Weather Trivia: January 8

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Weather Trivia January 8

• 1991 A wild hailstorm moved across Calgary, AB,
  causing 300 to 400 million in damages a
  record insurance loss for any single storm event
  in Canadian history. Companies flew in adjusters
  to handle nearly 80,000 property claims. The
  30-minute storm split trees, flooded basements,
  and broke windows and siding. Raging sewer
  waters blew off manhole covers and plugged catch
  basins.

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Energy Warming the Earth and the
Atmosphere Chapter 2
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Energy Warming the Earth the Atmosphere

• This chapter discusses
• The role of solar energy (e.g. short wave
  radiation) in generating temperature heat
• Earth's processes for heat transfer in the
  atmosphere, including long wave radiation, to
  maintain an energy balance

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Energy Temperature
Figure 2.1

• When solar radiation collides with atmospheric
  gas molecules, they move.
• This produces
• temperature, defined as the moving molecules
  average speed
• kinetic energy
• Total energy increases with greater molecule
  volumes.

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Temperature Scales
Thermometers detect the movement of molecules to
register temperature. Fahrenheit and Celsius
scales are calibrated to freezing and boiling
water, but the Celsius range is 1.8 times more
compact.
Figure 2.2
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Heat and Temperature

• Temperature is proportional to average kinetic
  energy of individual molecules 
• temperature scales are Celsius (oC), Fahrenheit
  (oF) or Kelvin (K) 
• at 0 K (absolute zero), molecular motion ceases
• the Kelvin temperature scale is used by
  scientists
• Unit of heat is the calorie (cal) it is heat
  needed to raise temperature of 1 gram of water by
  1oC
• SI system unit of energy is Joule (1 cal 4.186
  J)

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• Figure 2 Comparison of the Kelvin, Celsius, and
  Fahrenheit scales.

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Temperature and Density

• Warm air
• molecules moving faster
• more and stronger collisions
• more separation between molecules
• less dense
• Cool air
• the opposite
• more dense

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Earth's Magnetic Field
Figure 2.17
Earth's molten metal core creates a magnetic
field that covers earth from the south to north
pole.
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Solar Wind
High energy plasma is blown from the sun in a
dangerous solar wind, and the magnetosphere
deflects this wind to shield the earth.
Figure 2.18
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Ions Aurora Belts
Solar winds entering the magnetosphere excite
atmospheric gas electrons. When the electron
de-excites it emits visible radiation.
Figure 2.19A
The aurora is created by these solar winds and
de-exciting ions, and has belts of expected
occurrence at both poles.
Figure 2.20
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Energy

• Energy is capacity to do work
• Energy stored in object is internal energy
• Gravitational potential energy mass
  gravitational acceleration height mgh
• Chemical potential energy
• Moving object possesses kinetic energy ½mv2 (v
  is speed)
• Radiant energy is received by the Earth from Sun

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Conservation of Energy

• Law of Conservation of Energy or
• First Law of Thermodynamics
• Energy cannot be created or destroyed, it merely
  changes form

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Internal Energy and Heat

• Atmosphere and oceans contain internal energy (
  potential kinetic energy of molecules)
• A warmer object has more kinetic energy but not
  necessarily more potential energy
• For two objects of different temperature, energy
  (heat) is transferred from warm to cold object,
  due to temperature difference between them

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Heat Transport in Atmosphere

• Temperature change of given substance to heat
  input depends on its specific heat 
• Specific heat is amount of heat needed to raise 1
  gram of substance by 1oC (unit is cal/gram/oC)

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Latent Heat

• Latent heat energy required to change phase
  (gas, liquid, solid) of substance
• Example evaporation is associated with change
  from liquid to gas, this requires heat input
• Energy needed for evaporation (resulting in
  cooling of environment) is stored within water
  vapour molecules and is latent
• Energy will reappear when the vapor condenses
  back to a liquid (and heating occurs)

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Latent Heating
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Heat Transport in Atmosphere

• Transport of heat is accomplished by conduction,
  convection and radiation 
• conduction transfer of kinetic energy of
  molecules by collisions of molecules
• convection transport of heat within a fluid by
  bulk motion of fluid itself 
• heat transported by conduction and convection is
  "sensible heating" 
• radiation energy transfer which can take place
  in a vacuum, with no intervening physical medium
  (unlike conduction and convection)

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Heat Conduction
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Heat Conductivity
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Wind Chill

• Wind chill is increased heat loss from our body
  due to presence of wind
• thin layer of still air (several mm thick) hugs
  the skin and acts as an insulating layer, as air
  is a poor conductor of heat
• wind would reduce the thickness of this layer,
  thus leading to increased heat loss from the body

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Convection

• Possible in liquids and gases (not solids)
• Convection naturally occurs in atmosphere

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A Thermal
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Advection

• Horizontally moving part of circulation
• Advection is transfer of properties (such as
  temperature and moisture) from one location to
  another due to bulk motion of air
• Thus we speak of warm or cold air advection,
  moisture advection

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Larger scale advection

• air mass control  
• advection is the movement of air mass from one
  region to another  
• warm advection occurs when the wind blows from
  warm to colder areas, i.e., wind direction cuts
  across isotherms (lines of constant temperature)
  from warm to cold opposite for cold advection

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Air Pressure and Air Density

• pressure decreases as we ascend in vertical
  direction

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A rising air parcel cools Why?

• Rising air parcel enters a region of lower
  pressure, as pressure decreases with height
• Air molecules push against the surrounding ones
  to equalize pressure, thus doing work
• Energy source for work comes from the parcel
  itself, from its internal energy
• As internal energy depends on temperature, the
  parcel cools
• Conversely, sinking parcels warm
• Almost all clouds are due to rising motion of air
  parcels

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Rising and Sinking Air
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Weather Maps Revisited

• Surface highs (H) are fair weather systems, winds
  around a high blow clockwise and spiral outward
• Surface lows (L) are stormy weather systems,
  winds around a low blow counterclockwise and
  spiral inward
• Inward motion around low leads to rising motion,
  due to conservation of mass
• This in turn results in cooling, condensation and
  precipitation, thus lows are associated with
  stormy weather!