TransportTracers simulation

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  9. TransportTracers simulation


This page contains information about the TransportTracers (formerly Rn-Pb-Be) simulation in GEOS-Chem.

Overview

The Rn-Pb-Be simulation in GEOS-Chem was based on that of the old Harvard/GISS CTM model. The current simulation follows Liu et al (2001).

In GEOS-Chem 12.2.0 the Rn-Pb-Be simulation was extended to include additional passive species for benchmarking purposes and for diagnosing transport in GEOS-Chem. At this time the simulation was renamed to the TransportTracer simulation.

In GEOS-Chem 14.2.0 the TransportTracers simulation was further modified so that species names and definitions are now consistent with GMAO's tracer gridded component (aka TR_GridComp). This will facilitate comparison of transport within GEOS-Chem, GCHP, and GEOS.

List of species

The transport tracers are summarized below.

Species name Description Source Sink Purpose
Rn222 Radon-222 isotope
  • Half-life of 3.83 days (Liu at al., 2001).
    • Decays into Pb210 according to the exponential law:
EXP( -ΔT * 2.097d-6 )
Used to evaluate convection over land and strat-trop exchange
Pb210 Lead-210 isotope
  • Radioactive decay from Rn222 according to the exponential law:
EXP( -ΔT * 2.097d-6 )
Where ΔT is the emission timestep in seconds.
  • Half-life of 22.3 years (Liu et al., 2001).
    • Decays according to the exponential law:
EXP( -ΔT * 9.725d-10 )
  • Wet deposition
  • Dry deposition
Used to evaluate wet scavenging and transport
Pb210s Lead-210 isotope stratospheric-source tracer
  • Same as Pb210 (restricted to the stratosphere)
  • Same as Pb210
Used to evaluate strat-trop exchange
Be7 Beryllium-7 isotope
  • Produced by cosmic rays as described in Lal and B. Peters, 1967
  • Plus the following modifications from Liu et al. (2001):
  1. Replace data at (0 hPa altitude, 70°S latitude) following Koch (1996):
    • old value = 3000 disintegrations/g air/s
    • new value = 1900 disintegrations/g air/s
  2. The original Lal & Peters data ended at 70°S
    • Copy the data values at 70°S to 80°S and 90°S at all levels
  • Half-life of 53.3 days (Liu et al., 2001).
    • Decays according to the exponential law:
EXP( -ΔT * 1.506d-7 )
  • Wet deposition
  • Dry deposition
Used to evaluate wet scavenging and strat-trop exchange
Be7s Beryllium-7 isotope stratospheric source tracer
  • Same as Be7 (restricted to the stratosphere)
  • Same as Be7
Used to evaluate strat-trop exchange
Be10 Beryllium-10 isotope
  • Be10 has an identical source distribution as Be7 following Koch and Rind (1998).
  • Half-life of 5.84e8 days (Koch and Rind, 1998).
    • Decays according to the exponential law:
EXP( -ΔT * 1.506d-7 )
  • Wet deposition
  • Dry deposition
Used to evaluate wet scavenging and strat-trop exchange
Be10s Beryllium-10 isotope stratospheric source tracer
  • Same as Be10 (restricted to the stratosphere)
  • Same as Be10
Used to evaluate strat-trop exchange
PassiveTracer Passive tracer with initial concentration of 100 ppb
  • None
  • None
Used to evaluate mass conservation in transport
SF6 Sulfur hexafluoride
  • Anthropogenic emissions from EDGAR v4.2
  • None
Used to evaluate inter-hemispheric transport of anthropogenic emissions
CH3I Methyl iodide
  • Emissions over the oceans of 1 molec/cm2/s
  • 5-day e-folding lifetime
Used to evaluate marine convection
CO_25 Anthropogenic CO 25-day tracer
  • Emissions from CEDS v2
  • 25-day e-folding lifetime
CO_50 Anthropogenic CO 50-day tracer
  • Emissions from CEDS v2
  • 50-day e-folding lifetime
e90 Constant burden 90-day tracer
  • Emitted globally at the surface such that the mixing ratio is maintained at 100 ppbv
  • 90-day e-folding lifetime
e90_n Constant burden Northern Hemisphere 90-day tracer
  • Emitted at the surface such that the mixing ratio is maintained at 100 ppbv. Emissions source is restricted to 40N - 90N.
  • 90-day e-folding lifetime
e90_s Constant burden Southern Hemisphere 90-day tracer
  • Emitted at the surface such that the mixing ratio is maintained at 100 ppbv. Emissions source is restricted to 90S - 40S.
  • 90-day e-folding lifetime
aoa Age of air uniform source tracer
  • Increases by a value of 1 each emissions timestep
  • Sink at the surface
Used for evaluating residual circulation and mixing
aoa_bl Age of air uniform source tracer with sink restricted to the boundary layer
  • Increases by a value of 1 each emissions timestep
  • Sink in the boundary layer
Used for evaluating residual circulation and mixing
aoa_nh Age of air uniform source tracer with sink restricted to a zone in the Northern Hemisphere
  • Increases by a value of 1 each emissions timestep
  • Sink at 30N - 50N
Used for evaluating residual circulation and mixing
nh_5 Northern Hemisphere 5-day tracer
  • Constant source of 100 ppbv at latitudes 30N - 50N
  • 5-day e-folding lifetime
nh_50 Northern Hemisphere 50-day tracer
  • Constant source of 100 ppbv at latitudes 30N - 50N
  • 50-day e-folding lifetime
st80_25 Stratospheric source 25-day tracer
  • Constant source of 200 ppbv above 80 hPa
  • 25-day e-folding lifetime

References

  1. Liu, H., D. Jacob, I. Bey, and R.M. Yantosca, Constraints from 210Pb and 7Be on wet deposition and transport in a global three-dimensional chemical tracer model driven by assimilated meteorological fields, J. Geophys. Res, 106, D11, 12109-12128, 2001.
  2. Jacob et al., Evaluation and intercomparison of global atmospheric transport models using 222Rn and other short-lived tracers, J. Geophys. Res, 102, 5953-5970, 1997.
  3. Koch, D.M., D.J. Jacob, and W.C. Graustein, Vertical transport of tropospheric aerosols as indicated by 7Be and 210Pb in a chemical tracer model, J. Geophys. Res, 101, D13, 18651-18666, 1996.
  4. Koch, D., and D. Rind, Beryllium 10/beryllium 7 as a tracer of stratospheric transport, J. Geophys. Res., 103, D4, 3907-3917, 1998.
  5. Lal, D., and B. Peters, Cosmic ray produced radioactivity on the Earth. Handbuch der Physik, 46/2, 551-612, edited by K. Sitte, Springer-Verlag, New York, 1967.



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