Dry deposition

NOTE: Page under construction!

This page describes the current dry deposition scheme used in GEOS-Chem.

Overview

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Validation

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References

1. Baldocchi, D.D., B.B. Hicks, and P. Camara, A canopy stomatal resistance model for gaseous deposition to vegetated surfaces, Atmos. Environ. 21, 91-101, 1987.
2. Brutsaert, W., Evaporation into the Atmosphere, Reidel, 1982.
3. Businger, J.A., et al., Flux-profile relationships in the atmospheric surface layer, J. Atmos. Sci., 28, 181-189, 1971.
4. Dwight, H.B., Tables of integrals and other mathematical data, MacMillan, 1957.
5. Guenther, A., et al, A global model of natural volatile organic compound emissions, J. Geophys. Res., 100, 8873-8892, 1995.
6. Hicks, B.B., and P.S. Liss, Transfer of SO2 and other reactive gases across the air-sea interface, Tellus, 28, 348-354, 1976.
7. Jacob, D.J., and S.C. Wofsy, Budgets of reactive nitrogen, hydrocarbons, and ozone over the Amazon forest during the wet season, J. Geophys. Res., 95, 16737-16754, 1990.
8. Jacob, D.J., et al, Deposition of ozone to tundra, J. Geophys. Res., 97, 16473-16479, 1992.
9. Levine, I.N., Physical Chemistry, 3rd ed., McGraw-Hill, New York, 1988.
10. Munger, J.W., et al, Atmospheric deposition of reactive nitrogen oxides and ozone in a temperate deciduous forest and a sub-arctic woodland, J. Geophys. Res., in press, 1996.
11. Price, H., L. Jaeglé, A. Rice, P. Quay, P.C. Novelli, R. Gammon, Global Budget of Molecular Hydrogen and its Deuterium Content: Constraints from Ground Station, Cruise, and Aircraft Observations, submitted to J. Geophys. Res., 2007
12. Walcek, C.J., R.A. Brost, J.S. Chang, and M.L.Wesely, SO2, sulfate, and HNO3 deposition velocities computed using regional landuse and meteorological data, Atmos. Environ., 20, 949-964, 1986.
13. Wang, Y., D.J. Jacob, and J.A. Logan, Global simulation of tropospheric O3-NOx-hydrocarbon chemistry, 1. Model formulation, J. Geophys. Res., 103, D9,10,713-10,726, 1998.
14. Wesely, M.L, Improved parameterizations for surface resistance to gaseous dry deposition in regional-scale numerical models, Environmental Protection Agency Report EPA/600/3-88/025, Research Triangle Park (NC), 1988.
15. Wesely, M. L., Parameterization of surface resistance to gaseous dry deposition in regional-scale numerical models, Atmos. Environ., 23, 1293-1304, 1989.

Known issues

Dependency between dry deposition and soil NOx emissions

In GEOS-Chem there is a code dependency between the dry deposition routines soil NOx emissions routines. This is purely historical baggage that goes back to the days of the old 9-layer Harvard-GISS CTM (from which these routines were taken).

The dry deposition routine DEPVEL (in drydep_mod.f) computes a quantity called CANOPYNOX, which is the bulk surface resistance of the canopy to NOx deposition. This is computed in the following lines of code:

C** Get the bulk surface resistance of the canopy, RSURFC, from the network
C** of resistances in parallel and in series (Fig. 1 of Wesely [1989])
               DTMP1=1.D0/RIXX
               DTMP2=1.D0/RLUXX
               DTMP3=1.D0/(RAC(LDT)+RGSX)
               DTMP4=1.D0/(RDC+RCLX)
               RSURFC(K,LDT) = 1.D0/(DTMP1 + DTMP2 + DTMP3 + DTMP4)
C  Save the within canopy depvel of NOx, used in calculating the 
C  canopy reduction factor for soil emissions.
               ! Remove hardwire for CANOPYNOX (bmy, 1/24/03)
               IF ( K == DRYDNO2 ) THEN
                  CANOPYNOX(IJLOOP,LDT)=DTMP1+DTMP2+DTMP3+DTMP4
               ENDIF

However, the CANOPYNOX variable is not defined within drydep_mod.f, but is found instead within the soil NOx emissions code header file commsoil.h:

     REAL*8 CANOPYNOX(MAXIJ,NTYPE) !track NOx within canopy dry dep.

and is then also used within the soil NOx emissions function SOILCRF, as follows:

     IF ((XLAI(IREF,JREF,K).GT.0.D0).AND.
    &    (CANOPYNOX(IJLOOP,K).GT.0.D0))THEN

        VFNEW=VFNEW*SQRT(WINDSQR/9.D0*7.D0/XLAI(IREF,JREF,K))*
    *        (SOILEXC(2)/SOILEXC(NN))
        SOILCRF=CANOPYNOX(IJLOOP,K)/(CANOPYNOX(IJLOOP,K)
    *        +VFNEW)
     ELSE
    
        SOILCRF=0.D0
     END IF

This is not necessarily a problem as long as dry deposition is always turned on whenever you are doing a full-chemistry simulation that requires soil NOx emissions. In the driver routine main.f, dry deposition is always done before emissions. However, this is bad coding style and a potential source of error. (This also must be corrected for the GEOS-Chem column code, in which all inputs must come thru the argument list.)

In the new soil NOx emissions code being developed by Rynda Hudman (much of which is based on the GEOS-Chem column code being developed by Bob Yantosca and Philippe Le Sager), there is a new module called canopy_nox_mod.f. This module computes the CANOPYNOX quantity independently of routine DEPVEL in drydep_mod.f, which allows for a totally clean separation between dry deposition routines and emissions routines.

At present, the new canopy_nox_mod.f is not available in the standard mainline GEOS-Chem code. It is slated to be incorporated with the soil NOx emissions update.

--Bob Y. 13:51, 18 February 2010 (EST)