Unit 2 Seasons and Atmosphere
Revolution ¥ Motion of a body along a path
around some point in space. ¥ Earth’s orbit is elliptical ¥ Earth’s distance from the sun
varies ¥ Perihelion
¥ Earth is closest to the sun ¥ 147 million km away ¥ Occurs on January 3rd
¥ Aphelion ¥ Earth is farthest from the sun ¥ 152 million km away ¥ Occurs on July 4th
Rotation ¥ The turning or spinning of
a body on its axis ¥ Causes day and night ¥ Two kinds of measurement
¥ Mean Solar Day – time interval from one noon to the next (24 hours)
¥ Sidereal Day – time it takes for Earth to make one complete rotation (360’) with respect to a star other than the sun (23 hours, 56 minutes, 4 seconds)
¥ Seasons are caused by the tilting of the earth on its axis (23.5°) ¥ When the Earth is
tilted towards the Sun – warmer seasons
¥ When the Earth is tilted away from the Sun – cooler seasons
How Does Weather differ from Climate?
¥ Weather is constantly changing and it refers to the state of the atmosphere at any given time and place
¥ Climate is based on observations of weather that have been collected over many years to help describe a place or region
Composition of the Atmosphere ¥ Main Components
¥ Nitrogen – 78% ¥ Oxygen – 21%
¥ CO2 < 1% ¥ Argon < 1%
Layers of the Atmosphere ¥ The Troposphere - the
bottom layer ¥ Temperature decreases with an
increase in altitude. ¥ Where weather occurs ¥ Tropopause: boundary of the
troposphere
¥ The Stratosphere ¥ Above the troposphere ¥ Temperature remains constant,
then gradually starts to increase ¥ Contains the ozone layer ¥ Stratopause: boundary of the
stratosphere
¥ The Mesosphere ¥ Above the stratosphere ¥ Temperature decreases with
height ¥ Mesopause: boundary of the
mesosphere ¥ The Thermosphere:
Upper layer of the atmosphere ¥ Temperature increase with
height ¥ Auroras occur here ¥ Fades into space
Pressure and Temperature Changes u The atmosphere rapidly
thins as you travel away from Earth until there are too few gas molecules to detect.
♦ Pressure Changes ♦ As you increase in altitude, or
travel away from Earth, pressure decreases
♦ Temperature Changes u As you increase in altitude in the
Troposphere the temperature decreases.
u Density Changes
Human Influences and Primary Pollutants
¥ Air pollution is airborne particles and gases that occur in concentrations large enough to endanger the health of organisms
¥ Primary Pollution: emitted directly from identifiable sources
¥ Secondary Pollutions: not emitted directly into air (agriculture)
Heating the Atmosphere ♦ Heat: the energy
transferred from one object to another because of a direct difference in their temperature
¥ Temperature: measure of the amount of heat
¥ Convection ¥ The transfer of heat
by a mass movement or circulation within a substance
¥ Radiation ¥ Travels out in all
directions ¥ Solar energy reaches
earth by radiation
The Heating Song
Ways Heat Can be Transferred
¥ Heat transfer from HOT to COLD objects
¥ Conduction ¥ The transfer of heat
through matter by molecular activity
¥ Transfer by touching
What Happens to Solar Radiation? Reflection vs. Scattering
¥ Reflection ¥ occurs when light
bounces off an object. ¥ 30 % of all radiation is
reflected back to space
¥ Scattering produces a larger number of rays that travel in many directions.
¥ Absorption:
¥ 50 % of the solar energy that strikes the top of the atmosphere reaches the Earth’s surface
¥ 20% is absorbed in the clouds
¥ 30% is reflected back to space
Ozone • Ozone is a form of
oxygen that combines three oxygen atoms into each molecule (O3)
• Ozone filters and absorbs harmful UV radiation by the sun
Ozone Video
Why Do Temperatures Vary?
¥ Factors: ¥ Heating of land ¥ Heating of water ¥ Altitude ¥ Geographic
position ¥ Cloud cover ¥ Ocean currents
Land and Water Temperatures
¥ Land heats and cools more rapidly and to higher temperatures than water
¥ Water – heats up longer and will retain the heat longer
Albedo ¥ the fraction of total
radiation that is reflected by any surface.
Daylight Cloud Cover ¥ Clouds reflect solar
radiation back to space ¥ Temperatures are lower
than on a clear day
Nighttime Cloud Cover ¥ Clouds absorb radiation
from land and reradiates some of it back to Earth
¥ Temperatures are higher than on a clear night
VIDEO
World Distribution and Temperatures
Isotherms - lines on a weather map that connect points that have the same temperatures
© Precipitation is any form of water that falls from a cloud.
© When it comes to understanding atmospheric processes, water vapor is the most important gas in the atmosphere
Think about it…
¥ Have you ever been outside and the air seemed “sticky” or “wet”? Maybe it gave you “frizzy” hair…what causes this?
¥ TURN AND TALK…discuss this with your partner
Video Link: http://www.youtube.com/watch?v=7GS5jl4nLek
© Ratio of the air’s actual water-vapor content compared with the amount of water vapor air can hold at that temperature and pressure.
© Lowering air temperature causes an increase in relative humidity
© Raising air temperature causes a decrease in relative humidity
⬜ Instrument: Hygrometer ⬜ Psychrometer : a type of
hygrometer consisting of two identical thermometers mounted side by side
⬜ Dry bulb: give the present air temperature
⬜ Wet bulb: has thin wet wick tied around the end
Cirrus (cirrus = curl of hair) high, white, and thin
Cumulus (cumulus = a pile) rounded individual cloud masses that have a flat base and the appearance of rising domes or towers
Stratus (stratus = a layer) best described as sheets or layers that cover much or all of the sky
© The type of precipitation that reaches Earth’s surface depends on the temperature profile in the lower few km of the atmosphere
© Rain: drops of water that fall from a cloud and have a diameter of at least 0.5 mm
© Snow: light, fluffy, six-sided ice crystals
© Sleet: fall of small particles of clear to translucent ice
© Glaze: when raindrops become
supercooled as they fall through subfreezing air and turns to ice when they impact objects
© Hail: form of solid precipitation
which consists of balls of irregular lumps of ice produced in cumulonimbus clouds