P. M. Inness, D. Gregory, 1997: Aspects of the intraseasonal
oscillation Center Atmosphere Model simulated by the Hadley Center Atmosphere
Model. Climate Dynamics,13, 441-458.
Abstract. The period and amplitude of the tropical intraseasonal oscillation
in the Haley Center Global Climate Model have been examined by applying
time filtering and spectral analysis techniques to time series of daily
velocity potential. Results from an AMP integration of the model, forced
with observed sea surface temperatures for the decade 1979-88 show that
the model has a reasonable degree of skill in simulating the main features
of the oscillation, although the signal in the model is rather noisy compared
to NWT analyses. The model also shows internal variability of the oscillation
similar in magnitude to that in the analyses. The impact on the oscillation
of including a parameterization of momentum transport by cumulus convection
is assessed. This parameterization significantly improves the mean circulation
of the model, reducing systematic errors particularly in the tropics. However,
the strength and coherence of the tropical intraseasonal oscillation are
significantly reduced by this parameterization. It is speculated that this
may be related to a reduction in westerly flow in the tropical central
and east Pacific and a reduction in the strength of the SPCZ in DJF.