Transcript centrifugal force

Department of Training
AUXWEA CHAPTER FOUR
WINDS AND EFFECTS OF
EARTH’S ROTATION
prepared by
Weather Branch
Copyright  2004 U.S. Coast Guard Auxiliary Association, Inc.
EXAMPLES OF CIRCULATION
BOILING
WATER
SEA
BREEZE
GLOBAL
ATMOSPHERE
EQUATOR
HADLEY’S THEORY
ONE CELL PER HEMISPHERE
DOES NOT ACCOUNT FOR EARTH’S ROTATION
OV4-1
UPPER AIR PRESSURE GRADIENT
SAME PRESSURE
COLD
ALTITUDE DECREASES
TOWARD POLES
SAME ALTITUDE
EQUATOR
WARM
OV4-2
PRESSURE DECREASES
TOWARD POLES
ROTATION – A SIMPLE EXAMPLE
THROWER
THROWER’S
BIRD’S EYE
VIEW
VIEW
BALL
PLATFORM
PLATFORM
ROTATES
THROWER
THROWS BALL
BALL MOVES TO OBSERVER’S RIGHT
CORIOLIS EFFECT
OV4-3
CORIOLIS EFFECT ON THE EARTH
NORTH POLE
LIKE BALL
THROWER
MIDLATITUDE
EQUATOR
SOME EFFECT
NO EFFECT
EXPLAINS WHY NORTH OR SOUTH WIND TURNS RIGHT
OV4-4
CORIOLIS EFFECT – II
CENTRIFUGAL FORCES CAUSES EAST & WEST WINDS TO TURN RIGHT
LOOK FIRST AT A BUBBLE OF STILL AIR
AXIS OF ROTATION
CENTRIFUGAL
FORCE
CTF
VERTICAL
LOCAL
VERTICAL
GRAVITY
CENTRIFUGAL
FORCE
G
G + CTF
OV4-5
CORIOLIS EFFECT – III
WEST
WIND
STILL AIR
(AIR MOVES EAST)
PRESSURE
GRADIENT
LOCAL
VERTICAL
G
CTF
G + CTF
PRESSURE
GRADIENT
FASTER ROTATION
BALANCES
G + CTF
CTF INCREASES
G + CTF MOVES AIR SOUTH
OV4-6
CORIOLIS EFFECT – SUMMARY
TWO CAUSES – EQUALLY EFFECTIVE
HORIZON CIRCLE ROTATION (NORTH & SOUTH WINDS)
CENTRIFUGAL FORCE (EAST & WEST WINDS)
WIND FROM ANY POINT OF THE COMPASS TENDS TO TURN
RIGHT IN THE NORTHERN HEMISPHERE
LEFT IN THE SOUTHERN HEMISPHERE
GREATEST EFFECT AT POLES
DECREASES AS LATITUDE DECREASES
NO EFFECT AT EQUATOR
OV4-7
GLOBAL WEATHER PATTERNS
EVIDENCE OF ACTUAL GLOBAL CIRCULATION
SEMI-PERMANENT PRESSURE BELTS
PREVAILING SURFACE WINDS
HIGH ALTITUDE JET STREAMS
OV4-8
SEMI-PERMANENT PRESSURE BELTS
POLAR
HIGH
ICELANDIC
LOW
POSITIONS
DURING
SUMMER
WINTER
ITCZ – INTER-TROPICAL CONVERGENCE ZONE
OV4-9
PREVAILING SURFACE WINDS
HORSE LATITUDES AND DOLDRUMS
WINDS USUALLY CALM OR LIGHT AND VARIABLE
OV4-10
JET STREAMS
NORMAL
MEANDERING NORTH-SOUTH
CONVERGED
GOOD WEATHER
STORMY WEATHER
OV4-11
GLOBAL CIRCULATION
POLAR
CELL
N
COOL
E
MIDLATITUDE CELL
BIRD’S EYE VIEW
LOW
J
60o N
W
30o N
J
HORSE
LATITUDES
HIGH
VIEW STANDING ON
HADLEY CELL
EARTH’S SURFACE
T
LOW (ITCZ)
DOLDRUMS
0o
HIGH
30o S
WARM
WIND LEGEND
SURFACE
ALOFT
LOW
E – POLAR EASTERLIES
J – JET STREAMS
T – TRADE WINDS
W – MIDLATITUDE WESTERLIES
S
OV4-12
60o S
WIND DEVELOPING – WITHOUT FRICTION
MAP VIEW
1
LOWER
PRESSURE
2
1004
WIND STARTS
TO BLOW
ISOBARS
1008
P
G WIND
F
CF
P
G
F
1012
1016
3
WIND TURNS
PICKS UP SPEED
CORIOLIS
FORCE
INCREASES
CORIOLIS
FORCE
APPEARS
4
P
G
F
P
G
F
WIND PARALLEL
TO ISOBARS
CF
C
F
COLIOLIS
FORCE
BALANCES PGF
OV4-13
HOW FRICTION AFFECTS THE WIND
WITHOUT FRICTION
PARALLEL TO ISOBARS
WITH FRICTION
ACROSS ISOBARS
P
G
F
P
G
F
PGF
FF
FF
C
F
BALANCE
OF FORCES
C
F
CF
CF + FF = PGF
OV4-14
WINDS BLOWING ALONG CURVED TRACKS
LOCAL CENTRIFUGAL FORCE ENTERS THE BALANCE
PRESSURE
GRADIENT
FORCE
FRICTION
FORCE
CORIOLIS
FORCE
LOCAL
CENTRIFUGAL
FORCE
TROUGH
ISOBARS CONVEX TOWARD EQUATOR
CENTRIFUGAL FORCE HELPS CORIOLIS
LESS CORIOLIS NEEDED TO BALANCE
WIND SPEED SLOWER
1008
1012
AXIS OF
ROTATION
1008
AXIS OF
ROTATION
1012
RIDGE
ISOBARS CONVEX TOWARD POLE
CENTRIFUGAL FORCE HELPS PGF
MORE CORIOLIS NEEDED TO BALANCE
WIND SPEED FASTER
OV4-15
ROSSBY WAVES
RIDGES AND TROUGHS CIRCLE THE GLOBE IN A WAVE PATTERN
WAVES MOVE FROM WEST TO EAST
MOST PROMINENT AT HIGH LATITUDES
POLAR JET FOLLOWS WAVE PATTERN
WAVES INFLUENCE MIDLATITUDE WEATHER
OV4-16
ANSWER TO CHALLENGE QUESTION
NORTHERN HEMISPHERE
WEST WIND (BUBBLE MOVES EAST)
PRESSURE
GRADIENT
CF
G
OBSERVER
ROTATES
TO LEFT
G + CTF
FASTER ROTATION
CTF INCREASES
BUBBLE MOVES SOUTH (RIGHT)
SOUTHERN HEMISPHERE
WEST WIND (BUBBLE MOVES EAST)
OBSERVER
ROTATES
TO RIGHT
G + CTF
G
CTF
PRESSURE
GRADIENT
FASTER ROTATION
CTF INCREASES
AIR MOVES NORTH (LEFT)
OV4-17