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Warnings: The True Story of How Science Tamed the Weather by Mike Smith tells the story of our storm warning system. See our online store book collection.

Earth's Atmosphere

The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds Earth. High above the planet, the atmosphere becomes thinner until it gradually reaches space. It is divided into five layers. Most of the weather and clouds are found in the first layer.

The atmosphere is an important part of what makes Earth livable. It blocks some of the Sun's dangerous rays from reaching Earth. It traps heat, making Earth a comfortable temperature. And the oxygen within our atmosphere is essential for life.

Over the past century, greenhouse gases and other air pollutants released into the atmosphere have been causing big changes like global warming, ozone holes, and acid rain.

<a
  href="/earth/Atmosphere/clouds/mammatus.html&edu=high">Mammatus
  clouds</a> are pouches of clouds that hang underneath the base of a cloud.
  They are usually seen with <a
  href="/earth/Atmosphere/clouds/cumulonimbus.html&edu=high">cumulonimbus
  clouds</a> that produce very <a
  href="/earth/Atmosphere/tstorm.html&edu=high">strong
  storms</a>. This photograph of mammatus clouds was taken on June 21, 2006 in
  Boulder, Colorado, at sunset. Notice how the light from the sun highlights
  the round features of these clouds.<p><small><em>       Courtesy of Roberta Johnson</em></small></p><a
  href="/earth/Atmosphere/clouds/stratocumulus.html&edu=high">Stratocumulus
  clouds</a> belong to the <a
  href="/earth/Atmosphere/clouds/low_cloud.html&edu=high">Low
  Cloud</a> (surface-2000m) group. These clouds are low, lumpy, and gray.  Only light <a
  href="/earth/Atmosphere/precipitation.html&edu=high">precipitation</a>,
  generally in the form of <a
  href="/earth/Atmosphere/precipitation/drizzle.html&edu=high">drizzle</a>,
  occurs with stratocumulus clouds. To distinguish between a stratocumulus and
  an <a
  href="/earth/Atmosphere/clouds/altocumulus.html&edu=high">altocumulus</a>
  cloud, point your hand toward the cloud. If the cloud is about the size of
  your fist, then it is stratocumulus.<p><small><em>            Courtesy of Carlye Calvin/UCAR</em></small></p>Anti-crepuscular rays are beams of sunlight that appear to converge on a point opposite the sun. They are similar to crepuscular rays, but are seen opposite the sun in the sky. Anti-crepuscular rays are most frequently visible near sunrise or sunset. This photo of anti-crepuscular rays was taken at sunset in Boulder, Colorado. Crepuscular rays are usually much brighter than anti-crepuscular rays.<p><small><em> Image Courtesy of Carlye Calvin</em></small></p>Greenlandís <a href="http://www.windows2universe.org/earth/polar/cryosphere_glacier1.html">ice sheet</a> saw a record <a href="http://www.windows2universe.org/headline_universe/olpa/greenland_10dec07.html">melt</a> in July 2012.  Scientists studying this event have found that this melting event was triggered by an influx of unusually warm air and amplified by the presence of a blanket of thin low-level <a href="http://www.windows2universe.org/earth/Atmosphere/cloud.html">clouds</a> which pushed temperatures up above freezing.  For more information see the <a href="http://www.news.wisc.edu/21638">press release</a> from the University of Wisconsin Madison.<p><small><em>Image courtesy of University of Wisconsin-Madison</em></small></p>An image of Hurricane Sandy taken by the GOES-13 satellite on October 28.  This category 1 <a href="/earth/Atmosphere/hurricane/hurricane.html&edu=high">hurricane</a> was huge, spanning a horizontal distance of about one-third the US continental landmass.  The storm came onshore in New Jersey, and gradually moved northeast.  The storm disrupted the lives of tens of millions in the eastern US, doing billions of dollars in damage, resulting in over 30 deaths.  Visit the National Hurricane Center's webpage on <a href="http://www.nhc.noaa.gov/">Hurricane Sandy</a> for details.<p><small><em>Image courtesy of NASA</em></small></p>How did life evolve on <a href="/earth/earth.html&edu=high">Earth</a> during the <a href="/earth/past/Archean.html&edu=high">Archean</a>, when the <a href="/sun/sun.html&edu=high">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&edu=high">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&edu=high">greenhouse</a> gas concentration was the same as today.  <a href="http://www.manchester.ac.uk/aboutus/news/display/?id=10798">Researchers</a> studying the <a href="/physical_science/physics/atom_particle/isotope.html&edu=high">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&edu=high">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&edu=high">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&edu=high">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=high">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA