MADISON’S CURRENT WEATHER
Madison Weather at
1000 AM CDT 8 JUL 2002
Updated twice an hour at :05 and :25
Sky/Weather: MOSUNNY
Temperature: 83 F (28 C)
Dew Point: 71 F (21 C)
Relative Humidity: 67%
Wind: SW9 MPH
Barometer: 30.09F (1018.9 mb)
CURRENT
VISIBLE
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Current Surface Weather Map
with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar
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Current Temperatures (°F) & Isotherms
(“iso” = equal +”therm” = temperature)
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CURRENT IR
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Current Dewpoints (oF)
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Tomorrow AM Forecast Map
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Last 24 hrs in Madison
Local Noon
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Sunset
Sunrise
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LECTURE 9
THERMODYNAMICS:
BEHAVIOR OF GASES
IN THE ATMOSPHERE
A. INTRODUCTION
–
–
How are pressure & temperature related?
Why are lows cloudy and highs fair?
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B. KINETIC THEORY OF MATTER
•
•
Definitions
Historical
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B. KINETIC THEORY OF MATTER
•
•
•
Definitions
Historical
Assumptions for gases:
– Tiny molecules with large space;
– No attraction between molecules;
– Random molecular motion;
– Elastic molecular collisions.
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B. KINETIC THEORY OF MATTER (con’t.)
 Variables
–
–
–
describing molecular state of a gas
Density
= molecular mass per volume
Temperature
~ average molecular speed
Pressure
~ molecular momentum change
(~ molecular speed & mass)
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C. THE GAS LAWS
 Classical
approach to Ideal Gas Law
(or Equation of State)
Pressure = Density  Constant  Temperature
P =  R T (equivalent to PV = nRT)
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Pressure = Density  Constant  Temperature
P =  R T (equivalent to PV = nRT)
 Atmospheric
application of
Ideal Gas Law
If P = constant,
then increases as T decreases;
– If = constant,
then P increases when T increases;
– If T = constant,
then increases as P increases.
–
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C. THE GAS LAWS (con’t.)
 Dalton's
Laws of Partial Pressures
– Involves mixture of ideal gases;
–Each
gas species has
own partial pressure, p(i).
–Then:
Total Pressure =
Sum of partial pressures
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C. THE GAS LAWS (con’t.)
 Atmospheric
Applications of Dalton's Laws of
Partial Pressures
–
PTotal = p(N2) + p(O2) + p(Ar) + e + ...
–
Where p(N2), p(O2), p(Ar) are partial
pressures of major atmospheric gases
& e = (partial water) vapor pressure.
–
So for air with some moisture:
PTotal = 1020 mb  (780 + 210 + 9) mb +
e  (20 to 40 mb)
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D. THE THERMODYNAMIC LAWS
•
•
Introduction
First Law of Thermodynamics
Input = Output + Storage
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D. THE THERMODYNAMIC LAWS (con’t.)
•
Atmospheric application of
First Law of Thermodynamics
Heat exchange = Work + Internal energy
Change
– Heat exchange by radiation, etc.;
– Work by volume change;
– Internal energy change by temperature
change.
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D. THE THERMODYNAMIC LAWS (con’t.)
•
Adiabatic Processes
– No heat exchanged with environment;
Work = internal energy change
– Involves volume change only:
Volume change =
Temperature change
 Volume
decrease (or Pressure increase)
causes heating;
 Volume increase (or Pressure decrease)
causes cooling.
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E. THE VERTICAL MOTION PROBLEM
•
Response of an air parcel
• Rising motion:
Encounters lower pressure
Expansion & cooling
•
•
Sinking motion:
Encounters higher pressure
Compression & warming
Specification of the response
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Recall AIR PRESSURE CLIMATOLOGY
See Fig. 5.4 Moran & Morgan (1997)
ALTITUDE [km]
VERTICAL PRESSURE PROFILE
US STANDARD ATMOSPHERE, 1976
5
4
3
1 mb drop for 10 meter height rise
2
1
0
500
600
700
800
900
1000
AIR PRESSURE [millibars]
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Response of Ascent/Descent of Air Parcel:
Dry Adiabatic Lapse Rate (10C°/1000m)
See Fig. 6.8 Moran & Morgan (1997)
P  600 mb, V= 1.44 m3
P  700 mb, V= 1.28 m3
P  800 mb, V= 1.16 m3
P  900 mb, V= 1.07 m3
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T = 20C, P  1000 mb,
V= 1.00 m3
38
E. VERTICAL MOTION (con’t.)
•
•
Specification of parcel response
• describes cooling/heating by adiabatic
expansion/compression process;
• assume dry air parcel.
