Abstract
What processes control large-scale variations of deep convection (LSVDC) in the tropics? Here ‘large-scale’ is taken to mean any coherent variations, in either space or time, comprised of statistical populations of separate convective cloud systems. This essay highlights the distinction between processes which supply moisture or available energy over the depth of the convecting layer (equilibrium control), versus inhibition and initiation processes at low levels (activation control), as hypotheses for explaining LSVDC.
Conceptual separations of the LSVDC problem are reviewed. Scale separation, though rigorous, is artificial, since net heating makes deep convective clouds multiscale, or spectrally red. Moist-dry, or diabatic-adiabatic, separation is more useful. An ill-posed hybrid separation — ‘the interaction of moist convection with large scales’ — has spawned confusion. Correlations between deep convection and its own large-scale components (suggestively labeled ‘forcing’) have been misinterpreted as evidence for equilibrium control. This externalization of large-scale vertical velocity also encourages overinterpretation of a fictitious ‘compensating subsidence’ term.
Published evidence for equilibrium control theories is critically re-examined. The deep-cloud quasi-equilibrium observations of Arakawa and Schubert would hold for arbitrarily determined variations of convection, because stratified fluid dynamics efficiently redistributes localized heating, not because convection is controlled by slow deep large-scale ‘forcing.’ A more sensitive test indicates that most tropical LSVDC are not forced by preexisting deep upward motions.
Activation-control processes can operate on the large space scales and long time scales that define LSVDC. Modulation of convection by easterly waves and upper-tropospheric troughs, and the climatological distribution of convective cloudiness, are examined as examples. Lower boundary flux enhancements and deep lifting exert both equilibrium and activation influences on convection. The hypothesis that activation control may prevail on all scales short of globally-averaged climate is difficult to refute.
Systematic study of convective cloud-ensemble sensitivities is badly needed. Unfortunately, current cloud ensemble modeling strategies, based on unnatural equilibrium-control assumptions, render the results merely diagnostic.
To represent activation controls, large-scale models need multiple levels, and some prognostic representation of the subgridscale inhomogeneity of low-level fields.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Addis, R.P., M. Garstang, and G.D. Emmitt, 1984: Downdrafts from tropical ocean cumuli. Boundary-layer Met., 28, 23–49.
Arakawa, A., and W.H. Schubert, 1974: Interaction of a cumulus cloud ensemble with the large-scale environment, Part I. J. Atmos. Sci., 31, 674–701.
Arakawa, A., 1993: Closure assumptions in the cumulus parameterization problem. Pages 1–16 in The Representation of Cumulus Convection in Numerical Models, K.E. Emanuel and D.J. Raymond, Eds. Meteorological monographs, v24, No. 46, AMS, Boston, USA, 246 pp.
Betts, A.K., 1974: Thermodynamic classification of tropical convective soundings. Mon. Wea. Rev., 102, 760–764.
Betts, A.K., J.H. Ball, A.C.M. Beljaars, M.J. Miller, and P.A. Viterbo, 1996: The land surface-atmosphere interaction: a review based on observational and global modeling perspectives. J. Geophys. Res., 101, 7209–7225.
Bretherton, C.S., and P.K. Smolarkiewicz, 1989: Gravity waves, compensating subsidence, and detrainment and detrainment around cumulus clouds. J. Atmos. Sci., 46, 740–759.
Bretherton, C.S., 1993: The nature of adjustment in cumulus cloud fields. Pages 63–74 in The Representation of Cumulus Convection in Numerical Models, K.E. Emanuel and D.J. Raymond, Eds. Meteorological monographs, v24, No. 46, AMS, Boston, USA, 246 pp.
Colby, F.P.,Jr., 1984: Convective inhibition as a predictor of convection during AVE-SESAME II. Mon. Wea. Rev., 112, 2239–2252.
Emanuel, K.A., 1994: Atmospheric Convection. Oxford University press, 580pp
Frank, W.M., 1983: The cumulus parameterization problem. Mon. Wea. Rev., 111, 1859–1871.
Emanuel, K.A., J.D. Neelin, and C.S. Bretherton, 1994: On large-scale circulations in convecting atmospheres. Quart. J. Roy. Meteor. Soc., 120, 1111–1143.
Gaynor, J.E., and C.F. Ropelewski, 1979: Analysis of the convectively modified GATE boundary layer using in situ and acoustic sounder data. Mon. Wea. Rev., 107, 985–993.
Gill, A.E., 1982: Studies of moisture effects in simple atmospheric models: the stable case. Geophys. Astrophys. Fluid Dyn., 19, 119–152.
Gregory, D., and P.R. Rowntree, 1990: A mass flux convection scheme with representation of cloud ensemble characteristics and stability dependent closure. Mon. Wea. Rev., 118, 1483–1506.
Grell, G.A., 1993: Prognostic evaluation of assumptions used by cumulus parameterizations. Mon. Wea. Rev., 121, 764–787.
Grube, P.G., 1979: Convection induced temperature change in GATE. Atmospheric science paper no. 305, Colorado State University, Fort Collins, CO, USA.
Hack, J.J., W.H. Schubert, and P.L. Silva Dias, 1984: A spectral cumulus parameterization for use in numerical models of the tropical atmosphere. Mon. Wea. Rev., 112, 704–716.
Houze, R.A. Jr., and A.K. Betts, 1981: Convection in GATE. Rev. Geoph. Space Phys., 19, 541–576.
Houze, R.A., Jr., S.G. Geotis, F.D. Marks, Jr., and A.K. West, 1981: Winter monsoon convection in the vicinity of north Borneo, Part I: Structure and time variation of the clouds and precipitation. Mon. Wea. Rev., 109, 1595–1614.
