Geography [3 Mark Question Answer]

Tropical Cyclones :

1. Tropical cyclones are produced mainly over the sea.
2. They generally originate in the tropical region between 8° and 20°N and S.

Temperature Cyclones :

1. Temperate cyclones are produced both on land and on the sea.
2. They originate in the mid latitudinal region between 35° latitude and 65° latitude.

The three chief types of winds are Trade winds, Westerlies, and polar winds.
Trade winds: blow along the tropical belt from sub-tropical High to equatorial low-pressure belts. The name trade is given due to the last time when trade ships were sailed according to the direction of these winds.
Westerlies: are the winds blowing from the western direction. These are south-westerly in northern and north-westerly in the southern hemispheres.
The Polar: winds are icy cool winds blowing from poles towards Circum polar low-pressure belts, which are also known as Blizzards.

Atmospheric Pressure refers to the force per unit area exerted against a surface by the weight of the air above that surface. The pressure is expressed in millibars (mb) and measured with a mercury barometer. The average atmospheric pressure at sea level is 1013.25 mb or 760 mm (the) height of the column of mercury in a barometer at sea level). Atmospheric Pressure decreases with height.

Due to the earth’s changing aspect with respect to the sun, the pressure belts shift northwards by 5° in summer and southwards in winter resulting in particular seasonal changes, e,g. The cold waves blow in India in winter due to the sub-tropical belt shifting along 30°N touching the Himalayas. On the other hand in summer the trade winds become powerful in India and push the monsoon winds from east to west in Northern Plain of India.

Summer Monsoon :

1. These blow in the summer season from July to September.
2. These bring heavy rainfall with thunder lightning

Winter Monsoon :

1. These blow in winter mainly in December and January.
2. These bring dry cold weather and cold waves.

Permanent winds :

1. These blow throughout the year.
2. These are named Trade winds, Westerlies, and Polar winds.

Periodic winds :

1. These blow in particular areas and seasons.
2. These are named monsoon winds, Chinook, Foehn, Mistral winds, etc.

Vertical Variation :

1. The Temperature decreases as the height increases
2. The rate is 1°C for every 166 metres of height.

Horizontal Variation :

1. The temperature decreases as the latitude increases.
2. Highest temperatures are found along Equatorial and tropical regions, while the least temperature is recorded in polar areas.

Isobars :

1. These are the lines joining the places of the same air pressure.
2. The closeness of these lines indicates the intensity of pressure.

Isotherms :

1. These are the lines joining the place of the same air temperature.
2. The closeness of these lines indicates the intensity of temperature.