Cap 10 Local Wind

Question 1

Devices to mesure the wind?

Answer 1

10 metres above ground to measure the wind
And devices used are :wind vane,cup anemometre
Speed is in knots and true north

Question 2

Wind strength

Answer 2

Calm&raquo_space;» is 1knt or less
Gale force»> mean 34-47 kts
Storm force»> 48-63kts
Hurricane force»> Greater or equal to 64kts

Question 3

Gust ?

Answer 3

Sudden increase of 10kts or more less tha n 1 min

Question 4

Squall

Answer 4

Similiar to gust but last more than 1min

Question 5

Lull

Answer 5

Is a sudden drop in wind speed

Question 6

Veering mean

Answer 6

When wind is changing in clockwise direction

Question 7

Backing

Answer 7

When wind changes in anticlockwise

Question 8

Isotach line

Answer 8

Area of equal wind strength

Question 9

Four type of forces

Answer 9

> pressure gradient
Coriolis effect
centrifugal force
friction force (below 1000ft -3000ft above the surface)

Question 10

Coriolis force at the equator and poles

Answer 10

Coriolis force is greater at the poles and least at the equator

Question 11

Coriolis force

Answer 11

Coriolis force= 2 X omega X density X V X sin lattitude

Question 12

Cs proportinality

Answer 12

> Cs is proportional to wind speed
cs is proportional to latitude (higher =more deflection)
cs is proportional to density ( greater density ,more deflection)

Question 13

Geostrophic wind

Answer 13

Blowing parallel to isobars.

PGF=CF

Question 14

WIND SPEED PROPORTINALITY

Answer 14

~WIND SPEED IS PROPORTIONAL TO pgf
~WIND IS INVERSELY PROPORTIONAL TO DENSITY
~WIND IS INVERSELY PROPORTIONAL TO LATITUDE

At baout 5 degrees from equator cs become s neglibile

Question 15

Speed formula

Answer 15

V= (PGF)/(2X OMEGA X DENSITY X SIN lat

Question 16

For reading the wind scale

Answer 16

For same isobars spacing the windspeed is faster at low latitudes

Question 17

Gradient wind

Answer 17

In a low pressure sys the PGF IS LESS BECAUSE THE Centrifugal forceis opposing it.

In a high pressure sys the PGF become stronger because the Centrifugal force is helping the pfg

Question 18

Gradient wind is less stronger in a low

Answer 18

In a low pressure system the PGF becomes less stronger because the centrifugal force acting in the opposite direction (same direction as Coriolis force) of the PGF.

Answer 19

In a high sys the speed is hegher

In a low sys the speed is low

Question 20

Friction layer

Answer 20

2ft -3000ft vertical extent

Mainly affected by wind speed and terrain and stability

Question 21

Night time friction layer

Answer 21

Night time may reduce to 1 to 1500ft

Question 22

Friction layer

Answer 22

Surfaces friction reduces wind speed

Coriolis force reduces as wind speed reduces ,so its more like to go direct to the low from high

Question 23

Sea and land surface wind

Answer 23

Surfaces wind is 50% and 30 degrees less (backing) from geostrophic wind over the land.

Surfaces wind 70% and 10 degrees less (backing) than geostrophic wing over sea

Question 24

Diurnal variation of surface wind

Answer 24

Daytime thermal turbalence mixes slow moving surface air with the faster free stream air above (high wind speed at the surface )
At night no thermal activity so no mixing,just slow moving surface air (slow moving air at the surface) but could find wind shear because of the inversion and the high speed over the friction layer

Wind backing by 45 degree and is 1/4 of the geostrophic wind (northern hemispher)

Question 25

Sea breeze

Answer 25

Air is blowing from the sea
Over the sea at bottom is high pressure,and above is low press.
Low pressure at the land.
Sign of sea breeze is cumulus cloud over land

Tming: around 10am peaks 2-4pm
Strength : 10-15kts
Extent: ABOUT 25-40 KM INLAND AND 2-3000HIGH
CLOUD: CUMULUS OVER LAND
TREMP: AIR OVER THE LAND IS REPLACED BY COLD SEA AIR
SYNOPTIC: USUALLY DURING ANTICYLONE DUE TO PGF

Question 26

Low level jet stream

Answer 26

Is when ther e is high difference in pressure at the shore

Question 27

LAND BREZEE

Answer 27

OPPOSITE OF SEA BREEZE
SPEED 10-5 KTS
CUMULUS PVER SEA

Question 28

ANABATIC

Answer 28

SUN WILL HEAT THE SIDE OF THE MOUNTAIN,WILL CREAT UPHILL WIND AND IS WEAK WIND DUE TO GRAVITY(5KTS)

Question 29

KATABATIC

Answer 29

THE SIDE OF THE MOUNTAIN COOLS DOWN AND THE HEAVY AIR SINKS TO THE VALLEY AND THE SPEED IS VERY HIGH.IT HAPPENS AT NIGHT

Question 30

BORA

Answer 30

WIND CAN EXCEED 100KTS STRONGER IN WINTER
HIGH COLD PRESSURE COMING FROM THE BALTICS OVERFLOW THE MOUNTAINS AND REPLACE THE HOT LESS DENSER AIR IN THE ADRIATIC SEA

Question 31

THE MISTRAL

Answer 31

COLD AND DRY NORTHERLY WIND .GOING FROM HIGH TO LOW PRESSURE OVER SEA
THE NORTHERLY WIND WILL ACCELRATE PASSING BETWEEN THE ALPS. 70 KTS

Question 32

TRAMONTAMNA

Answer 32

TRAMONTANA IS A WIND COMING FROM NORTH WESTERLY

LESS STRONG THAN THE MISTRAL

Question 33

FOH WIND

Answer 33

AIR NEEDS TO STABLE WHICH THE AIR IS OROGRAPHICILY LIFTED AND COLLED AT SALR ,AND RAINS OVER UPWIND SIDE SO HAVING LESS HUMIDITY ON THE OTHER SIDE AND THEN IT STARTS TO HEAT AT SALR FIRST AND THERN AT DALR

Question 34

PAMPEROS

Answer 34

PAMPEROS
BLOWS ON THE PAMPAS OF SOUTH AMERCA
ITS ORIGIN : LOW PRESSURE CENTRE LOCATED ON THE PLAINS OF CENTRAL AND NORTHWETERN ARGENTINA

Question 35

MOUNTAIN WAVES

Answer 35

MOUNTAIN WAVE PROPAGATE FRO MLOW TO HIGH LEVELS.(UPTO FL600)
A DEGREE OF STABILITY IS REQUIRED .
ROTOR ZONES ON LEE SIDE
STRONGER WINDS 15KTS CONDITIONS UNPREDICTABLE.
LIGHT WIND (LESS THAN 15 ) PREDICTABLE .
DISTANCE FROM MOUNTAIN 100NM TO 300NM ON THE LEE SIDE.(USUALLY 20-50NM)
STABILITY IS CENTRAL TO THE DEVELOPMENT OF MOUNTAIN WAVES.
IF IS LESS STABLE IT CREATES MOUNTAIN WAVES IF IS TOO STABLE IS CREATES FOEHN EFFECT.
ROTORS ARE THE MOST DANGEROUS PART OF MOUNTAIN PART