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NATS 101
Lecture 3 TRWeather & Climate
Temperature Heat Transfer
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3” by 5” Cards
• Name
• SID
• Clicker Number• Clicker Setup Instructions
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What is Pressure at 0.8 km?(Tucson, Arizoina)
Use Equation for Pressure Change
p(at elevation Zin km) pMSL 10 Z /(16km)
set Z = 0.8 km, pMSL 1013 mb
p(0.8 km) 1013mb 10 (0.8km)/(16km)
p(0.8 km) 1013mb 10 0.05
p(0.8 km) 1013mb 0.891903mb
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What is Pressure at 1.6 km?(Denver, Colorado)
Use Equation for Pressure Change
p(at elevation Zin km) pMSL 10 Z /(16km)
set Z = 1.6 km, pMSL 1013 mb
p(1.6 km) 1013mb 10 (1.6km)/(16km)
p(1.6 km) 1013mb 10 0.10
p(1.6 km) 1013mb 0.794805mb
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What is Pressure at 8.7 km?(Mt. Everest)
Use Equation for Pressure Change
p(at elevation Zin km) pMSL 10 Z /(16km)
set Z = 8.7 km, pMSL 1013 mb
p(8.7 km) 1013mb 10 (8.7 km)/(16km)
p(8.7 km) 1013mb 10 0.54375
p(8.7 km) 1013mb 0.286290mb
Lecture 2-Nats 101 6
WeatherWeather – The state of
the atmosphere:
for a specific place
at a particular time
Weather Elements
1) Temperature
2) Pressure
3) Humidity
4) Wind
5) Visibility
6) Clouds
7) Significant Weather
Lecture 2-Nats 101 7
Surface Station Model
Temperatures
Plotted °F in U.S.
Sea Level Pressure
Leading 10 or 9 is not plotted
Examples:
1013.8 plotted as 138
998.7 plotted as 987
1036.0 plotted as 360Ahrens, p 431
Responsible for boxed parameters
Lecture 2-Nats 101 8
Sky Cover and Weather Symbols
Ahrens, p 431
Ahrens, p 431
Wind Speed
How to read:
Half barb = 5 knots
Full barb = 10 knots
Flag = 50 knots
1 knot = 1 nautical mile per hour = 1.15 mph
= ______ knots
Wind direction
WESTERLYFrom the west
NORTHERLYFrom the north
EASTERLYFrom the east
SOUTHERLYFrom the south
270°
360°
90°
180°
Lecture 2-Nats 101 14
Surface Station Model
Temperate (oF)Pressure (mb) Last
Three Digits (tens, ones, tenths)
Dew Point (later) Moisture
Wind Barb Direction and Speed
Cloud Cover Tenths total coverage
Ahrens, p 431
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Decimal point
What are Temp, Dew Point, SLP, Cloud Cover, Wind
Speed and Direction?
Lecture 2-Nats 101 15
Practice Surface Station
Sea Level Pressure
Leading 10 or 9 is not plotted
Examples:
1013.8 plotted as 138
998.7 plotted as 987
1036.0 plotted as 360Ahrens, p 431
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18
998
Decimal point
What are Temp, Dew Point, SLP, Cloud Cover, Wind
Speed and Direction?
Lecture 2-Nats 101 16
temperature dew point
SLP pressure
wind
cloud cover
Ohio State website
Lecture 2-Nats 101 17
Surface Map Symbols
• Fronts
Mark the boundary between different air masses…later
Significant weather occurs near fronts
Current US MapAhrens, p 432
So what’s happening above the ground?
Lecture 2-Nats 101 20
Radiosonde
Weather balloons, or radiosondes, sample atmospheric to 10 mb.
They measuretemperaturemoisturepressure
They are tracked by GPS to get winds
Lecture 2-Nats 101 21
Radiosonde Distribution
Radiosondes released at 0000 and at 1200 GMT for a global network of stations.
Large gaps in network over oceans and in less affluent nations.
Stations ~400 km apart over North America
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What is Climate?
Statistics of weather (averages, ranges, extremes) computed over many years.
Year (annual precipitation for Tucson)
Season (e.g Winter: Dec-Jan-Feb)
Month (e.g January rainfall in Tucson)
Date (e.g. Average & record high and lows temperatures for Jan 30 in Tucson)
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Climate of TucsonMonthly Averages
Individual months can show significant deviations from long-term, monthly means.
