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Lecture

EESB18H3 Lecture Notes - Environment And Climate Change Canada, Heat Stroke, Humidex


Department
Environmental Science
Course Code
EESB18H3
Professor
Jovan Stefanovic

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Lecture Eight
x Energy ± Ability or capacity to do work
o Force (F = m * a; unit ± Newton N) ± moving a mas with a particular
acceleration
o Work (W = F * distance; unit ± Joule J)
o Power (P = W / time; unit ± J/s = watt) ± rate of doing work
o Types of Energy
Potential Energy ± Stored Energy ± PE = mgh
Kinetic Energy ± Energy of Motion ± KE = ½mv2
o Heat Energy and Heat Transfer
Kinetic energy of atoms and molecules within a substance
x Sensible Heat
x Latent Heat (Stored/hidden heat)
o Evaporation ± 600 calories per gram of water are
added ± called latent heat of vaporization
o Condensation ± heat energy is released
Convection ± Movement of heat energy within a medium (Ex:
boiling water)
Conduction ± Transfer of heat energy between two surfaces in
direct contact
x Electromagnetic Energy ± Energy emitted by the sun.
x Radiation, Absorption, Scattering and Temperature
o Hot objects radiate more rapidly and short waves than do cool objects
o &ROGREMHFWRQ(DUWKVVXUIDFHDEVRUEDODUJHDPRXQWRILQFRPLQJVRODU
energy
o Reflection (albedo) ± ability to reflect electromagnetic energy (%
reflected)
o Scattering ± Short wavelengths of visible light (blue & violet) are
scattered more effectively than longer wavelength (red). Ex: midday and
sunset
x Composition of the Atmosphere
o Major components of clean, dry air
Nitrogen (N) ± 78%
Oxygen (O2) ± 21%
Argon and other gases
Carbon Dioxide (CO2) ± 0.036%
x Absorbs heat energy from Earth
o Relative humidity ± UDWLRQRIWKHDLUVDFWXDOZDWHUYDSRUFRQWHQW
compared with the amount of water vapor required for saturation at that
temperature (and pressure)
x Atmospheric Pressure ± Weight of air at sea level
o 14.7 lbs per square inch
o 1 kg per square centimeter
o Milibar (mb) ± standard sea level pressure is 1013.2 mb
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x Changes in temperature, water vapor content and movement of air are responsible
for horizontal variation in atmospheric pressure
x Coriolis Effect ± Effect of the rotation of the Earth on the objects on it.
x Adiabatic Cooling ± As air moves up it expands and cools, as it moves down it
compresses and warms.
o For dry air the cooling rate is 10° C for every 1000m
x Adiabatic Lapse Rates
o The saturated adiabatic lapse rate is less than the dry adiabatic lapse rate
due to the release of energy during condensation
o Temperature to which a parcel of air would need to be cooled to reach
saturation
x Stable vs. Unstable Air
o Tendency of parcel of air to remain in place or to change its vertical
position is referred as atmospheric stability
o Air mass is said to be unstable if its parcels rise until they reach air of
similar temperature and density
o Thunderstorms form when an air mass becomes so unstable
Unstable means that the air in the lowest layers is unusually warm
and humid, or that the upper layers are unusually cool, or both.
x Convection ± +HDWLQJRIWKH(DUWKVVXUIDFHleads to rapidly rising parcels of air
(convection) with subsequent condensation and cloud formation.
x Condensation and Cloud Formation
o Condensation
Water vapor in the air changes to a liquid and forms dew, fog, or
clouds
Water vapor requires a surface to condense on
x Possible condensation surfaces on the ground can be the
grass, a car window, etc.
x Possible condensation surfaces in the atmosphere are tiny
bits of particulate matter called condensation nuclei
o Dust, smoke, etc.
o Ocean salt crystals which serve as hygroscopic
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x Cumulonimbus ± The main type of cloud when talking about thunderstorms and
other storms.
x Cold and Warm Fronts
o Cold Front ± cold air rapidly displaces relatively warm air as it advances.
Heavy precipitation results along a narrow band.
o Warm Front ± advancing warm air rises slowly over the adjacent cooler air
mass. Associated with widespread cloud with moderate, steady
precipitation.
x Stationary and Occluded Fronts
o Stationary Front
Flow of air on both sides of the front is almost parallel to the line
of the front
Surface position of the front does not move
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