Category: Geography

Inversion of temperature in Geography

Usually, the temperature decreases as the elevation increases. It is known as the Normal Lapse Rate.

Sometimes, this situation is reversed and the Normal Lapse Rate is inverted. It is called Inversion of Temperature in Geography.

It is the rate at which an atmosphere variable, the normal temperature in the atmosphere falls with altitude. A lapse in the sense is a gradual fall. That is in the dry air, the adiabatic lapse rate is 9.8 °C/km. It refers to the vertical component of the spatial gradient of temperature. This concept is mostly applied to the earth’s troposphere.

The Temperature inversion is also known as Thermal Inversion. It is a reversal of the behaviour of temperature in the Troposphere. In which the layer of cool air at the surface is overlaid by a layer of warmer air. The inversion is mostly of short duration and quite common.

“The ideal situation for inversion is long winter night with clear skies and still air.”

The day’s heat radiated off during the night. And during the early morning hours, the earth is cooler than the air above it. In polar areas, the temperature inversion is normal throughout the years.

Surface Inversion

The surface inversion promotes stability in the atmosphere’s lower layers. Then the lower strata of the atmosphere are filled with smoke and dust. This smoke and dust get collected under the inversion layer and spread horizontally.

During the Winter, the dense fogs in the morning are common. It lasts for a few hours until the sun warms the earth.

Air Drainage

The Dense fog also occurs in mountains and hills because of the Air Drainage. Then the cold air from the mountains and hills, which are produced at the night flows under the effect of gravity.

The cold air is heavy and dense. It acts like water and flows down the slope to pile up deeply in valley bottoms with warm air above. This phenomenon is called Air drainage and it protects plants from frost damage.

The harmful effect of temperature inversions

May result in deadly smog concentrations. When it lasts for several days, it may cause a build-up of pollution. When this pollution is prolonged, it severely affects the health of livings beings.

Conclusion

This article is written on the topic ‘temperature inversion upsc‘. This post is referred to the Ncert Geography book.

FAQ

What is DALR?

It is the rate at which the temperature of unsaturated air, becomes saturated and behaves like dry air. DALR is almost 3°C/1000 feet

Distribution of Temperature

The global distribution of temperature can well be understood by studying the temperature distribution in January and July. The temperature distribution is generally shown on the map with the help of isotherms.

Isotherms geography

The Isotherms are lines joining places having an equal temperature. In general, the effect of the latitude on temperature is well pronounced on the map, as the isotherms are generally parallel to the latitude.

The deviation from this general trend is more pronounced in January than in July, especially in the northern hemisphere. In the northern hemisphere, the land surface area is much larger than in the southern hemisphere.

Hence, the effects of landmass and the ocean currents are well pronounced. In January the isotherms deviate to the north over the ocean and to the south over the continent.

This can be seen in the North Atlantic Ocean. The presence of warm ocean currents, Gulf Stream, and North Atlantic drift, make the Northern Atlantic Ocean warmer, and the isotherms bend towards the north.

Over the land, the temperature decreases sharply and the isotherms bend towards the south in Europe. It is much pronounced in the Siberian plain. The mean January temperature along 60° E longitude is minus 20° C both at 80° N and 50° N latitudes.

The mean monthly temperature for January is over 27° C, in equatorial oceans over 24° C in the tropics and 2° C – 0° C in the middle latitudes and –18° C to –48° C in the Eurasian continental interior.

The effect of the ocean is well pronounced in the southern hemisphere. Here the isotherms are more or less parallel to the latitudes and the variation in temperature is more gradual than in the northern hemisphere.

The isotherm of 20° C, 10° C, and 0° C runs parallel to 35° S, 45° S and 60° S latitudes respectively. In July the isotherms generally run parallel to the latitude. The equatorial oceans record warmer temperatures, more than 27°C.

Over the land, more than 30°C is noticed in the subtropical continental region of Asia, along the 30° N latitude. Along the 40°, N runs the isotherm of 10° C and along with the 40° S, the temperature is 10° C.

The highest range of temperature is more than 60° C over the north-eastern part of the Eurasian continent. This is due to continentality. The least range of temperature, 3°C, is found between 20° S and 15° N.

