Geography 131 UTK Exam 3

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