Weather Flashcards
What is the atmosphere
The envelop of air that surround earth
By weight, how much of the atmosphere is located below 18,000?
1/2
What is the movement of air around the surface called
atmospheric circulation
What gas accounts for 78% of the gas in our atmosphere?
Nitrogen
What affects pressure changes
Altitude, temperature, density of air.
Pressure charts use what pressure indication?
milibars
what is the acronym for milibars
(mb)
What are local barometric pressure readings converted to?
sea level pressure
What are isobars
pressure area outlines
On a pressure chart how far apart are isobars placed
4 mb apart, unless significant pressure gradient then 2 mb apart
What does rising pressure indicate
Approach of fair weather
What does falling pressure usually indicate?
approaching of bad weather
What is temperature
Measurement of amount of heat, expresses a degree of molecular activity
what is incoming solation heat called
insolation
what is radiating heat from earths surface called?
Terrestrial radiation
On the Fahrenheit scale what is freezing
32 degrees
on the Fahrenheit scale what is boiling
212 degrees
on the Celsius scale what is freezing
0 degrees
on the Celsius scale what is boiling
100 degrees
how do you convert Fahrenheit to Celsius
subtract 30 and then divide by 2
how do you convert Celsius to Fahrenheit
multiply by 2 add 30
what causes atmospheric circulation
temperature variations
What is Diurnal Variation
Change of temperature from day to night
when does terrestrial radiation cease?
After sunrise when insolation overtakes terrestrial radiation
Does water absorb or radiate heat quickly or slowly
quickly
where does abrupt temperature changes occur?
along water shorelines
where prevailing winds come from a large body of water what happens to temperature changes
slow temperature changes with small gradient
where prevailing winds come from dry barren areas what happens to temperature changes
quick temperature changes with large gradient
What happens to temperature with increasing altitude?
Temperature typically decreases
What is a lapse rate
the decrease of temperature with increase of altitude
What is an inversion
a layer of warmer air over a layer of colder air
What is conduction
the transfer of heat energy from one substance to another
what is convection
The transfer of heat in a fluid
where does conduction occur
a few centimeters off of the surface
when does convection ocur
as the ground is heated by the sun.
When do inversions develop
cool clear nights with light and variable winds
Why do inversions occur
Grounds air cools faster than moist air above
Whey do low level inversions dissipate
as air is heated with insolation the inverted air begins to mix due to convections
List 3 ways heat is transferred to the atmosphere
Radiation, Conduction, convection
What is radiation
transfer of heat by electromagnetic waves
Is there a medium needed for heat transfer in radiation
no
What are principle reflectors in meterology
water vapor, particulate matter and the earths surface
what is advenction
the horizontal transfer of heat, usually by wind
what is the adiabatic process
change of temperature without the transfer of heat
in the adiabiatic process what results in warming
compression
in the adiabiatic process what results in cooling
expansion
What happens to air as it rises
pressure decreases, volume increases, temperature decreases
what happens to air as it descends
pressure increases, volume decreases and temperature increases
what are the basic characteristics of any air mass
temperature and humidity
what is the primary factor in determining air mass characteristics
terrain
what is an air mass
a large body of air that has uniform characteristics
What are characteristics of an air mass
Stability, cloud type, sky coverage, visibility precipitation, icing, turbulence
how are air masses grouped
by region of origination
what types of airmasses are there
polar or tropical and maritime or continental
what happens to air masses as they move over a warm surface
the air is heated from below and becomes unstable
what happens to air masses as they pass over a cold surface
air is cooled from below creating a stable air mass with poor visibility
why is poor visibility a characteristic of stable air
Particles are trapped and cant rise
what local weather can be found with cold, stable air
low stratus clouds and fog
what does moist unstable air cause
Cumulus clouds, good visibility , localized showers and turbulence
The heating and cooling of air can cause what in density
it can cause density variations
what happens to a barometer in a low pressure
pressure decreases towards the center
which way does the wind spin in a low
counter clockwise
What are the flying conditions noted with a low pressure system
poor flying conditions, low clouds, restricted visibility (fog and precipitation) strong gusty winds, turbulences
what happens to air if it passes over a colder surface
creates a stable air mass with poor visibiltiy
Why is poor visibility a characteristic of stable air
particles are trapped and cant rise
what local weather can be found with cold stable air
low stratus clouds and fog
What happens to air as it is heated from below
it becomes unstable
what can unstable air cause
cumulus clouds, good visibility localized showers and turbulence
What are flying conditions of a low
low clouds, restricted visibility (fog and precipitation) strong gusty winds, turbulences
what is the general airflow of a low pressure?
