Here we are going to discuss a Geography topic which is ” Solar Radiation – Heat Balance, Transfer & Distribution of Temperature “. This topic is a part of the general awareness of many competitive exams. This article covers the entire essence of the topic by which you get the most out of it. This article is very helpful for SSC, Banking, Railway and for other competitive exams.
What is Solar Radiation:
The phrase “solar radiation” is used to refer to the electromagnetic radiation that the sun emits. A lot of devices can be used to collect solar radiation and transform it into useful forms of energy, such as heat and electricity. The sun provides almost all of the energy that the earth needs. The energy that the earth receives from the sun is then radiated back into space. As a result, throughout time, neither the earth’s temperature rises nor falls.
The amount of energy received by the earth’s surface is different for the different time periods because of the change in the distance between the earth and the sun.
On July Fourth, the earth is 152 million kilometres from the sun at its farthest distance during its cycle around the sun. This position of the earth is called “Aphelion”.
The closest day to the sun for the earth is January 3rd (147 million km). This position of the earth is called “Perihelion”.
Factors influencing Insolation:
On the surface of the earth, insolation is not distributed equally. It changes depending on the location and the time. The amount of solar radiation reaches its peak in the tropics and then steadily diminishes as it moves toward the poles. Summer is the time of year when insolation is highest and winter is the time when insolation is lowest. The following are the main factors that influence the amount of solar radiation received:
1. The rotation of the earth on its axis
2. The angle of inclination of the rays of the sun
3. Duration of the day
4. The transparency of the atmosphere
5. The configuration of the land in terms of its aspect
Insolation is majorly influenced by the first three factors. The amount of insolation received at various latitudes is more affected by the earth’s axis’ of 66.5° with the plane of its orbit around the sun. The angle of inclination of the rays is the second component that affects how much insolation is received. This is based on a location’s latitude. Slanting sun rays are caused by the sun’s rays making a smaller angle with the earth’s surface as latitude increases. The area that vertical rays cover is always less than the area covered by slant rays. The energy is spread as more area is covered, resulting in a reduction in the net energy received per unit area. Additionally, because the slant rays must penetrate the atmosphere at a greater depth, there will be more absorption, scattering, and diffusion.
The earth’s surface cannot receive solar radiation because of thick clouds. The amount of cloud cover, its thickness, the presence of dust and water vapour, and other factors affect how transparent the atmosphere is. They either transmit, reflect, or absorb sunlight. . Similar to water vapour, solar radiation is absorbed by it, resulting in less of it reaching the surface.
Heating and Cooling of Atmosphere :
There are different ways of heating and cooling the atmosphere. The main are as follows:
1. Terrestrial Radiation
2. Conduction
3. Convection
4. Advection
1. Terrestrial Radiation:
The earth receives insolation in short waves, which heats the surface. The earth, once heated, transforms into a radiating body and emits energy in the form of long waves into the atmosphere. The atmosphere is heated from below by this energy. It is known as Terrestrial Radiation.
2. Conduction:
The process of transfer of heat from a warmer object to a cooler object by contact is known as “Conduction”. It is important for the lower layers of the atmosphere.
3. Convection:
The movement of a mass or substance from one location to another, usually vertically, with the purpose of transferring heat, is known as Convection.
4. Advection:
The transfer of heat through the horizontal movement of air is known as Advection. Variation in daily weather is due to the Advection.
Heat Budget of the Planet Earth :
The entire planet does not store or release heat. It keeps its temperature constant. This is only possible if the heat absorbed from insolation equals the heat the earth loses from terrestrial radiation. 35% of solar energy is reflected back to space even before it reaches the earth’s surface when 100% of it enters the atmosphere of the planet. The quantity of reflection is referred to as the earth’s albedo. The earth or the atmosphere is not heated by this energy.
The amount of radiation reflected by the earth is known as “Albedo”.
35% of solar energy is reflected back to space even before it reaches the earth’s surface when 100% of solar energy enters the atmosphere of the planet. The remaining 65 units are absorbed, with the atmosphere absorbing 14 units and the surface of the planet absorbing 51 units. The form of radiant energy that the earth emits back is 51 units. Of these, 34 units are absorbed by the atmosphere, leaving only 17 units that are directly emitted into space. In addition to being reflected back into space, the atmosphere absorbs 48 units (14 from insolation plus 34 from terrestrial radiation). In order to balance the total of 65 units received from the sun, the total radiation returning from the earth and the atmosphere, respectively, is 17 + 48 = 65 units. This process is known as “The Heat Budget of Earth”.
