Temperature and Temperature inversion

Temperature & Temperature inversion

Temperature - It is the measure of the degree of hotness or coldness of a body.

Factors Affecting the distribution of temperature on the Earth.

1.   Insolation - 

        (a) Angle of Incident

        (b) Length of the day

        (c) Transparency of the Atmosphere

Note - Although the Sun's rays are vertical along the Equator throughout the year, the Equator will not have the maximum temperature because of cloud cover. The maximum temperature is experienced at Sub-tropical regions.

2.   Nature of the Surface (Specific heat of the surface) -

• Specific heat - It is the amount of the heat required to increase the temperature of the surface by 1℃.
• Specific hear of land is less than specific heat of water. That's why land gets heated up faster and also cools faster than that of water.
• The Earth behaves differently depending on the specific heat of the surface.
• The land surface with lower specific heat heats up more rapidly and intensely than water surface and also land cools rapidly.

3.   Albedo - 

• The surface with higher Albedo reflects more insolation resulting in less absorption of the heat.

4.   Distance from the ocean/sea (Continentality effect) - 

• Those regions which are located in the interior will have higher range of temperature, i.e., summer is too hot and winter is too cold than coastal regions which are near to the ocean.
• Example - Delhi experiences hotter summer and colder winter.

5.   Distribution of Continents -

• Northern hemisphere with more proportion of land than oceans experiences higher range of temperature than Southern hemisphere where there is more water surface.

6.   Altitude -

• The temperature decreases with increase in altitude.

7.   Wind -

• Winds transport temperature prevailing in one area to another.
• Example - Planetary winds

8.   Ocean Currents -

• Ocean currents transport warm water from the tropics to polar regions and vice-versa, helping in global distribution of temperature.

Isotherms - Line connecting points having same temperature at a given time at the surface of the Earth is called Isotherm.

Distribution of Temperature -

• Movement of Isotherms - Isotherms moves northwards between January to July and moves southwards between July to January.
• Bending of Isotherms - Isotherms bend equatorward over the ocean in July and bends away from the equator (poleward) over the ocean in January.
• Seasonal variations are less marked in the Southern hemisphere than over Northern hemisphere. It means the Northern hemisphere will experience higher summer temperature and lower winter temperature than Southern hemisphere.
• Range of temperature (between summer and winter) increases as we move from equator towards the poles.

Terminology

1. Mean daily temperature - It is the average temperature of a day and is equals to Sum of temperatures of 24 hours divided by 24.
2. Mean monthly temperature - It is the mean temperature of the mean daily temperature of a month and is equals to the sum of mean daily temperatures of 30 days divided by 30.
3. Diurnal range - It is the difference of maximum temperature and minimum temperature experienced in a day.
4. Annual range - It is the difference of highest monthly mean temperature and the lowest monthly mean temperature.

Highest recorded temperature = 58℃ @ Al-Azizia, Libya & 56.7℃ @ Death valley, USA.

Lowest recorded temperature = -8.8℃ @ Vostock Station, Antarctica.

Temperature inversion- The average rate of decrease of temperature as we move upward in the atmosphere is known as Normal Lapse rate. 

But during some certain conditions in the atmosphere, it may lead to a reversal of normal lapse rate, i.e., temperature increases with increase in altitude and this behaviour is known as Temperature inversion.

Types of Temperature inversion 

1.   Radiation inversion

Conditions required - Winter night (longer night), Clear sky (no cloud to reflect back the radiation) and calm windless condition.

• It is produced during a long winter night, clear sky (cloudless) and calm air condition.
• The land surface radiates heat more rapidly during the night, therefore the air just above the surface is colder and is overlaid by the warmer air.
• Therefore, temperature increases with the altitude creating a temperature inversion layer.
• It is more frequent in winter nights or snow covered areas.

2.   Air drainage inversion 

• The mountain slopes experiences rapid fall in the temperature during night time.
• However, the valley sides and floor will be warmer due to radiation exchange.
• The colder and denser air along side the hills start to slide/sink to the valley floor due to gravity.
• The warmer air therefore rests over the cooler air producing temperature inversion.
• That's why Hill Stations are located at the top of the mountains not on the valley side.

3.   Advection inversion

• It is produced when a thick layer of warm air mass passes over a cold water surface or land making the air near to the surface cold.

4.   Frontal inversion 

• It is caused due to the frontal convergence of air masses of different temperature.
• The warmer air mass is forced upward from the ground by undercutting of cold air mass leading to temperature inversion where warmer air is lying over the colder air.

Significance of Temperature inversion -

1. Formation of fog - Temperature inversion results in the formation of fog which reduces the visibility disturbing the entire transportation network.
2. When fog gets mixed up with the smoke, it results in the formation of Smog, which is very harmful for the environment.
3. The clear and stable conditions reduce the dispersal of pollutants causing them to be trapped for longer duration at the same place.
4. Temperature inversion leads to stability in the atmosphere and prevents the convection of air and hence prevents precipitation.
5. Along the mountainous region, the valley floor is avoided for human settlement and fruit orchards. Example - Coffee plantation is avoided in valley in Brazil.

PYQs

1.   Normally, the temperature decreases with the increase in height from the Earth's surface because -

1. Temperature can be heated upward only from the Earth's surface.
2. There is more moisture in the upper atmosphere.
3. The air is less dense in upper atmosphere.

Ans - 1 and 3 only

2.   The annual range of temperature in the interior of the continents is high as compared to coastal areas. What is/are the reasons/reasons?

1. Thermal difference between land and water.
2. Variation in altitude between continents and oceans.
3.  Presence of strong winds in the interior.
4. Heavy rains in the interior as compared to the coasts.

Ans - 1 only

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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own. 

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