Role of Vertical Structure of Convective Heating in MJO Simulation in NCAR CAM5

Role of Vertical Structure of Convective Heating in MJO Simulation in NCAR CAM5 AbstractObservational studies suggest that the vertical structure of diabatic heating is important to MJO development. In particular, the lack of top-heavy heating profile was believed to be responsible for poor MJO simulations in global climate models. In this work, we investigate the role of vertical heating profile in MJO simulation by modifying the convective heating profile to different shapes, from top-heavy heating to bottom cooling, to mimic mesoscale heating in the NCAR CAM5. Results suggest that incorporating a mesoscale stratiform heating structure can significantly improve the MJO simulation. By artificially adding stratiform-like heating and cooling in the experiments, many observed features of MJO are reproduced, including clear eastward propagation, a westward-tilt vertical structure of MJO-scale anomalies of dynamic and thermodynamic fields and strong 20-80-day spectral power. Further analysis shows an abundance of shallow convection ahead of MJO deep convection, confirming the role of shallow convection in preconditioning the atmosphere by moistening the lower troposphere ahead of deep convection during MJO life cycle. Additional experiments show that lower-level cooling contributes more to improving the MJO simulation. All these features are lacking in the control simulation, suggesting that the mesoscale stratiform heating, especially its lower-level cooling component, is important to MJO simulation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Role of Vertical Structure of Convective Heating in MJO Simulation in NCAR CAM5

Journal of Climate , Volume preprint (2017): 1 – Jun 26, 2017

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-16-0913.1
Publisher site
See Article on Publisher Site

Abstract

AbstractObservational studies suggest that the vertical structure of diabatic heating is important to MJO development. In particular, the lack of top-heavy heating profile was believed to be responsible for poor MJO simulations in global climate models. In this work, we investigate the role of vertical heating profile in MJO simulation by modifying the convective heating profile to different shapes, from top-heavy heating to bottom cooling, to mimic mesoscale heating in the NCAR CAM5. Results suggest that incorporating a mesoscale stratiform heating structure can significantly improve the MJO simulation. By artificially adding stratiform-like heating and cooling in the experiments, many observed features of MJO are reproduced, including clear eastward propagation, a westward-tilt vertical structure of MJO-scale anomalies of dynamic and thermodynamic fields and strong 20-80-day spectral power. Further analysis shows an abundance of shallow convection ahead of MJO deep convection, confirming the role of shallow convection in preconditioning the atmosphere by moistening the lower troposphere ahead of deep convection during MJO life cycle. Additional experiments show that lower-level cooling contributes more to improving the MJO simulation. All these features are lacking in the control simulation, suggesting that the mesoscale stratiform heating, especially its lower-level cooling component, is important to MJO simulation.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Jun 26, 2017

References

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