Variation in the Net Heat Budget at the Earth’s Surface :
- The amount of radiation that the earth’s surface receives varies. While certain areas of the globe have an excess of radiation, others are in deficit.
- Between 40 degrees north and south, there is a surplus of net radiation balance, whereas the areas close to the poles have a deficit. The tropics do not gradually get warmer due to the buildup of excess heat or the high latitudes do not become permanently cold due to excess deficiency because the surplus heat energy from the tropics is reallocated polewards.
Temperature :
- Heat, which is expressed in terms of temperature, is produced by the interaction of insolation with the atmosphere and the earth’s surface.
- In other words, we can say that the measurement of a thing’s or a place’s temperature in degrees is called the temperature.
Factors Controlling Temperature Distribution :
The factors are as follows :
- The latitude of the place
- The altitude of the place
- Distance from the sea
- Air mass and Ocean currents.
- local aspects
Global Distribution of Temperature :
- By examining the temperature distribution in January and July, it is possible to comprehend the global distribution of temperature.
- Isotherms are typically used to depict the temperature distribution on a map.
- Lines that connect areas with the same temperature are called isotherms. The distribution of surface air temperature in the months of January and July.
- Particularly in the northern hemisphere, the departure from this overall pattern is more pronounced in January than in July.
January Isotherm :
- As we know that the northern hemisphere experiences winter in January, while the southern hemisphere experiences summer.
- The isotherms over the ocean and the continent diverge in January to the north and south, respectively. On the North Atlantic Ocean, this can be seen. The Gulf Stream and North Atlantic Drift warm the Northern Atlantic Ocean, which causes the isotherms to bend towards the north. In Europe, the land experiences a dramatic drop in temperature and the isotherms curve southward.
- At latitudes, 80° N and 50° N, the average January temperature along the 60° E longitude is minus 20° C. January’s average monthly temperature is above 27° C, over 24° C in the tropics, 2° C to 0° C in the intermediate latitudes, and -18° C to -48° C in the interior of the Eurasian continental plate.
- In the southern hemisphere, the influence of the ocean is very noticeable. Here, the temperature changes more gradually than in the northern hemisphere because the isotherms are more or less parallel to the latitudes. The latitudes at which the isotherm of 20°, 10°, and 0° C run parallel are 35°, 45°, and 60° S, respectively.
July Isotherm :
- The northern hemisphere experiences summer in July, whereas the southern hemisphere experiences winter.
- The isothermal behaviour that is seen in July is the reverse of that seen in January. In most cases, the isotherms follow the latitudes parallel.
- The hot tropical winds migrate into the interior of the northern hemisphere as land masses get overheated. The oceans, which are significantly cooler, have a moderating impact on tropical interiors.
- Along the 30° N latitude, the subtropical continental region of Asia experiences land temperatures of over 30°C. The temperature is 10° C along the 40° N isotherm and 10° C along the 40° S isotherm.
Inversion of Temperature :
- Typically, the temperature drops as elevation rise. It’s known as the usual lapse rate. The typical lapse rate can occasionally be flipped when the circumstances are reversed. It is known as a temperature inversion. Inversions are often brief but nonetheless relatively frequent.
- An optimal environment for an inversion is a long winter night with calm air and clear skies. By early morning, the earth is colder than the atmosphere because the heat of the day has dissipated during the night. Temperature inversion is typical year-round over polar regions.
- Inversion at the surface encourages stability in the lower atmosphere. Under the inversion layer, smoke and dust particles gather and expand horizontally to cover the lower layers of the atmosphere. Morning-dense fogs are not uncommon, especially throughout the winter. Typically, this inversion only lasts a few hours before the sun starts to rise and warm the ground.
- Hills and mountains experience inversion because of air drainage. Gravity causes the cold air formed at the hills and mountains during the night to flow. Due to its weight and density, the cold air flows down the hill and piles up deeply in pockets and the valley bottoms with warm air above it. It is known as air drainage. It shields plants from damage caused by frost.