADE 2011, Atmos. Chem. Phys., 16, 6011-6025, 2016
Berkes, F., Hoor, P., Bozem, H., Kunkel, D., Sprenger, M., and Henne, S.
(See online at https://doi.org/10.5194/acp-16-6011-2016) - The tropopause inversion layer in baroclinic life cycles experiments: the role of diabatic processes, Atmos. Chem. Phys., 16, 541-560, 2016
Kunkel, D., Hoor, P., and Wirth, V.
(See online at https://doi.org/10.5194/acp-16-541-2016)
