Download Wind Essen als

Atmospheric
and
Oceanic
Circula4on
• 
• 
• 
• 
Wind
Essen)als
Driving
Forces
Within
the
Atmosphere
Atmospheric
Pa9erns
of
Mo)on
Oceanic
Currents
Wind
Essen4als
•  Air
Pressure
and
Its
Measurement
•  Wind:
Descrip4on
and
Measurement
•  Global
Winds
AIR PRESSURE IS THE PRESSURE PRODUCED BY THE
MOTION, SIZE, AND NUMBER OF GAS MOLECULES IN
THE AIR AND EXERTED ON SURFACES IN CONTACT
WITH THE AIR
THE WEIGHT OF THE ATMOSPHERE, THE AIR
PRESSURE, EXERTS AN AVERAGE FORCE OF 14.7
POUNDS PER SQUARE INCH AS SEA LEVEL
AIR IS COMPRESSED AND IS DENSER NEAR EARTH’S
SURFACE . . .
AND RAPIDLY THINS OUT WITH INCREASED
ALTITUDE
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ANY INSTRUMENT THAT MEASURES AIR
PRESSURE IS CALLED A BAROMETER
THE BAROMETER WAS DEVELOPED BY GALILEO’S
STUDENT EVANGELISTA TORRICELLI IN 1643
WIND
WIND IS THE HORIZONTAL MOTION OF AIR
RELATIVE TO THE EARTH’S SURFACE . . .
IT IS PRODUCED BY DIFFERENCES IN AIR
PRESSURE FROM LOCATION TO ANOTHER . . .
AND THE TWO PRINCIPLE VARIABLES ARE SPEED
AND DIRECTION
WINDS ARE NAMED FOR THE DIRECTION FROM
WHICH THEY ORIGINATE
Driving
Forces
Within
the
Atmosphere
• 
• 
• 
• 
Gravity:
Pressure
Gradient
Force
Coriolis
Force
Fric4on
Force
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GRAVITY EQUALLY COMPRESSES THE ATMOSPHERE
WORLDWIDE WITH DENSITY DECREASING AS ALTITUDE
INCREASES
PRESSURE GRADIENT FORCE
THE FORCE THAT CAUSES AIR TO MOVE FROM AN
AREA OF HIGHER BAROMETRIC PRESSURE . . .
TO AN AREA OF LOWER BAROMETRIC PRESSURE DUE
TO THE PRESSURE DIFFERENCE THEREBY CAUSING
WINDS
COLD, DENSE AIR AT THE POLES EXERTS GREATER
PRESSURE THAN WARM, LESS DENSE AIR AT THE
EQUATOR
THE EFFECT OF DRAG BY THE WIND . . .
AS IT MOVES ACROSS A SURFACE . . .
IS THE FRICTION FORCE
SURFACE FRICTION SLOWS THE WIND . . .
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Atmospheric
PaBerns
of
Mo4on
•  Primary
High‐Pressure
and
Low‐Pressure
Areas
•  Upper
Atmospheric
Circula4on
–  Jet
Streams
•  Local
Winds
–  Monsoonal
Winds
Primary
High‐Pressure
and
Low‐
Pressure
Areas
• 
• 
• 
• 
Equatorial
low‐pressure
trough
Polar
high‐pressure
cells
Subtropical
high‐pressure
cells
Subpolar
low‐pressure
cells
Equatorial
low‐pressure
trough
•  Intertropical
convergence
zone
(ITCZ)
•  Trade
winds
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THE EQUATORIAL LOW-PRESSURE TROUGH
ALSO KNOWN AS THE ITCZ . . .
OR THE INTERTROPICAL CONVERGENCE ZONE
THE EQUATORIAL LOW-PRESSURE TROUGH IS
AN ELONGATED . . .
AND NARROW BAND OF LOW PRESSURE THAT
CIRCLES THE EARTH
Subpolar
low‐pressure
cells
•  Aleu4an
low
•  Icelandic
low
•  Polar
front
SUMMARY
HERE ARE OUR PRIMARY HIGHPRESSURE AND LOW-PRESSURE AREAS:
TWO HIGH-PRESSURE AREAS: 1. SUBTROPICAL HIGH-PRESSURE (dry, hot))
20* - 35*
DYNAMIC
BERMUDA/AZORES HIGH
HAWAIIAN/PACIFIC HIGH
2. POLAR HIGH-PRESSURE CELLS (DRY, FRIGID)
AROUND 90*
THERMAL AND VERY WEAK
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TWO LOW-PRESSURE AREAS:
1. THE EQUATORIAL LOW-PRESSURE TROUGH
THERMAL
10* N AND S OF EQUATOR
FORMS THE ITCZ
WARM, MOIST
2. THE SUBPOLAR LOW-PRESSURE CELLS
DYNAMIC, COOL AND MOIST
60*N
ALEUTIAN AND ICELANDIC LOWS
Local
Winds
•  Land‐sea
breezes
•  Mountain‐valley
breezes
•  Kataba4c
winds
LAND-SEA BREEZES
CAUSED BY DIFFERENT HEATING CHARACTERISTICS
OF LAND AND WATER SURFACES
DURING THE DAY LAND HEATS FASTER THAN WATER
OFFSHORE
BECAUSE WARM AIR IS LESS DENSE IT RISES . . .
TRIGGERING AN ONSHORE FLOW OF COOLER MARINE
AIR WHICH IS USUALLY STRONGER IN THE
AFTERNOON
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