wind

Question 1

\__ how many knots is this?

Answer 1

10 knots

Question 2

\__ (small) how many knots is this?

Answer 2

5knots

Question 3

/\____ how many knots is this?

Answer 3

50 knots

Question 4

what is a gust?

Answer 4

a sudden but brief increase in windspeed- often assoicated with rapid fluctuations in wind direction.

Question 5

what is a lull?

Answer 5

corresponding decrease in wind speed

Question 6

where are gusts and lulls most frequent?

Answer 6

near the ground caused by friction between moving air and obstacles like cliffs and buildings and by variation of earth temperature.

Question 7

what is a squall?

Answer 7

they are blasts of wind which sets in suddenly- lasts for several minutes and faces usually associated with a rapidly moving cold front or thunderstorm.

Question 8

how is surface wind measured?

Answer 8

using an anemometer, mounted at a standard height of 10m above ground in an open situation. Consisting of 3 hemispherical cups mounted on a vertical spindle that rotates as the wind blows.

Question 9

what are the two groups of wind?

Answer 9

mean and variable

Question 10

what acronym is added if wind speed is too hard to read?

Answer 10

VRB

Question 11

what strength do windsocks come in?

Answer 11

15 and 25kts.

Question 12

what are the different ways to detect wind?

Answer 12

smoke, dust and windsocks, cloud shadow, wind ripples, waves

Question 13

how fast does wind have to be to produce wave ripple caps?

Answer 13

7-10kts

Question 14

what does wind produce on the surface of water and what happens when it goes over 15kts?

Answer 14

wind lanes

over 15kts it may spray or foam in parllel lines called spindrifts.

Question 15

what is the force that is responsible for starting a parcel of air to move?

Answer 15

pressure gradient force

Question 16

what will the pressure gradient force always act on?

Answer 16

right angles(perpendicular) to isobars

Question 17

what happens when isobars are closer together?

Answer 17

pressure changes occur over a short distance and gradent is said to be stronger.

Question 18

what happens if isobars are far apart?

Answer 18

pressure changes are more gradual and so the pressure gradient is weak.

Question 19

what is the relationship between wind speed and pressure gradient?

Answer 19

the speed of the air will increase with the magnitude of the pressure gradient.

Question 20

what will the winds do in isobars?

Answer 20

it will blow across isobars and equalize the pressure distribution - pressure gradients will weaken.

Question 21

what is the correlation between wind and pressure gradient?

Answer 21

the wind is caused by the strength of the pressure gradient, the stronger the gradient stronger the wind.

Question 22

what is coriolis force?

Answer 22

The rotation of the Earth produces the same deviating force on objects in motion whether they
are bullets or wind.

Question 23

what does the Coriolis force act as?

Answer 23

a deviating force on objects moving over rotating surfaces.

Question 24

how is the Coriolis force strength increased?

Answer 24

its strength increases with rate of rotation and speed of an object.

Question 25

what way does the Coriolis force deflect to in the northern hemisphere

Answer 25

right

Question 26

what way does the Coriolis force deflect to in the southern hemisphere

Answer 26

left

Question 27

what happens to wind at the equator of the earth and how does the Coriolis force affect it?

Answer 27

wind at the equator isn't deflected because they're completely parallel to the axis of rotation between two poles.

Question 28

what is the strength of the Coriolis force immediately north or south at the equator and at the poles?

Answer 28

at the equator north or south it immediately begins, and gets stronger the closer it is to the poles.

Question 29

what is geostrophic wind?

Answer 29

geostrophic flow is the theoretical wind that would result from an exact balance between the Coriolis force and the pressure gradient

Question 30

what is coriolis force dependent on?

Answer 30

the latitude due to the spherical shape of the earth

Question 31

what is wind veering?

Answer 31

wind that changes direction in a clockwise direction

Question 32

what is wind backing?

Answer 32

wind that changes direction in a counterclockwise direction

Question 33

what is the limitation of windsocks?

Answer 33

Wind direction indicators are reactionary, i.e. you will only see the results of what the wind has been doing a short time later. They are also useful as trend indicators, but they are not reliable in rapidly changing conditions

Question 34

how are shadow clouds used to detect wind direction?

Answer 34

The movement of cloud shadow over the ground gives the wind direction and some indication of speed, at the cloud’s altitude. This is used only as a guide, however, as the wind on the ground will probably be different.

Question 35

how are wind ripples used to detect wind direction?

Answer 35

Wind ripples may be evident on water or crop fields. | Waves and ripples form at right angles to the wind and move downwind

Question 36

how are wind shadows used to detect wind direction?

Answer 36

Wind shadow may be seen on the upwind side of a lake or pond | or around a coastline which will indicate wind direction

Question 37

what can geostrophic force be defined as?

Answer 37

a wind blowing along straight parallel isobars, not changing with time, under the balance of pressure gradient and coriolis forces only. if either forces become stronger isobars curve

Question 38

what is the steady flow of wind around isobars called?

Answer 38

gradient wind.

Question 39

state buys ballots law.

Answer 39

If the wind is Geostrophic and you stand (or sit) with your back to the wind in the Southern Hemisphere, the low-pressure region will be on your right. By applying Buys Ballot Law, certain general rules can be stated.

Question 40

how can buys ballots law be used to determine pressure areas and how can it be used as a forecasting tool?

Answer 40

Let's say you're flying an aircraft in the Southern Hemisphere, and you are experiencing drift towards your left (wing tip). If this wind is Geostrophic, then your aircraft is therefore flying towards a Low-pressure area. Wind, however, does not always conform to Geostrophic flow pattern

Question 41

what is surface friction?

Answer 41

Friction always reduces the speed of the air. So, surface friction can affect the course of the parcel of air quite substantially.

Question 42

what are the factors affecting surface friction?

Answer 42

the type of terrain and air density. during a cold night, friction layer is very dense and when its warm its less dense.

Question 43

what is the friction layer? and at what height is it generally not effective?

Answer 43

The Friction Layer. The lowest layer of the earth's atmosphere, usually up to 3,300 feet. Surface friction is effective in slowing down wind up to approximately 1,500 to 3,000 feet above the ground.

Question 44

what is the relationship between the surface frictions reduction in wind strength with the coriolis force and pressure gradient force?

Answer 44

The reduction in wind strength from surface friction causes the Coriolis force to reduce, making the Gradient force more dominant, thereby causing the air to flow across the isobars. Therefore, surface friction over the sea, particularly with a warm evening, will cause the surface wind to deviate slightly towards the low-pressure area.

Question 45

what happens to surface friction after sunset?

Answer 45

After sunset, the surface friction becomes higher then during the day due to the colder, denser air.

Question 46

what happens to the wind strength when surface friction affects it after sunset?

Answer 46

This causes the wind strength to decrease and for the wind to “Veer’ as it blows across the isobars from High to Low pressure

Question 47

what happens to the wind strength when surface friction affects it after sunrise?

Answer 47

After sunrise (during the day), the wind strength increases, and the wind “Backs” as the wind flows along the isobars.