Tropical gravity waves and superclusters simulated by 40-level GFDL SKYHI general circulation model experiments with higher horizontal resolutions (0.6° longitude×0.72° latitude) and (1.0°×1.2°) are compared with those simulated by a lower-resolution (3.0°×3.6°) experiment.
Results indicated that simulated precipitational heating appears to excite tropical gravity waves. At higher resolutions, precipitation is more confined in space and time, resulting in a broader wavenumber-frequency spectral distribution. Grid-scale precipitation, which is thought to mimic the precipitation associated with cloud clusters, is organized into larger-scale superclusters. The westward propagation of cloud clusters and eastward propagation of superclusters can be more clearly seen in the high-resolution experiments.
The high-resolution (0.6°×0.72°) model indicates that the lower-stratospheric gravity-wave momentum flux is dominated by high-frequency components having periods shorter than one day. This flux doubles as the resolution is increased from (3.0°×3.6°) to (0.6°×0.72°). It is speculated that a further increase in both the horizontal and vertical resolutions could substantially enhance the gravity-wave momentum flux convergence, thus forcing a stronger quasi-biennial oscillation.