Three-dimensional transport and concentration of SF6. A model intercomparison study (TransCom 2)

Sulfur hexafluoride (SF 6 ) is an excellent tracer of large-scale atmospheric transport, because it has slowly increasing sources mostly confined to northern midlatitudes, and has a lifetime of thousands of years. We have simulated the emissions, transport, and concentration of SF 6 for a 5-year period, and compared the results with atmospheric observations. In addition, we have performed an intercomparison of interhemispheric transport among 11 models to investigate the reasons for the diVerences among the simulations. Most of the models are reasonably successful at simulating the observed meridional gradient of SF 6 in the remote marine boundary layer, though there is less agreement at continental sites. Models that compare well to observations in the remote marine boundary layer tend to systematically overestimate SF 6 at continental locations in source regions, suggesting that vertical trapping rather than meridional transport may be a dominant control on the simulated meridional gradient. The vertical structure of simulated SF 6 in the models supports this interpretation. Some of the models perform quite well in terms of the simulated seasonal cycle at remote locations, while others do not. Interhemispheric exchange time varies by a factor of 2 when estimated from 1-dimensional meridional profiles at the surface, as has been done for observations. The agreement among models is better when the global surface mean mole fraction is used, and better still when the full 3-dimensional mean mixing ratio is used. The ranking of the interhemispheric exchange time among the models is not sensitive to the change from station values to surface means, but is very sensitive to the change from surface means to the full 3-dimensional tracer fields. This strengthens the argument that vertical redistribution dominates over interhemispheric transport in determining the meridional gradient at the surface. Vertically integrated meridional transport in the models is divided roughly equally into transport by the mean motion, the standing eddies, and the transient eddies. The vertically integrated mass flux is a good index of the degree to

[1]  M. Holzer.  Analysis of Passive Tracer Transport as Modeled by an Atmospheric General Circulation Model , 1999 .

[2]  P. Crutzen,et al.  Trace Gas Measurements Between Moscow and Vladivostok Using the Trans-Siberian Railroad , 1998 .

[3]  D. Rind,et al.  Improved surface and boundary layer models for the Goddard Institute for Space Studies general circulation model , 1997 .

[4]  P. Bakwin,et al.  Behavior of trace gas mixing ratios on a very tall tower in North Carolina , 1997 .

[5]  P. Patra,et al.  Observed vertical profile of sulphur hexafluoride (SF6) and its atmospheric applications , 1997 .

[6]  James W. Elkins,et al.  Tropospheric SF6: Observed latitudinal distribution and trends, derived emissions and interhemispheric exchange time , 1997 .

[7]  Inez Y. Fung,et al.  Variations in modeled atmospheric transport of carbon dioxide and the consequences for CO2 inversions , 1996 .

[8]  A. Scott Denning,et al.  Simulations of terrestrial carbon metabolism and atmospheric CO2 in a general circulation model: Part 1: Surface carbon fluxes , 1996 .

[9]  P. Ciais,et al.  Influence of two atmospheric transport models on inferring sources and sinks of atmospheric CO2 , 1996 .

[10]  I. Levin,et al.  Refining of atmospheric transport model entries by the globally observed passive tracer distributions of 85krypton and sulfur hexafluoride (SF6) , 1996 .

[11]  Shoichi Taguchi,et al.  A three‐dimensional model of atmospheric CO2 transport based on analyzed winds: Model description and simulation results for TRANSCOM , 1996 .

[12]  Jochen Harnisch,et al.  Tropospheric trends for CF4 and C2F6 since 1982 derived from SF6 dated stratospheric air , 1996 .

[13]  L. Paul Steele,et al.  Sulfur hexafluoride—A powerful new atmospheric tracer , 1996 .

[14]  D. Randall,et al.  A Revised Land Surface Parameterization (SiB2) for Atmospheric GCMS. Part I: Model Formulation , 1996 .

[15]  D. Randall,et al.  Liquid and Ice Cloud Microphysics in the CSU General Circulation Model. Part 1: Model Description and Simulated Microphysical Processes , 1996 .

[16]  Anthony D. Del Genio,et al.  A Prognostic Cloud Water Parameterization for Global Climate Models , 1996 .

