More about Temperature

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Lecture 4

• More about Temperature

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Incoming vs. Outgoing Radiation
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Controls of Temperature

• Latitude
• Land and Water
• Ocean Currents
• Elevation

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Average Temperature in January
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Average Temperature in July
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Contouring
EXAMPLE
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Contouring
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Contouring
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Daytime Warming
On a clear, windless day, joggers may experience
a temperature of 122oF near their feet, and a
temperature of 90oF near their waist.
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Daytime Warming
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Peak Temperature
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Nighttime Cooling
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Radiation Inversion Ingredients

• Windless night
• Wind mixes the air with turbulent eddies
• A long night
• Cloudless night
• Clouds radiate infrared energy back to surface
• A dry night
• If dew forms, then latent heat of condensation is
  released.

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Radiational Inversion
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Daily Low Temperature

• The lowest temperature may be reached after
  sunrise. Why?
• After sunrise outgoing energy still exceeds
  incoming.
• The solar angle is low at sunrise
• If there is moisture, then evaporation cools the
  air.

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Peak Temperature
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How do we protect crops from freezing?
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How do we protect crops from freezing?
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Diurnal Range
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Heating Degree-Day
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Cooling Degree-Day
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Growing Degree-Day
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Mean Annual Temperature
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Measuring Temperature
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Measuring Temperature

• Liquid in Glass Thermometers (mercury or alcohol)
• Electric Thermometers (used in Automated Weather
  Stations)
• Thermocouples
• Platinum Resistance Thermometers
• Radiometers (on satellites, weather balloons)
• Bimetallic Thermometer (thermographs)

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Wind Chill

• Why doe the wind make it feel colder?
• On cold days our body warms a thin layer of air
  around us.
• When the wind blows, this warm layer is replaced
  by cold air.
• The faster the wind blows the colder we feel.

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The wind chill equivalent temperature tells us
how cold it would have to be with no wind, in
order for us to lose the same amount of heat.

• This is new as of 2001!
• - Replaces Paul Siples original work in
  Antarctica
• - A bit warmer than the old formula
• -Will be updated in the near future for sunshine

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Controls of Temperature

• Latitude
• Land and Water
• Ocean Currents
• Elevation

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Urban Heat Island
Stanley Park
Downtown Vancouver
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Urban Heat island

• Decrease in
• Wind speed
• Humidity (drainage systems take away water!)
• Increase in
• Temperatures
• Cloudiness
• Precipitation
• Fog
• Pollution

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Causes of Urban Heat Island

• Surfaces
• Low albedos of asphalt and concrete
• Heat trapping
• Tall structures reflect and absorb outgoing
  radiation
• Lack of water (rapid water run-off)
• Less water ? less evaporative cooling
• Surface friction
• Low wind speed ? less mixing

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Causes of Urban Heat Island

• Human produced heat
• In buildings, automobiles
• Particulates and Smog
• Greenhouse enhancer, traps heat
• Snow Removal
• Decreases the albedo

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Heat Island Example
Areas that are warm appear in white/light gray.
Areas that are cool appear dark.
Atlanta
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Heat Island Example
Trees and vegetation appear in red. Buildings,
streets and urban land cover is
white/blue-green/black.
Note the shape of the downtown region.
Atlanta
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Heat Island Example
Remember the shape of the downtown!
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Heat Trapping