Docstoc

Weather

Document Sample
Weather Powered By Docstoc
					    Meteorology

12.1 The Causes of Weather
Weather
 Meteorology is the study of atmospheric
  phenomena
 Weather is the current state of the
  atmosphere.
    This is usually measured in minutes, days

     and weeks
    Climate
   Climate is the weather
    for a long period of time
    for a given location.

   Usually averaged over
    30 or more years.

   Ex. The climate is hot
    and humid in Miami, but
    it is snowing there today.
     Air Masses


   An air mass is a large
    body of air that takes
    on the characteristics
    of the area over which
    it forms.
    Types of Air Masses
   Moisture
   Maritime vs.
    Continental:
     Maritime air masses
      form over water-
      have more moisture
     Continental air
      masses form over
      land- they are drier
    Types of Air Masses
   Temperature
   Tropical vs. Polar
      Tropical air masses
       form closer to the
       equator- warm
      Polar air masses
       form closer to the
       poles- cold
   Arctic air masses are
    extremely cold
Source Regions
 Combine Moisture and Temperature titles to
  name air masses.
    Name them after the regions where they
     form.
 Continental Tropical(cT) will form over
  land near the equator. Ex. Brazil, Mexico
 Maritime Tropical(cM) will form over
  water near the equator. Ex. Gulf of Mexico
Examples:
 Continental Polar(cP)
 Continental Tropical(cT)
 Maritime Polar(mP)
 Maritime Tropical(mT)
 Arctic(A)
Coriolis Effect
   The Earth spins on its axis. This causes air
    particles to deflect to the left in the N.
    Hemisphere & to the right in the S.
    Hemisphere
R
     Wind Systems
   Three wind
    zones in each
    Hemisphere
      Trade
       Winds
      Prevailing
       Westerlies
      Polar
       Easterlies
Wind Zones
•The trade winds occur from the
equator to 30ºN and 30ºS. The winds at
the equator are called the doldrums and
the ones at the 30º mark are called the
horse latitudes.
•The prevailing westerlies are
between 30ºN and S up to 60ºN and S
in a pattern opposite of the trade winds.
They are responsible for moving most
weather across the US and Canada.
•The polar easterlies are between
60ºN and S and the poles. (90ºN and S)
Jet Stream
   A stream of air
    that circulates the
    globe. Caused by
    differences in
    pressure between
    the wind systems.
      Trade and
       Westerlies
      Westerlies and
       Easterlies
      Fronts
   A front is the narrow
    region separating two air
    masses of different
    densities. These
    differences are due to
    differences in temperature,
    humidity, and pressure.
      Cold

      Warm

      Stationary

      Occluded
                        Page 308- 309 in RED BOOK!

Cold Front – Cold dense air displaces
warm air and forces the warm air up
along a steep front
-Thunderstorms often occur along the
front

On a weather map:
solid blue line with
blue triangles that
point in direction of
the front’s motion
Cold Fronts
   Cold Fronts occur when a cold air mass
    runs into a warm air mass, forcing the warm
    mass to rise.(notice cloud types!)
Warm Front – Advancing warm air
displaces cold air
- Extensive cloudiness and
precipitation

                 On a map: solid red line
                 with regularly spaced,
                 solid red semicircles
                 pointing in the direction
                 of the front's motion.
Warm Fronts
   When warm masses run into cold masses
    and slowly displaces it. (notice clouds!)
Stationary Front – Two air masses
meet and neither advances; air masses
“stall”
- Light wind and precipitation

                    On a map:
                    combination of
                    short segments
                    of cold and
                    warm front
                    symbols
Stationary Fronts
   Stationary Fronts occur when front run in
    parallel opposite directions
Occluded Front – Cold air mass
moves so rapidly that it overtakes a
warm front
- Strong winds, heavy precipitation


 On a map: alternating
 purple triangles and
 semicircles that point
 toward the direction
 of motion.
Occluded
   Occluded Fronts occur when two cold
    fronts “pinch” a warm front up.
Front Video
     High Pressure Systems
   High Pressure Systems-
    Air sinks, then hits the
    Earth’s surface and
    spreads out.
      Wind blows away from
       high pressure.
      Clockwise in N.
       Hemisphere
      Associated with fair
       weather
Low Pressure System
   Low Pressure System- Air rises, must be
    replaced.
      Wind blows toward center of low

       pressure
      Counter-Clockwise in N. Hemisphere

      Associated with clouds and precipitation

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:4
posted:2/24/2013
language:English
pages:41