exam 3 Flashcards
the weight of air above a given surface
air pressure
as you climb in elevation, there are fewer air molecules above you, therefore , air pressure always ______ with height
decreses
two identical columns of air (fixed width):
if we move air into the column with no temperature change…
surface pressure would increase
two identical columns of air (fixed width):
if we move air out of the column with no temperature change…
surface pressure would decrease
two identical columns of air (fixed width with same air pressure):
if we warm one column…
the molecules move faster and spread farther apart, the air becomes less dense and the column expands in height
two identical columns of air (fixed width with same air pressure):
if we cool one column…
the molecules move more slowly and crowd closer together, the air becomes more dense and the column shrinks in height
it takes a ____ (shorter/taller) column of cold, dense air to exert (less, more, same) surface pressure as taller column of warm, less dense air
shorter, same
atmospheric pressure decreases more rapidly with elevation in a ______ (warm/cold) column of air
cold
true/false: high pressure is always cold
false ; high pressure is not always hot or cold, it depends on where it is in the atmosphere
atmospheric pressure decreases more slowly with elevation in a _____ (warm/cold) column of air
warm
warmer air aloft is normally associated with ________ (higher/lower) atmospheric pressure aloft
higher (resulting in a more stable atmosphere)
colder air aloft is normally associated with _________ (higher/lower) atmospheric pressure aloft
lower (resulting in a more unstable atmosphere)
unequal heating of the Earth’s surface causes…
the wind to blow (lack of equilibrium)
how do we measure air pressure
barometers (mercurial vs. aneroid)
corrections must be made for what factors when measuring air pressure
- temperature
- instrument
- gravity
- sea level
atmospheric pressure decreases, on average, ____ inch of ______ for each ______ foot rise in altitude
one ; mercury ; 1000
what is the standard surface atmospheric pressure
- 2 mb (milibars)
- 7 lbs/inch
- 92 “ mercury
high pressure is also referred to as…
“anticyclone”
(rising/sinking) air is more stable ; is this more associated with high or low pressure?
sinking ; high pressure
a “mountain” of air above a given location
high pressure
a “valley” of air above a given location
low pressure
low pressure is also referred to as…
“cyclone”
(rising/sinking) air is more unstable ; is this more associated with high or low pressure?
rising ; low pressure
storminess is generally brought by (high/low) pressure
low pressure (rising air)
low pressure:
warm core lows
tropical ; tropical cyclones
low pressure:
cold core lows
extratropical ; frontal lows
planes should always take off or land (against/into) the wind
INTO
high pressure in the NORTHERN HEMISPHERE always rotates (clockwise/counterclockwise)
clockwise
low pressure in the NORTHERN HEMISPHERE always rotates (clockwise/counterclockwise)
counterclockwise
if you see a front drawn on a map…
it is a surface weather map
troughs = (low/high) pressure
low pressure
ridges = (low/high) pressure
high pressure
with corrections made to surface pressure readings, surface pressure charts use ______ to depicts lines of _________________________
isobars ; lines of equal surface pressure
upper air charts are also called…
constant height charts
“ASL”
“above sea level”
upper air charts are constructed to show…
height variations along a constant pressure height surface
on upper air charts, height contour lines depict…
pressure
on upper air charts, higher heights =
higher pressure @ respective height
on upper air charts, lower heights =
lower pressure @ respective height
850 mb chart
4,000 ft ASL
700 mb chart
9,800 ft ASL
500 mb chart
18,500 ft ASL
300 mb chart
30,000 ft ASL
250 mb chart
34,250 ft ASL
200 mb chart
38,500 ft ASL
Newton’s 1st Law of Motion
an object at rest will remain at rest and an object in motion will remain in motion (and will travel at a constant velocity along a straight line) as long as no force is exerted on the object
Newton’s 2nd Law of Motion
the force exerted on an object equals its mass times the acceleration produced
(F=ma)
Newton’s 3rd Law of Motion
for every action, there’s and opposite and equal reaction
hurricanes and tornadoes are (high/low) pressure systems
low pressure systems
90% of tornadoes will turn (clockwise/counterclockwise)
counterclockwise (in Northern Hemisphere; because low pressure rotates counterclockwise)
pressure gradient force
air will always move from higher to lower pressure
THINK : tire blowouts
define the coriolis force
deflection cause by a rotating object
in the northern hemisphere, deflection from the coriolis effect is towards the (left/right)
right
coriolis force is ________ at equator and ________ near poles
NEGLIGIBLE at equator and STRONGER near poles
coriolis force only affects wind __________, not wind ___________
direction ; NOT speed
the amount of deflection depends on…
- rotation of the earth
- latitude
- objects’ speed
large scale wind systems are associated with…
