Scientific Results

Tropical troposphere to stratosphere transport of carbon monoxide and long-lived trace species in the Chemical Lagrangian Model of the Stratosphere (CLaMS)

Year: 2014

Authors: Pommrich R., Muller R., Grooss J.U., Konopka P., Ploeger F., Vogel B., Tao M., Hoppe C.M., Gunther G., Spelten N., Hoffmann L., Pumphrey H.C., Viciani S., D\’Amato F., Volk C.M., Hoor P., Schlager H., Riese M.

Autors Affiliation: Forschungszentrum Julich, IEK 7, D-52425 Julich, Germany; Univ Toulouse 3, Lab Aerol, CNRS, INSU,UMR5560, F-31400 Toulouse, France; Meteo France, CNRM GAME, Grp Etud Atmosphere Meteorol, URA 1357, F-31057 Toulouse 1, France; Forschungszentrum Julich, JSC, D-52425 Julich, Germany; Univ Edinburgh, Sch Geosci, Edinburgh, Midlothian, Scotland; CNR INO, I-50125 Florence, Italy; Berg Univ Wuppertal, Wuppertal, Germany; Johannes Gutenberg Univ Mainz, D-55122 Mainz, Germany; Deutsch Zentrum Luft & Raumfahrt, Inst Physik Atmosphare, Oberpfaffenhofen, Germany

Abstract: Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact of these transport fluxes on the composition of the tropical lower stratosphere. Anomaly patterns of carbon monoxide (CO) and long-lived tracers in the lower tropical stratosphere allow conclusions about the rate and the variability of tropical up-welling to be drawn. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F (CFC-11), CCl2F2 (CFC-12), and CO2) in the lower tropical stratosphere. For the long-lived trace substances, the boundary conditions at the surface are prescribed based on ground-based measurements in the lowest model level. The boundary condition for CO in the lower troposphere (below about 4 km) is deduced from MOPITT measurements. Due to the lack of a specific representation of mixing and convective uplift in the troposphere in this model version, enhanced CO values, in particular those resulting from convective outflow are underestimated. However, in the tropical tropopause layer and the lower tropical stratosphere, there is relatively good agreement of simulated CO with in situ measurements (with the exception of the TROCCINOX campaign, where CO in the simulation is biased low approximate to 10-15 ppbv). Further, the model results (and therefore also the ERA-Interim winds, on which the transport in the model is based) are of sufficient quality to describe large scale anomaly patterns of CO in the lower stratosphere. In particular, the zonally averaged tropical CO anomaly patterns (the so called \”tape recorder\” patterns) simulated by this model version of CLaMS are in good agreement with observations, although the simulations show a too rapid up-welling compared to observations as a consequence of the overestimated vertical velocities in the ERA-Interim reanalysis data set. Moreover, the simulated tropical anomaly patterns of N2O are in good agreement with observations. In the simulations, anomaly patterns of CH4 and CFC-11 were found to be very similar to those of N2O; for all long-lived tracers, positive anomalies are simulated because of the enhanced tropical upwelling in the easterly shear phase of the quasi-biennial oscillation.

Journal/Review: GEOSCIENTIFIC MODEL DEVELOPMENT

Volume: 7 (6)      Pages from: 2895  to: 2916

More Information: The authors thank Nicole Thomas for excellent programming support, which constituted an essential contribution to the work reported here. We also thank Felix Schaps for technical support in implementing the use of AIRS data as a lower boundary condition in the model. We are grateful to both the MOPITT and the MLS team for making such great research products publicly available. We thank the European Centre for Medium-Range Weather Forecasts (ECMWF) for providing meteorological analyses and the ERA-Interim reanalysis data. We further thank the experimental teams active in the M55-Geophysica campaigns TROCCINOX, SCOUT-O3, and AMMA and the teams of the research aircraft Falcon (TROCCINOX) and Lear-Jet (SPURT) for conducting the measurements, which were used in this work. The TROCCINOX campaign (including the M55-Geophysica research flights) was partially funded by the Commission of the European Community under the contract EVK2-CT-2001-00122 and by other TROCCINOX partners; the M55-Geophysica and Falcon flights in the frame of the SCOUT-O3 campaign in Darwin in early 2005 have been supported by an European Community grant through the project SCOUT-O3 under contract COCE-CT-2004-505390; the M55-Geophysica campaign within the frame of AMMA was supported by the EEIG-Geophysica Consortium, CNRS-INSU, EC Integrated Projects AMMA-EU (contract number 004089-2), SCOUT-O3 and CNES. Part of the present work is also supported by the European Commission under the grant number StratoClim-603557-FP7-ENV.2013.6.1-2.
KeyWords: atmospheric pollution; carbon monoxide; Lagrangian analysis; mixing ratio; ozone; pollutant transport; quasi-biennial oscillation; stratosphere; trace gas; tropical meteorology; troposphere, Bivalvia
DOI: 10.5194/gmd-7-2895-2014

Citations: 39
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