About

• The interaction of insolation with the atmosphere and the earth’s surface creates heat which is measured in terms of temperature.
• While heat represents the molecular movement of particles comprising a substance, the temperature is the measurement in degrees of how hot (or cold) a thing (or a place) is.

Factors Controlling Temperature Distribution

1. the latitude of the place;
2. the altitude of the place;
3. distance from the sea, the air- mass circulation;
4. the presence of warm and cold ocean currents;
5. Local aspects.

1. The latitude: The temperature of a place depends on the insolation received. It has been explained earlier that the insolation varies according to the latitude hence the temperature also varies accordingly.

2. The altitude- The atmosphere is indirectly heated by terrestrial radiation from below.

• Therefore, the places near the sea-level record higher temperature than the places situated at higher elevations.
• In other words, the temperature generally decreases with increasing height.
• The rate of decrease of temperature with height is termed as the normal lapse rate. It is 6.5°C per 1,000 m.

3. Distance from the sea: Another factor that influences the temperature is the location of a place with respect to the sea.

• Compared to land, the sea gets heated slowly and loses heat slowly.
• Land heats up and cools down quickly.
• Therefore, the variation in temperature over the sea is less compared to land.
• The places situated near the sea come under the moderating influence of the sea and land breezes which moderate the temperature

4. Air-mass and Ocean currents: Like the land and sea breezes, the passage of air masses also affects the temperature.

• The places, which come under the influence of warm air-masses
• Experience higher temperature and the places that come under the influence of cold air- masses experience low temperature.
• Similarly, the places located on the coast where the warm ocean currents flow record higher temperature than the places located on the coast where the cold currents flow.

Distribution Of Temperature

• The global distribution of temperature can well be understood by studying the temperature distribution in January and July.
• The Isotherms are lines joining places having equal temperature.
• 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. This can be seen on 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 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 temperature, 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 the 40° S the temperature is 10° C.

Inversion Of Temperature

• Normally, temperature decreases with increase in elevation. It is called normal lapse rate.
• The situations are reversed and the normal lapse rate is inverted. It is called Inversion of temperature.
• Inversion is usually of short duration but quite common nonetheless.
• A long winter night with clear skies and still air is ideal situation for inversion.
• The heat of the day is radiated off during the night, and by early morning hours, the earth is cooler than the air above.
• Over polar areas, temperature inversion is normal throughout the year.
• Surface inversion promotes stability in the lower layers of the atmosphere. Smoke and dust particles get collected beneath the inversion layer and spread horizontally to fill the lower strata of the atmosphere.
• Dense fogs in mornings are common occurrences especially during winter season.
• This inversion commonly lasts for few hours until the sun comes up and beings to warm the earth.
• The inversion takes place in hills and mountains due to air drainage.
• Cold air at the hills and mountains, produced during night, flows under the influence of gravity.
• Being heavy and dense, the cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called air drainage.
• It protects plants from frost damages.