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

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

Abstract

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.

Keywords

Tropical convection Momentum flux G5NR Mesoscale Convection 

Notes

Acknowledgements

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.

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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

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