Transcript ATMOSPHERE

ATMOSPHERE
atmosphere = mixture of gases, solids, and
liquids that surrounds Earth
Composition of atmosphere:
1. 0-4% water vapor: amount at any given time or place
changes constantly
a. percentage varies with seasons, altitude of particular
mass of air, and surface features beneath air
b. when volume is high percentages of other gases is
slightly lower
c. helps prevent heat loss from Earth
d. added by evaporation and transpiration; removed by
condensation and precipitation
e. moist air → up to 4%; dry air → less than 1%
f. exists in atmosphere in all three forms
1) gaseous form is source of clouds, rain, and snow
2) when changes from one state to another, heat is
absorbed or released
3) affects atmospheric motions that create weather and
climate
2. atmospheric dust, ice, & salt = three common solids found in
atmosphere
a. dust:
1) enters air by wind picking it up off ground and erodes it
2) includes mineral particles from soil, ash from fires,
volcanic dust, microscopic organisms, meteor particles,
tiny salt crystals
3) larger particles remain only briefly due to weight
causing them to fall
b. ice - in the form of hailstones and snow
c. salt: picked up from ocean spray
d. role in cloud formation
3. ozone layer = acts as a shield between people and harmful
energy from sun
a. ozone = form of oxygen with three atoms bonded together
(O3)
b. absorbs most of the ultraviolet (UV) radiation that enters
the atmosphere
c. ultraviolet radiation = energy from the sun that can cause
you to burn
1) too much causes skin cancer
2) also causes other health problems for plants and
animals
d. if ozone disappeared:
1) number of people dying from
skin cancer would increase
2) could destroy most plants
e. has become thinner all over world
4. 21% oxygen
a. amount is result of natural processes that maintain
chemical balance
b. used/removed by: animals, bacteria, plants, forest fires,
burning of fuels, weathering of rocks
c. added by land and ocean plants
1) released as product of photosynthesis
d. second most abundant gas
e. needed by most life forms
5. 78% nitrogen
a. amount maintained by nitrogen cycle
b. removed by nitrogen-fixing bacteria in soil on roots of
certain plants
c. added by process of denitrificaton during decay of dead
organisms
d. most abundant gas
e. living things (plants and animals) use this to make protein
6. 1% other gases (argon, carbon dioxide, neon, helium, etc.)
7. other components = liquids
(most common = water)
Structure of the Atmosphere (divided into layers according to
major changes in temperature)
1. troposphere = closest layer to the ground
a. contains 75% of all atmospheric gases, as well as dust,
ice, and liquid water
b. most active portion of atmosphere because weather,
clouds, and smog occur
c. temperature decreases as altitude increases
1) decreases at average rate of 6.5oC/km
2) stops decreasing at average altitude of 10km
d. tropopause = upper boundary of troposphere (varies
around 9 – 16 km above surface)
1) altitude is not constant - changes
with latitude and seasons of year
2) temperature does not change
here = isothermal layer
3) ceiling to weather zone
2. stratosphere = lies above troposphere
a. extends upward to altitude of 50 km
b. temperature increases as altitude increases
1) base is ~ -60oC
2) warmer at upper boundary = stratopause (about 50 km
above surface)
3) forms another isothermal layer
c. contains ozone layer
d. clear and dry with strong, steady
winds and few weather changes
e. jet streams make up lower portion
3. mesosphere = above stratosphere
a. extends to an altitude of ~ 80 km
b. temperature decreases as altitude
increases
1) upper region has coldest zone of
atmosphere; drops to -90oC
2) get another isothermal layer at upper
boundary = mesopause
c. helps protect Earth from meteoroids →
may see streaks of light = “shooting” stars
4. thermosphere = above mesosphere
a. temperature increases steadily with altitude
1) due to absorption of energy from the sun
2) can be more than 1000oC in areas
b. air is very thin
c. has two parts:
1) ionosphere = lower portion
a) altitude of 80 km to 550 km
b) layer of electrically charged particles (ions and free
electrons)
c) important in radio communications
1] AM radio waves can be bounced off layer allowing
great distances to be covered
2] if ions increase then can cause interference
d) area where the auroras are produced
2) exosphere = upper portion
a) zone of indefinite altitude
b) very few particles in air
c) gases can escape to space
d) outer layers from Van Allen Belts
e) artificial satellites orbit Earth
in this area
SOLAR ENERGY AND ATMOSPHERE
1. sun is source of all energy
2. radiation = transfer of energy through space by visible light,
ultraviolet radiation, and other forms of electromagnetic
waves
a. can travel at speeds of 300,000 km/s
b. wavelength = distance from one wave crest to next
1) types differ in wavelength
c. electromagnetic waves = make up all forms of radiation
d. electromagnetic spectrum = complete range of
wavelengths
e. produced by all substances that have temperatures above
absolute zero
f. almost all shorter wavelengths absorbed in upper
atmosphere
2. scattering = water droplets and dust suspended in
atmosphere reflect and bend rays
a. clouds, dust, and gas molecules affect path of radiation
from sun
b. sends rays out in all directions without changing
wavelength
c. send some back into space
d. makes sky appear blue and sun appears red at sunrise
and sunset
3. reflection:
a. atmosphere is heated from Earth’s surface outward.
