Lucrezia Ricciardulli

Remote Sensing Systems, 438 First Street, Suite 200 Santa Rosa, California, 95401, USA

Abstract:

Understanding tropical convection and its variability is an essential step towards a realistic
simulation of tropical dynamics with General Circulation Models (GCMs). The aim of our
research is to show the extent to which misrepresentation of convective variability and resolved
equatorial waves in GCMs are responsible for deficiencies in the simulation of tropical dynamical
phenomena such as the quasi-biennial oscillation (QBO) and the semiannual oscillation (SAO).
For this purpose, we tested the behavior of the NCAR Community Climate Model CCM3 and
other GCMs in a set of simulations using different parameterizations of deep convection.
Convective heating spectra, space and time scale of simulated convective activity, and equatorial
wave excitation are investigated. A similar analysis conducted on convective heating inferred
from observed cloud data is considered here for model validation. The role of convectively-excited
equatorial waves in tropical dynamics of the middle atmosphere is then investigated comparing
momentum flux spectra inferred from the observation with the spectra from several models
which were more or less successful in the simulation of the QBO and SAO.