Describe conditions that influence the in-coming solar radiation in an area.
Latitude
The angular distance of a place from the equator partially determines the distance from the sun to the earth’s surface. This further determines the angle of incidence at which the sun’s rays fall upon the earth’s surface.
Thus, there is always maximum insolation in low latitudes because the sun’s rays strike the earth’s surface at right angles and have a short distance to travel through the atmosphere. There is intensive heating since there is a smaller surface area per ray. The sun’s rays are however less intensive towards the mid-latitudes and Polar Regions because of the long desistance they travel through the atmosphere and the oblique angle at which they strike the earth’s surface.
Rotation of the earth
The rotation of the earth on its axis causes changes in solar radiation received in a place. Within the tropics the sun is overhead and higher amounts of solar radiation are received. Absence of the overhead sun at the poles, artic and sub-arctic regions reduces radiation rates.
Revolution of the earth:
This cause seasonal variation in the amount of radiation received in the different places of the global earth. More solar radiation in experienced during summer season compared to winter season.
Cloud cover:
Clouds in the atmosphere do absorb, reflect and refract radiation and this reduces the amount of solar radiation reaching the earth’s surface. This implies that areas with a dense cloud cover receive less solar radiation as compared to areas with clear skies.
Aspect:
Areas in the direct path of the sun’s rays and especially in the mid and high latitude areas receive more solar radiation as compared to those areas sheltered from the sun’s rays e.g. in the mid-latitudes of the Northern hemisphere; the South facing slopes receive more solar radiation than North facing slopes. This is because the South facing slopes in northern hemisphers are in the direct path of the sun rays.
Humidity:
The amount of water vapor in the atmosphere may absorb or reflect solar radiation. It prevents some percentage of the solar radiation from reaching the earth’s surface. Areas with less humidity e.g. arid and semi-arid regions receive more solar radiation on their surface because direct heat from the sun is received.
Impurities in the atmosphere:
Impurities in atmosphere such as smoke and dust particles tend to absorb part of the solar radiation reaching the earth’s surface. This means that areas with much atmospheric impurities will receive less solar radiation as compared to clear atmospheric conditions.
Amount of the greenhouse gases (GHE)
The increase in the amount of Greenhouse gases such as CFCs in the atmosphere may affect the ozone layer. The depletion of ozone layer will trigger the occurrence of global warming- a condition that increases the amount of solar radiation. On the other hand, areas with less/ limited atmospheric Greenhouse gases have the ozone layer still intact and therefore experience less solar radiation reaching the earth’s surface.
