Chapter 6: Air Sea interactions

what heats the earth

solar energy heats the earth and generates winds which drive ocean currents

how is the atmosphere heated

from below, bc atm is particularly transparent to visible radiation directed at Earth from sun and absorbs very little of it

why does earth have seasons

bc tilted axis, different side has warmth for a certain amount of time

how much is earth tilted

23\.5 degrees

vernal (spring) equinox

march 21, sun directly overhead at equator on equinox

autumnal equinox

sept 23, sun directly overheat at equator

summer solstice

june 21, sun stops at noon. sun directly over tropic of cancer, 23.5 degrees N lat

winter solstice

Dec 22, directly overhead tropic of capricorn. 23.5 d S lat

declination

angular distance of sun from equatorial plane (varies btwn. 23.5 degrees N and 3.5 d S lat

arctic circle

N of 66.5 D N lat. No direct solar radiation during N hemisphere

antarctic circle

S of 66.5 d S latitude

How is heat transferred from high and low latitudes

atmospheric winds and ocean currents

solar footprint

solar radiation is concentrated in a small area such as low latitude areas. in high lat areas, strikes at an angle therefore spread out

atmospheric absorption

atm absorbs radiation. thickness varies with latitude, high latitude has greater thickness

albedo

0-100% of incident radiation that is reflected back to the space. reflectivity is dependent on material, ice (high reflectivity)

physical properties of atm

transfers heat and water from place to place. complex relationships btwn. air comp, temp, density, water vapor content, pressure.

mostly N2 and O2, other gases significant for heat trapping properties

troposphere

lowest layer of atm. where weather occurs, temp decreases with altitude. extends from surface to 12km (7 mi).

convection cells

rising and sinking air. warm air rises (less dense), cool air sinks (more dense), moist air rises (less dense), dry air sinks (more dense

atm water vapor content

warm air is moist, cool air dry, water vapor less dense than air

atmospheric pressure

thick column of air at sea level. high surface pressure equal to 1 atm (14.7 pounds/in2). decreases with increasing altitude. thin column of air means lower surface pressure.

air movement

cool dense air sinks, high surface pressure

warm moist air rises, low surface pressure

what are the global air patterns

air rises at equator (low pressure), sinks at poles of high pressure, flows from high to low pressure.

coriolis

Gaspard Gustave de Coriolis: 1792-1843. rotating frame of reference, effects objects in motion in N Hemisphere to veer right of intended course, while it causes objects in S to veer left.

coriolis effect

inertial force that acts on objects that are in motion relative to a rotating reference frame.

circulation cell types

hadley cell, ferrel cell, polar cell

hadley cell

0-30 d latitude

ferrel cell

30-60 d latitude

polar cell

60-90 d latitude

high pressure zones

descending air. subtropical highs (30 d lat), polar highs (90 d lat)

low pressure zones

rising air. equatorial low (equator), subpolar lows (60 d lat)

trade winds

from subtropical high pressure to equatorial low pressure belt

NE trade winds

in N hemisphere, blows from NE to SW due to coriolis

SE trade winds

S Hemisphere, blows from SE to NW

prevailing westerly wind belts

from 30-60 d latitude, blows from SW to NE

polar easterly wind belts

60-90 d lat, blows from NE in N hemisphere and SE in S hemisphere

doldrums

intertropical convergence zone (ITCZ) at equator

horse latitudes

30 degrees

polar fronts

60 degrees

weather

conditions of atm at particular time and place

climate

long term average of weather

cyclonic flow

counterclockwise around low pressure cells in N hemisphere. clockwise around low pressure cells in S. Hemisphere

anticyclonic flow

clockwise around high pressure cells in N hemisphere. counterclockwise around low pressure cells in S hemisphere

sea breeze

land heats air around it, during afternoon, warm low density air over land rises. creates low pressure region over land, causing cool air over ocean to be pulled in.