The dry adiabatic lapse rate (DALR)
• Recall that lapse rate is how temperature
decreases with height;
• DALR  10 Co per 1000 meters or
5.5 Fo per 1000 feet.
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E. VERTICAL MOTION (con’t.)
•
Response of an air parcel
• An example
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U.S. STANDARD ATMOSPHERE
See Fig. 1.9 Moran & Morgan (1997)
Altitude [km]
140.
120.
100.
80.
Thermosphere
Mesopause
60.
Stratopause
Stratosphere
Tropopause
Troposphere
40.
20.
0.
-100.
Mesosphere
-50.
0.
50.
100.
Temperature [deg C]
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GREEN BAY RADIOSONDE SOUNDING Sunday PM
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Why does the
Hot Air Balloon Rise?
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When Convection?
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F. STATIC STABILITY
•
•
•
Importance
Stability-Instability Concept
• Stable:
Return to initial state
• Unstable: Continuation away from
initial state
Criteria for Static Stability (Instability)
Determination
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STABLE CONDITIONS
Compare Environment with DALR
Colder parcel sinks & returns to start
ALTITUDE (m)
2500 Parcel is colder &
more dense
2000
Environment is warmer &
less dense
1500
1000
500
0
0
5
10
15
20
25
30
TEMPERATURE (C)
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UNSTABLE CONDITIONS
Compare Environment with DALR
Warmer parcel continues upward
Parcel is warmer &
less dense
ALTITUDE (m)
2500
2000
1500
1000
500
0
Environment is colder
& more dense
0
5
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15
20
TEMPERATURE (C)
25
30
48
F. STATIC STABILITY (con’t.)
•
Processes which change static stability
(instability)
• Cool below, but warm above (stabilize)
• Warm below, but cool above (destabilize)
•
Visual stability indicators
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Example of Stabilization–
An Inversion
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Example of Destabilization-Cumulonimbus
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F. STATIC STABILITY (con’t.)
•
•
•
Processes which change static stability
(instability)
Visual stability indicators
Graphical Analysis:
The Thermodynamic Diagram
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GREEN BAY RADIOSONDE SOUNDING Sunday PM
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MADISON’S CURRENT WEATHER
Madison Weather at 1000 AM CDT
THU JUL 5 2001
Updated twice an hour at :05 and :25
Sky/Weather: SUNNY
Temperature: 63 F (17 C)
Dew Point: 42 F (5 C)
Relative Humidity: 46%
Wind: N7 MPH
Barometer: 30.10S
Surface Weather Map from Today
with Isobars & Fronts
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Current Temperatures (oF) & Isotherms
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Current Dewpoints (oF)
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Tomorrow’s 7AM Forecast
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Current UVI Forecast
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Last 24 hrs in Madison
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At Southern Lake Michigan Buoy
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U.S. STANDARD ATMOSPHERE
See Fig. 1.9 Moran & Morgan (1997)
Altitude [km]
140.
120.
100.
80.
Thermosphere
Mesopause
60.
Stratopause
Stratosphere
Tropopause
Troposphere
40.
20.
0.
-100.
Mesosphere
-50.
0.
50.
100.
Temperature [deg C]
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GREEN BAY RADIOSONDE SOUNDING Sunday PM
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GREEN BAY RADIOSONDE SOUNDING Sunday PM
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GREEN BAY RADIOSONDE SOUNDING Wednesday PM
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GREEN BAY RADIOSONDE SOUNDING FRIDAY AM
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Current Temperatures (oF) – 24 Hrs Ago
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