Modeling the interaction between cumulus convection and linear waves in a limited domain cloud system resolving model

Zhiming Kuang

Journal of Atmospheric Sciences, accepted, 2007

Abstract

A limited domain cloud system-resolving model (CSRM) is used to simulate the interaction between cumulus convection and 2-dimensional linear gravity waves, a single horizontal wavenumber at a time. With a single horizontal wavenumber, soundings obtained from horizontal averages of the CSRM domain allow us to evolve the large-scale wave equation and thereby model its interaction with cumulus convection. It is shown that convectively coupled waves with phase speeds of 8-13m/s can develop spontaneously in such simulations. The wave development is weaker at long wavelengths (> ~10000km). Waves at short wavelengths (~2000km) also appear weaker, but the evidence is less clear because of stronger influences from random perturbations. The simulated wave structures are found to change systematically with horizontal wavelength, and at horizontal wavelengths of 2000-3000km they exhibit many of the basic features of the observed 2-day waves. The simulated convectively coupled waves develop without feedbacks from radiative processes, surface fluxes, or wave radiation into the stratosphere, but vanish when moisture advection by the large-scale waves is disabled. A similar degree of vertical tilt is found in the simulated convective heating at all wavelengths considered, consistent with observational results. Implications of these results to conceptual models of convectively coupled waves are discussed. Besides being a useful tool for studying wave-convection interaction, the present approach also represents a useful framework for testing the ability of coarse-resolution CSRMs and Single Column Models in simulating convectively coupled waves.

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Zhiming Kuang <lastname at fas.harvard.edu>