Internal Waves tn Channels of Vartable Depth 
2 gl 
d 0 
5 sae Be 0 ., (20) 
dk 
where 
at+b 
fz Zz 
I = ff: aay , J = feiGex (21) 
a 
One consequence of (20) is that the group velocity c 
the same sign as the wave velocity c, since 
g is always of 
qe re = eS 2 
e = S6 aE (22) 
so that 
do 
ce, (= My es Oi (23) 
: dk 
Now we wish to see how c” varies with k*. Rewriting (19) 
as 
2 
1 4 isa: ue 
ee ie = = = a[gis 
; (ogi cscs gal (ko - ky) dig : Bro}, (24) 
and going to the limit, we have 
2 2 
Lo oe. ac c 
Le ef bot a who eile ee 25 
3 5 ween ed (25) 
dk 
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