atmospher and temperature

8/11/2019 Atmospher and Temperature

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Atmosphere - Composition and Structure

99 per cent of the total mass of the atmosphere is confined to the height of 32 km from the earths surface.

The atmosphere is composed of gases, water vapour and dust particles.

Nitrogen (78.1%) and Oxygen (20.9%) are the two main gases of the atmosphere.

Other gases like Argon, carbon dioxide, hydrogen, neon, helium, krypton, Ozone etc. form the remaining part of

atmosphere.

Oxygen will be almost in negligible quantity at the height of 120 km.

Carbon Dioxide : It is transparent to the incoming solar radiation but opaque to the outgoing terrestrial

radiation. It is largely responsible for the green house effect.

Ozone : Ozone is another important component of the atmosphere found between 10 and 50 km above the

earths surface and acts as a filter and absorbs the ultra-violet rays.

Gases of the Atmosphere :

Water vapour is the source of all kinds of precipitation. Its maximum amount in the atmosphere could be upto

4 percent.

The amount of water vapour goes on decreasing from low latitudes to high latitudes, also decreases with

altitude.

Evaporation takes place in the oceans, seas, rivers, ponds and lakes while transpiration takes lace from the

plants, trees and living beings.

Water Vapour :

Dust particles are generally concentrated in the lower layers of the atmosphere. They are found in the form of

sand, smoke and oceanic salt.

Dust and salt particles act as Hygroscopic(absorbing moisture) nuclei around which water vapour condenses to

produce clouds.

Dust Particles :

Structure of the AtmosphereAtmosphere extends upto about 1600 kilometres from the earths surface. 97 percent of the total amount of weight of

the atmosphere is limited upto the height of about 30 kilometres.

The atmosphere can be divided into five layers according to the diversity of temperature and density.

Lowest layer of the atmosphere; 18 kms on the equator and 8 kms on the poles; higher height at the equator is

due to presence of hot convection currents that push the gases upward.

All kinds ofweather changes take place only in this layer; air never remains static in this layer. So this layer is

called changing sphere or Troposphere.

Environmental temperature decreases with increasing height of atmosphere. It decreases at the rate of 1C at

the height of 165 metre. This is called Normal lapse rate.

Upper limit of the troposphere is called tropopause. The Temperature here is nearly constant, and hence, it is

called the tropopause.

Troposphere :1.

It is found above the tropopause and extends up to a height of 50 km. One important feature of the

stratosphere is that it contains the ozone layer.

The temperature increases slowly with increase in the height. The temperature increases due to the presence

of ozone gas in the upper part of this layer.

Weather related incidents do not take place in this layer. The air blows horizontally here. Therefore this layer is

considered ideal for flying of aircrafts.

Stratosphere :2.

It lies above the stratosphere, which extends up to a height of 80 km. In this layer, once again, temperature

starts decreasing with the increase in altitude and reaches up to minus 100C at the height of 80 km.

The upper limit of mesosphere is known as the mesopause.

Mesosphere :3.

It is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as

ions.

Temperature starts increasing again with increasing height in this layer.

Ionosphere :4.

Atmosphere and Temperature08 July 2014 18:04

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Radio waves are reflected back on the earth from this sphere and due to this radio broadcasting has become

possible.

Exosphere : Outermost layer. Gases are very sparse in this sphere due to the lack of gravitational force.5.

Solar Radiation, Heat Balance, and Temperature

Earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from

the sun. As a result, the earth neither warms up nor does it get cooled over a period of time.

Thus, the amount of heat received by different parts of the earth is not the same. This variation causes pressure

differences in the atmosphere. This leads to transfer of heat from one region to the other by winds.

Solar Radiation :

The earths surface receives most of its energy in short wavelengths. The energy received by the earth is known as

incoming solar radiation in short insolation.

Earth is farthest from the sun (152 million km on 4th July). This position of the earth is called aphelion.

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.

Variability of Insolation at the Surface of the Earth

the rotation of earth on its axis;(i)

the angle of inclination of the suns rays : higher the latitude the less is the angle they make with the surface of

the earth resulting in slant sun rays.

(ii)

Moreover, the slant rays are required to pass through greater depth of the atmosphere resulting in more

absorption,scattering and diffusion.

the length of the day : The longer the duration of the day, the greater is the amount of insolation received.(iii)

the transparency of the atmosphere : transparency depends upon cloud cover, its thickness, dust particles and

water vapour, as they reflect, absorb or transmit insolation

(iv)

the configuration of land in terms of its aspect.(v)

The factors that cause these variations in insolation are :

Very small-suspended particles in the troposphere scatter visible spectrum. Red colour of the rising and the setting

sun and the blue colour of the sky are the result of scattering of light within the atmosphere.

Maximum insolation is received over the subtropical deserts, where the cloudiness is the least.

Equator receives comparatively less insolation than the tropics.

Heating and Cooling of Atmosphere :

Earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave

form.

When the source of heat transmits heat directly to an object through heat waves, it is known as radiation

process.

Temperature of an object determines the waves length of radiation. Temperature and wave length are

inversely related. Hotter the object shorter is the length of the wave.

Atmosphere is transparent to short waves and opaque to long waves. Hence energy leaving the earths

surface i.e. terrestrial radiation heats up the atmosphere more than the incoming solar radiation i.e.

insolation.

