GLOBAL CLIMATIC FACTORS
1)Quality of Solar Radiation
The earth receives almost all its energy from the sun in the from of radiation, thus the sun is the dominating influence on climate.The spectrum of solar radiation extends from 290 to 2300nm(nanometer).
According to human mears of perception we can distinguish:
a)ultra-violet radiation,290 to 380nm, producing photo chemical effects bleaching, sun burn etc.
b)visible light 38(violet)to 700nm (rad).
c)short infra-red radiation,700 to 2300nm, radiant heat with some photo-chemical effects.
The spectral energy distribution various with altitude due to the filtering effect of the atmosphere. Some of the shorter wave length are absorbed by the atmosphere and reradiated at much longer wave length eg; long infra-red, up to 10000nm. As the lumirous efficiency of energy –radiation depents an its spectral composition, there is no constant relationship between radiation intensity and its lighting effect.
However, the value of 100 lumens/watt can be used for solar radiation. This would give an illumination of 100 lux per kW/m².
2)Quantity of Solar Radition
The intensity of radiation searching the upper surface of the atmosphere is taken as solar constant 1395 w/m², but it may actually vary 12% due to variations in the output of the sun itself and it varies ±35% due to changes in the earth-sun distance. The earth move around te sun in a slightly eliptical orbit.
One revolution is completed in 365 days, 5 hour, 45 minute and 46 second. This orbit results from the centrifugal force due to the earth´s inertia and momentum. At the aphelion, the solar distance is 152 millions km and at porihelion is 147 million km.
3)Tilt of The Earth΄s Axis
The earth rotates around its own axis,each rotaion making one 24 hour day. The axis of this rotation is tilted to the plane of the elliptical orbit, at an angle of 66.5˚ and the direction of this axis is constant. Maximum intensity is received on a plane normal to the direction of radiation.
On 21 June areas along latitude 23.5˚ N are normal to the sun´s rays ,the sun΄s appparent path goes through the zenith at the latitude and the longest daylight period is experienced the shortest day and radiation minimum. On 21 March and 23 September areas along the Equator are normal to the sun´s rays and expensience a zenith path of the sun. For all areas of the earth these are equinox days.
1)Quality of Solar Radiation
The earth receives almost all its energy from the sun in the from of radiation, thus the sun is the dominating influence on climate.The spectrum of solar radiation extends from 290 to 2300nm(nanometer).
According to human mears of perception we can distinguish:
a)ultra-violet radiation,290 to 380nm, producing photo chemical effects bleaching, sun burn etc.
b)visible light 38(violet)to 700nm (rad).
c)short infra-red radiation,700 to 2300nm, radiant heat with some photo-chemical effects.
The spectral energy distribution various with altitude due to the filtering effect of the atmosphere. Some of the shorter wave length are absorbed by the atmosphere and reradiated at much longer wave length eg; long infra-red, up to 10000nm. As the lumirous efficiency of energy –radiation depents an its spectral composition, there is no constant relationship between radiation intensity and its lighting effect.
However, the value of 100 lumens/watt can be used for solar radiation. This would give an illumination of 100 lux per kW/m².
2)Quantity of Solar Radition
The intensity of radiation searching the upper surface of the atmosphere is taken as solar constant 1395 w/m², but it may actually vary 12% due to variations in the output of the sun itself and it varies ±35% due to changes in the earth-sun distance. The earth move around te sun in a slightly eliptical orbit.
One revolution is completed in 365 days, 5 hour, 45 minute and 46 second. This orbit results from the centrifugal force due to the earth´s inertia and momentum. At the aphelion, the solar distance is 152 millions km and at porihelion is 147 million km.
3)Tilt of The Earth΄s Axis
The earth rotates around its own axis,each rotaion making one 24 hour day. The axis of this rotation is tilted to the plane of the elliptical orbit, at an angle of 66.5˚ and the direction of this axis is constant. Maximum intensity is received on a plane normal to the direction of radiation.
On 21 June areas along latitude 23.5˚ N are normal to the sun´s rays ,the sun΄s appparent path goes through the zenith at the latitude and the longest daylight period is experienced the shortest day and radiation minimum. On 21 March and 23 September areas along the Equator are normal to the sun´s rays and expensience a zenith path of the sun. For all areas of the earth these are equinox days.