b. sun - source of all energy in our atmosphere
c. energy Earth receives:
1) 35% reflected back to space by clouds, Earth’s surface,
and atmosphere
2) 15% absorbed by atmosphere
3) 50% absorbed by surfaces
* balance among these determine characteristics of
atmosphere and life that it supports
d. albedo = fraction of solar radiation reflected by particular
surface
1) energy reflected back without being absorbed by
Earth’s system
2) earth = 0.3 (30% reflected or scattered)
4. absorption:
a. part is infrared rays and visible light
b. absorbed by rocks, soil, water, and other earth materials
c. greenhouse effect = atmosphere traps infrared rays over
earth’s surface
1) absorb long wavelength infrared rays by gas molecules
2) lower atmosphere becomes warmer making surface
warmer
3) objects re-emit some in changed form which prevents it
from leaving atmosphere back to space
4) measurements show amount of carbon dioxide has
been increasing in recent years
5. variations in temperature
a. earth not heated equally at all places all the time
b. warmth of atmosphere determined by:
1) latitude
a) average temperature higher near equator than poles
b) direct rays heat more effectively than slanting rays
c. elevation
1) high elevations cool quickly at night
2) thinner air has less water vapor and CO2 to trap heat
d. water temperature changes less than land temperature
1) releases heat slower than land
2) winds off ocean have more moderate temperature than
those off land
e. delay in heating of atmosphere both seasonally and daily
1) warmest time of year – July
2) warmest time of day - ~2:00 in afternoon
conduction = transfer of energy that occurs when molecules
bump into one another
1. energy moves from fast moving molecules to slow moving
molecules until all move at same rate
2.actual contact of molecules
Ex: warm cup in your hand
3. only affects very thin atmospheric layer near Earth’s surface
convection = transfer of heat that occurs because of density
differences in air
1. warmed air causes molecules to move apart, increasing
volume and decreasing density
2. cold air has lower volume and higher density
3. warm air will rise when cold air moves in and pushes it up
4. constant exchange of cold/warm produces a convection
current (wind)
5. atmospheric pressure generally lower beneath a warm air
mass
6. main mechanism responsible for
vertical motions of air which cause
different types of weather
Temperature vs. Heat
1. temperature = how rapidly or slowly molecules move around
a. more molecules or faster-moving molecules in given
space creates higher temperature
b. slow moving molecules cause substance to cool
c. used to measure and interpret flow of energy
2. heat = transfer of energy that occurs because of a difference
in temperature between substances
a. direction of heat flow depends on temperature
b. flows from object of higher temperature to object of lower
temperature
c. fuels atmospheric
processes
Heat Energy:
1. when added to ice molecules move more rapidly changing
position creating a liquid (melting)
2. when liquid is heated molecules move even faster changing
position creating a gas (evaporation)
3. sublimation = solid changes directly into a gas without
becoming a liquid
a. air dry, temperature below freezing →
ice change to water vapor
b. deposition = water vapor changes
directly to solid without becoming
a liquid
Ex: frost formation
4. water absorbs heat energy from sun
a. causes molecules to evaporate and pass into air
b. takes place in areas near the equator
c. principal source is ocean
Atmospheric Measurements:
dew point = temperature at which air is saturated and
condensation takes place
1. often called condensation temperature
2. more water vapor the air starts with, higher its dew point
3. temperature of air will drop more slowly after reaching dew
point
4. also forms clouds and fog
5. dew = water vapor condensed on surfaces in form of liquid
6. frost = temperature below freezing water vapor sublimes to a
solid
a. not frozen dew (clear beads of
ice - not common)
b. indicates temperature is low
enough to damage growing
plants
Vertical temperature changes:
1. adiabatic temperature changes = result solely from
expansion or compression of air
a. air mass will cool off by about 10oC for every 1000m
increase in altitude; moisture influences rate
b. dry adiabatic lapse rate = rate at which unsaturated air to
which no heat is added or removed will cool
c. moist adiabatic lapse rate = rate at which saturated air
cools
1) above LCL air becomes
saturated and cools more
slowly
2) rate ranges from ~ 4oC/1000 m
in very warm air to almost
9oC/1000 m in very cold air
2. lifted condensation level (LCL) = height at which
condensation occurs
a. clouds form when water vapor condenses into water
droplets
b. often corresponds to base of clouds
c. further condensation allows cloud to expand above
atmospheric pressure = ratio of weight of air to area of
surface on which it presses
1. force of air pushing against surface due to weight of gas
molecules and gravity
2. greatest at sea level and decreases as you move out
toward space
a. 99% of total mass of gases found within 32 km of
surface
b. remaining 1% extend upward hundreds of kilometers
1) gets thinner at higher
altitudes
2) lower pressure at
higher altitudes
3. standard sea level pressure = average weight is
14.7 lbs/in2 (15 lbs/in2) or 10.1 N/cm2
4. varies at different places due to differences in air’s density
5. cold air more dense than warm air therefore higher
pressure
a. temperature is directly proportional to pressure
b. temperature is inversely proportional to density → air
rises as increase in temperature
6. acts in all directions always pushing down on us
Ex: hand
a. measures 8” X 4” = 32 in2 X 15 lbs/in2 =
480 lbs. pressure
* don’t feel because hand pushes back as much
as atmospheric pressure pushes down
b. pressure pushes on body in all places but
internal body pressure equalizes external
pressure
If there was no external body pressure → body
would explode!!
