plane of the ecliptic
flat plane traced by the orbital paths of the planets in the solar system
subsolar point
single point at which the Sun’s rays are perpendicular to Earth’s surface at or near noon; restricted to between 23.5° north and south latitude
tropic of cancer
the 23.5° north parallel; the maximum latitude of the subsolar point in the northern hemisphere
tropic of capricorn
the 23.5 south parallel; the maximum latitude of the subsolar point in the southern hemisphere
circle of illumination
line separating night from day, where sunrise and sunset are occurring
solar altitude
altitude of the Sun above the horizon in degrees
December solstice
seasonal marker that occurs when the subsolar point is at 23.5° south, on about December 21.
March equinox
seasonal marker that occurs when the subsolar point is over the equator about March 20
June solstice
a seasonal marker that occurs when the subsolar point is 23.5° north latitude about June 21
September Equinox
seasonal marker that occurs when the subsolar point is over the equator about September 22
Arctic Circle
the 66.5° north parallel
Antarctic Circle
the 66.5° south parallel
heat-index temperature
temperature perceived by people as a result of high atmospheric humidity coupled with high air temperatures.
temperature
average kinetic movement of atoms and molecules of a substance
heat
internal energy transferred between materials or systems due to their temperature differences
conduction
process by which energy is transferred through a substance or between objects in direct contact
convection
transfer of heat through movement of mass within a fluid (liquid or gas)
radiation
process by which wave energy travels through the vacuum of space or through a physical medium such as air or water
continental effect
increase in seasonality with distance from the oceans
specific heat
heat required to raise the temperature of any object or material by a given amount
Radiant Energy (radiation)
energy propagated in the form of electromagnetic waves, including visible light and heat
electromagnetic spectrum (EMS)
full range of wavelengths of radiant energy
longwave radiation (LWR)
radiation with wavelengths longer than 4 Mm
shortwave radiation (SWR)
solar radiation with wavelengths shorter than 4Mm; includes visible sunlight
visible radiation (or light)
portion of the electromagnetic spectrum that people can see
infrared radiation (IR)
electromagnetic radiation that has wavelengths longer than visible radiation
insulation (incoming solar radiation)
solar radiation that reaches earth
transmission
unimpeded movement of electromagnetic energy through a medium such as air, water, or glass
scattering
process of redirecting solar radiation in random directions as it strikes physical matter
reflection
process of returning a portion of the radiation striking a surface in the general direction from which it came
albedo
reflectivity of a surface, given as the percentage of incoming radiation that it reflects
urban heat island
urbanized region that is significantly warmer than surrounding rural areas
radiative equilibrium temperature
temperature of an object resulting from the balance between incoming and outgoing energy
greenhouse effect
process by which the atmosphere is warmed as greenhouse gases (water vapour, CO2, and methane) and clouds absorb and counterradiate heat
global heat engine
movement of heat from low to high latitudes and low to high altitudes as a result of heating differences
renewable energy
energy that comes from sources that are not depleted when used, such as sunlight or wind