Solar Radiation, Heat Balance And Temperature Class 11 Notes Geography Chapter 8 - CBSE

Chapter : 8

What Are Solar Radiation, Heat Balance And Temperature ?

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We breathe in and out, but when the air is moving, we can feel it. It demonstrates that wind is air in motion.
The term "atmosphere" refers to the air envelope. Numerous gases that make up its composition enable life to exist on the surface of the globe.
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.
Different sections of the world experience varying amounts of heat.
Differences in atmospheric pressure are brought on by this variation.
The majority of the energy that reaches the earth's surface is in short wavelengths.
The sun's rays strike the planet obliquely at the top of the atmosphere because it is a geoid that resembles a sphere, and the earth only absorbs a very small amount of the sun's energy.
Due to differences in the distance between the earth and the sun, the solar output received at the top of the
atmosphere varies slightly over the course of a year.
The earth is furthest from the sun during its orbital revolution (152 million km on 4th July). The term aphelion refers to this location of the earth.
The day when the sun is closest to the earth is January 3rd (147 million km). Perihelion is the name for this position.
On January 3rd, the earth receives a little bit more annual insolation than it does on July 4th.
Insolation varies throughout the day, season, and year in terms of both quantity and intensity.
The factors that cause these variations in insolation are: the slant of the sun's rays, the length of the day, the transparency of the atmosphere, and the way the land is arranged in relation to its aspect.
The earth’s axis that makes an angle of 66½ with the plane of its orbit round the sun has a greater influence on the amount of insolation received at different latitudes.
The angle of inclination of the rays is the second component that affects how much insolation is received.
Short wave solar radiation can pass through the atmosphere relatively unimpeded.
A large portion of the near infrared radiation is absorbed by gases such as water vapour, ozone, and others in
the troposphere.
In the tropics, the insolation received at the surface ranges from approximately 320 Watt/m² to approximately 70 Watt/m² in the poles.
Over the subtropical deserts, where there is the least cloud cover, the sun shines most.
Comparatively less solar radiation hits the equator than the tropics.
After being heated by insolation, the earth radiates heat in the form of long waves to nearby atmospheric layers.
Over the subtropical deserts, where there is the least cloud cover, the sun shines most.
Comparatively less solar radiation hits the equator than the tropics.
After being heated by insolation, the earth radiates heat in the form of long waves to nearby atmospheric layers.
Conduction is a process in which the air in contact with the land gets heated slowly and the upper layers in
contact with the lower layers also get heated.
When heated, the air in contact with the earth rises vertically, carrying the heat of the atmosphere with it. Convection is the term used to describe this upward heating of the atmosphere.
Advection is the term used to describe the transmission of heat by horizontal air movement. The air's horizontal movement is generally more significant than its vertical movement.
The planet receives short wave type of insolation, which heat up the surface. The ground, 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. Terrestrial radiation is the term of this process.
The top of the atmosphere receives 100% of its insolation. Some energy is reflected, dispersed, and absorbed
as it travels through the atmosphere.
The albedo of the earth is the quantity of radiation reflected.
The latitude, elevation, distance from the sea, air circulation, the existence of warm and cold ocean currents, and local factors all affect the temperature of the air at any given location.
Isotherms are lines connecting locations with the same temperature.
Elevation causes a drop in temperature.
Surface inversion encourages stability in the atmosphere's lower layers.
Below the inversion layer, smoke and dust particles gather and spread horizontally, filling the lower layers of the atmosphere.
Because of air drainage, inversion occurs on hills and mountains.
The cold air travels down the slope nearly like water and piles up deeply in pockets and valley bottoms with warm air above because it is heavy and thick. This is termed air drainage.
Air drainage shields plants from harm caused by frost.