Heat Energy of Atmosphere PDF

**Heat energy of atmosphere: Process of heat transmission, Heating of atmosphere** **Heat energy of atmosphere** All the energy that reaches the earth comes from the sun. Energy travels from the sun to earth by means of electromagnetic waves. The shorter the wavelength, the higher the energy assoc...

**Heat energy of atmosphere: Process of heat transmission, Heating of atmosphere** **Heat energy of atmosphere** All the energy that reaches the earth comes from the sun. Energy travels from the sun to earth by means of electromagnetic waves. The shorter the wavelength, the higher the energy associated with it. Intercepted first by the atmosphere, a small part is directly absorbed, particularly by certain gases such as ozone and water vapour. Some energy is reflected back to the space by clouds and the earth surface. Energy is transferred between the earth's surface and the atmosphere via conduction, convection and radiation. The process of heating and cooling of the atmosphere are, - Conduction - Convection - Radiation and - Advection **Conduction** Conduction is the process in which heat flows from objects with higher temperatures to objects with lower temperatures through **molecular movement.** It primarily heats the atmosphere's **lower layers.** **Air is a poor conductor of heat**, resulting in a slow transfer of heat in a mass of air. Conduction heats a **thin layer close to the Earth's surface**, but its significance is limited. As air molecules are not densely packed, conduction has a **minor role** in heating the atmosphere. Once heated, **Air becomes lighter and less dense**, moving upward. **Convection: ** Convection is the transfer of heat by the **movement of a fluid (liquid or gas) **between areas of different temperatures.** **Earth's surface is heated by incoming solar energy. Heating of the surface **warms the air **in contact with it. Warmed air becomes **less dense** and rises upward. Rising air creates convection, moving **large quantities of air upward**. Expansion of air at ground level creates **low pressure**, causing cooler air nearby to move in to fill the gap. Heat is transferred upward by vertically moving air. Convection occurs **locally and on larger regional scales**, illustrated by phenomena like **Hadley, Ferrel**, and **Polar cells**. Convection transfers heat energy from the **sun to the surface and from the surface to the atmosphere**. It is **limited to the troposphere. ** **Advection: ** Advection is the heat transfer that occurs when air moves horizontally. Air movement in the horizontal direction is more crucial than in the vertical direction. Most diurnal (day and night) fluctuations in daily weather are driven solely by advection in middle latitudes. Local winds are known as 'loo' resulting from the advection process in tropical locations, particularly in northern India during the summer season. Differences in atmospheric pressure at local, regional, and global levels cause continuous movement of gases. - **Local Advection**: can be observed in phenomena like monsoon winds. - **Regional Advection**: is exemplified by the planetary permanent wind system. Both local and regional advection transfer heat from one area to another. - **Hydrospheric Advection**: involves movement of water, such as ocean currents. Ocean currents redistribute energy from high to low concentration zones. Ocean currents are also influenced by atmospheric advection movements. **Terrestrial Radiation: ** Heat transfer from one body to another without actual contact or movement. Terrestrial radiation is a significant method of atmospheric heating.  **Absorption and Emission by Earth**: Earth absorbs shortwave radiation (UV and Visible portion of electromagnetic spectrum) warming the surface; It emits long wave radiation (Infrared rays) which heats up the atmosphere. Terrestrial radiation occurs continuously, maintaining a static temperature[ ]on Earth. **Earth's Temperature Regulation: Greenhouse** gases and water vapor trap outgoing longwave radiation, contributing to the greenhouse effect. Cloud Cover: reduces incoming radiation and traps outgoing radiation, behaving similarly to greenhouse gases. Without the greenhouse effect, Earth's average temperature would plummet to minus 170°C. **Plank's law** states that the hotter body radiates more energy and short wavelength radiation. **Heating of the atmosphere** The atmosphere does not absorb short wave radiation. Therefore, most of the radiation is transmitted to earth without heating the atmosphere. The insolation chiefly heats up the earth's surface. The heated surface of the earth reflects back the heat to atmosphere I the form of long-waves. Isolation is received only during the day-time. But transmission of terrestrial radiation takes place all through the day and night. As a result of this phenomenon nights are cooler than the day. **Heat budget of the earth** The average temperature of the earth generally does not change. The amount of heat reflected back by earth through terrestrial radiation equals to the amount of insolation or incoming solar radiation. In the way there is balance between insolation and terrestrial radiation. This balance is known as the heat budget of the earth. Heat budget Notes for UPSC Exam **Insolation** The energy for all the atmospheric processes is derived from the sun. The sun radiates energy at a temperature of 6000⁰C. Incidence of the solar radiation on the earth's surface is referred as isolation. The sun's rays suffer depletion due to absorption, scattering ad reflection and by the atmospheric constituents, particulates or aerosols and clouds. Most of the ultraviolet radiation is absorbed by ozone layer. Part of the radiation is reflected back to space by water, snow and deserts and rest is absorbed by land and water. Early 19% of the incoming solar radiation is absorbed in the atmosphere and 34% scattered or reflected back space. The rest 47% of the radiant energy is absorbed by earth and transformed into heat. Heating extends to considerable depth in water due to turbulent mixing and overturning. Ocean store energy for long periods. Overland, however the heating effect is restricted to a few centimeters. Heat is transferred upward by conduction and eddy transfer. Large masses of heated air become buoyant and are carried upward by convection. Cooling takes place in the vertical uplift and water vapour condenses into liquid water drops, liberating latent heat. The amount of insolation received at a place on the earth at any time depends on, - Solar output, i.e. energy emitted from the sun - Distance of earth from the sun - Transparency of the atmosphere. - Period of insolation. - Angle at which sun's rays strike the earth. - Composition of the earth's surface.  **Albedo** The term albedo denoted the reflectivity for sunlight of a rough surface (diffusely reflecting) or of an entire planet. It is defined as the ratio of diffusely radiation to the incident radiation. Thus an albedo of 1(or 100%) would apply to a perfectly white diffuse reflector, while an albedo of zero (or 0 %) would apply to a perfectly black body. The average or overall albedo of a planet determines its mean temperature. **Irregular heating of atmosphere** Uneven heating of the planet also occurs because of the curvature of the Earth. The planet receives most of its energy near the equator, where the sun's rays are directly hitting the planet. Towards the poles, the sun's energy becomes more diffused and spread out over a greater area. The equator receives more energy from the sun than it can radiate back into space, producing a surplus of energy at 0 degrees latitude. At the poles, the planet radiates more energy out into space than it receives from the sun. There is a deficit of energy in these regions. The ultimate purpose of weather is to transfer the surplus of energy and heat from the equator to the poles, bring colder air toward the equator and find equilibrium.