Basic Model

---

Take two upward propagating waves which are equal and opposite in zonal phase speed. These

waves are assumed to only interact with the mean wind not each other. As the waves propagate upward

their amplitude are dampened. In the figure above you can see the two waves. Positive is

westerly(eastward) waves and negative is easterly (westward) waves. The solid line in the middle

represents the mean velocity of the wind. The westerly wave will be absorbed below the peak in the

westerly winds which causes an acceleration which leads to the downward propagation of the westerly

peak. The easterly wave very weakly interacts with the westerly mean wind field and propagates up to

the easterly peak, it too produces an acceleration below the peak and causes the easterly peak to move

downward. Eventually the westerly wind field will get too narrow and viscous effects take over and

the peak breaks, this is what has happened in part b. Now the westerly wave very slowly dampens and

will get absorbed in the upper levels causing an westerly acceleration which begins to establish a new

westerly peak.

(Plumb, 1984)


Main Page History Basic Equations (The Math) Skip the Math