Houze, R.A., Jr., 1993: Cloud dynamics. Academic press, New York.
Jenkins, M.A., 1995: The cold-core temperature structure in a tropical easterly wave. J. Atmos. Sci., 52, 1168–1177.
Kiladis, G.N., and K.M. Weickmann, 1992: Extratropical forcing of tropical pacific convection during northern winter. Mon. Wea. Rev., 120, 1924–1938.
Kung, E.C., and L.T. Merritt, 1974: Kinetic energy sources in large-scale tropical disturbances over the Marshall Islands area. Mon. Wea. Rev., 102, 489–502.
Madden, R.A., and P.R. Julian, 1994: Observations of the 40–50 day tropical oscillation–a review. Mon. Wea. Rev., 122, 814–837.
Mapes, B.E., and R.A. Houze, Jr., 1992: An integrated view of the 1987 Australian monsoon and its mesoscale convective systems. Part I: Horizontal structure. Quart. J. Roy. Meteor. Soc., 118, 927–963.
Mapes, B.E., 1993: Gregarious tropical convection. J. Atmos. Sci., 50, 2026–2037.
Mapes, B.E., and R.A. Houze, Jr., 1995: Diabatic divergence profiles in western Pacific mesoscale convective systems. J Atmos. Sci., 52, 1807–1828.
Mapes, B.E., 1997: The large-scale part of mesoscale convective system circulations: a linear vertical spectral band model. J. Meteor. Soc. Japan,in press.
Mapes, B.E., 1997b: What controls large-scale variations of deep convection? Report of ECMWF workshop on new insights and approaches to cumulus parameterization, November 1996.
Neelin, J.D., and I.M. Held, 1987: Modeling tropical convergence based on the moist static energy budget. Mon. Wea. Rev., 115, 3–12.
Nicholls, M.E., R.A. Pielke, and W.R. Cotton, 1991: Thermally forced gravity waves in an atmosphere at rest. J. Atm. Sci., 48, 1869–1884. (see also 1993 J. Atmos. Sci., 50, 4097–4103 )
Ooyama, K.V., 1971: A theory on parameterization of cumulus convection. J. Meteor. Soc. Japan, 49, special issue, 744–756.
Ooyama, K.V., 1982: Conceptual evolution of the theory and modeling of the tropical cyclone. J. Meteor. Soc. Japan, 60, 369–379.
Qian, L., G.S. Young, and W.M. Frank, 1996: An integrated cumulus ensemble and turbulence model (ICET) parameterization scheme for global circulation models. Part I: Convection wake/Gust front component. Personal communication.
Raymond, D.J., 1983: Wave-CISK in mass flux form. J. Atmos. Sci., 40, 2561–2572.
Raymond, D.J., 1995: Regulation of moist convection over the west Pacific warm pool. J. ‘limos. Sci., 52, 3945–3959.
Riehl, H., 1954: Tropical Meteorology. McGraw-Hill, New York.
Riehl, H., 1977: Venezuelan rain systems and the general circulation of the summer tropics II: Relations between low and high latitudes. Mon. Wea. Rev., 105, 1421–1433.
Riehl, H., and J.S. Malkus, 1958: On the heat balance in the equatorial trough zone. Ceophysica, 6, 503–538.
Schubert, W.H., 1974: Cumulus parameterization theory in terms of feedback and control. Atmospheric science paper no. 226, Colorado State University, Fort Collins, CO, USA.
Stevens, B., D.A. Randall, X. Lin, and M.T. Montgomery, 1996: A comment on: On large-scale circulations in convecting atmospheres, by Emanuel, Neelin, and Bretherton. Quart. J. Roy. Meteor. Soc., in review.
Takayabu, Y., 1994: Large-scale cloud disturbances associated with equatorial waves. Part I: Spectral features of the cloud disturbances. J. Meteor. Soc. Japan, 72, 433–449.
Thompson, R.M., Jr., S.W. Payne, E.E. Recker, and R.J. Reed, 1979: Structure and properties of synoptic-scale wave disturbances in the intertropical convergence zone of the eastern Atlantic. J. Atmos. Sci., 36, 53–72.
Thorncroft, C.D., and B.J. Hoskins, 1994: An idealized study of African easterly waves. I: A linear view. Quart. J. Roy. Meteor. Soc., 120, 953–982.
Wang, J., and D.A. Randall, 1994: The moist available energy of a conditionally unstable atmosphere. Part II: Further analysis of GATE data. J. Atmos. Sci., 51, 703–710.
Weckwerth, T.M., J.W. Wilson, and R.M. Wakimoto, 1996: Thermodynamic variability within the convective boundary layer due to horizontal convective rolls. Mon. Wea. Rev., 124, 769–784.
Xu, K.-M., 1991: The coupling of cumulus convection with large-scale processes. Ph.D. dissertation, University of California, Los Angeles, 250 pp.
Xu, K.-M., A. Arakawa, and S.K. Krueger, 1992: The macroscopic behavior of cumulus ensembles simulated by a cumulus ensemble model. J. Atmos. Sci., 49, 2402–2420.
Yanai, M., S. Esbensen and J. Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci., 30, 611–627.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1997 Springer Science+Business Media Dordrecht
About this chapter
Cite this chapter
Mapes, B.E. (1997). Equilibrium Vs. Activation Control of Large-Scale Variations of Tropical Deep Convection. In: Smith, R.K. (eds) The Physics and Parameterization of Moist Atmospheric Convection. NATO ASI Series, vol 505. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-8828-7_13
Download citation
DOI: https://doi.org/10.1007/978-94-015-8828-7_13
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-4960-5
Online ISBN: 978-94-015-8828-7
eBook Packages: Springer Book Archive