Horizontal and vertical distribution of temperature

Horizontal distribution

The distribution of temperature across the latitudes of the surface of the earth is called Horizontal distribution. The most basic horizontal temperature variation is the decrease in air temperature slowly from the equator towards the pole.

Vertical distribution

This is the distribution of temperature in the different layers of the atmosphere at the different latitudes from the earth’s surface. The temperature slowly decreases with elevation (Increase in Height).

This vertical distribution of temperature, also the pressure, density, and composition of the atmosphere constitute the atmospheric structure. The decrease in temperature with an increase in height is because the air cools as it expands into lower pressure regions, but this does not happen everywhere.

This distribution is characterized by the vertical temperature gradient γ, which is expressed in degrees per 100 m. In the troposphere, the temperature decreases with height at an average rate of 0.6° per 100 m—that is, γ = 0.6°/100 m.

That is the average rate of temperature decrease upward in the troposphere is about 6 C per km, extending to the tropopause.

Factors controlling temperature distribution

Latitude, Distribution of Land and Water, Prevailing Winds, Ocean Currents, distance from the sea, altitude, etc.

Heating and cooling of atmosphere

The heating and cooling of the atmosphere happen in the atmosphere in different ways. The earth gets heated due to insolation. Then it transmits the heat using the long waveform to its nearest layer of the atmosphere.

The Air which is in contact with land gets heated slowly. Also, the upper layers of the atmosphere get heated by the lower layers. This process is called Conduction.

Conduction

The Conduction takes place when two bodies of unequal temperature get in contact with each other. There occurs a flow of energy between them, in the direction from warmer to cooler body.

This transfer of energy takes place until the temperature between two bodies becomes equal or their contact is broken. Conduction is an important process in heating the lower layers of the atmosphere.

Advection vs Convection Upsc

Convection

The Air, which is in contact with the earth, rises above vertically due to heating. In heated Air is in the form of current and further transmits the heat of the atmosphere. This process of heating the atmosphere is called convection.

Convection transfer of energy is confined only to the troposphere.

Advection

The transfer of heat through the horizontal movement of air is called Advection. The horizontal movement of air is relatively more important than the vertical movement.

In middle latitudes, most diurnal (day and night) variations in daily weather are caused by advection alone.

In tropical regions particularly in northern India during the summer season, local winds called ‘loo’ are the outcome of the advection process.

Terrestrial Radiation

The insolation received by the earth is in short waves forms and heats up its surface. The earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in the long waveform.

This energy heats up the atmosphere from below. This process is known as terrestrial radiation.

The longwave radiation is absorbed by atmospheric gases, particularly carbon dioxide and other greenhouse gases. Thus, the atmosphere is indirectly heated by the earth’s radiation.

The atmosphere in turn radiates and transmits heat to space. Finally, the amount of heat received from the sun is returned to space, thereby maintaining a constant temperature at the earth’s surface and in the atmosphere.

Heat Budget of the Planet Earth

The earth as a whole does not accumulate or lose heat. It maintains its temperature.

This can happen only if the amount of heat received in the form of insolation equals the amount lost by the earth through terrestrial radiation. Consider that the insolation received at the top of the atmosphere is 100 per cent.

While passing through the atmosphere some amount of energy is reflected, scattered, and absorbed.

Only the remaining part reaches the earth’s surface. Roughly 35 units are reflected back to space even before reaching the earth’s surface. Of these, 27 units are reflected back from the top of the clouds and 2 units from the snow and ice-covered areas of the earth.

The reflected amount of radiation is called the albedo of the earth. The remaining 65 units are absorbed, 14 units within the atmosphere and 51 units by the earth’s surface.

The earth radiates back 51 units in the form of terrestrial radiation.

Of these, 17 units are radiated to space directly and the remaining 34 units are absorbed by the atmosphere (6 units absorbed directly by the atmosphere, 9 units through convection and turbulence, and 19 units through latent heat of condensation).

48 units absorbed by the atmosphere (14 units from insolation +34 units from terrestrial radiation) are also radiated back into space.

Thus, the total radiation returning from the earth and the atmosphere respectively is 17+48=65 units which balances the total of 65 units received from the sun.

