10:00 AM - 10:15 AM
[MTT41-05] Surface pressure variation excited by cumulus convection
Keywords:cumulus convection, microbaroms, free oscillation, infrasound
Numerical experiment reproduced a typical life cycle of convective cloud. We examine the temporal evolution of the horizontal average of surface pressure, whose horizontal wavenumber (zero) is the nearest to the wavenumber of the earth's free oscillation ( O(1/1000km)) in all of the waves in the model. The result shows that the temporal variation of surface pressure contains both a slow variation corresponding to the development of cloud as a whole and much faster variation, whose frequency corresponds to that of the enhancement of the earth's free oscillation.
The pressure variation is compared with the runs of the linearlized one-dimensional model driven by the horizontal averages of various non-linear or diabatic terms sampled in the full model. The result shows that the slow variation is mainly excited by the sink of water vapor due to condensation and the drag force of liquid water, whereas the fast component is excited by the latent heating of condensation.
On the other hand, non-averaged pressure time series contains much higher frequency components. The details will be examined in the presentation.