Seven sins in dynamical meteorological education The mathematics is always correct, the computers are given the right equations, but the explanations do not only contradict Nature but also the mathematics they are supposed to illuminate. Seven sins in dynamical meteorological education
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The mathematics is always correct, the computers are given the right equations, but the explanations do not only contradict Nature but also the mathematics they are supposed to illuminate
Professor Richard Reed, Univ. Of Seattle 1988:
-Our understanding of the cyclogenesis process has increased tremendously during the last 40 years – at least the computers seem to understand!
“-I have never understood what a Rossby waves is…”
Professor Harold Jeffreys on his deathbed 1987
Lunch discussion at ECMWF 1995:
Scientist: -How is the weekend going to be?
AP: -Fine, a Rossby wave is seen coming in!
Scientist: -But you can’t see Rossby waves??
C= phase speed, U= zonal flow at 500 hPa, L=wave length, =df/dy
c < 0 for large L c >0 for small L
Rossby et al (1939)
Only when the paper was published did Rossby realize that he could not use gradient wind balance - it is only applicable on stationary patterns
gradient wind explanation of the progression of waves
Short waves - the curvature effect dominates
Bjerknes´ gradient wind idea to illustrate the retrogression of waves
Long waves - the latitude effect dominates
This is NOT a Rossby wave!
low high f
high low f
…but a Constant Absolute Vorticity Trajectory!
There are 5-6 other misleading or erroneous explanations of the Rossby wave before it finally was explained in a kinematically consistent way
Rossby (1940), Petterssen (1956), Persson (1993)
notice of a Rossby (1940)
correction - and even fewer
understood what he meant
trajectories in a progressive flow
and wave lengths
lines and trajectories in a
and wave lengths
Let us go back to the Constant Absolute Vorticity Trajectory (which is NOT a Rossby wave)
Rossby asked: -Which non-stationary streamlines would correspond to this trajectory?
One and the same CAV trajectory satisfies two types of streamlines (waves)
Short progressive waves
Long retrogressive waves