Symmetric instability. Sources: Texts: Martin p. 224228 Holton p. 277281 Meted modules: homework assignment: an operational approach to slantwise convection : highly recommended (by Kent Johnson), 28 min Try the case exercise (location: BC)
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Symmetric instability
Sources:
Texts:
Martin p. 224228
Holton p. 277281
Meted modules:
homework assignment: an operational approach to slantwise convection : highly recommended (by Kent Johnson), 28 min
Try the case exercise (location: BC)
listen to in class: heavy banded snow (by J. Moore), 34 min
This is a survey of conveyor belts, trowal, and (in section 3) symmetric instability
CSI pitfalls: the use and misuse of CSI : more advanced (by David Schultz), 33 min
Required reading material
Realtime charts (PV and SI):
Canadian maps (chart description)
Example
What causes this precip?
N. Dakota
S. Dakota
Example 2
E. Nebraska
Jet
M
PSI?
relative humidity (%)
Jet
relative humidity (%)
0
PV min
0
pvor (thte,wnd)
But: MSI only occurs if the atmosphere is potentially and inertially stable
or: dqe/dz < 0 along M lines
or: dM/dx <0 along qe lines
Rimoist
Emanuel (1983)
PV (EPV)
Example:
M = absolute zonal momentum
30
40
M = fyug
dM/dy>0
60
70
see also: Jim Moore’s meted module on frontogenetic circulations & stability)
Potential
Potential Symmetric INstability
Potential Symmetric Stability

Dash: qe
Solid: Mg









Where does MSI occur?
EPVg
Also important for the effective release of the instability: moisture
Overlay RH
And frontogenesis … why?
EPVg
Mapping PI, PSI, frontogenesis, and RH
900700 mb
EPVg
Characteristics of bands due to the release of MSI
Frontal boundary