Transcript G107 Physical Geography

G107 Physical Geography
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Section II Power Point Slides
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Winds and Global Circulation
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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)
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Inches of mercury (29.92 in)
Centimeters (76 cm)
Millibars 91013 mb)
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Winds
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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 earth’s 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
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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
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Note the pattern of cyclone/anticyclone in
both the northern and southern hemispheres
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Circular Moving Air
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Note the convergent and
divergent winds
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Circular moving air in Ft. Wayne
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Photos my Burnet
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Tornado Pictures from Ft. Wayne
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Global Air Pattern
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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.
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Global wind pattern
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Local Winds
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Land & Sea breezes
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Heating of the land and sea
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Mountain and Valley Winds
Drainage winds (e.g. Chinook, Bora, Taku,
Foehn, Mistral, & Santa Ana)
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Winds Aloft- winds at high altitude
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Geostrophic winds (Jet stream & Rosby waves)winds flow parallel to isobars
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Ocean Currents
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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
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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
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Humidity – amount of water vapor in the air
Humidity can be measured three different ways
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Absolute Humidity…mass 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
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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
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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 > 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
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Drizzle
Rain
Snow
Hail
Sleet
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Classification of Precipitation
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Orographic- rain shadow effect
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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
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Air mass- covers large area with similar
temperature, pressure and moisture
Air Mass properties depend on
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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
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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
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When air masses move, the leading edge is called
a FRONT
There are four types of fronts
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Warm
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Cold
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Stationary
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Occluded
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Traveling Cyclones
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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
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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
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Takes into account the extreme weather conditions
also.
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Physical components of climate
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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
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Latitude
Distribution of land & water
Ocean current
Mountain
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Climate classification Criteria
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Thermal regimes
Precipitation
Air masses and Frontal zones
Koppen-Geiger climate system
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Five major climate groups
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A
B
C
D
E
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Key words
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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
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