Solar Radiation, the Seasons and the Atmosphere

Radiation

form of heat transfer in which energy emitted by one body travels through a medium or through space, ultimately to be absorbed by another body

electromagnetic wave

electric and magnetic components which move as waves outward in all directions from the energy source

The heat from the Sun is transferred by radiation

True

What is the Sun’s source of heat?

Sun generates its energy by converting hydrogen into helium by nuclear fusion

what are the wavelengths of visible light?

electromagnetic waves

if you are wearing a red shirt, why does it look red?

The human eye sees light that is reflected off an object -light from a source (like the sun or a light bulb) strikes an object, object reflects some of the light (in this example red wavelengths), the eye "sees" the reflected light

rotation

Earth rotates about an axis
- axis intersects surface at the north and south geographic poles
- completes one rotation in 24 hours (one day)

revolution

Earth revolves around the Sun
- completes one revolution in 365 and 1/4th days
- a year is 365 days - leap year every four years (366 days)
- Earth's revolution about the Sun is not circular, it is slightly elliptical - this means that during one revolution the Earth is further away and closer to the Sun at certain times of the year

perihelion

date when Earth is closest to the Sun- the occurs on January 3rd

Aphelion

date when Earth is furthest away from the Sun- this occurs on July 4th

What causes the seasons?

The Earth’s rotational axis being tilted relative to the Sun- this causes different parts of the Earth’s surface to receive higher/lower intensity of solar radiation

Solstice

The two days of the year on which the sun reaches its greatest distance north or south of the equator
-marks the start of the winter and summer seasons(lag time for Earth to warm/cool)
- in the northern hemisphere - June 21st is the summer solstice
- in the northern hemisphere - December 21st is the winter solstice
- Sun is directly overhead at noon at 23.5 S latitude

equinox

The two days of the year on which neither hemisphere is tilted toward or away from the sun
- marks the start of the spring and fall seasons(lag time for Earth to warm/cool)
- in the northern hemisphere - March 20th is the spring(vernal) equinox
- The Sun is directly overhead at noon at the equator (fall (autumnal) equinox in the southern hemisphere)

Tropic of Cancer

When the sun is directly overhead at noon 23.5 N latitude (winter solstice in southern hemisphere)

Tropic of Capricorn

The Sun is directly overhead at noon at 23.5 S latitude (summer solstice in Southern hemisphere)

Circle of illumination

the half of the earth illuminated by the sun. this half of the Earth is in daylight, the other half is in darkness

Why are the hours of daylight shorter in the winter and longer in the summer?

The Earth’s rotational axis being tilted relative to the Sun causes different parts of the Earth to spend longer/shorter times within the circle of illumination during the seasons

4 most abundant gases in the Earth’s atmosphere

Nitrogen 78%, Oxygen 21%, Argon 0.93%, Carbon dioxide 0.038%

5 most significant components of the atmosphere

oxygen, ozone, carbon dioxide, dust, water vapor

oxygen

fundamental to life

ozone

important greenhouse gas- helps to keep heat within the atmosphere

carbon dioxide

in atmosphere’s stratospheric layer, protects Earth from harmful ultraviolet radiation from the sun

dust

surface on which water vapor initially condenses to form water droplets (clouds) in the atmosphere

water vapor

fundamental part of hydrologic cycle

atmospheric pressure

force per unit area exerted against a surface by weight of air above that surface

what happens to atmospheric pressure as the height above the Earth’s surface increases?

the amount of air in the atmosphere rapidly decreases as you move higher in the atmosphere

Trophosphere

lowermost layer extends from the surface to 10 km, the “weather sphere", temperatures decrease from surface temperatures to -60 C

Stratosphere

10 km to 50 km above the surface, temperatures increase from -60 C to 0 C, increase due to presence of ozone (O3) absorbing ultraviolet (UV) radiation from the Sun

Mesosphere

50 km to 80 km, temperatures decrease from 0 to -90 C

Thermosphere

80 km to top of atmosphere, temperatures slightly increase from -90 C to -60 to -30 C, transition layer to outer space

why does temperature increase in the stratosphere?

the presence of ozone absorbs ultraviolet radiation from the sun

evaporation

a change of state from liquid to gas, it requires heat to occur, it draws this heat from surrounding air/material

condensation

the change of state from gas to liquid, it releases heat to surrounding air/material thus warning surrounding air/material

what happens to heat when you have evaporation

H2O+heat—→ H2O + cooling of surrounding air

what happens to heat when you have condensation

H2O + cooling —> H2O + warming of surrounding air

humidity

the measure of amount of water vapor in the air, the amount of water vapor that can be held in aid is function of temperature of water

relative humidity

the amount of water vapor in air divided by capacity (maximum amount of water vapor that can be held in air at that temp)

dew point

the temperature at which air becomes saturate with water vapor/condensation

what are clouds

condensed water vapor

how do clouds form

by moving air with water vapor upward in the troposphere, air cools as it moves upward, when saturation is reached (100% RH)- water vapor condenses- a cloud is formed

dry adiabatic lapse rate

cooling by expansion (due to pressure decrease) before condensation of water vapor- 10 C per km

wet adiabatic lapse rate

cooling by expansion (due to pressure decrease) before condensation of water vapor begins- condensation releases heat- so wet adiabatic cooling rate is less than dry cooling rate- 5-6 C per km

normal lapse rate

rate at which air cools as you go up in the troposphere, depending on the location- lapse rate varies between 5-15 degrees C per km

stable air

rising air is colder than surrounding air, colder air is heavier, denser air- must be forced upward (heavier and denser than surrounding warm air)

unstable air

rising air is warmer than surrounding air, warmer air is lighter, less dense air- will naturally rise upwards (it is lighter and less dense than surrounding colder air)

absolute stability

temperature of rising air is always colder than surrounding air- this rising air is stable air- it must be forced upward

absolute instability

temperature of rising air is always warmer than surrounding air- this rising air is unstable air- it naturally rises upwards

conditional instability

temperature of rising air is colder, then warmer than surrounding air- initially rising air is stable air (forced upwards)- it becomes unstable air (naturally moves upwards)

how is air forcefully uplifted

convective lifting, convergence lifting, orographic lifting

cirrus clouds

thin, wispy, high clouds

cumulus clouds

fluffy, puffy, high clouds

stratus clouds

sheet-like, can cover entire sky, medium clouds

which cloud is the chief precipitation-producing cloud

nimbostratus, associated with long time-period gentle rain

which cloud is associated with storms

cumulonimbus, associated with thunderstorms, hurricanes, and tornadoes

wind

the horizontal movement of air

factors that affect the movement of wind

pressure gradient force, coriolis effect, friction

how does pressure gradient force affect the movement of wind

related to how fast atmospheric pressure changes- wind always blow from areas of high pressure to areas of low pressure- faster the pressure changes over a given horizontal distance, faster the wind blows

affects the direction and speed of the winds

how does the Coriolis Effect affect the movement of wind

wind blows from areas of high pressure to areas of low pressire- on a rotating Earth the Coriolis Effect deflects this moving air

Causes wind in the northern hemisphere to be deflected towards the right, southern hemisphere to the left

how does friction affect the movement of wind

slows down the speed of the wind- both land and water surfaces slow down winds as they blow across- higher winds are above Earth’s surface less friction, faster they can blow

cyclonic winds

counterclockwise wind directions

anticyclonic winds

clockwise wind directions