Download lift air

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e.
copying forecast text
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figure
captions
linking figures with text
citing source material
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In the News:
http://www.reuters.com
In the News:
• warmer waters
t
iin
the Pacific
• wind shear in the
Atlantic
http://www.cnn.com
In the News:
Rainfall from
Typhoon Parma
http://www.nasa.com
Guest Lecture Tuesday:
Forecasting:
Mike Heard
Cloud Development and Forms
((ERTH 303,, 15 October 2009))
a. Mechanisms that
lift air [and
[ d cooll air
i to the
h
dew point]
b St
b.
Static
ti stability
t bilit
and the ELR
c. Factors
Influencing the
ELR
d Limitations
d.
Li it ti
and
d
inversions
6
Clouds enveloping the Bridger Range, with sundog.
Review: How does air become saturated?
1. Add water vapor to the air
e.g. Warm shower: add vapor to air
2. Mix cold air with warm, moist air
e.g. Contrails
C
behind jets traveling at high
altitudes; steam fog
3. Cool air to the dewpoint
7
http://www.crystalinks.com/contrail607.jpg
a. Mechanisms that lift air
1. Orographic uplift:
ƒ Upward displacement
of air that leads to
adiabatic cooling
ƒ Responsible for
creating a rain shadow,
an area of lower
precipitation on the
leeward side of a
mountain (range).
c. Adiabatic cooling
Dry adiabatic lapse rate = 10 °C / 1 km
Wet adiabatic lapse rate = 5 °C / 1 km
Dew p
point lapse
p rate = 2 °C / 1 km
Lifting condensation level =
elevation at which an air
parcel reached the dew
point temperature
Leeward Side
Windward Side
Elev.
(m)
Temp
(°C)
Dew
Point
(°C)
Elev.
(m)
Temp
(°C)
Dew
Point
(°C)
2500
2000
2000
1500
1. At what
1
hat elevation
ele ation
would cloud bases form?
1000
2. How do sea-level
temperature, dew point, and
humidity on the leeward vs. windward
side of the mountain range vary?
500
Sea
level
25
13
3. Which side of the mountain is more often
cloudy and which side is more often clear?
1000
Sea
level
9
c. Adiabatic cooling
Dry adiabatic lapse rate = 10 °C / 1 km
Wet adiabatic lapse rate = 5 °C / 1 km
Dew p
point lapse
p rate = 2 °C / 1 km
Lifting condensation level =
elevation at which an air
parcel reached the dew
point temperature
Leeward Side
Windward Side
Elev.
(m)
Temp
(°C)
Dew
Point
(°C)
2500
5
5
2000
7.5
7.5
1500
10
10
Lifting condensation level
1000
15
11
500
20
12
Sea
level
25
13
Elev.
(m)
Temp
(°C)
Dew
Point
(°C)
2000
10
6
1000
20
8
Sea
level
30
1. At what
1
hat elevation
ele ation
would cloud bases form?
2. How do sea-level
temperature, dew point, and
humidity on the leeward vs. windward
side of the mountain range vary?
3. Which side of the mountain is more often
cloudy and which side is more often clear?
10
10
a. Mechanisms that lift air
2. Frontal lifting:
ƒ Air flow along frontal boundaries resulting
in widespread cloud development
ƒ Cold front
ƒ Warm front
a. Mechanisms that lift air
3. Convergence:
ƒ Horizontal movement towards a common
location
a. Mechanisms that lift air
4. Localized convection:
ƒ Lifting from heating of the boundary layer
(Chap. 3)
http://nepalmountaintrek.com/images/paragliding.JPG
b. Static Stability and the ELR
Static stability:
ƒ air’s
i ’ susceptibility
ibili to uplift
lif
Statically
y unstable: becomes buoyant,
y ,
continues to rise
Statically stable: resists upward
displacement, sinks to original level
Statically neutral: neither rises on its own
nor sinks, rests where it was displaced.
b. Static Stability and the ELR
Buoyancy of a rising air parcel
depends on its rate of cooling
relative to the surrounding air.
Air p
parcel: dry
y or moist adiabatic
lapse rate (DALR or MALR)
Surrounding air: environmental
lapse rate (ELR)
b. Static Stability and the ELR
Absolutely unstable air:
ƒ Air
Ai parcels
l cools
l less
l
than
th ambient
bi t air
i
ƒELR > DALR
(If ELR > DALR, then ELR also > MALR)
b. Static Stability and the ELR
Absolutely stable air:
ƒ Air
Ai parcels
l cools
l more than
th ambient
bi t air
i
ƒELR < MALR
(If ELR < MALR, then ELR also < DALR)
b. Static Stability and the ELR
Conditionally unstable air:
ƒ Buoyancy of air changes
ƒ DALR < ELR < MALR
Levell off free
L
f
convection:
ti
Altitude a parcel of air
Reach for it to become
buoyant and rise on its
on
b. Static Stability and the ELR
ELR > DALR
b. Static Stability and the ELR
ELR < MALR
b. Static Stability and the ELR
DALR < ELR < MALR
06.02
Uplift along a cold front occurs because the cold
air is _____ than the air it pushes against.
1. lighter
g
2. denser
3. slower
4. more unstable
06.02
Uplift along a cold front occurs because the cold
air is _______ than the air it pushes against.
1. lighter
g
2. denser
3. slower
4. more unstable
06.04
This is an example of air that is _______.
1. conditionallyy stable
2. conditionally unstable
3. absolutelyy stable
4. absolutely unstable
06.04
This is an example of air that is _______.
1. conditionallyy stable
2. conditionally unstable
3. absolutelyy stable
4. absolutely unstable
Cloud Development and Forms
((ERTH 303,, 15 October 2009))
a. Mechanisms that
lift air [and
[ d cooll air
i to the
h
dew point]
b St
b.
Static
ti stability
t bilit
and the ELR
c. Factors
Influencing the
ELR
d Limitations
d.
Li it ti
and
d
inversions
26
Clouds enveloping the Bridger Range, with sundog.
c. Factors influencing the ELR
1. Heating or cooling the atm.
ƒ
Di
Diurnal
l temperatures:
t
t
c. Factors influencing the ELR
2. Advection of cold and warm air
at different levels
c. Factors influencing the ELR
3. Advection of an air mass with a
different ELR
Cloud Development and Forms
((ERTH 303,, 15 October 2009))
a. Mechanisms that
lift air [and
[ d cooll air
i to the
h
dew point]
b St
b.
Static
ti stability
t bilit
and the ELR
c. Factors
Influencing the
ELR
d Limitations
d.
Li it ti
and
d
inversions
30
Clouds enveloping the Bridger Range, with sundog.
d. Limitations on lifting unstable air
1. Unstable air stops ascent when it
reaches a layer of stable air
d. Limitations on lifting unstable air
2. Entrainment:
mixing of air
parcel with
ambient air
Pyrocumulus cloud, Alaska.
d. Extremely stable air: Inversions
Inversions:
temperature increases with altitude
d. Extremely stable air: Inversions
Inversions:
Radiation inversion – diabatic
cooling
g
F
Frontal
t l inversions
i
i
Subsidence inversions