towards the center and up
what is a high pressure system
barometric pressure increases towards the center
heating and cooling of the air can do what to density
it can cause density variations
what happens to pressure in a low
barometric pressure decreases towards the centre
which way does the wind spin in a low
counterclockwise
what is advection
the horizontal transfer of heat
what is the adiabatic process
the change of temperature without the thansfer of heat
In the adiabiatic process what results in warming
compression
in the adiabiatic process what results in cooling
expansion
what is conductions
transfer of heat energy from one substance to another
where does conduction occur
a few centimeters off the surface
what is convection
the transfer of heat in a fluid
when does convection occur
when the ground is heated by the sun (insolation)
what is raiation
the transfer of heat by electromagnetic waves
is there a medium needed for heat transfer in radiation
no
what are principle reflectors in meterology
water vapor, particulates, earths surface
where do abrupt temperature changes occur
along water shorelines
what is the general pattern of air flow in a high pressure system
clockwise
what are flying conditions of a high pressure system
few clouds, light and calm winds less turbulence
what type of front moves most rapidly
cold fronts
how fast do cold fronts move
about 25-30 miles per hour
what weather pattern could you see with a cold front
rain showers, haze, wind from the S.W. high dew point and falling barometric pressure
how is visibility in a cold front
poor
what types of clouds are present in a cold front
cirriform, cumulus and cumulonimbus
what winds can be seen in a cold front
light and variable
when is the movement of pressure systems more rapid?
winter
what is a front
it is the boundary between two masses
how are fronts classified
which type of air mass is replacing another
what are fronts boundaries for
two air masses with different densities
what is primary control in air density
temperature
what types of fronts are there
Cold, Warm Stationary and occulded
how are fronts determined
movement of air masses involved
what is a cold front
advancing edge of a cold air mass
when does a cold front occur
a mass of cold dense air replaces a body of warmer air
what is a warm front
trailing edge of a cold air mass
how fast to warm fronts move
10-15 mph
what causes the wind to move
the corilois force, pressure gradient and surface friction
what is atmospheric circulation
movement of air around the surface of the earth caused by uneven heating
in general atmospheric theory states ow pressure exists over what region
equatorial
In general atmospheric pressure theory states high pressure exists over what region
polar regions
where is the greatest amount of air deflection noted
around the poles
Coriolis force deflection is perpendicular to what
airflow
which direction in Northern Hemisphere does air get deflected
to the right
what are pressure gradients
difference in pressure between high and low
wind speed is directly proportional to
pressure gradient
what are the three components that affect wind
Coriolis, pressure gradients, surface friction
what is the humidity like in a high pressure system
dry
is the air in a high pressure system stable or unstable
stable
does the air descend or ascend in a high pressure
descend
Is air in a low stable or unstable
unstable
what weather is associated with a low
increase in cloudiness and precipitaitaion
what is anabatic wind
winds that blow up a steep mountain side
when do anabatic winds occur
day time, calm sunny weather
what is a katabatic wind
winds flowing down slope
when do katabatic winds occur
at night
how are cloud types determined
height, shape and behavior
how are clouds classified
height at bases
what are the 4 major cloud types
low, middle, high, and clouds with vertical development
what are specific cloud types
cumulous, stratus, cirrus, castellans, lenticularis, nimbus, fracto and alto
what are outward appearance of cumulous clouds
heaped towering clouds, piles
what are the outward appearance of stratus clouds
formed in layers
what are the outward appearance of cirrus clouds
ringlets, fibrous clouds at high level
