general earth science final

wind

movement of air with respect to the surface

air pressure

force exerted by the atmosphere

barometric pressure, atmospheric pressure

pressure gradient force

force causing air to move from high pressure areas to low pressure areas

affects the velocity of wind wind; strong force results in strong winds

coriolis effect

apparent deflection of wind caused by Earth’s rotation

deflection to the right in the northern hemisphere and to the left in the southern hemisphere

friction

resistance to airflow

most significant effect near the surface

friction layer

lowest 1 km of atmosphere, where friction reduces wind velocity

circulations

driven by global imbalances of insolation which generate poleward hear transport

global atmospheric circulations follow broad belts of latitude

hadley cells

huge convective circulation extending from the equator to 30 degrees in latitude

trade winds

easterly winds in the low latitudes (0-30 degrees)

coming from the east

ITCZ

ITCZ

intertropical convergence zone

boundary between the trade winds of northern and southern hemispheres

subtropical high

dome of high pressure centered near 30 degrees in latitude

mid latitude westerlies

belt of westerly winds between 30 and 60 degrees in latitude

jet streams

jet streams

fast moving rivers of air within midlatitude westerlies

not surface winds, higher altitude

polar front

belt of convergence centered near 60 degrees in latitude

polar easterlies

easterly winds in high latitudes (60-90 degrees)

polar high

dome of high pressure centered over the poles

cyclone

center of low pressure and rising air

convergence at the surface

cloud cover and precipitation

counter clockwise circulation in the northern hemisphere

anticyclone

center of high pressure, sinking air

divergence at the surface

fair weather (horse latitudes)

clockwise circulation in northern hemisphere

monsoon

seasonal shift in regional circulations

may result in a wet season/dry season effect

ex. southern asia

land breeze/ sea breeze

land heats quickly during the day, air rises, sea breeze moves onshore to replace rising air over land

land cools quickly at night, sinks, land breeze blows out to sea from high to low pressure

urban heat island

convection circulation due to build up of heat within a city

katabatic wind

cold dry wind moving downslope from high, snow covered terrain, driven by gravity

chinook wind

warm dry wind moving downslope due to regional circulations (cyclones/anticyclones)

responsible for dramatic temperature increases

air stability

tendency for a parcel of air to either remain in place or begin to rise freely

conditions are determined by the local temperature profile in the atmosphere

stable

air parcels resist lifting

unstable

air parcels freely rise (convection)

air mass

huge body of air that is uniform throughout, in terms of temperature and humidity characteristics

classifies based on its source region

source region

surface over which air mass forms

humidity classifications

c=continental

m=maritime

temperature classifications

t=tropical

p=polar

a=arctic

atmospheric lifting

critical factor in formation of precipitation

rising air cools, causing relative humidity to increase and the air to become saturated

convection

heated air rises and cools, relative humidity increases

LCL (lifting condensation level)

LCL

lifting condensation level

altitude at which condensation occurs within rising air

where clouds start forming

orographic

air that is forced to rise over a mountain

convergence

colliding air currents at the surface

frontal lifting

air forced to rise along a front

front

boundary between air masses

cold front

leading edge of an advancing cold air mass

stronger lifting

thunderstorms, heavy rain

warm front

leading edge of an advancing warm air mass

calmer, more spread out

light to moderate precipitation over large area

stationary front

front has become stalled

alternating warm and cold symbols on a map

rain for several days

occluded front

boundary between cool and cold air

losing severity in storms

thunderstorms

localized atmospheric disturbance involving lightning, heavy rainfall, strong wind, and possibly hail

associated with cumulonimbus clouds

most common in areas dominated by tropical (mT) air masses (equatorial regions, ITCZ)

requirements for thunderstorm

warm humid air at surface

strong lifting

lightning

electrical discharge in the atmosphere, caused by the separation of charges within the thunderstorm

during discharge, channel of air is heated to 50,000 degrees of more in less than a second, air expands creating thunder

intracloud

80-85% of lightning in storms

heavy rainfall

actual hazard risk'

determined by: rainfall rate (intensity, rate per hour), duration (determined by size and movement of storm), and surface conditions (runoff vs infiltration)

strong winds

straight line winds causes by downdrafting within the storm

gustfront

leading edge of thunderstorm downdraft

microburst

localized and damaging downdraft (100+mph)

hail

caused by updrafts within storms

cyclonic storms

atmospheric disturbances that exhibit cyclonic characteristics

low pressure, convergence at surface, divergence aloft, rising air near center

midlatitude wave cyclone

large atmospheric disturbance on earth

associated with frontal weather

local weather depends of storm track

tropical cyclone

forms in the low latitudes, entirely within mT (warm humid) air masses

no frontal conditions

begins as an area of convectional thunderstorms along ITCZ

requirements of tropical cyclone

warm water (80 degrees)

coriolis effect (no hurricanes at the equator)

calm winds aloft (no shearing)

shear

sudden change in speed and direction

eye

central area of hurricane; area of fair weather and low pressure

fair weather caused by sinking of air and centrifugal force

characteristics: clarity and organizations, diameter (small generally with intense storms), and pressure (lower with more intense storms)

eye wall

ring of intense thunderstorms surrounding the eye; intense updrafting within eye wall leads to subsidence within the eye

most intense weather, heaviest rainfall, strongest winds, etc

rain bands

lines of thunderstorms extending outward from the eye wall

may lead to flooding problems if the bands “train” across the landscape

storm surge

abnormal rise in sea level due to strong, enduring winds and low pressure

deadliest feature; 90% of all hurricane fatalities worldwide

violent winds

minimum of 74 mph; exceeding 150 mph in rare cases; causes by low central pressure

torrential rainfall

often extended far inland; even minor tropical cyclones may cause flooding depending on rainfall rates and storm track

tornadoes

often form as hurricane makes landfall and begins to weaken

generally weaker than plains tornadoes

tornadoes

violently rotating column of air (mesocyclone) usually associated with a strong thunderstorm (supercell)

very short lived erratic circulation

most common during spring (march-june)

most common in the sourthern plains of the US (tornado alley)

mesocyclone

rotating updraft within a strong thunderstorm

wall cloud

lowered portion of the thunderstorm cloud base; formation form which tornado usually forms

tornado requirements

warm humid air at the surface

cold dry air aloft: creates instability in the lower atmosphere

temperature inversion

strong winds aloft (jet stream and wind shear promote rotation)

triggering mechanism to promote lifting of warm humid air (could be cold front or daytime heating)

temperature inversion

increase in air temp with altitude within troposphere

puts a lid of lower atmosphere; preventing convection

air pollution

accumulation of harmful compounds within atmosphere

as of 2017, approximately 92% of the world’s population was living in areas that exceeded WHO air quality guidelines

primary pollutants

pollutants that are harmful in the form in which they are released into the air

(ex. carbon monoxide)

secondary pollutants

pollutants that form through chemical reactions in the atmosphere

(ex. smog/ozone)

natural air pollution

most can be offset by natural cleansing processes in the atmosphere

generally not a long term issue

sources: volcanic eruptions, forest fires, wind-blown dust

human induced air pollution

most are linked to the burning of fossil fuels (oil, coal, natural gas)

excessive persistent emissions of pollutants overwhelm the natural cleansing processes

wind as a factor

strong winds act to dilute air pollutants; calm winds cause air pollutants to become concentrated

atmospheric lifting as a factor

instability (convection) promotes the mixing/dilution of air pollutants

temp inversion near surface prevents free lifting and causes air pollutants to become concentrated