TransportTracers simulation

Overview

The GEOS-Chem Rn-Pb-Be simulation was based on that of the old Harvard/GISS CTM model. In version 12.2.0, this 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 TransportTracers 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.

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.

List of species

Rn222

  • Description: Radon-222 isotope

  • Purpose: Used to evaluate convection over land and strat-trop exchange.

  • Formula: Rn222

  • Molecular weight (g): 222.0

  • Source: Emitted naturally from soils based on Zhang et al., 2021.

  • Sinks: Radioactive decay into Pb210 with a half-life of 3.83 days (cf Liu et al., 2021).

Pb210

  • Description: Lead-210 isotope

  • Purpose: Used to evaluate wet scavenging and transport.

  • Formula: Pb210

  • Molecular weight (g): 210.0

  • Source: Radioactive decay from Rn222.

  • Sinks:

    1. Radioactive decay with a half-life of 22.3 years (Liu et al., 2001).

    2. Wet deposition

    3. Dry deposition

Pb210s

  • Description: Lead-210 isotope stratospheric-source tracer

  • Purpose: Used to evaluate strat-trop exchange.

  • All other properties are identical to Pb210.

Be7

  • Description: Beryllium-7 isotope

  • Purpose: Used to evaluate wet scavenging and strat-trop exchange.

  • Formula: Be7

  • Molecular weight (g): 7.0

  • Source: Produced by cosmic rays as described in Lal and B. Peters, 1967, with the following modifications (cf. Liu et al, 2001):

    1. Use 1900 disintegrations / g air / s (instead of 3000) at 0 hPa altitude and 70°S latitude.

    2. The original Lal & Peters data ended at 70°S. The values at 70°S were copied to 80°S and 90°S at all levels.

  • Sinks:

    1. Radioactive decay with a half-life of 53.3 days (Liu et al., 2001).

    2. Wet deposition

    3. Dry deposition

Be7s

  • Description: Beryllium-7 isotope stratospheric-source tracer

  • Purpose: Used to evaluate wet scavenging and strat-trop exchange.

  • All other properties are the same as for Be7.

Be10

  • Description: Beryllium-10 isotope

  • Purpose: Used to evaluate wet scavenging and strat-trop exchange.

  • Formula: Be7

  • Molecular weight (g): 7.0

  • Source: Identical to Be7.

  • Sinks:

    1. Radioactive decay with a half-life of \(5.84 \times 10^{8}\) days (Koch and Rind 1998).

    2. Wet deposition

    3. Dry deposition

Be10s

  • Description: Beryllium-10 isotope stratospheric-source tracer

  • Purpose: Used to evaluate wet scavenging and strat-trop exchange.

  • All other properties are the same as for Be10.

aoa

  • Description: Age of air uniform source tracer

  • Purpose: Used for evaluating residual circulation and mixing.

  • Molecular weight (g): 1.0

  • Source: Increases by a value of 1 each emissions timestep.

  • Sink: At the surface.

aoa_bl

  • Description: Age of air uniform source tracer with sink restricted to the boundary layer

  • Purpose: Used for evaluating residual circulation and mixing.

  • Molecular weight (g): 1.0

  • Source: Increases by a value of 1 each emissions timestep.

  • Sink: In the boundary layer.

aoa_nh

  • Description: Age of air uniform source tracer with sink restricted to a zone in the Northern Hemisphere

  • Purpose: Used for evaluating residual circulation and mixing.

  • Molecular weight (g): 1.0

  • Source: Increases by a value of 1 each emissions timestep.

  • Sink: At 30°N - 50°N.

CH3I

  • Description: Methyl iodide

  • Purpose: Used to evaluate marine convection

  • Formula: CH3I

  • Molecular weight (g): 141.94

  • Source: Emissions over the oceans of 1 molec/cm2/s

  • Sink: 5-day e-folding lifetime

CO_25

  • Description: Anthropogenic CO 25 day tracer

  • Formula: CO

  • Molecular weight (g): 28.01

  • Source: Anthropogenic emissions

  • Sink: 25-day e-folding lifetime

CO_50

  • Description: Anthropogenic CO 50 day tracer

  • Formula: CO

  • Molecular weight (g): 28.01

  • Source: Anthropogenic emissions

  • Sink: 50-day e-folding lifetime

e90

  • Description: Constant burden 90 day tracer

  • Molecular weight (g): 1.0

  • Source: Emitted globally at the surface such that the mixing ratio is maintained at 100 ppbv

  • Sink: 90-day e-folding lifetime

e90_n

  • Description: Constant burden Northern Hemisphere 90 day tracer

  • Molecular weight (g): 1.0

  • Source: Emitted at the surface such that the mixing ratio is maintained at 100 ppbv. Emissions source is restricted to 40°N - 90°N.

  • Sink: 90-day e-folding lifetime

e90_s

  • Description: Constant burden Southern Hemisphere 90 day tracer

  • Molecular weight (g): 1.0

  • Source: Emitted at the surface such that the mixing ratio is maintained at 100 ppbv. Emissions source is restricted to 90°S - 40°S.

  • Sink: 90-day e-folding lifetime

nh_5

  • Description: Northern Hemisphere 5 day tracer

  • Molecular weight (g): 1.0

  • Source: Constant source of 100 ppbv at latitudes 30°N - 50°N

  • Sink: 5-day e-folding lifetime

nh_50

  • Description: Northern Hemisphere 50 day tracer

  • Molecular weight (g): 1.0

  • Source: Constant source of 100 ppbv at latitudes 30°N - 50°N

  • Sink: 50-day e-folding lifetime

PassiveTracer

  • Description: Passive tracer for mass conservation evaluation

  • Purpose: Used to evaluate mass conservation in transport

  • Molecular weight (g): 1.0

  • Source: None

  • Sink: None

SF6

  • Description: Sulfur hexafluoride

  • Purpose: Used to evaluate inter-hemispheric transport of anthropogenic emissions

  • Formula: SF6

  • Molecular weight (g): 146.06

  • Source: Anthropogenic emissions

  • Sink: None

st80_25

  • Description: Stratosphere source 25 day tracer

  • Molecular weight (g): 1.0

  • Source: Constant source of 200 ppbv above 80 hPa

  • Sink: 25-day e-folding lifetime