This is termed the heat budget or heat balance of the earth. This explains, why the earth neither warms up nor cools down despite the huge transfer of heat that takes place.

Variation in the Net Heat Budget at the Earth’s Surface

As explained earlier, there are variations in the amount of radiation received at the earth’s surface.

Some part of the earth has a surplus radiation balance while the other part has a deficit.

The figure shows that there is a surplus of net radiation balance between 40 degrees north and south and the regions near the poles have a deficit.

The surplus heat energy from the tropics is redistributed polewards and as a result, the tropics do not get progressively heated up due to the accumulation of excess heat, or the high latitudes get permanently frozen due to excess deficit.

FAQ

Conduction in geography?

The earth is heated by insolation and then the earth transmits the heat to the atmosphere layers in form of the long waves. The air in contact with land gets heated gradually and the upper layers in contact with the lower layers get heated too. This over process is known as Conduction.

References

• https://ncert.nic.in/ncerts/l/kegy209.pdf

Solar Insolation

Solar Insulation is the amount of solar radiation incident upon a unit horizontal surface over a specified time for a given place. It mostly depends on the solar zenith angle and also on the ratio (d/d_m) of the actual distance to the mean distance of the Earth from the Sun.

The surface of the earth receives solar radiation in form of short wavelengths. This energy received by the earth is known as Incoming Solar Radiation also called Insolation.

Insolation on Earth’s Surface

The earth gets a very small amount of solar energy. This is because the earth is a geoid that resembles a sphere. Due to this, the sun’s rays fall obliquely at the top of the atmosphere.

What time of year is insolation greatest?

The solar output received at the top of the atmosphere varies slightly in a year due to variations in the distance between the earth and the sun.

Aphelion

During its revolution around the sun, the earth is farthest from the sun (152 million km) on the 4th of July. This position of the earth is called aphelion.

Perihelion

On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion. Therefore, the annual insolation received by the earth on 3rd January is slightly more than the amount received on 4th July.

However, the effect of this variation in the solar output is masked by other factors like the distribution of land and sea and atmospheric circulation.

Hence, this variation in the solar output does not have a great effect on daily weather changes on the surface of the earth.

Variability of Insolation at the Surface of the Earth

The amount and the intensity of insolation vary during a day, in a season, and in a year.

The factors that cause these variations in insolation are :

• The rotation of the earth on its axis
• The angle of inclination of the sun’s rays
• The length of the day
• The transparency of the atmosphere
• The configuration of land in terms of its aspect.

But the transparency of the atmosphere and configuration of the land has less influence.

Rotation of the Earth on its Axis

The fact that the earth’s axis makes an angle of 66 with the plane of its orbit around the sun has a greater influence on the amount of insolation received at different latitudes.

The angle of inclination of the sun’s rays

The second factor that determines the amount of insolation received is the angle of inclination of the rays. This depends on the latitude of a place. The higher the latitude the less the angle they make with the surface of the earth resulting in slant sun rays.

The area covered by vertical rays is always less than the slant rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases.

Moreover, the slant rays are required to pass through a greater depth of the atmosphere resulting in more absorption, scattering, and diffusion.

Transparency of the Atmosphere

The atmosphere is largely transparent to short-wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth’s surface.

Within the troposphere water vapour, ozone, and other gases absorb much of the near-infrared radiation.

Very small-suspended particles in the troposphere scatter visible spectrum both to space and towards the earth’s surface. This process adds colour to the sky. The red colour of the rising and the setting sun and the blue

Spatial Distribution of Insolation at the Earth’s Surface

The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. The Equator receives comparatively less insolation than the tropics.

Generally, at the same latitude, the insolation is moreover the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer.

FAQ

Why is less insolation received at the equator in June?

During June, especially around June 21 of the year, the position of the earth in its orbit is inclined directly towards the sun. This is called the Summer solstice in the Northern Hemisphere.

As a result during June, maximum insolation is received at the Tropic of Cancer, as Sun is directly perpendicular to the Tropic of Cancer. The Equator is below the Tropic of Cancer, and thereby receives less insolation at the equator in June.

The Composition of Atmosphere are Gases, Water, Vapour and Dust Particles and the below table shows details of different gases in the air particularly in the lower atmosphere. Next, we’ll look into its chemical composition.

