Transcript Meteorology powerpoint - Lynn English Faculty Pages

Where are
they?
Why is there
no weather?
Meteorology
The study of weather
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Good sites for weather info:
weather.com
http://www.weatherunderground.com/
www.weathernet.com
nws
Describe the weather outside
right now
• The variables measured are:
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Temperature
Humidity (Dew point and RH)
Pressure (High /Low)
Wind (speed and direction)
Precipitation (rain, sleet, snow, etc)
Cloud (percentage and type)
Will these variable change over the next minute?
Hour?day?week?
Air Temp
• Instrument:
Thermometer
• Temp decreases as you
increase in altitude
What affects our temperature?
• Latitude (New England vs Miami)
• Altitude (Lynn vs Mt Washington)
• Closeness to Ocean (NE vs Omaha)
• Cloud cover (Clear vs cloudy)
• Land use
Humidity
• Absolute Humidity – amount of water vapor in the
air
• Relative Humidity (RH) – amount of water vapor
in the air vs the amount it can hold at a specific
temp.
• Dew Point (DP) – the temp to which air has to
cool for dew to form
• What is the relationship between DP and RH?
• Instrument: Sling psychrometer
DP and RH
• Dew Point
The closer the DP temp is
the air temp more
likely
clouds/dew/precip will
form.
How does this relate to
RH?
• Relative Humidity
– Written as a percent.
– The closer to 100%,
the more likely clouds
and precip.
Sling Psychrometer
Dry Bulb – AirTemp
Wet Bulb - fabric
Barometric Pressure
• Force or weight of air pushing on the
surface of earth
• Pressure decreases as altitude increases
(why)
• Moist air light (Low)
• Dry air heavy (High)
• Instrument: barometer
Barometric
Pressure
Pressure
High (H)
• Dry conditions
• Air circulates clockwise
and outward
• Air is sinking from above
Low (L)
• Wet Condition
(Precipitation)
• Air circulates
counterclockwise and
inward
nws-goes sat
•Air flows from High to Low causing wind!
•H
L
diastudio.org/DataDiscovery/Hurr_ED_Center/Hurr_Structure_Energetics/S
Wind
• Horizontal movement of air.
• Caused by difference in heating of Earth
(difference in air pressure [H to L])
• Sun heats Earth, Earth heats atmosphere
(conduction, convection, radiation)
Instrument: Anemometer,
Wind vane
Insolation and re-radiation
Local vs GlobalWinds
• Local
examples
Land and Sea Breezes
Mountain Ranges
Global winds
– Move weather systems
– Coriolis effect – shift in
the path of fluid moving along
the surface of the earth due to
the rotation of the earth
– Doldrums (equator)
– Prevailing westerlies
– Polar easterlies
m/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm
Land and Sea Breeze
Mountain Ranges
Air Masses
• CP – Continental Polar – from the northwest
• Cold and dry
• CT – Continental tropical – from the south west
• Warm and dry
• MP – maritime polar – from the northeast
• Cold and wet
• MT – maritime tropical – from the southeast
• Warm and wet (hurricanes)
Air masses
Fronts
• Warm Front – a warm air mass overtakes a
colder air mass  creates cirrus clouds
• Cold front – Cold air mass overtakes a warm air
mass  cumulus &/or storms
• Stationary front – two air masses moving
parallel or transformly  sluggish moving precipitation
• Occluded front – Fast moving cold front
overtakes a warm front  high winds and heavy
precipitation.
Fronts
Precipitation and Clouds
Clouds form when rising air reaches the dew point
temperature and there are condensation nuclei
(particles of dust, pollen, ash, etc) present.
Precipitation occurs when the air is saturated and
water vapor becomes either a solid or a liquid.
What is condensation? What are other phase
changes? When is energy released? Absorbed?
//www.classzone.com/books/earth_science/terc/content/visualizations/es180
This method of cloud classification was proposed by Luke Howard
(1803) who named the clouds based on their form:
Cirrus - curl
Stratus - layer
Cumulus - heap
Nimbus - rain
and on their height:
High
Middle
Low
Contrails fall into the category of cirrus as they are high level clouds
that consist entirely of ice crystals
Reading a weather map
Sample weather map