chapter 3 Flashcards
The isentropic potential vorticity (P) is defined as:
The isentropic potential vorticity P is a multiplicative function of two factors:
Isentropic potential vorticity is a large positive value when
cyclonic rotation is strong (n > 0) and/or where static stability is large
Isentropic potential vorticity is a large positive value when cyclonic rotation is strong (n > 0) and/or where static stability is large, representing
isentropes that are tightly packed in the vertical (-do -O/do p >>0)
normally, -do -O/do p, such that …………….. only occurs when ……………
p<0
n<0
positive potential vorticity anomalies
Localized maxima in isentropic potential vorticity
Localized maxima in isentropic potential vorticity are known as positive potential vorticity anomalies, whereas ……………………………………………………… are known as negative potential vorticity anomalies
localized minima in isentropic potential vorticity
It can be shown that the isentropic potential vorticity is …………………….. following the ……………………………………………., when ……………………………
conserved following the motion along an isentropic surface (i.e., under dry adiabatic conditions), when friction is neglected.
The non-conservation of isentropic potential vorticity following the motion on an isentropic surface thus allows us to
infer where diabatic heating is occurring and/or where friction is important.
Because IPV is conserved following the flow, if static stability or absolute vorticity change in value, the other must
change in the inverse in order to keep the value of the IPV constant
Because IPV is conserved following the flow, if static stability or absolute vorticity change in value
, the other must change in the inverse in order to keep the value of the IPV constant
Because IPV is conserved following the flow, if static stability or absolute vorticity change in value, the other must change in the inverse in order to keep the value of the IPV constant, that is:
- If the static stability increases, the absolute vorticity must decrease
- If the static stability decreases, the absolute vorticity must increase
On the synoptic-scale, IPV anomalies evolve through
a combination of translation (motion/advection), rotation, and deformation by the synoptic-scale wind field.
On the synoptic-scale, IPV anomalies evolve through a combination of translation (motion/advection), rotation, and deformation by the synoptic-scale wind field. For these processes, IPV is
conserved following the motion.
For typical mid-latitude, synoptic-scale flow, we can obtain a characteristic valueof P=
P=1x10-6 m2 Ks-1 kg-1.
………………………………………………………… we can obtain a characteristic valueofP=1x10-6 m2 Ks-1 kg-1.
For typical mid-latitude, synoptic-scale flow
For typical mid-latitude, synoptic-scale flow, we can obtain a characteristic valueofP=1x10-6 m2 Ks-1 kg-1.
For simplicity, we term this value to be equal to
1 PVU,
For typical mid-latitude, synoptic-scale flow, we can obtain a characteristic valueofP=1x10-6 m2 Ks-1 kg-1.
For simplicity, we term this value to be equal to 1 PVU, where PVU stands for
“potential vorticity unit.”
For typical mid-latitude, synoptic-scale flow, we can obtain a characteristic valueofP=1x10-6 m2 Ks-1 kg-1.
For simplicity, we term this value to be equal to 1 PVU, where PVU stands for “potential vorticity unit.”
In the troposphere, P is typically
less than or equal to 1.5 PVU.
For typical mid-latitude, synoptic-scale flow, we can obtain a characteristic valueofP=1x10-6 m2 Ks-1 kg-1.
For simplicity, we term this value to be equal to 1 PVU, where PVU stands for “potential vorticity unit.”
In the ……………………………., P is typically less than or equal to 1.5 PVU.
troposphere
In the stratosphere, where the static stability is ……………as …………………………………………………..
………….. is typically ………………………………………………..
very large as potential temperature rapidly increases with height, P is typically greater than 2.0 PVU.
in ……………………….where ………………………………… is very large as potential temperature rapidly increases with height, P is typically greater than 2.0 PVU.
In the stratosphere, where the static stability
In the stratosphere, where the static stability is very large as potential
temperature rapidly increases with height, P is typically greater than 2.0 PVU.
This gives rise to the
construct of the dynamic tropopause
In the stratosphere, where the static stability is very large as potential
temperature rapidly increases with height, P is typically greater than 2.0 PVU.
This gives rise to the construct of the dynamic tropopause, which is commonly
represented by
the 1.5 PVU or 2.0 PVU surface of constant potential vorticity.
Where potential temperature is relatively warm on the dynamic tropopause, the tropopause itself is at a
relatively high altitude, inferring an upper tropospheric ridge.
where potential temperature is relatively cold on the dynamic tropopause, the tropopause itself is at a
relatively low altitude, inferring an upper tropospheric trough.
If we take the dynamic tropopause to be the 1.5 PVU surface, we observe that it is found at
relatively low altitudes
If we take the dynamic tropopause to be the 1.5 PVU surface, we observe that it is found at relatively low altitudes and on
relatively cold isentropic surfaces near the poles.
If we take the dynamic tropopause to be the 1.5 PVU surface, we observe that it is found at relatively low altitudes and on relatively cold isentropic surfaces near the poles.
Conversely, it is found at
relatively high altitudes
Conversely, it is found at relatively high altitudes and on
relatively warm isentropic surfaces near the equator.
Figures a and b, demonstrate
the link between potential temperature anomalies on the dynamic tropopause and troughs and ridges on upper tropospheric isobaric charts
Figures a and b, demonstrate the link between potential temperature anomalies on the dynamic tropopause and troughs and ridges on upper tropospheric isobaric charts, that is:
- lower values of …………………………………………. imply…………………………………………………..
potential temperature on the dynamic tropopause imply lower tropopause heights and upper tropospheric troughing
Figures a and b, demonstrate the link between potential temperature anomalies on the dynamic tropopause and troughs and ridges on upper tropospheric isobaric charts, that is:
- Lower values of potential temperature on the dynamic tropopause imply lower tropopause heights and upper tropospheric troughing and
- Higher values of ……… . . . .. . . . . .
potential temperature on the dynamic tropopause imply higher tropopause heights and upper tropospheric ridg
A positive potential vorticity anomaly is associated with
A negative potential vorticity anomaly is associated with
locally large anticyclonic absolute vorticity (η < 0) and reduced static stability with weakly-packed isentropes in the vertical (-∂θ/∂p > 0).
We first examine the structure of a ………………. potential vorticity anomaly, as depicted in Figure. A positive potential vorticity anomaly is associated with
positive
a depressed height of the dynamic tropopause.
We first examine the structure of a positive potential vorticity anomaly, as depicted in Figure. A positive potential vorticity anomaly is associated with a depressed height of the dynamic tropopause.
Accompanying this is
upper tropospheric cyclonic rotation
We first examine the structure of a positive potential vorticity anomaly, as depicted in Figure. A positive potential vorticity anomaly is associated with a depressed height of the dynamic tropopause.
Accompanying this is upper tropospheric cyclonic rotation. Isentropes are
tightly packed in the vertical direction through the positive potential vorticity anomaly,
Accompanying this is upper tropospheric cyclonic rotation. Isentropes are tightly packed in the vertical direction through the positive potential vorticity anomaly, indicative of
high static stability.
Thus, relatively warm potential temperature is found in
the stratosphere above the positive anomaly
relatively cold potential temperature is found in
the middle to upper troposphere below the positive anomaly.
A B C
D E F G H
I J K L