Abstract Submission for NETW ’11

by Joe Archive on April 28, 2011

Moist Static Energy Budget of MJO-like disturbances in the atmosphere of a zonally symmetric aquaplanet

Joseph Andersen & Zhiming Kuang

Harvard

Abstract

 

A Madden-Julian Oscillation (MJO)-like spectral feature (enhanced power in the intraseasonal-planetary spectral range) is observed in the time-space spectra of precipitation, Outgoing Longwave Radiation, and Moist Static Energy (MSE) for a zonally symmetric aquaplanet simulated with Super-Parameterized Community Atmospheric Model (SP-CAM), which uses small Cloud System Resolving Models at each grid point in place of a more traditional convective parameterization. The propagation and structure of the disturbances shows that it shares the basic features of the observed MJO.

To probe the processes responsible for propagation and maintenance of this disturbance, we analyze the MSE budget of the disturbance. We observe that the disturbances propagate both eastwards and polewards, with propagation and maintenance dominated by a combination of horizontal and vertical advection of MSE, anomalous longwave heating and surface latent heat fluxes. The column integrated long-wave heating is the only significant source of column integrated MSE acting to maintain the MJO-like anomaly balanced against the combination of column integrated horizontal and vertical advection of MSE and Latent Heat Flux. Propagation of the MJO-like disturbance is dominated by eastward contributions from both column integrated horizontal and vertical advection of MSE, with the column long-wave heating retarding the propagation.

In the MJO region, the column integrated horizontal advection of MSE is dominated by eddies. The eddy advection is shown to be well approximated by an eddy diffusive parameterization. Further decomposition indicates that the advection contribution to the eastward propagation is dominated by meridional advection of MSE by anomalous synoptic eddies caused by the suppression of eddy activity ahead of the MJO convection. This suppression is linked to the barotropic conversion mechanism, with the gradients of the net wind experienced by the eddies within the MJO envelope acting to modulate the Eddy Kinetic Energy. The meridional eddy advection’s contribution to poleward propagation is dominated by the mean state’s eddy activity acting on the anomalous MSE gradients associated with the MJO.

 

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