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Geography 131 UTK Exam 3

Terms in this set (85)

Convection
vertical flow of air that occurs if an atmosphere is unstable
Convergence
when air collides (ITCZ)
Rossby waves
Air in trough move against Coriolis, causing it too slow. Slowing causes convergence aloft (east of ridge) Air speeds up and diverges east of trough
Topography (orographic effect)
mountains cause adiabatic cooling and warming
Topography process
-Air rises near the base of the mountain and cools
-It cools to Td, where it forms clouds and cools slower
-The air begins to move downslope on the leeward side
-It warms quickly, causing sublimation of snow
Fronts
Boundaries between two air masses with different temperature or humidity
why cold fronts work
Cool air is more dense, so it can lift a mass of warm air
how do clouds and precipitation form
lifting
cumuliform
taller than wide, puffy
stratiform
layers, blankets
cirriform
feathery, wispy
cirr
high
alto
middle
strat
loq
rain-maker
nimbus
cirrus clouds
high and whisky, ice crystals, 1st sign of weather change
cirrocumulus
icy cotton balls
cirrostratus
blanket of ice, more moisture and lifting aloft
altocumulus
sheet of small mid level cotton balls
altostratus
mid level blanket (fill the sky), large scale lifting
stratus
low level blanket, large scale lifting (very humid)
stratocumulus
blanket of puffballs
nimbostratus
wet blanket, continuous rain and cloud cover
cumulus humilis
fair weather clouds
cumulonimbus
causing rain, intense vertical development, severe weather
evaporation fog
cool air over top of warm water; air quickly reaches Td with the addition of evaporated water
valley fog (by warming)
katabatic winds bring moisture to valley and trap it; moisture loads into the valley, reaching saturation
precipitation fog
Rising warm air causes precipitation in cold air beneath; If the cold air is dry, rain can evaporate causing fog
radiation fog
clear skies and calm winds at night allow LW radiation cooling; surface may cool to Td
advection fog
warm air flows over a cooler surface - air cools to saturation (also happens along coastline- warm humid air blows onto coastline)
upslope fog
orographic lift creates clouds which are fog on mountains surface
valley fog (by cooling)
night time cooling causes cold air drainage; cool to Td
Pacific NW fog
upslope and advection fog
Southeast fog
all types of fog
Continental interior
Radiation fog
Appalachians & New England
Precipitation fog & Advection fog
Condensation Nuclei
Particle on which water condenses
Cloud droplets
water drops too small to fall
Raindrops
water drops heavy enough to fall
collision-coalescence
Multiple cloud droplets collide to form precipitation
Bergeron Process
Ice crystals grow together through deposition, at the expense of evaporating water molecules
virga
rain evaporating before hitting the ground
return period
describes frequency of rainfall
drought
persistent high pressure, wind (offshore flow), cold ocean currents
Mid Latitude weather
Polar front jet stream separates air masses; rossby waves cause weather changes by moving air masses
air mass
A body of air with uniform temperature and moisture characteristics
c or m
dry; humid
T or P
warm; cold
A
Arctic; very cold
E
Equatorial; very warm
Cold front
cold air displaces warm, humid air
warm front
warm air moves and displaces colder air
stationary front
neither air mass is displacing the other
mid latitude cyclone
low pressure system traveling across the mid-latitudes
formation of mid latitude cyclone
-air is stretched vertically on leeward side of the mountain
-warmer water causes lower pressure offshore of land
-rossby waves
Gulf of Alaska low
Cool, humid air (mP); Heavy rain along coast (snow at higher elevations)
Hatteras Low
Nor'easters; form in the winter; intense and hard to forecast
Colorado Low and Alberta Chipper
Leeside low; AC incorporates very cold air
Gulf Low
usually in winter, warm water comes over the land; summer forms hurricanes
pre-cyclogenesis
There is a boundary between two different air masses
cyclogenesis
there is some convergence along the boundary; counterclockwise in NH
mature(open wave)
central L; warm front moving northward, cold front moving southward
occlusion
cold front caught warm front; warm front aloft
Single-cell thunderstorms
short lived; weak
stages of a single-cell thunderstorm
1. cumulus stage (updraft forms from warm surface; convection; condensation at LCL)
2. mature stage (rainfall begins and lightning occurs; downdraft and outflow)
3. dissipating stage (dry air can't fuel the storm; storm dies down and rainfall stops; stable)
Multi-cell thunderstorms
Outflow from one storm can cause an updraft and another storm in front "outflow boundary"
squall line
line of thunderstorms along a cold front(main threats: heavy rain and high winds)
Super-cell Thunderstorm
large longlasting thunderstorm; requires a lot of instability, moisture, and vertical wind shear
mesocyclone
rotating updraft (formed by vertical wind shear)
Parts of a supercell thunderstorm
Wall Cloud - Rotating lower base
Two Downdrafts: Forward Flank, Rear Flank
Severe thunderstorms
Capability of 1-inch Hail, 58mph winds, or tornadoes
Hail; wet growth
Water slowly freezes around ice crystal. Clear layer of hail.
Hail; dry growth
supercooled water freezes quickly, traps air bubbles
lightening formation
-Charge Separation in cloud
-Stepped Leader travels toward ground and ionizes the air
-Ground sends up positive charge in Streamers
-Streamers and stepped leader meet
-Positive charge flows upward as Return Stroke. This is the flash of light.
-Soon after, Dart Leaders may flow through existing channels (Multiple flashes)
thunder
air heats, expands, instantaneously rushes back in (colliding air streams cause sounds)
Tornado
Rapidly rotating column of air extending from a cumulonimbus cloud to the ground
Tornado formation
If there is a lot of moisture in the updraft, a wall cloud will form
RFD will wrap around the mesocyclone (Rear Flank Downdraft)
Mesocyclone rotation tightens, may lower into wall cloud
Wall cloud will then rotate
Wall cloud rotation may tighten, creating funnel cloud
Becomes a tornado if it touches the ground
weather systems that produce tornadoes
Supercells near frontal boundaries (warm sector of an MLC)
tropical cyclones
(rare- single cell thunderstorms)
Tornado time variability
Spring & Summer > Fall & Winter
Night > Day (SE)
Airborne instruments
Launched twice a day at 800 locations globally; Travel to around 200mb; Report back temperature, moisture, and wind data
Satellite Data
Estimates of temperature, humidity, wind speed, etc.
Provide some of the only data from less populated areas; Some are fixed, while others travel
Radar
Emits microwave energy that is reflected off hydrometeors and back to a receive; Can be altered by ground clutter
Mid-latitude cyclone
fueled by temperature difference
tropical cyclones
fueled by warm water
Naming
Atlantic - Tropical Cyclone
Pacific - Typhoon
Indian - Cyclone
Australia - Willy-willy
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