Extended Abstract (168K)17A.3
Statistical signature of the surface waves in the wind over the ocean
Tihomir Hristov, Johns Hopkins University, Baltimore, MD
The surface waves at sea substantially perturb the mean
flow and distort the wind turbulence in the marine
atmospheric boundary layer. The perturbation is
responsible for the wind-wave momentum and energy
transfer, but also, by moving the refractive
inhomogeneities in the air, it influences the
propagation pattern of electromagnetic signals. While
the spatio-temporal structure of this perturbation
allows to identify the mechanism of wind-wave
interaction, the perturbation's statistical composition
determines the intensity, phase, and angle of arrival
variation of the signals being transmitted. In the past,
extensive effort has been devoted to studying the
influence of the turbulent motion on signal
(radio-frequency, optical, acoustic)
propagation. However, because of the limited
observational and theoretical information regarding the
wave signature in the wind, virtually nothing has been
known about the surface wave influence on signal
transmission.
In this work we present meteorological field data
collected over the coastal Atlantic in the summer of
2003 during the Coupled Boundary Layers Air-Sea Transfer
(CBLAST) experiment. The data persuasively demonstrate
that especially in low-wind conditions, rather prevalent
at sea, the surface waves modulation dominates the
motion in the marine atmospheric boundary layer. We
invoke a linear model for wave-mean flow interaction to
describe the spatio-temporal structure of the wave
signature and we establish a connection between the
statistics of the surface motion and that of the
wave-induced fields in the atmosphere. Both these are
further used to express the characteristic functions of
the velocity and pressure, as well as the characteristic
function of two-point velocity differences. We observe
that the wave effects depend distinctly on the vertical
coordinate, thus none of the considerations for
isotropy, commonly invoked in studies of turbulence, is
applicable. Similar approach and results apply to the
statistics of wave motion in the boundary layer of the
upper ocean, which influences the propagation of
acoustic signals.
Session 17A, MARINE BOUNDARY LAYERS—II
Friday, 13 June 2008, 10:30 AM-12:15 PM, Aula Magna Vänster
Previous paper Next paper