Effect of atmospheric stability on the growth of surface gravity waves |
| |
Authors: | Peter A E M Janssen Gerbrand J Komen |
| |
Institution: | (1) Department of Oceanography, Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands |
| |
Abstract: | In this paper we study the effect of atmospheric stability on the growth of surface gravity waves. To that end we numerically solved the Taylor-Goldstein equation for wind profiles which deviate from a logarithmic form because stratification affects the turbulent momentum transport. Using Charnock's relation for the roughness height z
0 of the wind profile, it is argued that the growth rate of the wave depends on the dimensionless phase velocity c/u
* (where u
* is the friction velocity) and a measure of the effect of atmospheric stability, namely the dimensionless Obukhov length gL/u
*
2, whereas it only depends weakly on gz
t
/u
*
2 (where z
t
is the roughness height of the temperature profile). Remarkably for a given value of u
*
/c, the growth rate is larger for a stable stratification (L > 0) than for an unstable one (L < 0). We explain why this is the case. If, on the other hand, one considers the growth rate as a function of c/U
10 (where U
10 is the windspeed at 10 m), the situation reverses for c/U
10 < 1. For practical application in wave prediction models, we propose a new parameterization of the growth rate of the waves which is an improvement of the Snyder et al. (1981) proposal because the effect of stability is taken into account. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|