Next Week: QUIZ
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Transcript of Next Week: QUIZ
HEIG
HT
(km
)
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TEMPERATURE (oC)3020100-10-20-30-40-50-60
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LCL
LFC
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CAPE
TpTe
HEIG
HT
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TEMPERATURE (oC)3020100-10-20-30-40-50-60
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LCL
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TpTe
TEMPERATURE (oC)3020100-10-20-30-40-50-60
0
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LCL
LFC
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CAPE
TpTe
Next Week: QUIZ
• One question from each of week:– 9 normal lectures + global warming lecture– Over main topic of lecture and homework
• Multiple choice, short answer, matching, map question
• Powerpoints: http://www.aos.wisc.edu/~ahulme/aos101/
AOS 101
April 15/17
Thickness and Thermal Wind
Thickness
• The vertical distance in meters between two pressure levels
1000 hPa = 0 m
500 hPa = 5600 m
THICKNESS = 5600 m –
0 m = 5600 mZ
Consider a column…
• Cool the average temperature of the column by 20 K
• Air becomes more dense, mass stays the same so volume must decrease
• Air takes up less space
• COLUMN SHRINKS 1000 hPa = 0 m
500 hPa = 5600 m
COOL
Consider a column…
• Cool the average temperature of the column by 20 K
• Air becomes more dense, mass stays the same so volume must decrease
• Air takes up less space
• COLUMN SHRINKS 1000 hPa = 0 m
500 hPa = 5000 m
COOLZ = 5000 m
Consider a column…
• Warm the average temperature of the column by 20 K
• Air becomes less dense, mass stays the same so volume must increase
• Air takes up more space
• COLUMN EXPANDS 1000 hPa = 0 m
500 hPa = 5600 m
WARM
Consider a column…
• Warm the average temperature of the column by 20 K
• Air becomes less dense, mass stays the same so volume must increase
• Air takes up more space
• COLUMN EXPANDS 1000 hPa = 0 m
500 hPa = 6200 m
WARM
Z = 6200 m
Summary
• COOL air will result in LOW THICKNESS• WARM air will result in HIGH
THICKNESS
• Thus, the thickness between two pressure layers is proportional to the average temperature of that layer
Z ≈ const x Tave
Thermal Wind
• Not an actual wind• “Blows” along thickness contours with cold
(low thickness) air to the left • Stronger temperature gradients imply
stronger thermal wind• Equal to the SHEAR of the wind (i.e. is
related to the observed wind)
V850
V200
VT
VT
5660 m
COLD
WARM
5600 m
5540 m
Clockwise turning of winds with height
Veering Backing
850 hPa
300 hPa
850 hPa
300 hPa
VT
VT
Counterclockwise turning of winds with height
WARM AIR ADVECTION COLD AIR ADVECTION
Midlatitude Weather
• Upper-level winds will be much stronger than low-level winds– i.e. thermal wind will be very close to
upper-level wind
• Consider a front with cold air to the north and warm air to the south.
COOL WARM
P = 500 hPa
Geostrophic wind into page Thermal wind into
page
LOW heights
HIGH heights
NORTH
PGF
P = 700 hPa
Thermal Wind Balance
• Pressure gradient increases with height– Winds increase with height
• Thus, areas of strong temperature (thickness) gradient will have strong winds above them.
700 hPa Temperature
500-850 hPa Thickness
500 hPa Height
500 hPa Wind Speed
500-850 hPa Thickness
500 hPa Wind Speed
Cyclone
• Symbols:
• Point in direction of front movement
COLD
WARM
OCCLUDED
STATIONARY
Warm Front
COOL
WARM
Associated Weather (WF)
• Gradual Slope• Stratiform rain
– long lasting light rain– occurs on cool side of front
• Temperature increases prior to frontal passage
• Wind becomes southerly after passage
Cold Front
COOL
WARM
Associated Weather (CF)
• Much Steeper Slope• More intense (convective) rain
– Thunderstorms for a shorter period– occurs on warm side of front
• Temperature decreases after frontal passage
• Wind becomes northerly after passage
LLLIGHTER RAIN
HEAVIER
RAIN
WARM AIR
COLD AIR
COOL AIR
Finding a Front
• Temperature (dewpoint) Gradient• Change in wind direction
– Converging winds at the front
• “Kink” or “trough” in isobars (lower pressure)
• Banded precipitation
Upper-level terminology
• TROUGH: area of lower heights• RIDGE: area of higher heights
LL
HH