Attenuation Rate

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This attenuation rate tells us three very important things about how the momentum flux (think energy) is

damped as the waves propagate through a mean wind field. First, as the buoyancy (N) increases all waves

will be damped quicker. Second, as the thermal dissipation (µ) of a region increases all wave will also be

damped. Third, that as the Doppler-shifted velocity decreases a wave is attenuated more. This last

point allows for the frequency filtering in the stratosphere that produces the QBO. Let's say you have

two waves identical except for one wave is propagating easterly and the other westerly:



If we have a mean flow that is westerly (̄u>1) we can see just by looking at the attenuation rate we

can see that the Doppler-shifted velocity makes the attenuation of the westerly wave much greater than

for the easterly wave.

But why does the peak of the mean velocity travel downward?

Main Page Basic Equations Downward Peak