Observational validation of parameterized gravity waves from tropical
convection in the Whole Atmosphere Community Climate Model (WACCM)
Abstract
Tropical gravity waves that are generated by convection are generally
too small in scale and too high in frequency to be resolved in global
climate models, yet their drag forces drive the important global-scale
quasi-biennial oscillation (QBO) in the lower stratosphere, and models
rely on parameterizations of gravity wave drag to simulate the QBO. We
compare detailed properties of tropical parameterized gravity waves in
the Whole Atmosphere Community Climate Model Version 6 (WACCM6) with
gravity waves observed by long-duration super-pressure balloons, and
also compare properties of parameterized convective latent heating with
satellite data. Similarities and differences suggest that the WACCM6
parameterizations are excellent tools for representing tropical gravity
waves, but the results also suggest detailed changes to the gravity wave
parameterization tuning parameter assumptions that would bring the
parameterized waves into much better agreement with observations. While
WACCM6 currently includes only non-stationary gravity waves from
convection, addition of the component that is stationary relative to
convective rain cells is likely to improve the simulation of the QBO in
the model. The suggested changes have the potential to alleviate common
biases in simulated QBO circulations in models.