what are the outward appearance of Casellanus clouds
common base with separate vertical development
What are the outward appearances of lenticular clouds
lens shaped over mountains, indicate strong winds
What are nimbus clouds
rain bearing clouds
what are fracto clouds
ragged or broken
what are alto clouds
high elevation clouds
where do low level clouds form
near earths surface
what cloud groups make up low level clounds
stratus and stratcumulous
Where do strato clouds form
near the surface
what flying conditions do strato clouds form
poor visibility flying conditions
where can mid level clouds form
6500 to 20k agl
What cloud groups make up mid level clouds
Altocumulus, alto stratus, nimbostratus
what are high clouds
clouds that form above 20k feet AGL
where do high clouds form
above 20k in stable air
what are high cloud groups
cirrus, cirruscumulus, cirrostratus
what are cumulous clouds known for
extensive vertical development
what do clouds with extensive vertical development develop into
thunderstorms
what do towering cumulous clouds indicate
instability and turbulance
flight in cumuliform can be
turbulent in and around cloud masses
flight in stratoform clouds can be
smooth
nimbus means
rain or precipitation producing clouds
what is dew point
point where air can hold no more moisture
at what rate does unsaturated air cool?
5.4 degrees f per 1,000
what happens to dew point as altitude increases
dew point decreases 1 degree f per 1,000 feet
what is convergence of temp and dew point
4.4 degrees
What is the formula for determining cloud bases
temperature-dew point = temperature dew point spread, temperature dew point spread is divided by convergence rate multiplied by base of clouds gives elevation AGL
Temp-D.P=TDS
TDS/CR*1000=base of clouds
what is fog
clouds that begin within 50 feet of surface
what are natural conditions for fog to occur
relative high humiditiy
what wind condition is favorable for fog
light wind causing mixing of cooled air
What is radiation fog
when heat in the air is given back to atmosphere causing cooling and ambient air reaching dew point
when is radiation fog most likely
Clear Skies, High moisture content, and wind less than 7 knots
What does an unstable air mass allow
upward and downward movement of air
what happens to rising air
expands and cools
what does moisture do to air densitiy
decreases air density
what air mass is more stable moist or dry
Dry air masses are more stable
Cool Dry air is very
stable
Cool Dry air resists
vertical movement
what type of air mass does the greatest instability occur
moist warm air.
what does air stability depend on?
vertical distribution of airs weight
what are types of air stability
Absolute stability Absolute instability conditional stability neutral stability convective stability
when does absolute stability occur
when actual lapse rate is less than adiabatic lapse rates
when does absolute instability occur
when the actual lapse rate is greater than the dry adiabatic process
list the 4 categories of turbulance
thermal
mechanical
frontal
wind shear
what is a thermal
updraft in a small scale convective current
what is Mechanical turbulance
when air flows over irregular surfaces
What does Mechanical turbulence depend on
speed of wind,
nature of obstruction
stability of air
angle at which air moves over obstacle
what is frontal turbulance
lifting of warm air by frontal surface
what is the most severe frontal turbulence associated with
Fast moving cold fronts
What is a wind Shear
a steep grade of wind velocity
what are low level wind shears associated with
passing frontal storms, thunderstorms and temperature inversions
how many convective cells does a mature thunderstorm have
one or more
How many stages are in a thunderstorm
3 stages
What are the three stages of a thunderstorm
Cumulous, Mature, dissipating
what is the chief distinguishing feature of the cumulous stage
up drafts
What initiates the mature stage of a thunderstorm
surface rain, and adjacent updrafts and down drafts
what happens to pressure in a thunderstorm
abrupt fall in pressure as storm approaches
abrupt rise in pressure as with rain as storm moves on
what are frontal thunderstorms caused by
lifting of warm moist conditionally unstable air
