What will QG Theory do for us?
–It reveals how ............................................ and ....................................... constrain and simplify atmospheric motions, but in a realistic manner
hydrostatic balance and geostrophic balance
What will QG Theory do for us?
It provides a simple framework within which we can understand and diagnose the ..........................................
evolution of threedimensional synopticscale weather systems
What will QG Theory do for us?
It predicts the evolution of synopticscale systems by
diagnosing changes in the local geopotential height field from the observed distributions of vorticity advection and temperature advection.
What will QG Theory do for us?
It estimates synopticscale ...................................................................
vertical motions from the observed distribution of vorticity and temperature advection.
What will QG Theory do for us?
It helps us to understand how the ..........................................................and the ............................................................................interact to create ......................................that result in realistic synoptic scale weather patterns
mass fields (via horizontal temperature advection)
momentum fields (via horizontal vorticity advection)
vertical circulations
What will QG Theory do for us?
It offers physical insight into the forcing of ....................................................... and ................................................................associated with midlatitude cyclones
vertical motion and the cloud/precipitation patterns
Rotational momentum:
Rotation around an axis (less effort)
Momentum equations and linear momentum
momentum equations: du/dt, dv/dt. dw/dt
linear momentum: ΣF = dp/dt = m* d/dt = ma
From our mathematical derivation of QG theory, QG theory has the following assumptions

Geostrophic balance (i.e. we neglect all local changes in the ageostrophic wind) >> No difference between geostrophic & wind (actual)

Hydrostatic balance >> No vertical motion (parcel of air at rest)

Horizontal advection by the geostrophic winds only (i.e. we neglect the advection of the ageostrophic momentum by the geostrophic wind and the vertical advection of momentum)
 No friction or orographic effects
 No diabatic heating / cooling

No spatial or temporal changes in static stability >> consider midlatitude weather is stable
meaning of adiabatic
No change of heat between air parcel and surrounding air "when air parcel is rising it will cool due to expansion/increase of volume"
(Source of heat must exist)
QG Height Tendency Equation
The following equation represents
QG height tendency equation
Term A corresponds to
local horizontal advection of geostrophic vorticity
Term B correspond to
change in temperature advection with height
QG omega equation
The following equation represents
QG omega equation
Term A correspond to
change in vorticity advection with height
Term B correspond to
local maximum in temperature advection
If large changes in the vorticity advection with height are observed, then you should expect...........................................
large vertical motions
The stronger the temperature advection, the stronger the ............................
vertical motion
If WAA is observed at several consecutive pressure levels, expect a.........................................................motion
deep layer of rising
The QG omega equation is proportional to
vorticity advection & advection of maximum temperature (local)
vorticity advection & advection of maximum temperature (local) usually work
opposite to each other
if term A in the QG omega equation is +ve and term B is ve the result is
rising air
you can find which is dominant cold advection or cyclonic by
Q vectors because they are working against each other
"rate of change of potential temperature in geostrophic balance"
If term A and B are working together
PVA and WAA are on top of each other
The Qvector is defined as
the change of the potential temperature gradient vector of a parcel following the geostrophic motion.
Qvector equation
the following equation is for
Qvectors
What does each term in the Qvector equation mean?
d_{g} /dt : rate of change of potential temperature gradient in geostrophic motion
gradient of potential temperature
0: potential temperature