This page contains information about the Radon-Lead-Beryllium simulation in GEOS-Chem.
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 .
The standard Rn-Pb-Be simulation uses the following tracers:
- Rn222, which is emitted naturally from soils
- Pb210, which is the primary decay product of Rn222
- Be7, which is produced by cosmic rays in the stratosphere
This simulation is most frequently used to validate the convection and advection processes in GEOS-Chem.
The source of #Rn222 is determined as follows (cf. Jacob et al ):
- Rn222 emission poleward of 70 degrees = 0.0 [atoms/cm2/s]
- For latitudes 70S-60S and 60N-70N (both land & ocean), Rn222 emission = 0.005 [atoms/cm2/s]
- For latitudes between 60S and 60N:
- Rn222 over land = 1 [atoms/cm2/s] over land
- Rn222 over land = 0.005 [atoms/cm2/s] over oceans
- Where the surface temperature is below 0° C, reduce Rn222 emissions by a factor of 3.
The source of Be7 is taken from Lal and Peters .
Rn222 decays into Pb210 according to the exponential law: EXP( -ΔT * 2.097d-6 )
Pb210 decays according to the exponential law: EXP( -ΔT * 9.725d-10 )
Be7 decays according to the exponential law: EXP( -ΔT * 1.506d-7 )
where -ΔT is the emission timestep in seconds.
See Liu et al .
- 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, 12,109-12,128, 2001.
- Jacob et al., Evaluation and intercomparison of global atmospheric transport models using Rn-222 and other short-lived tracers, J. Geophys. Res, 102, 5953-5970, 1997.
- Koch, D. J. Geophys. Res, 101, D13, 18651, 1996.
- 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.
None at this time
--Bob Y. 10:07, 2 March 2011 (EST)