Average Temperature = (MAX+MIN)/2
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Average and Record MAX and MIN
Temperatures for Date
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Climate of TucsonProbability of Last Spring Freeze
Cool Site: Western Region Climate Center
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Climate of TucsonProbability of Rain
Cool Site: Western Region Climate Center
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Climate of TucsonExtreme Rainfall
Cool Site: Western Region Climate Center
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Summary
• Weather - atmospheric conditions at specific time and place
Weather Maps => Instantaneous Values
• Climate - average weather and the range of extremes compiled over many years
Statistical Quantities => Expected Values
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Temperature Scales
• Fahrenheit (oF) - relative
US public standard • Celsius (oC) - relative
Freezing point 0oC
Boiling point 100oCoC= 5/9 (oF-32)
• Kelvin (K) - absolute
K= oC+273Ahrens p27
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What is Temperature?Microscopic ViewEnergy due to random
velocity of moleculesRelated to average
molecular speed; 500 m/s at room temperature for air
Maxwell DistributionK.E.=(1/2)mv2=(3/2)kT m=molecular weightk=Boltzmann constant =1.38065×10−23 joule/K
(joule is unit of energy)
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Temperature-Density: Charles Law
Consider volume of air
If air is warmed:
The molecules will move faster, have “stronger” collisions, and tend to become spaced farther apart
Volume increases, so density decreases
Warmer => less dense
Charles Law Applet
constant V
T(K) = constant x Volume at uniform pressure
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What is Heat?
Heat-Energy in the process of being transferred from a warmer object to a cooler object
Consider a pot of water on a hot burner.
Consider the following questions:
Williams, p. 19
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Heat Transfer Questions
What causes the…
Pan bottom and handle to get warmer?
Top of the water to become warmer?
Water temperature to not exceed 100oC?
Region away from side of pan to feel warm?
Williams, p. 19
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Conduction
Heat transfer due to collision of molecules.Conduction warms the bottom of the pan!Conductivity - rate of heat transfer across a 1 cm thick
slab of material if one side is kept 1oC warmer than the other
Do a Cheap Experiment: Touch metal on your chair!
1 cmMetal Water AirHeat
Transfer
1oC
0oC
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Heat Conductivity
Material Heat Conductivity (Cal s-1 cm-1 oC-1)
Still Air 6.1 x 10-5
Dry Soil 6.0 x 10-4
Still Water 1.4 x 10-3
Wet Soil 5.0 x 10-2
Granite (Rock) 6.5 x 10-2
Iron (Metal) 0.16
Silver (Metal) 1.01
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Convection
Heat transfer due to vertical exchange of mass
Occurs in fluids (liquids, gases) because of gravity
Warm, buoyant air rises - Cool, dense air sinks
Convection warms top of liquid!
Warm
Cool Warm
Cool
Warm
Cool
heat below - convection heat side - convection heat top - no convection
gravitygravity
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Convection Movies
2D Convection Tank Animation 2D Convection Model Ra=10**6
2D Convection Model Ra=10**7 IC12D Convection Model Ra=10**7 IC2
3D Rayleigh-Benard Convection Model
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Energy States and Water Phases
water molecules are tightly packed in a crystal alignment that prevents them from changing shape
LOW ENERGY STATE
attractive forces btw molecules weaken and individual molecules can move around each other, but they can not break away
SLIGHTLY HIGHER ENERGY STATE
water molecules move very rapidly and are
not bound together
EXTEMELY HIGH ENERGY STATE
Small Energy Change
Large Energy Change
SOLID LIQUID VAPOR
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Latent Heat
Ahrens, p 28
Weak attraction between
molecules+540 cal/gm+80 cal/gm
-540 cal/gm-80 cal/gm
-620 cal/gm
+620 cal/gm
Strong attraction between
molecules
Some attraction
More Ordered
Phase
Less Ordered
Phase
Surrounding air warms
Surrounding air cools
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Modes of Heat Transfer
Williams, p. 19
Latent Heat
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Take Home Points
• Heat-Energy transfer due to temperature differencesThree modes of heat transferConduction – molecule to moleculeConvection – transport of fluidRadiation – electromagnetic waves
Next lecture!• Latent Heat – energy of phase changes
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Next Class AssignmentRadiation
• Reading - Ahrens
3rd: 30-42
4th: 30-42
5th: 30-42• Homework01 - D2L (Due Monday Jan 25th)
3rd-Pg 52: 2.7, 9, 10, 11, 12
4th-Pg 52: 2.7, 9, 10, 11, 12
5th-Pg 52: 2.7, 9, 10, 11, 12