Cloud convection

This page describes the cloud convection (aka wet convection) algorithms of GEOS-Chem. We also invite you to read our Wet deposition wiki page, which contains information about the algorithms used for scavenging of soluble tracers.

Overview

From Section 2, paragraph 10 of Wu et al [2007]:

A major difference between the GEOS-3, GEOS-4, and GISS models is the treatment of wet convection. GEOS-3 [and now also GEOS-5, ed.] uses the Relaxed Arakawa-Schubert convection scheme [Moorthi and Suarez, 1992]. GEOS-4 has separate treatments of deep and shallow convection following the schemes developed by Zhang and McFarlane [1995] and Hack [1994]. The convection scheme in the GISS GCM was described by Del Genio and Yao [1993]. Unlike the GEOS models, the GISS GCM allows for condensed water in the atmosphere (i.e., condensed water is not immediately precipitated), resulting in frequent nonprecipitating shallow convection. In the wet deposition scheme, we do not scavenge soluble species from shallow convective updrafts at altitudes lower than 700 hPa in the GISS-driven model, whereas we do in the GEOS-driven model [Liu et al., 2001].

Updraft scavenging of soluble tracers (as applied to both the Relaxed Arakawa and Hack/Zhang-McFarlane schemes in GEOS-Chem) is described in Section 1 of Jacob et al [2000] and in Section 2.3.1 of Liu et al [2001].

--Bob Y. 13:13, 19 February 2010 (EST)

Relaxed Arakawa-Schubert scheme

This is the convection scheme that GEOS-Chem currently uses with GEOS-FP and MERRA-2 meteorology. The source code for this scheme is located in routine DO_CONVECTION in GeosCore/convection_mod.F.

Validation

See Bey et al [2001], Liu et al [2001], and Wu et al [2007].

References

1. Allen, D.J, R.B. Rood, A.M. Thompson, and R.D. Hidson, Three dimensional ²²²Rn calculations using assimilated data and a convective mixing algorithm, J. Geophys. Res, 101, 6871-6881, 1986a.
2. Allen, D.J. et al, Transport induced interannual variability of carbon monoxide using a chemistry and transport model, 101, J. Geophys. Res, 28,655-28-670, 1986b.
3. Bey I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073-23,096, 2001. PDF
4. Del Genio, A. D., and M. Yao, Efficient cumulus parameterization for long-term climate studies: The GISS scheme, in The Representation of Cumulus Convection in Numerical Models, Meteorol. Monogr., 46, 181–184, 1993.
5. Hack, J.J., Parameterization of moist convection in the National Center for Atmospheric Research Community Climate Model (CCM2), <u<J. Geophys. Res., 99, 5551–5568, 1994.
6. Jacob, D.J. H. Liu, C.Mari, and R.M. Yantosca, Harvard wet deposition scheme for GMI, Harvard University Atmospheric Chemistry Modeling Group, revised March 2000.
7. Liu, H., et al. (2001), 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, 12,109–12,128. PDF
8. Moorthi, S., and M. J. Suarez, Relaxed Arakawa-Schubert: A parameterization of moist convection for general circulation models, Mon. Weather Rev., 120, 978– 1002, 1992.
9. Wu, S., L.J. Mickley, D.J. Jacob, J.A. Logan, R.M. Yantosca, and D. Rind, Why are there large differences between models in global budgets of tropospheric ozone?, J. Geophys. Res., 112, D05302, doi:10.1029/2006JD007801, 2007. PDF
10. Zhang, G. J., and N. A. McFarlane, Sensitivity of climate simulations to the parameterization of cumulus convection in the Canadian Climate Centre general circulation model, Atmos. Ocean, 33(3), 407–446, 1995.

--Bob Y. 13:11, 19 February 2010 (EST)