Effect of Sun angle on climate
The amount ofheatenergy received at any location on the globe is a directeffect of Sun angle on climate,as theangleat whichsunlightstrikesEarthvaries by location, time of day, andseasondue toEarth's orbitaround theSunandEarth's rotationaround itstilted axis.Seasonal change in the angle of sunlight, caused by the tilt of Earth'saxis,is the basic mechanism that results in warmer weather in summer than in winter.[1][2][3]Change inday lengthis another factor.[2][3]
Geometry of Sun angle[edit]
This diagram illustrates how sunlight is spread over a greater area in thepolar regions.In addition to the density of incident light, thedissipationof light in theatmosphereis greater when it falls at a shallow angle.
One sunbeam one mile wide shines on the ground at a 90° angle, and another at a 30° angle. The one at a shallower angle covers twice as much area with the same amount of light energy.
Figure 1presents a case when sunlight shines on Earth at a lowerangle(Sun closer to the horizon), the energy of the sunlight is spread over a larger area, and is therefore weaker than if the Sun is higher overhead and the energy is concentrated on a smaller area.
Figure 2depicts a sunbeam one mile (1.6 km) wide falling on the ground from directly overhead, and another hitting the ground at a 30° angle.Trigonometrytells us that thesineof a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the sunbeam hitting the ground at a 30° angle spreads the same amount of light over twice as much area (if we imagine the Sun shining from the south atnoon,the north–south width doubles; the east–west width does not). Consequently, the amount of light falling on each square mile is only half as much.
This is a diagram of the seasons. Regardless of the time of day (i.e.Earth's rotation on its axis), theNorth Polewill be dark, and theSouth Polewill be illuminated; see alsoarctic winter.
Figure 3shows the angle of sunlight striking Earth in theNorthernandSouthernHemispheres when Earth's northern axis is tilted away from the Sun, when it is winter in the north and summer in the south.
Technical note[edit]
Heat energyis not received from the Sun. Rather,radiant energyis received and this results in change inenergy levelof receiving bodies in Earth's domain. Different materials have different properties for transmitting back received energy in the form ofheat energyat different rates.
See also[edit]
- Axial tilt
- Declination
- Solar irradiance(insolation)
- Sun path
References[edit]
- ^Windows to the Universe.Earth's Tilt Is the Reason for the Seasons!Archived2007-08-08 at theWayback MachineRetrieved on 2008-06-28.
- ^abKhavrus, V.; Shelevytsky, I. (2010)."Introduction to solar motion geometry on the basis of a simple model".Physics Education.45(6): 641.Bibcode:2010PhyEd..45..641K.doi:10.1088/0031-9120/45/6/010.S2CID120966256.Archived fromthe originalon 2016-09-16.Retrieved2011-05-13.
- ^abKhavrus, V.; Shelevytsky, I. (2012)."Geometry and the physics of seasons".Physics Education.47(6): 680.doi:10.1088/0031-9120/47/6/680.S2CID121230141.