Submitted as: model evaluation paper
18 May 2022
Submitted as: model evaluation paper | 18 May 2022
Status: this preprint is currently under review for the journal GMD.

Tropospheric transport and unresolved convection: numerical experiments with CLaMS-2.0/MESSy

Paul Konopka1, Mengchu Tao2, Marc von Hobe1, Lars Hoffmann3, Corinna Kloss1,a, Fabrizio Ravegnani4, C. Michael Volk5, Valentin Lauther5, Andreas Zahn6, Peter Hoor7, and Felix Ploeger1 Paul Konopka et al.
  • 1Forschungszentrum Jülich, IEK-7, Germany
  • 2Carbon Neutrality Research Center, Institute of Atmospheric Physics, Beijing, China
  • 3Jülich Supercomputing Centre, Forschungszentrum Jülich, Germany
  • 4National Research Council - Institute for Atmospheric Sciences and Climate (ISAC-CNR), 40129 Bologna, Italy
  • 5Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal, Germany
  • 6The Institute of Meteorology and Climate Research (IMK), Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 7Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
  • anow at: Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E), Universitè d’Orlèans, France

Abstract. Pure Lagrangian, i.e.~trajectory-based transport models, take into account only the resolved advective part of transport. That means neither mixing processes between the air parcels (APs) nor unresolved subgrid-scale advective processes like convection are included. The Chemical Lagrangian Model of the Stratosphere (CLaMS-1.0) extends this approach by including mixing between the Lagrangian APs parameterizing the small-scale isentropic mixing. To improve model representation of the upper troposphere and lower stratosphere (UTLS), this approach was extended by taking into account parameterization of tropospheric mixing and unresolved convection in the recently published CLaMS-2.0 version. All three transport modes, i.e. isentropic and tropospheric mixing as well as the unresolved convection can be adjusted and optimized within the model. Here, we investigate the sensitivity of the model representation of tracers in the UTLS with respect to these three modes.

For this reason, the CLaMS-2.0 version implemented within the Modular Earth Submodel System (MESSy), CLaMS-2.0/MESSy, is applied with meteorology based on the ERA-Interim (EI) and ERA5 (E5) reanalyses with the same horizontal resolution (1.0 x 1.0 degree) but with 60 and 137 model levels for EI and E5, respectively. Comparisons with in situ observations are used to rate the degree of agreement between different model configurations and observations. Starting from pure advective runs as a reference and in agreement with CLaMS-1.0, we show that among the three processes considered, isentropic mixing dominates transport in the UTLS. Both the observed CO, O3, N2O and CO2 profiles as well as CO-O3 correlations are clearly better reproduced in the model with isentropic mixing. The second most important transport process considered is unresolved convection. This additional pathway of transport from the Planetary Boundary Layer (PBL) to the main convective outflow dominates the composition of air in the lower stratosphere relative to the contribution of the resolved transport. This transport happens mainly in the tropics and sub-tropics, and significantly rejuvenates the age of air in this region. By taking into account tropospheric mixing, weakest changes in tracer distributions without any clear improvements were found.

Paul Konopka et al.

Status: open (until 13 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-97', Anonymous Referee #1, 16 Jun 2022 reply
  • RC2: 'Comment on gmd-2022-97', Anonymous Referee #2, 19 Jun 2022 reply

Paul Konopka et al.

Paul Konopka et al.


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Short summary
Pure trajectory-based transport models driven by meteorology derived from reanalysis products (ERA5) take into account only the resolved, advective part of transport. That means neither mixing processes nor unresolved subgrid-scale advective processes like convection are included. The Chemical Lagrangian Model of the Stratosphere (CLaMS) includes these processes. We show that isentropic mixing dominates unresolved transport. The second most important transport process is unresolved convection.