Empirically Evaluating Divergence Rates of Atmospheric Trajectories
Gidon Eshel
J. Atmos. Sci., Vol. 63(2), pp. 741-753, February 2006.
Abstract
I estimate observed northern hemisphere divergence rates of
phase-space trajectories initially emanating from neighboring
points. I use a simple, seasonal, weakly GCM-dependent, linear
method applied to Ertel potential vorticity on the 315K isentrope.
Using the same data and essentially the same method, I also estimate
atmospheric persistence, the rate of trajectory departure from an
initial state. With the results applying only to the truncated state
considered (comprising only a single variable observed at a single
level), I find that the time scale for divergence of two, initially
reasonably similar, trajectories is about 4-6 days, between the time
scales of cyclogenesis and blocking. I also find that the time
scale for divergence of a given trajectory from an earlier point
along it is about 3-5 days.