Radiation :1.

Heat energy flow from the warmer object to the cooler object and this process of heat transfer is known

as conduction.

The conduction in the atmosphere occurs at zone of contact between the atmosphere and the earths

surface. It only affects the air close to the earths surface.

Conduction :2.

Air in contact with the earth rises vertically on heating in the form of currents and further transmits the

heat of the atmosphere.

This process ofvertical heating of the atmosphere is known as convection. It is confined only to the

troposphere.

Convection :3.

Winds carry the temperature of one place to another. This process ofhorizontal transport of heat by

winds is known as advection.

Horizontal Movement is relatively more important than vertical movement.

In tropical regions particularly in northern India during summer season local winds called loo is the

Advection :4.

There are four heating processes directly responsible for heating the atmosphere. They are :



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outcome of advection process.

The annual mean temperature on the surface of the earth is always constant. Heat budget is the balance

between insolation (incoming solar radiation) and terrestrial radiation.

The amount of insolation received is directly related to latitudes. In the tropical region the amount of insolation

is higher than the amount of terrestrial radiation. Hence it is a region of surplus heat. In the polar regions

the heat gain is less than the heat loss. Hence it is a region of deficit heat.

Thus the insolation creates an imbalance of heat at different latitudes. This is being nullified to some extent by

winds and ocean currents, which transfer heat from surplus heat regions to deficit heat regions. This iscommonly known as latitudinal heat balance.

The reflected amount of radiation is called the albedo of the earth.

Heat Budget :

Temperature and its Distribution :

Distribution of temperature varies both horizontally and vertically.

Distribution of temperature across the latitudes over the surface of the earth is called its horizontal distribution.

On maps it is represented by Isotherms - the lines connecting the points that have equal temperatures.

Factors affecting the distribution of temperature :

Latitude : Temperature of a place depends on insolation received. Insolation varies according to latitude hence

temperature also varies accordingly.

Altitude : Places near the sea-level record higher temperature than the places situated at higher elevations.

Mountains are cooler than plains.

Land gets heated more rapidly and to a greater degree than water during sunshine. It also cools down

more rapidly than water during night. Hence, temperature is relatively higher on land during day time and

it is higher in water during night.

There are differences in the rate of heating of different land surfaces. A snow covered land as in polar

areas warms very slowly because of the large amount of reflection of solar energy. A vegetation covered

land doesnt get excessively heated because a great amount of insolation is used in evaporating water

from the plants.

Land and Sea Contrast :

Places that get warm air-masses and ocean currents experience higher temperatures than those which get

cold air and ocean currents.

Air-mass and Ocean currents :

Colour, texture and structure of soils modify temp to a great degree. Black, yellow and clayey soils absorb

more heat than sandy soils.

Nature of Soil :

The angle of incidence of suns rays is greater along a gentler slope and smaller along a steeper slope. So

temp are more on gentler slopes than on steeper slopes.

Slope and Aspect :

The temperature distribution is shown on the map with the help of isotherms. The Isotherms are lines

joining places having equal temperature.

Isotherms are generally parallel to the latitude.In northern hemisphere the land surface area is much larger than in the southern hemisphere. Hence, the

effects of land mass 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 in the

northern hemisphere. The opposite happens over the southern hemisphere.

Gulf Stream and North Atlantic drift, make the Northern Atlantic Ocean warmer and the isotherms bend

towards the north.

Horizontal Distribution of temp in january and July :

Horizontal Distribution of Temperature :



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Southern Hemisphere has more ocean than land, so isotherms are more or less parallel to the latitudes.

Difference between the average temperatures of warmest and the coldest months is known as annualrange of temperature.

Verkhoyansk in Siberia records 66C the highest annual range of temperature in the world. Its lowest

average winter temperature is-50C. Hence it is aptly called cold pole of the earth.

Long winter night, clear sky, dry air and absence of winds leads to quick radiation of heat from the earths

surface, as well as from the lower layers of

the atmosphere.

This results in the cooling of the air near the earths surface. The upper layers which lose their heat not so

quickly are comparatively warm.

Hence the normal condition in which temperature decreases with increasing height, is reversed.

Temperature increases with increasing height temporarily or locally. This phenomena is termed as inversion of

temperature.

The phenomenon of inversion of temperature is especially observed in intermontane valleys.

During winters the mountain slopes cool very rapidly due to the quick radiation of heat. The air resting above

them also becomes cold and its density increases. Hence, it moves down the slopes and settles down in the

valleys. This air pushes the comparatively warmer air of valleys upwards and leads to the phenomenon of

inversion of temperature.

Sometimes the temperature falls below freezing point in the valleys leading even to the occurance of frost.

In contrast, the higher slopes remain comparatively warmer. That is why plantations are made on higher slopes.

Thermal inversions can create extreme weather conditions. A good example of this is freezing rain. The snow

will melt as it moves through a warm inversion layer. Then when it hits the cold layer below it will become super

cooled, or cooled below freezing while remaining liquid, and turn to ice when it lands on things like trees and

cars. This creates freezing rain and ice storms. Intense thunderstorms and tornadoes can also be the result of atemperature inversion.

The worst thing about thermal inversion is that smog and air pollution can be trapped near the ground and stay

there until the thermal inversion is gone.

Inversion of Temperature :

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