The radiation that reaches the earth is then re-radiated to form convection currents.
It is the re-radiation that heats up the lowest parts of the atmosphere (troposphere).
The convection of heat in the atmosphere involves the movement of air. Air is a poor conductor of energy so convection is a major process of energy transfer in the earth’s atmosphere.
Particles in liquids and gases move more when heated and spread out and become less dense. Cooler more dense particles then fill their place producing alternating vertical currents known as convection currents.
Reference: http://apollo.lsc.vsc.edu
The albedo effect is the percentage of solar radiation reflected back from a surface. Scientists and meteorologists believe that global warming will trigger new process resulting in unpredictable climatic changes, an effect of which is the albedo effect.
The basis on which the albedo effect operates relates to the properties for reflection of heat and light on white shiny surfaces, whereas black dull surfaces tend to absorb it. The albedo effect occurs in various ways hence why there is diversity in the percentage of reflected and absorbed heat and light in the constituents of the earth’s surface. The term albedo is derived from the Latin name for white, hence its relevance for this process. A renowned example of the albedo effect is the snow-temperature feedback. There are phases in which this process happens.
- Land which is exposed is darker and absorbs energy. As the snow melts more land is exposed which absorbs more energy.
- Light coloured ice reflects the suns energy back efficiently.
- The altitude of ice of the melting ice is reduced so it becomes harder for new ice to form.
The planet’s albedo is a key climate variable in determining the radiant heat energy input to the planet combined with the solar constant. The planets annual average albedo is 0.30 (30%). The albedo varies according to geographical regions and times of year.
A table showing the percentage of reflected solar radiation.
The income of the earth’s solar radiation is from the sun. The energy that reaches us
from the sun is 148,800,000 km away providing us with an average surface temperature of 14 degrees C.
The earth is also reflecting and re-radiating the same amount of solar radiation that it is receiving.
Incoming solar radiation is absorbed by the Earth's surface, clouds, gases, the atmosphere and molecules in the atmosphere. This incoming solar radiation is also reflected by the Earth's surface, by clouds, and by the atmosphere.
Energy that is absorbed is emitted by the Earth-atmosphere system as long wave radiation in the form of infrared radiation i.e. it is re-radiated to be absorbed by another object. This radiation allows Earth to lose heat at the same rate it gains from the Sun.
The solar radiation emitted by the sun as a result of the furnace like processes that occurs in the sun reaches the peripheral boundaries of the atmosphere before being absorbed. Reigning on Earth's Climate - Only about 70% of the solar energy that reaches Earth is absorbed, while the other 30% is reflected back into space by atmosphere and aerosols, ocean/land and clouds as a consequence due to the albedo.
Through out the year there is fluctuation and change in the distance of the sun from the earth. This results in conjunctions of variation of the seasonal weather we experience because earth follows an orbital pattern.
The solar radiation received in one area can differ from that which is received in another. There are many influences that contribute to this such as continentality, the height above sea level, the albedo effect and as previously mentioned the orbital path of the earth. This is also why the temperatures and climate differ so much between the north and south poles. This also happens in the northern hemisphere and the southern hemisphere for the same reasons. During the winter period the northern hemisphere is naturally cold where as the southern hemisphere is warm and vice-versa for the southern hemisphere during the summer. This is due to the tilt of the earth on its axis and the positional location of the sun and further more the albedo of water and land. The temperature of an area depends on the strength of the sun's heat and light penetrating its surface, which is determined by the angle at which the suns energy hits the earth. The earth’s temperature is hotter at the equator and colder at the poles because of the difference in the angle of the solar radiations penetration, due to the angle of the earth’s tilt which causes seasonal variations. During the earth’s movement around the sun the earth’s axis of rotation does not move, consequently the northern hemisphere points towards the sun during summer periods where as it points away during the winter months. This is what causes seasons and for both the northern hemisphere and the southern hemisphere this has a significant impact on the weather experienced. The sun’s rays hit the equator at a direct angle where convection influences the intensity of the heat radiation experienced causing tropical climates
This graph shows the temperature variations through out the year with the northern hemisphere opposing the southern. Both Johannesburg and Punta Arenas are located in the southern hemisphere hence the temperature differences compared to those locations located in the northern hemisphere i.e. Los Angeles and Liverpool. Singapore located in Asia has relatively constant yearly temperature as it is situated towards the equator on the east.