Cumulus Friction in the Asian Monsoon of a Global Model with 7 km Mesh

  • Suvarchal K. Cheedela
  • Brian E. MapesEmail author
Part of the Springer Atmospheric Sciences book series (SPRINGERATMO)


Vertical transport of horizontal momentum by convective eddies (CMT) in the 7–400 km size range is examined comprehensively in data from the GEOS-5 Nature Run (G5NR), a 2-year global simulation with a 7 km horizontal mesh. This diagnosis is possible because NASA offers a coarse-grained dataset of the quadratic flux terms wu and wv in addition to the model velocity variables uvw. We assess the time tendency of large-scale vertically integrated shear kinetic energy (SKE) due to CMT. Negative values of a few tenths of \(1W m^{-2}\) prevail on average over warm tropical oceans, indicating that explicit convection on these scales exerts a viscous or frictional or downgradient transport effect on wind shear. However, positive as well as negative values do occur locally, based on spatial correlations u\(^\prime \)w\(^\prime \) and v\(^\prime \)w\(^\prime \) in the arrangement (“organization”) of convective motions. In the Asian monsoon, where convection and shear are both strong, the viscosity can be characterized by a regression coefficient with values of about 5% cm\(^{-1}\), meaning that convection which yields 1 cm of precipitation decrements SKE by about 5%. Adjustment of balanced monsoon flow to such a viscous effect implies adiabatic ascent to the north of existing convection, a mechanism that may be relevant to northward-propagating large-scale variability.


Tropical convection Momentum flux G5NR Mesoscale Convection 



The authors gratefully acknowledge the financial support given by the Earth System Science Organization, Ministry of Earth Sciences, Government of India (Grant no. / Project no \(MM/SERP/ Univ\_Miami\_USA / 2013/INT-1/002\)) to conduct this research under Monsoon Mission. We also acknowledge NASA grant NNX14AR75G, and Dr. Matthew Niznik for his initial work toward this project’s goals.


  1. Cheedela, S., M. Niznik, W. Putman, and B. E. Mapes, 2019: Mesoscale eddy momentum flux in a nonhydrostatic global atmosphere model: a global survey, cumulus friction coefficients, and negative viscosity cases. Manuscript in preparation.Google Scholar
  2. DeMott, C.A., C. Stan, and D.A. Randall. 2013. Northward propagation mechanisms of the boreal summer intraseasonal oscillation in the ERA-Interim and SP-CCSM. Journal of Climate 26: 1973–1992. Scholar
  3. Gelaro, R., and Coauthors, 2015: Evaluation of the 7-km GEOS-5 Nature Run. NASA Technical report NASA/TM–2014-104606/Vol. 36, available at
  4. LeMone, M.A. 1983. Momentum transport by a line of cumulonimbus. Journal of the Atmospheric Sciences 40: 1815–1834.CrossRefGoogle Scholar
  5. Mapes, B.E. 2017. Toward form-function relationships for mesoscale structure in convection: A review. Japan: Journal of the Meteorological Society. (in press).Google Scholar
  6. Mapes, B.E., and X. Wu. 2001. NOTES AND CORRESPONDENCE Convective Eddy Momentum Tendencies in Long Cloud-Resolving Model Simulations. Journal of Atmospheric Sciences 58: 517–526.<0517:NACCEM>2.0.CO;2.CrossRefGoogle Scholar
  7. Moncrieff, M.W. 1992. Organized convective systems: Archetypal dynamical models, mass and momentum flux theory, and parametrization. Quarterly Journal of the Royal Meteorological Society 118: 819–850. Scholar
  8. Nishimoto, E., S. Yoden, and H.H. Bui, 2016: Vertical Momentum Transports Associated with Moist Convection and Gravity Waves in a Minimal Model of QBO-like Oscillation. Scholar
  9. Putman, W., A. M. da Silva, L. E. Ott, and A. Darmenov, 2014: Model Configuration for the 7-km GEOS-5.12 Nature Run, Ganymed Release (Non-hydrostatic 7 km Global Mesoscale Simulation), GMAO Office Note, bf 5. (Version 1.0), 86 pp, available from
  10. Putman, W.M., and M. Suarez. 2011. Cloud-system resolving simulations with the NASA Goddard Earth Observing System global atmospheric model (GEOS-5). Geophysical Research Letters 38: L16809. Scholar
  11. Steinheimer, M., M. Hantel, and P. Bechtold. 2008. Convection in Lorenz’s global cycle with the ECMWF model. Tellus 60A: 1001–1022.CrossRefGoogle Scholar
  12. Tung, W., and M. Yanai. 2002. Convective Momentum Transport Observed during the TOGA COARE IOP. PartII: Case Studies. Journal of Atmospheric Science 59: 2535–2549.<2535:CMTODT>2.0,CO;2.CrossRefGoogle Scholar

Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.Department of Atmospheric Sciences, Rosenstiel School of Marine and Atmospheric Science (RSMAS)University of MiamiMiamiUS

Personalised recommendations