4.
[10 points]A sudden stratospheric warming has occurred, caused by a wavenumber 2 wave propagating into the stratosphere at about 60 N. At this latitude, we can assume
fo = 1.25 x 10-4 sec-1 b=1.1 x 10-11 m-1s-1
N2 = 4 x 10-4 s-2 H=6 km
Suppose meridional wavenumber l = 0 and that for wavenumber 2, k = 2/a, where a = 6.37 x 10**6 m is the Earth's radius.
If this wave has phase speed c = 0, what is the maximum zonal average zonal wind [u] that will allow the wave to penetrate into the stratosphere at this latitude?