Chp 2. – Solar Energy & Seasons

We exist because of the energy that the sun produces (from nuclear fusion – Hydrogen atoms smashed together, creating Helium)

Universe has at least 200 billion galaxies. Our solar system is in one of them, the Milky Way. The Milky way alone has over 100 billion stars. Our solar system revolves around one of those 100 billion stars.

Our solar system is is found in the Orion SPUR. Light travels 300,000 km/s.  In one year, light will travel 9.5 trillion km. The distance light travels in a year is a light year. The milky Way is 100,000 light years in diameter. Our solar system is only 11 hours in diameter. The moon is 1.28 seconds away.

Sun’s energy powers everything on this planet.

Earth’s orbit is elliptical, meaning it’s distance from the Sun varies.

Average distance between the earth and the Sun is 150km.

We are closest to the sun around January 3rd (Perihelion).

We are furthest away from the sun around July 4th (Aphelion).

The tilt of the earth’s axis (and the fact that the tilt is constant) which influences the seasons.

Sunspots are found on the surface of the sun, and they follow a predictable 11-year cycle. Where there are more sunspots on the surface, the amount of energy made is slightly increased,

Solar wind are electrically charged particles that come from the sun and take 3 days to reach earth. The earth’s magnetosphere deflects the wind towards the poles so very little of it gets into the atmosphere.

Magnetosphere: magnetic field surrounding the Earth resulting from internal processes within the Earth’s core. It shields the inner atmosphere and surface from harmful iodizing radiation.

The interaction between solar wind and the magnetosphere leads to Aurora Borealis in the North and Aurora Australis in the South.

Energy – Ability to do work (electrical, chemical, thermal, or nuclear)

Joule (J) – Standard unit of energy

Watt (W) – Rate of energy Flow (W = 1 J/s)

The sun emits Electromagnetic Radiation, or EM Radiation.

Kinetic à in use, ie: motion (flowing water), or vibration (water molecules)

Potential à not yet used, ie: position (gravity), or food (not metabolized yet)

Energy transfer methods:

Conduction – Molecule to Molecule transfer. Heat flow: Warm to cold. Ie: leather seats in a car

Convection – Transferred by vertical movement. Mixing of a fluid. Ie: Boiling Water

Radiation – Propagated without medium (like a vacuum). Solar radiation provides nearly all energy.

Conduction has the energy transfer from molecule to molecule. Convection has the energy form from the molecules themselves moving.

All mater emits radiation through waves. Waves consist of electric and magnetic components à Electromagnetic Radiation. Visible, Microwaves, UV, Radio waves.

Amplitude – Wave Height

Wavelength – Distances between successive peaks, crests, or troughs

Frequency - # of waves passing a fixed point every second. Generally reported in microns.

The shorter the wavelength, the more intense the energy.

Absolute 0: the temperature where all molecular motion ceases. (-273 celsius)

EM radiation is broke into categories based on its wavelength: Shortwave, visible, and Infrared.

Shortwave – Gamma, X-rays, & Ultraviolet – Super dangerous radiation that can harm us. Gamma and X-ray are almost mostly blocked. Ozone blocks UV rays but the amount of Ozone has been decreasing.

Visible – The colors that we can see, ROYGBIV

Infrared - Near infrared, Shortwave infrared, Middle infrared, Thermal infrared.

Longwave – microwaves and radio waves

Radiant energy emitted by Sun consists of:

• 7% gamma, X-ray and UV

• 47% visible

• 46% infrared

Total amount of energy an object emits if a function of its temperature (f(x))

The hotter the object, the shorter the wavelength.

Sun avg. wavelength - .45 microns

Earth avg. wavelength – 8 microns

Thermopause – Outer boundary of earth’s atmosphere

Insolation – Intercepted solar radiation arriving at the top of Earth’s atmosphere and reaching Earth’s surface (not returned back to space)

Earth inputs the short wavelength energy from the sun and outputs its own longer wavelengths as well as some of the reflected short wavelengths from the sun back into space

Solar Constant – Average amount of energy reaching the top of Earth’s atmosphere (1372 W/meter^2)

Because the earth is a sphere, there is an unequal distribution of energy from the sun

Earth’s rays hit most directly near the equator, and the rays get more oblique as you get closer to the poles

Sub-Solar Point - Point on the earth’s surface where the sun’s rays are perpendicular to the surface (90 degrees)

Global Net Radiation – difference between incoming and outgoing radiation

Highest surplus over the equatorial and tropical regions, with a deficit below those values, such as Antarctica.