temperature inversion = increase in temperature with height
in atmospheric layer
1. temperature-altitude relationship is inverted
2. causes:
a. rapid cooling of land on cold, clear, winter night when
wind is calm
b. warm air traps cooler air near
earth’s surface
3. worsen air pollution problems by
trapping pollution under inversion
layer
wind = rush of air formed by imbalance between warm, less
dense air mass and cool, more dense air mass
1. cool air, being more dense, sinks & forces warm, less
denser air upward
2. for lower atmosphere, generally moves from areas of high
density to areas of low density
3. response to imbalances created by unequal heating and
cooling of Earth’s surface
4. will create areas of high and low pressure
5. usually measured in miles/hour or km/h; ships measure in
knots; 1 knot = 1.85 km/h
humidity = amount of water vapor in air
1. depends on temperature of air
a. cooler air → molecules close → less space for water
vapor → squeezed out
b. warmer air → molecules move apart → hold more water
vapor
2. warm air holds more moisture than an equal volume of cold
air
- as temperature increases the amount of moisture
holds increases
3. saturated = air is holding all the moisture it can at a given
temperature
RH = 100%
relative humidity (RH) = amount of water vapor in air
compared to maximum amount of water vapor air can hold
at that temperature (its capacity)
1. stated as a percent
2. varies with temperature
3. calculated by dividing humidity by the capacity
humidity X 100
capacity
Ex: humidity = 11
capacity = 22
RH = 11
X 100 = 0.50 X 100 = 50%
22
4. changes occur when:
a. air at fixed temperature, changes as moisture enters or
leaves air
b. amount of moisture in air remains same, temperature of
air changes
specific humidity = actual amount of moisture in air
1. number of grams of water vapor in 1kg of air
2. measured only in units of mass
3. not affected by changes in temperature or pressure
4. only a change in the amount of water vapor in air can
cause a change
clouds = visible masses of tiny water or ice particles
suspended in atmosphere
1. due to condensation of water vapor throughout large volume
of air
2. formation caused by:
a. condensation nulcei = solid matter that provides surfaces
for water condensation
b. orographic lifting = formation of cloud when wind
encounters a mountain and air has no place to go but up
c. collision of air masses of different temperatures
3. process:
a. lifted air cools → can’t hold
moisture so it condenses
out → cloud
b. where air lifts will also have air
descending which warms →
clouds re-evaporates
4. amount of water vapor air can hold decreases as
temperature goes down
5. stability = ability of air mass to resist rising (cooling)
a. rate at which air mass cools partially depends on
temperature of surface below it
b. also affected by temperature of surrounding air masses
and temperature of air mass itself
c. will become unstable if cooler than surface beneath it
6. latent heat = energy absorbed & stored in water vapor
a. released when water condenses
b. also involved when water
freezes or thaws
c. can provide energy to
weather systems
7. cooling leads to condensation
a. convective cooling = lowering of temperature of mass of
air due to it rising and expanding
1) compression warms air
2) expansion cools air
b. forced upward movement of
air
1) moving air mass meets
sloping terrain
2) storms events
c. temperature changes due to one body of moist air mixing
with another at different temperature
d. advective cooling = when wind carries warm, moist air
across cold ocean or region of land
Classification of Clouds
1. shape of a cloud depends on air movement that forms it
2. classified according to shape and altitude
3. reach higher altitudes in equatorial areas and lower altitudes
in polar areas
4. heights are measured above surface, not above sea level
5. forms: stratus, cumulus, cirrus, and nimbus
6. altitude groups: low (up to 2000 m), middle (2000 - 6000 m),
and high (above 6000 m)
Basic Types of Clouds:
1. stratus = low sheets or layers of clouds
a. form where layer of warm, moist air lies above a layer of
cool air
b. smooth, gray clouds that cover the whole sky and block
out the sun
c. form at altitude of about 2.5 km
d. usually longer than they are thick
e. associated with light rain and drizzle
f. nimbostratus = thick, dark, gray layers
1) associated with steady, long precipitation
(heavy rains/snows)
2) blocks out sun
g. altostratus = form at middle altitudes
1) thinner, can be either all liquid or mixture of liquid and
ice crystals
2) dark, but sometimes produce precipitation