the coriolis effect
generally hurricanes do not form within 5 degrees of __________
the equator
because the coriolis effect is weak at equator and strong at poles; and large wind systems are associated with CF
define friction
wind blowing across Earth’s surface and against other air molecules
friction causes _____% tilt towards (high/low) pressure
33% ; low pressure
Buys-Ballot Rule
says if you stand with your back to the wind and turn to the left 30 degrees, on your right will always be high pressure and on your left low pressure
geostrophic wind generally acts in absence of…
friction (because it is found higher up)
define geostrophic wind
theoretical horizontal wind blowing in a straight path, parallel to the isobars (constant contour lines) at a constant speed
geostrophic wind is caused by an exact balance of _______________ and ___________
pressure gradient force & coriolis force
define hydrostatic balance
in the vertical, an exact balance between vertical pressure gradient force and gravity
what allows the Earth’s atmosphere to remain in place
hydrostatic balance
REMEMBER :
outgoing pressure (geostrophic wind) is balanced by gravity, keeping us from being sucked into space! This is hydrostatic balance
wind is characterized by…
- direction
- speed
- gustiness
speed vs. gustiness
speed is always based on a two minute average
gustiness is instantaneous and a certain % above sustained wind
veering vs. backing wind
veering shifts clockwise
backing shifts counterclockwise
back wind shifts (clockwise/counterclockwise)
counterclockwise
veneering wind shifts
clockwise
what are wind roses/what do they do
graphical device to indicate frequencies of which wind direction is
**USDA and TCEQ
who uses wind roses
airport runways and architects
what is the average prevailing wind direction in ATX
south
wind instrumentation examples
wind vane anemometer ice free wind sensor aerovane wind sock rawinsonde doppler radar
***(located 30 feet above surface)
what are the scales of atmospheric motion
microscale, mesoscale, macroscale
scales of atmospheric motion:
microscale
- small area/footprint
- close to earth (turbulent flow)
- not very representative
scales of atmospheric motion:
mesoscale
- size of several state (regional view)
- big advancements have been on this scale
scales of atmospheric motion:
macroscale - synoptic
- weathermap scale
- map of US
scales of atmospheric motion:
macroscale - global
encompasses most
who invented the single cell global atmospheric circulation model and in what year
george hadley ; 1700s
describe the single cell global atmospheric circulation model
with higher pressure at the poles, sinking cold air flowed southward from the polar regions…once it got to the Equator, after warming, with lower pressure, air was lifted
**one big circulation cell ; too simple
Hadley Cell location
equator 30 degrees north or south latitude
what is the ITCZ
Intertropical Convergence Zone ; area around the equator (“Doldrums”)
in general during the WINTER in the northern hemisphere…higher pressure is over (land/water) and lower pressure over (land/water)
higher pressure is over LAND and lower pressure is over WATER
in general during the SUMMER in the northern hemisphere…higher pressure is over (land/water) and lower pressure over (land/water)
higher pressure is over WATER and lower pressure is over LAND
the troposphere is _________ (shallower/deeper) near the equator, and (shallower/deeper) near poles
DEEPER at equator, SHALLOW at poles
define jet streams
strong, mainly upper level, tropospheric steering wind
polar jet streams are found best at
300 mb height
subtropical jet streams are found best at
200 mb height
low level jet streams are found best at
850 mb to 700 mb heights ; common in central US
surface waters of oceans tend to move with the ________
surface wind (upwelling)
la nina
colder than average equatorial pacific ocean water temps
el nino
warmer than average equatorial pacific ocean water temps
notable el nino events:
1982 - 1983
strong event ; $8 billion in damage
notable el nino events:
1986 - 1987
weaker event ; ended drought in SE USA
notable el nino events:
1991 - 1992
strong event ; severe TX flooding ; 5 year drought ended in CA
what are monsoons
season wind shifts that result in heavy rain
where are monsoons most common
india/southeastern asia
**baby monsoon - southwestern usa (because of summer thermal low)
what are thermal lows
a low pressure circulation created by changes in air temperature
katabatic wind
- cold, downslope wind (gravity)
- can be quite destructive
- Greenland, Antarctica
- referred to as a “mistral” in the Alps
chinook wind
- warm downslope wind
- referred to as the “snoweater” wind by Native Americans
- eastern slopes Rockies in US/Canada
santa ana wind
- warm, dry downslope wind in California
- most common during fall months (october)
- strong surface high pressure over the Great Salt Lake Region
desert winds
- dust devils
- haboob (N. Africa/India)
wind shear
rapid change in wind direction and or wind speed in a small area
EX: tornadoes, thunderstorms, cold fronts
eddy
small whirlwind of water
