Laserfiche WebLink
<br />of 10 to 20 ms-1 (Gossard and Sweezy, 1974). Long gravity waves move <br />relative to the atmosphere with a speed <br /> <br />c=~V9h <br /> <br />(1 ) <br /> <br />where h is the height of the corresponding homogenous atmosphere. <br /> <br />These waves have relatively small vertical acceleration and are <br /> <br />therefore consistent with the quasi-hydrostatic approximation. <br />However, the horizontal divergence in both types of gravity waves is <br /> <br />not negligible. Figure 2 illustrates the relationship between the <br />phase velocity of the gravity wave in the height of the homogenous <br /> <br />atmosphere using equation 1. <br /> <br />Haltiner and Martin (1955) describe the shearing-gravitational waves <br /> <br />on an internal surface of discontinuity. They have derivl:!d an <br /> <br />equation for the phase velocity c of these waves: <br /> <br />c = <br /> <br />pu + plu' <br />p + p' <br /> <br />+ <br /> <br />{_'Jb_ ~ , <br />- - pp <br />2rr (p + pi) <br /> <br />(u-u')2 <br />(p + p') 2 <br /> <br />(2 ) <br /> <br />where pi and u' are the density and basic velocity of the upper <br /> <br />homogenous layer and p and u for the lower layer are all assumed <br /> <br />constant in time and space: L is the wavelength, g is the gravita- <br />tional acceleration. Representative values of mid-tropospheric <br />conditions produce phase velocities from 20 to 100 ms-1 using <br /> <br />this relationship. <br /> <br />3 <br />