Meteorology Lecture 1

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Meteorology Lecture 1

• Weather and Climate Review

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What drives our weather?

• The sun
• Insolation solar energy reaching the Earth
• Remember the suns output can vary, which impacts
  weather on Earth
• e.g. The Little Ice Age

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Folklore Sirius The Dog Star
Thought to produce heat at the end of summer
Worshipped by numerous civilizations The Dog
Days of Summer
Sirius
Sun
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What about the Moon?

• Does it warm the Earth?
• Why does it glow?

Albedo of insolation an object reflects High
light surfaces Low dark surfaces
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Solar Radiation and Earths Surface
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Why do we have seasons?
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Sun conditions at the Solstices and Equinoxes
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• Solar declination latitudinal change of
  subsolar points

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Energy Pathways
Figure 4.1
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Heat Transfer

• Heat energy produced by the motion of molecules
  and atoms in a substance
• 4 ways to transfer heat
• 1. Radiation electromagnetic waves
  (sunlight)
• 2. Conduction energy moved from high to low
• 3. Convection vertical movement of energy
• 4. Advection horizontal movement of energy

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Earths Modern Atmosphere

• The atmosphere is absolutely essential for life
  on Earth
• Earths atmosphere exists in a series of spheres
  or layers that grade into one another  
• Layers Composition, temperature, and function  

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Protective Atmosphere
Figure 3.6
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Energy Balance in the Troposphere  

• Greenhouse Effect where gases (carbon dioxide,
  water vapor, methane, nitrous oxide, and CFCs)
  absorb insolation and reradiate it back to Earth
  in longer wavelengths thereby warming the lower
  troposphere
• The Greenhouse Effect and Atmospheric Warming
• Atmosphere absorbs heat energy
• Atmosphere delays transfer of heat from Earth
  into space

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Local Factors Influencing Air Temperature

• Urban Effect
• Urban Heat Island
• Darker surfaces less reflection
• Less forest cover
• Less water on surface
• Heat from human energy use

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The Urban Environment
Figure 4.21
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Urban Heat Island
Figure 4.22
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Global NET R

• Surfaces lose heat in one of 3 ways
• Latent heat of evaporation energy released as
  water changes state cant feel it
• Sensible heat heat you can feel and measure
  convection and conduction
• Ground heating and cooling energy stored during
  warm periods and released during cool periods

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Radiation Budgets
El Mirage, CA
Pitt Meadows, BC
Figure 4.20
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Principal Temperature Controls

• Latitude
• Altitude
• Cloud Cover
• Land-Water Heating Differences

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Latitude and Temperature

• Latitude  
• Affects insolation
• Sun angles
• Daylength

Figure 5.4
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Altitude

• Altitude  
• High altitude has greater daily range
• High altitude has lower annual average

Figure 5.5
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Cloud Cover
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LandWater Heating Differences 

• Evaporation ( latent heat)
• Transparency ( penetration of insolation)
• Specific heat (differs among objects)
• Movement ( vertical mixing)
• Ocean currents and sea surface temperatures(
  spread of energy spatially)

All this leads to this important conceptMarine
vs. continental effects
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LandWater Heating Differences  
Figure 5.7
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Global Temperature Ranges
Figure 5.17
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Atmospheric Pressure Systems
High-pressure system -also called
anticyclone -circulating body of
air -descending air -clockwise circulation
in northern hemisphere Low-pressure
system -also called cyclone -circulating body
of air -rising air -counterclockwise circ. in
northern hemisphere
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Atmospheric Pressure Map
Isobars lines of equal air pressure on a map
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Wind Direction
Winds are named according to the direction FROM
which they are blowing
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Direction of Air Flow

• Unequal heating of land surfaces
• Pressure gradient force air flows from high to
  low
• Coriolis force deflection or change in
  direction caused by Earths rotation
• Frictional forces places a drag on that air flow

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Pressure Gradient Force
High pressure to low pressure, perpendicular to
isobars
Fluctuations in the Pressure Gradient
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Coriolis Force

• Due to Earths rotation
• Pulls wind to right in northern hemisphere
• Pulls wind to left in southern hemisphere
• Strongest at poles
• None at equator

Coriolis Force
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Frictional Forces

• Near surface, friction (f) works against pressure
  gradient force (pgf), so resulting wind direction
  is between pressure gradient force and coriolis
  force (cf)

WIND
pgf
cf northern hemisphere
f
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Three Forces Combined
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Rossby Waves
Figure 6.17
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The Polar Front and Jet Streams

• Strong boundaries often occur between warm and
  cold air. In the mid-latitudes, the polar front
  marks this thermal discontinuity at the surface.

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Relative Humidity

• Relative humidity is the indication of how close
  the air is to saturation and when condensation
  will begin
• Dew-point temperature not really a temperature,
  but a measure of moisture content
• When air temperature tries to decrease below the
  dew point, surplus water vapor is removed from
  the air by condensation

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Relative Humidity
Actualwater vapor
Figure 7.8
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Hydrologic Cycle