Equatorial Waves Excited by Convection Studied With the Whole Atmosphere Community Climate Model (WACCM)

Transient fluctuations of convection are an efficient mechanism for the excitation of equatorial waves. Vertically propagating waves transport energy and momentum upward and are an essential factor in coupling the troposphere to the stratosphere and upper atmosphere. Many climate models underestimate the convective variability at time scales shorter than 2 days, therefore severely impacting wave excitation. Here we used the Whole Atmosphere Community Climate Model (WACCM) to study the excitation of waves under different convective parameterizations. Unlike other convective parameterizations, the scheme by Tiedtke (1989) efficiently excites high frequency waves (Kelvin and inertia-gravity) that are able to propagate into the stratosphere and beyond. The horizontal resolution has an impact on the type of waves excited. A low-resolution (4x5) simulation produces a realistic spectrum of Kelvin waves, which are characterized by large scales, but gravity waves are deficient. A higher resolution (1.9x2.5) simulation, however, generates gravity waves with spectral power comparable to that derived from satellite observations. Using WACCM allows us to (1) Compare the dynamical perturbations simulated in the model to observations (e.g., the SABER/TIMED mission); and (2) study the impact of wave activity on the dynamics of the middle atmosphere.