Weather Flashcards
What is standard pressure in millibars?
1013.2 mb
What is the standard change in temperature and pressure per 1,000 feet?
2 degrees Celcius and one psi
What is Coriolis force?
In Northern Hemisphere, where areas of high pressure get deflected to the right when moving into areas of low pressure (ie. wind) and moving to higher altitude.
Air circulates ____ around a high pressure area, and ____ around a low
clockwise, counterclockwise
Lines denoting areas of equal pressure are called
isobars
Which moves faster, a cold or warm front
cold
Atmospheric stability is ______
resistance of atmosphere to vertical movement
What is difference between ambient temperature lapse rate and adiabatic lapse rate?
Ambient is the actual change in temperature by vertical height, and adiabatic is 3 degrees C/1000 ft
What is the dew point lapse rate?
Temperature and dewpoint converge by approximately 4.4 degrees F per 1000 ft
What are the four families of clouds?
High, middle, and low, and clouds with extensive vertical development
What causes sea breezes?
Sea breezes are caused by cool and more dense air moving inland off the water. Once inland over the warmer land, the air heats up and rises. Currents push the air over the water where it cools and descends, starting the process over again
A front is _________
A front is the zone of transition (boundary) between two air masses of different density, e.g., the area separating a high pressure system and a low pressure system.
There is always a change in ______ across a front
wind
The most recognizable change across a front is ______
temperature
What are the three phases of a thunderstorm?
Cumulus, mature, dissipating
What are the three requirements for a thunderstorm?
Sufficient water vapor, unstable lapse rate, initial upward boost to start the process
Structural icing requires which two conditions?
Visible moisture and temperature below or at freezing
What two conditions promote mountain waves?
stable air, winds over 40 kts
Expect wind sheer in temperature inversion when _____
2,500 to 4,000 AGL, winds at least 25 kts
diation fog (shallow fog) is most likely to occur when
there is a clear sky, little or no wind, and a small temperature/dew point spread.
Advection fog forms as a result of
moist air condensing as it moves over a cooler surface
Upslope fog results from
warm, moist air being cooled as it is forced up sloping terrain
Precipitation-induced fog occurs when
warm rain or drizzle falls through cool air and evaporation from the precipitation saturates the cool air and forms fog
Steam fog forms _________
in winter when cold, dry air passes from land areas over comparatively warm ocean waters. It is composed entirely of water droplets that often freeze quickly
What are two issues associated with steam fog?
Low-level turbulence can occur, and icing can become hazardous in steam fog.
What are the four families of clouds?
High clouds
Middle clouds
Low clouds
Clouds with extensive vertical development
What is the lapse rate for convective currents?
5.4 degrees F per 1000 ft.
The dew point _____ 1 degree F per 1000 ft
decreases
What are four characteristics of stable air?
Stratiform clouds
Smooth air
Fair-to-poor visibility in haze and smoke
Continuous precipitation
What are four characteristics of unstable air?
Cumuliform clouds
Turbulent air
Good visibility
Showery precipitation
Lapse rate means ______
decrease in temperature with increase in altitude
Lapse rate is used to determine ______
The stability of air masses
What is ballooning effect?
When on final approach, fly over region void of vegetation and convection currents cause you to miss runway
What is sinking effect?
When on final approach, you fly over body of water or other cool spot. Causes plane to sink
What is adiabatic heating?
When pressure on a gas from external source causes it to heat
What is adiabatic cooling?
When air expands, and cools down
What is adiabatic?
gas heats or cools without adding or subtracting heat
What is a trough?
elongated area of low pressure
What is a ridge?
elongated area of high pressure
What is a col?
Where ridge and trough intersect
What is relative humidity?
water vapor present in air/maximum it can hold at that temperature
What is latent heat of evaporation?
cooling of a surface when water evaporates (like precipitation on skin)
What is a frontal inversion?
When warm air spreads above cooler air, or colder air is forced under layer of warm air
What is difference between radiation fog and advection fog?
The latter requires wind
What type of clouds form from advection fog if winds are above 15 kts
stratus
Differentiate drizzle from rain
Drizzle is water droplets <0.02 inches, otherwise it is rain
What is virga?
rain that evaporates before it hits the ground
What two conditions lead to frost on airplane?
Temperature of collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing
