Chapter 4 Flashcards
How many knots does a full sock indicate?
15 knots
When is a Gust reported?
A gust is reported when there is at least 10 kn variation between peaks and lulls within the last 10 minutes
What does the letter V stand for in a metar?
Variable of the wind direction
Can you assume that there is no clouds above 15,000 feet if it says CLR IS?
No, there could be a cloud layer above it
What happens if the temperature and dew point are close together?
Less visibility
Low-pressure winds go in what direction?
Counterclockwise
Winds are always ________ to isobars ?
Parallel
Velocity = ?
Wind speed
What instrument do you use to measure wind?
Anemometer
What is the definition of a Lull?
Between the gust and your steady
What three forces effect wind or air motion?
Pressure gradient
Coriolis force
Friction force
Where will you find the boundary layer?
2,000 AGL
At what place do you find most of the friction or frequent turbulence?
The boundary layer
Where will you find a deeper boundary level?
higher wind speeds
A seabreeze comes from what direction?
Wind coming from the sea
What direction does the wind come from during a land breeze?
Wind comes from the land
At what time will you see a land breeze?
Night
At what time will you see a seabreeze
Day
When is there a frontal passage?
A frontal passage occurs during a change in pressure.
When pressure decreases and then increases what does this represent?
A frontal passage
“VV” stands for ?
Vertical visibility
Is vertical visibility considered a ceiling?
Yes
In the southern hemisphere wind rotates in what direction?
90° clockwise
In the northern hemisphere what rotates in what direction?
90° counterclockwise
What direction does a cyclone flow?
Counterclockwise to the right
what direction does an anti-cyclone flow?
Clockwise to the left
What force makes the wind want to go outward 90° to the right in the northern hemisphere and 90° left in the Southern Hemisphere?
Coriolis effect
If you are observing frontal activity what type of chart are you looking at?
A surface chart
Why is the wind skewed in surface charts?
Because of friction
When two air masses come together energy transfers creating what?
Weather
What does Coriolis effect need to work?
Wind
If the wind speed is zero, what is Coriolis speed at?
Zero
Friction is caused by high-pressure wanting to go ______ and low pressure wanting to go ________.
Outward and inward
What type of performance do you get with windshear?
An increase in performance
What type of changes do you see in wind sheer?
Instantaneous
On approach if you have a tailwind what kind of performance will you have?
A decrease in performance
If you have a headwind on approach what kind of performance will you have?
An increase in performance
Where is the lull in this metar :
33010G24K
10G
At what degree does variable wind have to be at to be present on a metar?
Greater than or equal to 60 degrees
What are the two causes of wind?
Pressure gradient and wind variation
What are the two types of wind?
Horizontal and vertical
Are cold fronts gradual or steep?
Steep
What is it called when air is being sucked up due to low-pressure
Convergence
What is it called when air is being sucked down due to high pressure
Divergence
What is it called when warm air moves upward over the cold air?
Frontal lifting
Gravity wave motions are typical in what state of air neutral, unstable or stable?
Stable
What is dry adiabatic process?
Cooling by expansion and warming by compressing
What is the temperature lapse rate for dry adiabatic process?
3° per thousand feet
Is sounding reality or theory?
Reality
What is Term sounding ?
A measurement meteorological conditions between the ground and some higher level of atmosphere
What is the result of temperature inversion?
When warmer air goes up
If LR>DALR what state is the air in stable or unstable ?
Unstable ,absolute
What state is the air in for a cumulus cloud ?
Unstable
What state is the air in a stratus cloud?
Stable air
If you are in a field and there is a low pressure system and the wind is hitting your back what direction is the low-pressure?
The low-pressure is to the left
Wind direction provided by weather observers will be oriented to_______ North
True
When direction provided by air traffic controllers will be oriented to ______north
Magnetic
The average speed of the wind is referred to as
Sustained speed
What kind of wind speed must occur to be reported as a gust________
At least A-10 not variation between peaks and Lulls
What change of wind speed must occur to be reported as a squall_________
Sudden increase of at least 60 kn to a sustained speed of 22 kn or more
What does VRB mean relative to wind direction?
Variable
Interpret this wind information-what is the wind direction 020V090?
020 variable 090
Interpret this wind information-what is the wind speed 15G27KT
Wind 15 kn gusting 27 kn
What three things make the wind “blow”?
Coriolis effect, Friction force, pressure gradient force
A pressure gradient is_____
Difference in pressure between two points
At what point on the planet is Coriolis force Least significant ?