The ocean and atmosphere work to balance this by evening the spread of energy and redistributing the energy,

The reason we have seasons is that the earth is tilted on it’s axis

Daylength – constant day length ONLY occurs along the equator. In Georgia, Summers have longer days than winters.

Declination – Latitude of the sub-solar point; point at which the suns rays hit at 90 degrees, always located between the two tropics, and the location changes with the seasons

Earth’s revolution Determines the length of the year and duration of the seasons

Summer solstice – June 21st Suns rays hit at Tropic of Cancer

Fall Equinox – Sept 22nd

Winter Solstice – Dec 21st Suns rays hit at Tropic of Capricorn

Spring Equinox – March 21st

Summer Solstice – Higher latitudes have longer days, Lower latitudes have slower days

Winter Solstice – Lower latitudes have longer days, Higher latitudes have slower days

Atmosphere:

Acts as a membrane – Protects organic life from harmful ionizing radiation (life would not exist without it)

Atmosphere reaches from Earth’s surface to 480km, but the exosphere extends to 32,000km above the surface

Three criteria to examine atmosphere: Composition, Temperature, and Function

The atmosphere exerts large downward pressure (pressure close to surface is much higher than the pressure higher in the sky)

½ of the atmosphere’s math is below 5500 meters (where planes fly)

Gravitational pull compresses the air near the surface

We will focus primarily on the temperature criteria

Homosphere: the atmosphere’s main gasses are really well mixed (Nitrogen, Oxygen, CO2, Ozone, etc)

Heterosphere: The gasses are not well mixed, they’re stratified based on their mass. Lighter elements, like Hydrogen and Helium, are found higher up.

Troposphere: roughly goes from the surface of the earth to 18 km. The tropopause acts as a cap. It has 90% of the atmosphere’s mass. Home of the biosphere – life processes and weather. Lapse rate: rate of temperature decrease in the atmosphere. The higher you go, the colder it gets. The troposphere’s energy comes from the earth’s surface.

Stratosphere: 18km – 50km. At 50km, the stratopause’s temperature is 0 celsius. Unlike the troposphere, temperature increases with altitude due to the ozone absorbing UV radiation and heat.

Mesosphere: 50-80km. Temperature decreases with altitude, with it being at its lowest at the Mesopause (-90 celsius)

Thermosphere: Roughly the same as the heterosphere. Its about 80km outwards. Temperatures increase with altitude. Thermopause is at 480km. It’s a high temperature, but its not “hot.” The molecules as so far apart from each other that they can’t generate heat, so even though temperatures are high, we would freeze to death.

Isosphere: Absorbs cosmic rays, gamma rays, X-rays, and some UV rays. Spans the mesosphere and thermosphere.

Ozonosphere: Part of the Stratosphere, has the Ozone layer. Absorbs UV energy and converts it to heat energy.

Depletion of Ozone layer:
Densest part is 29km.

The ozone layer is 3mm thick at sea level.

CFCs rise through the troposphere, get into the ozone, and pull apart the ozone layer by cleaning one oxygen molecule off of it. It leaves behind O2, which is useless. The hole in the ozone layer is less of a hole, but more of a weaker portion which lets through more UV.

Pollutants in the Atmosphere:

Natural sources of pollution:

Volcanoes (Sulfur oxides, ash, particulates)

Wildfires (Carbon monoxide, Carbon Dioxide, Nitrogen Oxides, smoke, ash)

Plants (Hydrocarbons, pollen)

Decaying Plants (Methane, Hydrogen Sulfate)

Soil (Dust, viruses)

Anthropogenic Pollution - Primarily an urban phenomenon (51% of the world lives in urban places, 1/3 exposed to unhealthy levels of pollution)

Carbon Monoxide – Burning of gasoline

Photochemical Smog – UV radiation / sunlight mixing with pollution from burning gasoline. Sunlight when mixing with Nitrogen Dioxide can clean off an oxygen atom, which can combine with molecular oxygen and create ozone, which is bad at the surface because it causes respiratory issues. Can also form nitric acid.

Industrial Smog / Sulfur Oxides – Burning fossil fuels (coal). Produces Sulfur Dioxide, CO2, and particulate matter. These can mix with water and lead to acid rain.

Particulates – Dust, soot, salt, etc.

Acid deposition – Formerly acid rain. What happens with Sulfur dioxide or Nitrogen dioxide combines with water vapor. They’re produced largely by the burning of fossil fuels.