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.

GLOBAL ATMOSPHERE EQUATOR EXAMPLES OF CIRCULATION OV4-1 BOILING WATER HADLEY’S THEORY ONE CELL PER HEMISPHERE DOES NOT ACCOUNT FOR EARTH’S ROTATION SEA BREEZE

UPPER AIR PRESSURE GRADIENT OV4-2 WARM COLD SAME PRESSURE ALTITUDE DECREASES TOWARD POLES SAME ALTITUDE PRESSURE DECREASES TOWARD POLES EQUATOR

ROTATION – A SIMPLE EXAMPLE OV4-3 BALL MOVES TO OBSERVER’S RIGHT CORIOLIS EFFECT THROWER BALL PLATFORM PLATFORM ROTATES THROWER THROWS BALL BIRD’S EYE VIEW THROWER’S VIEW

CORIOLIS EFFECT ON THE EARTH OV4-4 NORTH POLE LIKE BALL THROWER MIDLATITUDE SOME EFFECT EQUATOR NO EFFECT EXPLAINS WHY NORTH OR SOUTH WIND TURNS RIGHT

CORIOLIS EFFECT – II OV4-5 AXIS OF ROTATION CENTRIFUGAL FORCE G + CTF VERTICAL G CTF CENTRIFUGAL FORCES CAUSES EAST & WEST WINDS TO TURN RIGHT LOOK FIRST AT A BUBBLE OF STILL AIR CENTRIFUGAL FORCE LOCAL VERTICAL GRAVITY

CORIOLIS EFFECT – III OV4-6 PRESSURE GRADIENT LOCAL VERTICAL STILL AIR PRESSURE GRADIENT BALANCES G + CTF G + CTF G WEST WIND (AIR MOVES EAST) FASTER ROTATION CTF INCREASES G + CTF MOVES AIR SOUTH CTF

CORIOLIS EFFECT – SUMMARY OV4-7 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

GLOBAL WEATHER PATTERNS OV4-8 EVIDENCE OF ACTUAL GLOBAL CIRCULATION SEMI-PERMANENT PRESSURE BELTS PREVAILING SURFACE WINDS HIGH ALTITUDE JET STREAMS

SEMI-PERMANENT PRESSURE BELTS OV4-9 POSITIONS DURING WINTER SUMMER ITCZ – INTER-TROPICAL CONVERGENCE ZONE POLAR HIGH ICELANDIC LOW

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 OV4-12 N S 0o0o 30 o S 60 o N 30 o N 60 o S HORSE LATITUDES DOLDRUMS LOW HIGH LOW (ITCZ) LOW HIGH BIRD’S EYE VIEW VIEW STANDING ON EARTH’S SURFACE HADLEY CELL J WIND LEGEND SURFACE ALOFT E – POLAR EASTERLIES J – JET STREAMS T – TRADE WINDS W – MIDLATITUDE WESTERLIES COOL WARM T MIDLATITUDE CELL POLAR CELL E W J

WIND DEVELOPING – WITHOUT FRICTION OV4-13 WIND PARALLEL TO ISOBARS 4 WIND TURNS PICKS UP SPEED 3 LOWER PRESSURE WIND STARTS TO BLOW 2 PGFPGF 1 MAP VIEW PGFPGF ISOBARS PGFPGF WIND CF CORIOLIS FORCE APPEARS CORIOLIS FORCE INCREASES PGFPGF CF COLIOLIS FORCE BALANCES PGF CFCF

HOW FRICTION AFFECTS THE WIND OV4-14 CF BALANCE OF FORCES PGFPGF CFCF WITHOUT FRICTION PARALLEL TO ISOBARS PGFPGF FF C F WITH FRICTION ACROSS ISOBARS FF PGF CF + FF = PGF

WINDS BLOWING ALONG CURVED TRACKS OV4-15 LOCAL CENTRIFUGAL FORCE PRESSURE GRADIENT FORCE FRICTION FORCE CORIOLIS FORCE RIDGE ISOBARS CONVEX TOWARD POLE CENTRIFUGAL FORCE HELPS PGF MORE CORIOLIS NEEDED TO BALANCE WIND SPEED FASTER TROUGH ISOBARS CONVEX TOWARD EQUATOR CENTRIFUGAL FORCE HELPS CORIOLIS LESS CORIOLIS NEEDED TO BALANCE WIND SPEED SLOWER LOCAL CENTRIFUGAL FORCE ENTERS THE BALANCE AXIS OF ROTATION AXIS OF ROTATION

ROSSBY WAVES WAVES MOVE FROM WEST TO EAST MOST PROMINENT AT HIGH LATITUDES POLAR JET FOLLOWS WAVE PATTERN WAVES INFLUENCE MIDLATITUDE WEATHER OV4-16 RIDGES AND TROUGHS CIRCLE THE GLOBE IN A WAVE PATTERN

ANSWER TO CHALLENGE QUESTION OV4-17 WEST WIND (BUBBLE MOVES EAST) FASTER ROTATION CTF INCREASES BUBBLE MOVES SOUTH (RIGHT) G PRESSURE GRADIENT WEST WIND (BUBBLE MOVES EAST) FASTER ROTATION CTF INCREASES AIR MOVES NORTH (LEFT) NORTHERN HEMISPHERE SOUTHERN HEMISPHERE OBSERVER ROTATES TO RIGHT OBSERVER ROTATES TO LEFT G + CTF PRESSURE GRADIENT CF G + CTF CTF G