Chemical composition of atmosphere

In the atmosphere of the earth, the air is a mixture of gases that contains 78% Nitrogen, 21% oxygen, and 1% other gases which include Carbon dioxide, Argon, Neon, Helium, etc and also water vapour.

Composition of gases in Atmosphere

The proportion of gases gets changed in higher layers of the Atmosphere, in a way that the oxygen gets almost negligible in quantity at the height of 120km.

Carbon Di Oxide

Carbon dioxide and water vapor are found only up to the height of 90km from the earth’s surface. Carbon dioxide is a very important gas in the Earth’s Atmosphere, as it is transparent to the incoming solar radiation and it is opaque to the outgoing solar radiation.

This nature of Carbon dioxide absorbs some part of terrestrial radiation and reflects it back to the earth’s surface and it is the main factor for the Green House Effect.

The volume of Carbon dioxide keep raising for the past few decades due to human activities and other gases’ volume remains constant. This increase in the volume of Carbon dioxide in the atmosphere increases the temperature of the air.

Ozone

Ozone is one of the important constituents in the atmosphere and it is found between 10 to 50 km above the earth’s surface. This gas acts as a filter and absorbs the ultraviolet ray from the sun rays and prevents it from entering the earth’s surface.

Water Vapour

The water vapour is also a variable gas in the atmosphere, that decreases with altitude and it accounts for up to 4% by volume in warm and wet tropics.

But its volume is less than 1% in the cold and dry desert and also in the polar regions. It is to be noted that the Volume of the Water Vapour decreases from the Equator to towards the poles.

Another property of Water Vapour is, it acts similar to Carbon dioxide, by absorbing the parts of the insolation from the sum and preserves the earth’s radiated heat.

Just like a blanket, it neither allows the earth to become too hot or too cold. It also contributes to the stability and instability in the air.

Dust Particles

The atmosphere has enough capacity to keep the small solid particles and it originates from various sources.

Some of these small solid particles include sea salts, fine soil, smoke soot, ash, dust, pollen, and dust from meteors. These small solid particles called Dust particles are normally concentrated in the lower layers of the atmosphere.

And sometimes, convectional air currents transport the dust particles to greater heights.

The concentration of dust particles is high in the subtropical and temperate regions and it is because dry winds are higher in these regions compared to the equatorial and polar regions.

The dust and salt particles act as hygroscopic nuclei, using which the water vapor condenses to produces clouds.

Distribution of alluvial soil in India

Alluvial soil is distributed widely in the Northern Plains of India, also in eastern coastal plains in India such as the Mahanadi delta, Godavari delta, Krishna delta and Kaveri delta.

In Northern Plains, it is found throughout the Indo-Gangetic plain and especially along with the lower courses of India’s major rivers such as their deltas.

Areas of Distribution

It is the highest with about 43%. The region which is rich in Alluvial soil is the Great Northern Plains such as the Plains of river Ganga. This is because of the Himalayas, the rivers from where it is originated.

The Ganga carries, transports the soils and fine sediments, by its flowing water and deposits the silt, fine sediment of soil and rocks along their banks.

By a narrow corridor in Rajasthan, they extend into the Gujarat plains.

In the peninsular regions, these are distributed along the eastern coast and river valley.

In the Upper and Middle Ganga plain, two varieties of Alluvial soils developed and they are Khadar and Bhangar. The Khadar is new alluvium, which is deposited annually and consists of fine silts soil.

Bhangar is older alluvium, and it is deposited away from the flood plains. Both these Khadar and Bhangar have calcareous concretions (Kankars). These soils are distributed along the lower and middle Ganga plains and Brahmaputra valley.

The Alluvial soil distribution in India, states are Assam, Bihar, Chandigarh, Delhi, Haryana, Himachal Pradesh, Jammu and Kashmir, Madhya Pradesh, West Bengal.

In the Peninsula, the deltas of Mahanadi, Godavari, Krishna and Kaveri rivers.

The Alluvium is very fertile has a good proportion of potash, phosphoric acid and lime which are ideal for the growth of sugarcane, paddy, wheat, and other cereals and pulses.