[17]  D. Randall,et al.  Simulations of terrestrial carbon metabolism and atmospheric CO2 in a general circulation model: Part 2: Simulated CO2 concentrations , 1996 .

[18]  N. Mahowald,et al.  Cumulus parameterizations in chemical transport models , 1995 .

[19]  P. Ciais,et al.  A Large Northern Hemisphere Terrestrial CO2 Sink Indicated by the 13C/12C Ratio of Atmospheric CO2 , 1995, Science.

[20]  D. Randall,et al.  Latitudinal gradient of atmospheric CO2 due to seasonal exchange with land biota , 1995, Nature.

[21]  Ian G. Enting,et al.  A synthesis inversion of the concentration and δ 13 C of atmospheric CO 2 , 1995 .

[22]  R. Wilson,et al.  Climatology of the SKYHI Troposphere–Stratosphere–Mesosphere General Circulation Model , 1995 .

[23]  Philip J. Rasch,et al.  Examination of tracer transport in the NCAR CCM2 by comparison of CFCl3 simulations with ALE/GAGE observations , 1994 .

[24]  I. Levin,et al.  Global increase of SF6 observed in the atmosphere , 1994 .

[25]  J. Pinto,et al.  Transport, radiative, and dynamical effects of the antarctic ozone hole: A GFDL SKYHI' model experiment , 1994 .

[26]  A. Ravishankara,et al.  Atmospheric Lifetimes of Long-Lived Halogenated Species , 1993, Science.

[27]  David A. Randall,et al.  A second-order bulk boundary-layer model , 1992 .

[28]  J. Blanchet,et al.  The Canadian Climate Centre Second-Generation General Circulation Model and Its Equilibrium Climate , 1992 .

[29]  R. Law,et al.  APPLICATION OF AN ATMOSPHERIC TRACER MODEL TO HIGH SOUTHERN LATITUDES , 1992 .

[30]  I. Fung,et al.  Observational Contrains on the Global Atmospheric Co2 Budget , 1990, Science.

[31]  Radon‐222 as a test of convective transport in a general circulation model , 1990 .

[32]  P. Crutzen,et al.  Parameterization of vertical tracer transport due to deep cumulus convection in a global transport model and its evaluation with 222Radon measurements , 1990 .

[33]  M. Tiedtke.  A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models , 1989 .

[34]  R. A. Plumb,et al.  On the meridional structure of long-lived tropospheric constituents , 1988 .

[35]  H. Levy,et al.  Fate of US and Canadian combustion nitrogen emissions , 1987, Nature.

[36]  David Rind,et al.  Chemistry of the Global Troposphere' Fluorocarbons as Tracers of Air Motion , 2007 .

[37]  D. Jacob,et al.  Atmospheric distribution of 85Kr simulated with a general circulation model , 1987 .

[38]  C. D. Keeling,et al.  Simulating the atmospheric carbon dioxide distribution with a three-dimensional tracer model , 1986 .

[39]  Akio Arakawa,et al.  The parameterization of the planetary boundary layer in the UCLA general circulation model - Formulation and results , 1983 .

[40]  H. Sartorius,et al.  Large‐scale atmospheric mixing derived from meridional profiles of krypton 85 , 1983 .

[41]  U. C. Mohanty.  Parameterization of the planetary boundary layer for use in forecasting models , 1983, MAUSAM.

[42]  Peter H. Stone,et al.  Efficient Three-Dimensional Global Models for Climate Studies: Models I and II , 1983 .

[43]  G. J. Boer.  Diagnostic Equations in Isobaric Coordinates , 1982 .

[44]  G. Russell,et al.  A New Finite-Differencing Scheme for the Tracer Transport Equation , 1981 .

[45]  J. Louis.  A parametric model of vertical eddy fluxes in the atmosphere , 1979 .

[46]  W. Moxim,et al.  Tracer simulation using a global general circulation model: Results from a midlatitude instantaneous source experiment , 1978 .

[47]  C. Bhumralkar,et al.  Parameterization of the Planetary Boundary Layer in Atmospheric General Circulation Models - A Review , 1975 .

[48]  G. Czeplak,et al.  Studies of Interhemispheric Exchange in the Troposphere by a Diffusion Model , 1975 .