Where are we and how much are we getting right now? Autumnal equinox Fall in the northern hemisphere Winter solstice Winter in the northern hemisphere
Vernal Equinox Spring in the northern hemisphere Summer solstice Summer in the northern hemisphere
Duration of Insolation Length of time the sun is up. Relationship: longer duration of insolation, higher the temperature (more intense) Varies with latitude
Absorption of Insolation Only 50% of the sun’s energy is absorbed by Earth’s surface. Rest is reflected, scattered or absorbed by the atmosphere. The absorption of heat energy from the sun depends on the specific heat of the substance. Land has a lower specific heat, so takes less time to heat up, while water has a higher specific heat, thus taking more time to heat up.
Four Reasons water and land temperature differ: Water has a higher specific heat. Water reflects low angle insolation better. Water is transparent insolation penetrates more deeply, more quickly. Convection currents carry heat energy into hydrosphere land heats faster than water and land cools faster than water. GOOD ABSORBERS ARE GOOD RADIATORS
Color or structure of surface also determines if heat will be absorbed or reflected In general, light colored surfaces reflect While dark colored surfaces absorb Incoming energy from the sun: UV, visible and infrared Outgoing energy from Earth: terrestrial radiation – infrared.
Insolation – Temperature Lag A time lag exists between time of greatest intensity and time of highest air temperature. WHY? Ex: June at noon – Earth receives most solar energy but highest temperature is later. Because temperature depends on the balance between incoming energy and energy lost. Even after maximum insolation, Earth continues to receive more energy than lost temperature continues to rise during this ‘lag’ period. Following balance, energy lost > energy gained therefore about mid afternoon temperature drops.
INSOLATION Check point Angle of insolation = how high sun is in sky. Measured from the horizon (position of the sun) greatest angle = 90 ⁰ Changes with the seasons – in Northern Hemisphere: Lowest noontime angle =December 21, winter solstice Highest angle =June 21, summer solstice As angle of insolation increases and duration of insolation increases- temperature increases. Most energy gets to Earth’s surface as visible light. Ozone absorbs high energy radiation Infrared radiation is absorbed by water and carbon dioxide. A substances reflectivity = albedo
What is the Greenhouse Effect? http://earthguide.ucsd.edu/ea rthguide/diagrams/greenhous e/ http://earthguide.ucsd.edu/ea rthguide/diagrams/greenhous e/ Natural effect Keeps our planet inhabitable Other greenhouse planets- Venus Greenhouse gases in Earth’s atmosphere trap terrestrial radiation or heat in
What can you do? Lower your energy consumption (burning of fossil fuels) Recycle Lower your carbon footprint Check out these websites: http://www.breathingearth.net http://footprintnetwork.org/en/index.php/GFN/page/calcula tors/ http://footprintnetwork.org/en/index.php/GFN/page/calcula tors/