Betts-Miller Convective Adjustment Scheme

This page contains links to Fortran source code of the Betts-Miller convection scheme.

In the 1980's Alan Betts and Martin Miller developed a novel parameterization of convection for use in global atmospheric models (GCMs): see Betts (1986) and Betts and Miller (1986). In contrast to increasingly complex parameterizations which involve detailed models of cloud processes, the Betts-Miller scheme takes an "external" view of convection and simply adjusts the large scale convective environment towards thermodynamic profiles. Separate profiles are defined for shallow (non-precipitating) and deep precipitating convection, based on both observational evidence and theoretical considerations.

The original scheme was enhanced to include a representation of low-level, evaporatively-driven downdraughts and was documented in Betts and Miller (1993). The scheme was included in the UGAMP GCM, where its behaviour and effects on the modelled climate and tropical variability were documented (Slingo et al, 1994).

Subsequently the code was extensively rewritten, making it more modular and more portable, following the "plug compatibility" rules for GCM parameterizations. The code still contains some extensions to ANSI Fortran which are now easily removed to allow portability using Fortran90.

The scheme was also tested in offline single-column experiments as part of the European Cloud Resolving Modelling Project (EUCREM) in 1996-1997. EUCREM was linked to the international GCSS groups (superceded by GASS) which develop and evaluate convective parameterizations using cloud resolving models and observational data. A report of the EUCREM work on the Betts-Miller scheme is accessible below.

The ocean squall-line case study from EUCREM was published in Bechtold et al (2000).

References:

Betts, A. K.,   1986   A new convective adjustment scheme. Part I: Observational and theoretical basis. Q. J. R. Meteorol. Soc., 112, 677-692. (AKB link)

Betts, A.K. and Miller, M.J.   1986   A new convective adjustment scheme. Part II: Single column tests using GATE wave, BOMEX, ATEX, and Arctic Airmass data sets. Q. J. R. Meteorol. Soc., 112, 693-710. (AKB link)

Betts, A.K. and Miller, M.J.   1993   The Betts-Miller scheme. Chapter in The representation of cumulus convection in numerical models of the atmosphere. Eds. K.A. Emanuel and D.J. Raymond. American Meteorological Society. (AKB link)

Slingo, J.M., Blackburn, M., Betts, A.K., Brugge, R., Hodges, K.D., Hoskins, B.J., Miller, M.J., Steenman-Clark, L. and Thuburn,J.   1994   Mean climate and transience in the tropics of the UGAMP GCM. Part I: Sensitivity to convective parametrization. Q. J. R. Meteorol. Soc., 120, 881-922. (AKB link)

Bechtold, P., Redelsperger, J.L., Beau, I., Blackburn, M., Brinkop, S., Grandpeix, J.Y., Grant, A., Gregory, D., Guichard, F., Hoff, C. and Ioannidou, E.   2000   A GCSS model intercomparison for a tropical squall line observed during TOGA-COARE. II: Intercomparison of single-column models and a cloud-resolving model. Q. J. R. Meteorol. Soc., 126, 865-888. (QJRMS link)

EUCREM final report (Jan 1998) - single column tests

eucrem report

(Printable PDF, 500kb)

Source code and supporting information

ndeep4v2 bm.commons bm.init bm.physc

Betts-Miller source code in UGAMP GCM 2.1 - argument driven version. Common blocks from UGCM 2.1 called from Betts-Miller interface. Initialisation routines from UGCM 2.1 for Betts-Miller. Calling routine for Betts-Miller interface routine in UGCM 2.1.