Two problems in mesoscale wave dynamics are addressed: (i) wave-turbulence
interaction in a breaking mountain wave and (ii) gravity wave generation associated
with coastal heating gradients.
The mean and turbulent structures in a breaking mountain wave are considered
using an ensemble of high-resolution (essentially LES) wave-breaking calculations. A
turbulent kinetic energy budget for the wave shows that the turbulence production
is almost entirely due to the mean shear. Most of the production is at the top of
the leeside shooting
ow, where the mean-
ow Richardson number is persistently
less than 0:25. Computation of the turbulent heat and momentum
uxes shows that
the dissipation of mean-
ow wave energy is due primarily to the momentum
uxes.
The resulting drag on the leeside shooting
ow leads to a loss of mean
ow Bernoulli
function as well as a cross-stream PV
ux. The dependence of both the resolved-scale
and subgrid turbulent
uxes on the grid spacings is examined by computing a series
of ensembles with varying grid spacings. The subgrid parameterization is shown to
produce an overestimate of the PV
ux at low grid resolution.
The generation of gravity waves by coastal heating gradients is explored using linear theory calculations and idealized numerical modeling. The linear theory for
ow
without terrain shows that the solution depends on two parameters: a nondimensional
coastal width L and a nondimensional wind speed U. For U 6= 0 the solution is
composed of three distinct wave branches. Two of these branches correspond to the
no-wind solution of Rotunno, except with Doppler shifting and dispersion. The third
branch exists only for U 6= 0 and is shown to be broadly similar to
ow past a steady
heat source or a topographic obstacle. The relative importance of this third branch
is determined largely by the parameter combination U=L.
The e ect of terrain is explored in the linear context using an idealized linear
model and associated diagnostic computations. These results are then extended to
the nonlinear problem using idealized nonlinear model runs.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-284 |
| Date | 2009 May 1900 |
| Creators | Qian, Tingting |
| Contributors | Epifanio, Craig C., Zhang, Fuqing |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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