Large-scale convectively coupled gravity waves in a two-dimensional cloud resolving model: a vertical normal mode perspective Stefan Tullch

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Several competing theories have been proposed to explain the existence and dynamics of large-scale equatorial waves coupled to convection. Although these theories each make fairly definitive predictions regarding the structure and energetics of the waves (from a perspective of vertical normal modes), such predictions have largely gone untested. In this study, a vertical normal mode transform algorithm is used to analyze the structure and energetics of large-scale [O(1000 km)] convectively coupled gravity waves that spontaneously developed in a two-dimensional cloud resolving model. Results of the analysis indicate that the simulated waves primarily owe their existence to an unstable interaction between convection and higher-order vertical normal modes (as argued in stratiform instability theory). Surprisingly, however, it is found here that deep convective heating processes, as well as stratiform heating processes, play an important role in maintaining the energy of these higher-order modes. As expected, mid-level convective heating processes act to strongly remove energy in the higher-order modes. The implications of these findings towards the problem of convective parameterization are discussed.

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16 July, 2003
2 PM/ DSRC 1D 403

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