land breeze

land to ocean. at night, land cools. cool high density air sinks, creates high pressure region, wind blows from land, late evening to early morning hours

storms

atmospheric disturbances with strong winds and precip

air masses

large volumes of air with distinct properties. land air masses: dry (contintental), marine air masses: moist (maritime)

polar maritime air masses

N Pacific and N Atlantic oceans, polar continental air mass that originates over canada

tropical maritime air masses

originate from tropical pacific and atlantic oceans and caribbean. tropical continental air mass that originates over mexico also affects US weather

fronts

boundaries btwn air masses

warm front

contact where warm air mass moves to colder area

cold front

contact where cold air mass moves to warmer area

jet stream

narrow fast moving easterly air flow. exist at middle latitudes below top of troposphere.

cyclones

large rotating masses of low pressure characterized by strong winds and torrential rain

hurricanes

N and S America

Typhoons

alternate name for hurricanes in N Pacific

Cyclones

Name of hurricanes in Indian Ocean

how do hurricanes originate

a. water evaporates, stored heat in form of latent heat of evaporation

b. water condenses, heat released, air rises

c. rising air decreases surface pressure, draws more moist air into storm

d. as air rises, cools, releases more heat, powers storm, feedback loop, intensifies

tropical depression

winds less than 61 km/ hour (38 mph)

tropical storm

sinds 61-120 km/hr (38-74 mph)

hurricane or tropical cyclone

winds above 120 km (74 mph)

saffir simpson scale

hurricane intensity further divides cyclones into categories based on wind speed

how many hurricanes happen/year

100 worldwide. conditions needed for formation of a tropical cyclone: warm ocean water > 25 d C supplying heat energy to atm by evap. coriolis affect causes spinning

when is hurricane season

June 1-Nov 30

eye of a hurricane

low pressure center. Diameter of a hurricane is less than 200 km (124 mi). larger hurricanes can be 500 miles

what other factors affect hurricanes

warm waters, wind shear, El Nino, La Nina

what is most destructive about hurricanes

high winds, intense rainfall, storm surge which can be up to 40 ft high.

historically destructive storms

Galveston TX 1900,

Andrew 1992

Mitch 1998

Katrina 2005

Ike 2008

Irene 2011

Sandy 2012

Hurricane Sandy

2012, Cat 1, largest Atlantic hurricane on record. 1100 miles wide. Storm surge coincided with peak high tides in heavily populated N. York and N. Jersey. Coastal erosion, flooding, 233 deaths, $68 billion in damages

2005 hurricane season

27 named storms, 15 hurricanes. Season extended to 2006 Jan. 5 cat 4+5 hurricanes. Dennis, Emily, Katrina, Rita, Wilma.

Hurricane Katrina

costliest and deadliest US hurricane. Cat 3 landfall in Louisiana. Largest of its strength to make landfall

Hurricanes Rita and Wilma

Rita: Sept 2005, most intense gulf tropical cyclone.

Wilma: Oct 2005, most intense hurricane in Atl. basin. multiple landfalls, affected 11 countries

ocean’s climate zones

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equatorial, tropical, subtropical, temperate, subpolar, polar

tropical

N and S of equatorial, tropics of Cancer-Capricorn. strong trade winds, little precip, rough seas

equatorial

solar radiation high, rising air, weak winds, doldrums, rain, low salinity, tropical cyclone breeding ground

subtropical

high pressure, descending air, weak winds, sluggish currents

temperate

strong westerlies, severe storms, in N atlantic, fierce storms common

subpolar

extensive precip, summer sea ice

polar

high pressure, sea ice most of year

sea ice formation

forms directly from freezing seawater on ocean surface in contrast to icebergs that are pieces of a land based glacier.

slow water freezes easiest. needle like crystals become slush, slush becomes pancake ice and coalesces to ice floes

thick pressure ridges

ice floes thicken to form pressure ridges

icebergs

pieces of land based glacier that break away from glacier and float out to sea

shelf ice

thick floating sheets of ice formed when glaciers break into ocean

wind power

uneven solar heating generates winds, turbines harness it, offshore farms always generate electricity