  The observed power spectrum of high-degree solar p-modes (l>200) shows
discrepancies with the power spectrum predicted by the stochastic excitement
and damping theory. In an attempt to explain these discrepancies, the present
paper is concerned with the influence of the observed subsurface flows on the
trapped acoustic modes (p-modes). The effect of these inhomogeneous background
flows is investigated by means of a non-modal analysis and a multi-layer model.
It is shown that the rotational and meridional components of the velocity field
change the wavelengths of the oscillation modes which, in turn, results in
modifications of the corresponding modal frequencies. The magnitudes of the
frequency residuals depend on the spatial scales of the modes and on the
gradients of the different components of the flow velocity. Together with other
mechanisms (e.g. the scattering of modes by the large scale convection
(Goldreich & Murray 1994), the non-modal effect of the variation of the
frequencies in time may contribute: 1) to the observed widening of the
corresponding peaks in the observed power spectrum with increasing angular
degree; 2) to the partial dissipation of spectral power, and, as a result, 3)
to the discrepancies between the predicted and the observed power spectrum of
solar p-modes.
