Important topics in World Geography: Temperature Inversion and Pressure

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Important topics in World Geography:

World geography a subject with wide implication and huge possibilities of questions arising from this subject in various exams specially exams conducted by UPSC.

We at LST has designed special articles with important topics in World Geography for the candidates preparing for different exams.

Other Important Topics in World geography previously published can be seen here-

Agro-Climatic regions of India

Locations and Positions of Earth

Earth and Solar System

All about Moon

Atmosphere: All you need to know

Insolation, Heat budget and temperature distribution

Temperature inversion

When temperature increases with increasing altitude (instead of decreasing), it is called inversion of temperature. Mostly found in mountain valleys.

Air gets cooled and night and becomes heavier to move downwards to the valley and in the process pushing the warmer air upwards. This kind of inversion is also called drainage inversion. It is responsible for frosts at valley bottoms. This is the reason why fruit orchards in mountainous regions are laid on valley slopes instead of valley bottoms.

When inversion occurs due to rapid cooling of air near the surface it is called radiation inversion. It is common in plains in winter.

Advection inversion: When air from a warmer area blows over to a colder surface.

Frontal inversion: When warm air and cold air masses converge, the warm air will rise above the cold air. It is found in latitudes where polar air mixes with tropical air. It leads to foggy conditions.

Thermal anomaly: The difference between the average temperature of a place and the normal temperature of its latitude. They are caused by the factors mentioned before. Depicted on map using isanomals which are lines joining places with equal anomalies. In winter, oceans have postitive anomaly while continents have negative anomaly. Vice versa in summers.

The annual range of temperature is the lowest over the oceans and near the equator.

 

Thermal Equator: It is the isotherm of the highest mean annual temperature. It is generally taken as coinciding with the geographical equator. Annual range of temperature near  equator is lower than  daily range of  temperature.

You should also see-UPSC CSE topper’s geography notes for revision

Pressure

Pressure = force/area

1 milibar = 1000 dynes/sq.cm.

Measured through barometer. Aneroid barometer: no liquid. Barogram.

Distribution of Pressure:

Pressure is inversely related to temperature and altitude.

Depends on rotation of earth and effect of ascent and descent of air.

There are seven belts of pressure: the equatorial low, the subtropical high (two belts), sub-polar low (two belts) and the polar high (two belts). This is the planetary distribution of pressure.

Swing of pressure belts: Due to the shift in the position of vertical rays of the sun, the pressure belts move slightly northwards during summer solstice and southwards during winter solstice.

Interruption of pressure belts: Due to maritime and continental effects, the pressure belts are not continuous but subdivided into blocks of low and high pressure.

Isobar: lines joining places with equal pressure. Use to show distribution of pressure on map. Sea level affects here as well.

Planetary Winds

Winds are caused due to differences in pressure.

Pressure gradient: rate of decrease of pressure per unit of horizontal distance. It is measured in the direction of fall of pressure. Direction of the pressure gradient determines the direction of the wind. Its steepness determines the velocity of wind.

Coriollis effect: Deflection of winds due to the rotation of earth. Due to this the winds are deflected to their right in the northern hemisphere and to their left in the southern hemisphere. This is referred to as Farrel’s law.

 

 

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