The equator
At what point on the planet is Coriolis force most significant?
The poles
Must air move for Coriolis forced to take effect?
Yes
What Coriolis force affect a strong win more than a light wind ?
Yes
Geostrophic balance refers to the balance of what two forces?
Pressure gradient force and Coriolis force
What is Buys-Ballot’s law ?
With the wind at your back, below is always on your left ( in the northern hemisphere)
In the northern hemisphere, air moves_______, around the center of low pressure,_________ around the Center of high-pressure
Counterclockwise and clockwise
Why doesn’t Geostrophic balance occur in small-scale circulations?
Pressure gradient force is much greater than Coriolis force
On a 500 my constant pressure chart
A. What does the direction of the line out of the circle mean
Wind direction
On a 500 mb Constant pressure chart what does one wind Barb equal
10 knots
On a 500 mb constant pressure chart
C. What does 1028 mean?
Pressure is 1028 millibars
On a 500 mb Constant pressure chart
D. Relative to the circle, where would you look for temperature data
Top left side of the data block
On a 500 MB Constant pressure chart
E. What kind of temperature would that be
Centigrade
On a 500 MB Constant pressure chart
F. Relative to the circle, where would you look for pressure Data
To the right side of the data block
On a 500 MB Constant pressure chart
G. What kind of pressure would that be
Millibars of pressure
When the friction over the earths surface equates to__________ Aircraft drag
Form or surface
At what altitude does wind begin to change from parallels to our isobars?
2000 feet AGL
In the northern hemisphere, compared to wind altitude, wind at surface shifts which Way, (left or right)?
Left
Which wind is usually stronger- surface wind or wind aloft?
Winds aloft
Centripetal acceleration refers to what force?
Centrifugal force
Cyclostrophic balance is the balance of what two forces
Pressure gradient force and centrifugal force
What balance does a tornado or present?
Cyclostrophic balance
The two major lateral motions of the air are _______ and _______
Convergence and divergence
The three major forces that lift air (discounting Gust) are:
Orographic lifting, convention (heating from the surface) , frontal lifting
The lifting force that occurs because of displacement is
Frontal lifting
When Wind blows along the surface and becomes turbulent, that kind of turbulence is called
Mechanical turbulence
A mountain wave is an example of _______wind motion
Gravity wave
Stability primarily refers to what condition of an air mass
Constant temperature
Under what circumstance with someone describe the air as stable
No vertical movement
Air buoyancy refers to what air movement
Vertical
Archimedes principle is helpful in understanding air movement because
Heavier air displaces lighter air
What is the gas law
Pressure divided by density (temp) = ratio
How many adiabatic lapse rates are there-what are they called?
A. standard adiabatic lapse rate = 2°C per thousand feet
B. dry adiabatic lapse rate = 3° per thousand feet
C. Wet adiabatic lapse rate = 1° per thousand feet
As altitude increases, pressures changes how?
Decreases
During temperature changes, Expansion does what to____ Air and compression does what to______air
Cools and heats
Adiabatic cooling will always accompany______ Motion and adiabatic heating Will always accompany_______motion
Upward and downward
Atmospheric sounding is the process of measuring what?
Measuring the atmosphere
Unsaturated Air will flow upslope at a rate of ___per thousand feet
3°
The tropospheric(ISA) lapse rate(LR) is ____Per thousand feet
2°
The DALR is ____Per thousand feet
3°
The following formula represents what kind of atmospheric stability?
LR > DALR
Unstable
The following formula represent what kind of atmospheric stability?
LR
Stable
The following formula represent what kind of atmospheric stability?
LR = DALR
Neutral
What is the condition where warm air is above cold air?
Temperature inversion
In the lower stratosphere, what is the ISA lapse rate?
0°
What formula describes “superadiabatic” instability or an unstable air mass?
LR >DALR
What kind of air mass will have smoother air?
Stable
What kind of air mass will have bumpy air ?
Unstable
Which kind of clouds will be likely to occur and stable air?
Stratiform
Which kind of clouds will be likely to occur in unstable air?
Cumulus
Which conditions will be most likely to create low altitude temperature inversions?
Clear cool nights with Calm light winds (stable air)
How does heating from below affect air stability?
Decreases stability
Why are high pressure areas more stable than low-pressure areas?
High-pressure air sinks and become stable while low-pressure air rises and becomes unstable
If your reading a meter and it states that rain ended at what time did the metal come out ?
It was prior to when the metar came out
