G107 Physical Geography

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G107 Physical Geography

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• Section II Power Point Slides

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Winds and Global Circulation

• Wind is air in motion
• Results from difference in pressure between two
  areas
• Pressure is force acting on an area
• Standard Pressure Standard barometric pressure
  (SBP) is pressure at mean sea level
• Pressure Scales (numbers at mean sea level)
• Inches of mercury (29.92 in)
• Centimeters (76 cm)
• Millibars 91013 mb)

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Winds

• Pressure Gradient Force mass movement of air
• High temp results in low pressure low temp
  results in high pressure
• Pressure gradient, Friction, Gravity and Coriolis
  effect affect wind speed and direction
• Coriolis effect is due to earths rotation it
  is the deflection of wind to the right in the
  northern hemisphere or to the left in the
  southern hemisphere (imagine yourself going in
  the same direction as the wind)

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Circular Moving Air

• Cyclone is the circular moving air mass around a
  low pressure center
• Anticyclone is a circular moving air around a
  high pressure center
• Note the pattern of cyclone/anticyclone in both
  the northern and southern hemispheres

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Circular Moving Air

• Note the pattern of cyclone/anticyclone in
  
  both the northern and southern hemispheres

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Circular Moving Air

• Note the convergent and
  
  divergent winds

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Circular moving air in Ft. Wayne

• Photos my Burnet

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Tornado Pictures from Ft. Wayne
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Global Air Pattern

• Low and High pressure areas of the world (linked
  to solar radiation/temperature)
• Pressure zones include low equatorial zone and
  midlatitude high pressure zone
• The NE Trades and SE Trades air moves toward
  the equator from the north and south respectively
• Where the two trade winds collide, the area is
  called Intertropical Convergence Zone (ITCZ) and
  when they do not collide violently, the are is
  called Doldrum

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Global Air Pattern Contd.

• Global wind pattern

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Local Winds

• Land Sea breezes
• Heating of the land and sea
• Mountain and Valley Winds
• Drainage winds (e.g. Chinook, Bora, Taku, Foehn,
  Mistral, Santa Ana)
• Winds Aloft- winds at high altitude
• Geostrophic winds (Jet stream Rosby waves)-
  winds flow parallel to isobars

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Ocean Currents

• Currents- form when wind moves over water surface
  in a given direction... frictional force
• Ocean current could be warm or cold
• Some ocean currents are
• Alaska, Agulhas, Antartic circumpacific current,
  Benguela, Brazi, California, Canaries, Falkland,
  Guinea, Gulf Stream, Kuroshio (Japan), Labrador,
  North Atlantic drift, N. Equatorial, Oyashio
  (China), Pacific, Peru, S. Equatorial, and West
  Wind Drift.
• Circular moving ocean currents are called GYRES

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Atmospheric Moisture and precipitation

• Humidity amount of water vapor in the air
• Humidity can be measured three different ways
• Absolute Humiditymass of water vapor in a given
  volume of air
• Specific humidity the mass of water vapor in a
  given mass of air
• Relative humidity ratio of water vapor present
  in the air compared to the amount of water vapor
  that will be present when the air is saturated at
  the given temperature
• Concept of saturation point

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When air becomes Saturated

• Air can become saturated either with addition of
  water or cooling of the air.
• When air cools such that it becomes saturated,
  the temperature at which it becomes saturated is
  called the DEW POINT.
• Cloud is the first physical evidence that the air
  is saturated

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Clouds

• Several cloud types but they all begin as cirrus
  (high altitude clouds that are feather like),
  stratus (form layers), or cumulus (cotton
  bulb-like or cauliflower like)
• Clouds are classified based on elevations
• High gt 7.6 km e.g. Cirrus, cirrostratus, cirro
  cumulus
• Intermediate (middle) 2-7.6 km (stratus,
  stratocumulus
• Low 0.2 km. Cumulus, cumulonimbus
• Nimbus or Nimbo are prefix or suffix in cloud
  terminology that indicate precipitation

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Clouds
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Classification of Clouds
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Precipitation forms

• Drizzle
• Rain
• Snow
• Hail
• Sleet

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Classification of Precipitation

• Orographic- rain shadow effect
• Best found near the west coast effective side is
  east of the west coast mountains
• Convectional Precipitation
• Cyclonic/Frontal Systems
• Convergent

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Weather systems

• Air mass- covers large area with similar
  temperature, pressure and moisture
• Air Mass properties depend on
• a) source region and
• b) region over which the wind passes
• The area over which an air mass forms is called
  the Source Region

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Types of Air Masses

• Classified is based on latitudinal position and
  underlying surface (water or land)
• Artic (A) mA (maritime) cA (continental)
• Antarctic (AA) mAA cAA
• Polar (P) mP cP
• Tropical (T) mT cP
• Equatorial (E) mE cE

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Fronts

• When air masses move, the leading edge is called
  a FRONT
• There are four types of fronts
• Warm
• Cold
• Stationary
• Occluded

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Traveling Cyclones

• Wave cyclone (midlatitude and Artic regions)
• Tropical (Hurricanes Typhoons)
• Tornado (small storm related to sever
  convectional activity)
• Why do most storms occur in Spring and Summer?

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Weather and Climate

• Weather involves the every day weather related
  activities
• Elements of weather include temperature, cloud
  types, cloud cover, wind, wind direction, fog,
  precipitation, sunshine, etc.
• Climate is the average weather condition of a
  given location
• Takes into account the extreme weather conditions
  also.

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Physical components of climate

• Radiation
• Sensible heat
• Barometric pressure
• Winds
• Relative and Specific Humidity
• Dew Point
• Cloud cover and type
• Fog
• Precipitation type and intensity
• Evaporation and Transpiration
• Cyclones

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Climate Controls

• Latitude
• Distribution of land water
• Ocean current
• Mountain

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Climate classification Criteria

• Thermal regimes
• Precipitation
• Air masses and Frontal zones
• Koppen-Geiger climate system
• Five major climate groups
• A
• B
• C
• D
• E

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Key words

• Air mass, relative, specific, absolute humidity,
  dew point, rain shadow, pressure, cloud types,
  climatic controls, winds, cyclones, anticyclone,
  coriolis effect, winds aloft, Geostrophic wind,
  front types, precipitation types, climates,
  climographs, nimbos, nimbus, cumulonimbus,
  convergent, divergent