1 NATS 101 Lecture 3 TR Weather & Climate Temperature Heat Transfer

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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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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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Climate of TucsonSnow!

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