2. cumulus = puffy, vertical growing clouds
a. form when warm, moist air rises and cools
b. by vertically rising air currents
c. at altitudes of 2.4 to 13.5 km
d. may extend vertically
e. height depends on speed of upward movement and
amount of moisture in air
f. develop during the day over land
g. usually associated with fair weather
h. cumulonimbus = thunderheads
1) get larger and darker on bottom
2) become dark gray with ragged edges
3) associated with thunderstorms, heavy rain, and hail
i. altocumulus = middle altitudes
1) can be either all liquid or mixture of liquid & ice crystals
2) resemble white fish scales
j. stratocumulus = low clouds which are combination of
stratus and cumulus
cumulonimbus
stratocumulus
3. cirrus = feathery or fibrous clouds
a. form at very high altitudes between 6 - 12 km
b. composed of ice crystals or supercooled water
c. can see in fair weather; sunlight passes through easily
d. cirrocumulus = composed entirely of ice crystals
1) often appear before rain or snow falls
2) form quite rarely
e. cirrostratus = long and thin
1) form continuous layer that sometimes covers sky
2) vary in thickness from being almost transparent to
dense enough to block sun or moon
3) may cause halo effect around sun or moon due to ice
crystals bending light
4) may thicken and lower base to form altostratus
clouds
fog = result of condensation of water vapor in air
1. forms near surface when air close to ground is cooled
2. usually a form of stratus cloud
3. radiation fog = layer of air in contact with earth becomes
chilled at night below its dew point
a. results from lose of heat by radiation
b. also called ground fog
c. usually forms on calm, clear nights
d. thickest in valleys and low places
4. advection fog = form when warm moist air moves across
cold surface
a. common along coasts
b. may form over ocean
5. upslope fog = formed by lifting and adiabatic cooling of air
as it rises along land surfaces
6. steam fog = forms over rivers and lakes
a. shallow layer
b. cool air moves over warm body of water
precipitation = any moisture that falls from air to earth’s
surface
1. can have different forms depending on the temperature of
the air the water passes through
2. four main types:
a. rain = liquid precipitation
1) large drops of water that are far apart and fall fast
2) diameter between 0.5 mm and 5 mm
3) drizzle = very fine drops that are very close together
and fall very slowly
a) diameter smaller than 0.5 mm
b) small amount of total precipitation
4) vary from fine mist to torrential down pours
b. snow = solid precipitation
1) when water vapor changes directly to a solid
2) air temperature must be below freezing
3) may fall as small pellets, individual crystals, or
snowflakes
4) diameter ranges from several mm to several cm
5) small at low temperatures and larger at temp. near 0oC
6) size difference due to amount of moisture in air
c. sleet = clear ice pellets
1) form when rain falls through layer of freezing air
2) usually smaller than 0.3 inches in diameter
3) glaze ice = thick layer of sheet ice
a) rain does not freeze until strikes surface near ground
b) weight often breaks tree limbs and power lines
c) conditions that create are called ice storms
4) freezing rain = supercooled drops turn into ice when
come in contact with ice nucleus or something solid
5) freezing drizzle = smaller supercooled drops
sleet
d. hail = solid precipitation in form of lumps of ice
1) drops of water freeze in layers around a small nucleus of
ice
2) usually formed in cumulonimbus clouds
3) can range from 5 to 75 mm in diameter
4) grow larger as they are tossed up and down by rising
and falling air currents
5) falls when it grows too heavy for the updraft to continue
holding it up
6) can grow larger than
a softball
Causes of Precipitation:
1. cloud droplet must increase size 100X normal diameter
2. coalescence = combination of different sized cloud droplets
to form larger droplets
a. when too heavy to be supported by air, droplet falls
3. supercooling = water droplets are induced to remain liquid at
temperatures below 0oC
a. droplets have temperature less than 0oC
b. too few freezing nuclei present
c. freezing nuclei = condensation nuclei with crystalline
structure like that of ice
1) needed for ice crystals to form
2) increase in size until gain enough mass to fall
4. cloud seeding = method used to attempt to cause or
increase precipitation
a. freezing nuclei are added to supercooled clouds
b. methods used:
1) silver iodide crystals
2) powdered dry ice
c. may increase precipitation from some clouds and not
others
d. uses:
1) overcome droughts
2) control severe storms