NATS 101 Updates

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NATS 101 Updates

• Add your name to Class ListServe!
• First QUIZ on Thursday
• Review session tomorrow at 5PM
• Location TBD. Will be announced via Listserve
• Textbooks
• Note-takers takees meet after class
• PBS NOVA Mars Dead or Alive tonight 800
• 1st anniversary of Katrina this week
• Quick update on Ernesto

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4 by 6 Cards

• Todays assignment
• Name, SID legible penmanship
• What worked
• What didnt and needs clarification

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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 360

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Average and Record MAX and MIN Temperatures for
Date
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Climate of TucsonProbability of Last 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

10
NATS 101

• Lecture 3Temperature, Heat Transfer
• and begin
• Radiation

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What is Temperature?

• Microscopic View
• Energy due to random jiggling of molecules
• Related to average molecular speed 500 m/s
  (1100 mph) at room temperature for air

12
Temperature and Density

• 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

13
Temperature Scales

• Fahrenheit (oF) - relative
• US public standard
• Celsius (oC) - relative
• Freezing point 0oC
• Boiling point 100oC
• oC 5/9 (oF-32)
• Kelvin (K) - absolute
• K oC273

Ahrens p27
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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
• Cheap Experiment Touch your chair!

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Heat Conductivity
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Specific Heat Capacity

• Heat required to raise temperature of 1 gm of
  substance 1oC.
• Metal has lower heat capacity than water!

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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!

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Convection Movies

• 2D Convection Tank Animation ?
• 2D Convection Model Ra106
• 2D Convection Model Ra107 IC1
• 2D Convection Model Ra107 IC2
• 3D Rayleigh-Benard Convection Model ?
• Last hour movie of clouds and moist convection
• over Catalina mountains

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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
Large Energy Change
Small Energy Change
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Latent Heat
Surrounding air cools
Less Ordered Phase
More Ordered Phase
-620 cal/gm
-80 cal/gm
-540 cal/gm
Strong attraction between molecules
Weak attraction between molecules
Some attraction
540 cal/gm
80 cal/gm
620 cal/gm
Surrounding air warms
Ahrens, p 28
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Latent Heat

• Energy associated with phase of matter.
• Must be either added to or taken from a substance
  when it changes its phase.
• To turn liquid water into solid ice, must remove
  energy from the liquid water.
• To turn liquid water into vapor, must add a lot
  of energy to the liquid water.

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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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Modes of Heat Transfer
Latent Heat
Williams, p. 19
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Take Home Concepts

• Heat-Energy transfer due to temperature
  differences
• Three modes of heat transfer
• Conduction molecule to molecule
• Convection transport of fluid
• Radiation electromagnetic waves
• Latent Heat energy of phase changes

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Modes of Heat Transfer

• Energy is only converted from one form to another
  or transferred from one place to another.
• Energy is transferred from hot to cold.
• Conduction - Molecules colliding most efficient
  at interface.
• Convection - Requires movement of a fluid or gas.

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Radiation

• Any object that has a temperature greater than 0
  K, emits radiation.
• This radiation is in the form of electromagnetic
  waves, produced by the acceleration of electric
  charges.
• These waves dont need matter in order to
  propagate they move at the speed of light
  (3x105 km/sec) in a vacuum.

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Electromagnetic Waves

• Two important aspects of waves are
• What kind Wavelength or distance between peaks.
• How much Amplitude or distance between peaks and
  valleys.

Wavelength
Amplitude
Frequency
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Why Electromagnetic Waves?

• Radiation has an Electric Field Component and a
  Magnetic Field Component
• Electric Field is Perpendicular to Magnetic Field

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Photons

• NOT TO CONFUSE YOU, but
• Can also think of radiation as individual packets
  of energy or PHOTONS.
• In simplistic terms, radiation with
• shorter wavelengths corresponds to photons with
  more energy and
• higher wave amplitude to more BBs per second

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Electromagnetic Spectrum
Wavelengths of Meteorology Significance
Danielson, Fig. 3.18
WAVELENGTH
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Emitted Spectrum

• Emitted radiation has many wavelengths.

Prism
(Danielson, Fig. 3.14)
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Emitted Spectrum
Energy from Sun is spread unevenly over all
wavelengths.
Emission spectrum of Sun
Energy Emitted
Ahrens, Fig. 2.7
Wavelength
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Wiens Law
Danielson, Fig. 3.19

• The hotter the object, the shorter the brightest
  wavelength.

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Wiens Law

• Relates the wavelength of maximum emission to the
  temperature of mass
• ?MAX (0.29?104 ?m K) ? T-1
• Warmer Objects gt Shorter Wavelengths
• Sun-visible light
• ?MAX (0.29?104 ?m K)?(5800 K)-1 ? 0.5 ?m
• Earth-infrared radiation
• ?MAX (0.29?104 ?m K)?(290 K)-1 ? 10 ?m

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Wiens Law

• What is the radiative temperature of an
  incandescent bulb whose wavelength of maximum
  emission is near 1.0 ?m ?
• Apply Wiens Law
• ?MAX (0.29?104 ?m K) ? T-1
• Temperature of glowing tungsten filament
• T (0.29?104 ?m K)?(?MAX)-1
• T (0.29?104 ?m K)?(1.0 ?m)-1 ? 2900K

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Stefan-Boltzmanns (SB) Law

• The hotter the object, the more radiation
  emitted.
• When the temperature is doubled, the emitted
  energy increases by a factor of 16!
• Stefan-Boltzmanns Law
• E (5.67?10-8 Wm-2K-4 )?T4
• E2?2?2?216
• 4 times

Sun Temp 6000K
Earth Temp 300K
Aguado, Fig. 2-7
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How Much More Energy is Emitted by the Sun per m2
Than the Earth?

• Apply Stefan-Boltzman Law
• The Sun Emits 160,000 Times More Energy per m2
  than the Earth,
• Plus Its Area is Mucho Bigger (by a factor of
  10,000)!

40
Radiative Equilibrium

• Radiation absorbed by an object increases the
  energy of the object.
• Increased energy causes temperature to increase
  (warming).
• Radiation emitted by an object decreases the
  energy of the object.
• Decreased energy causes temperature to decrease
  (cooling).

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Radiative Equilibrium (cont.)

• When the energy absorbed equals energy emitted,
  this is called Radiative Equilibrium.
• The corresponding temperature is the Radiative
  Equilibrium Temperature.

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Key Points

• Radiation is emitted from all objects that have
  temperatures warmer than absolute zero (0 K).
• Wiens Law wavelength of maximum emission
• ?MAX (0.29?104 ?m K) ? T-1
• Stefan-Boltzmann Law total energy emission
• E (5.67?10-8 W/m2 ) ? T4

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Key Points

• Radiative equilibrium and temperature
• Energy In Energy Out (Eq. Temp.)
• Three modes of heat transfer due to temperature
  differences.
• Conduction molecule-to-molecule
• Convection fluid motion
• Radiation electromagnetic waves

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Reading Assignment

• Ahrens
• Pages 30-42
• Problems 2.7, 2.9, 2.10, 2.11, 2.12