Transcript Qvector551new15.ppt

Why Not Look Only at Model
Output?
Comparison of Various Forms of the Q-G
Omega Equation
• Classic (Two terms: differential vorticity advection,
Laplacian of the thermal wind)
• The result is the difference between two large terms
resulting in large truncation error.
• Cannot estimate reliably from vorticity advection at a single
level or from warm advection alone.
• Using at a single level, best done at 500 hPa for strong
events. Really need a 3D solution for an accurate answer.
Trenberth/Sutcliffe formulation (advection of absolute
vorticity by the thermal wind) is more accurate since no
cancellation problem.
Q-Vector approach is the best in many
ways
• No cancellation problems
• Includes deformation term
• Provides insights into the lower branch of the
ageostrophic circulation forced by the geostrophic
forcing
• Provides insights into frontogenesis
•Allows rapid and intuitive graphical interpretation
QG Diagnostics Online
• Classic approach:
http://www.mmm.ucar.edu/people/tomjr/files/
realtime/qg_diag/Omeg700Tot-NorAmer/res.html
• SutcliffeTrenberth:http://www.mmm.ucar.edu/people/tomj
r/files/realtime/qg_diag/OmegSutTren700TotNorAmer/res.html
• Q-vector
http://www.mmm.ucar.edu/people/tomjr/files/
realtime/qg_diag/OmegQvec700TotNorAmer/res.html
Vertical Motion
• Can be as the complex sum of:
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QG motions (relatively large scale and smooth)
Orographic forcing
Convective forcing
Gravity waves and other small-scale stuff
• QG diagnostics helpful for seeing the big
picture
Jet Streak Vertical Motions
For unusually straight jets, it
might be reasonable
But usually there is much more
going on, so be VERY careful in
application of simple jet streak
model
• Garp example…
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