Geography [2 Mark Question Answer]

In summer in the tropical region due to die shifting of Doldrums, the low-pressure region is strongly originated between 8° and 20° N and S. They mainly originate in the China sea and surrounding area. In Bangla Desh, these are known as ‘KalBaisakhi’ meaning ‘Time of Death’ and cause heavy calamities and destruction. These are known as ‘hurricanes’ in North America, ‘Typhoons’ in China, ‘willy willies’ in Australia.

Variable winds change their direction and force from place to place due to changing the pressure system. These blow for a short time or for a few days. These are cyclones and anticyclones. These are the circular winds with low pressure and high pressure in the center respectively.

Periodic winds blow at regular intervals or in regular cycles. They are winds that result from localised differences in pressure and temperature. For example, land and sea breezes and the seasonal winds.

In the northern hemisphere, the winds deflect towards the right and in Southern hemisphere deflect towards left due to the effect of the rotation of the earth, e.g. the trade winds take the Southwest direction in place of southern direction in northern tropical belt and in southern tropical belt these winds take northwest direction in place of northern direction.

Due to the lowest and highest temperatures recorded in January and July, respectively the pressure areas are also affected, so it is preferred to display the distribution of pressure distinctly in January and July.

Many factors like the slope of the land, presence of winds, and the temperature affect the pressure of air vertically. The rate of decrease is 100 millibars per 1000 meters of height gained. There is a thin air cover at high altitudes, so the percentage and amount of oxygen are also less.

 Monsoons — are the periodic seasonal winds blowing in the regions of South East Asia and Northern Australia. The word monsoon is derived from the Arabic word ‘Muslim’ meaning ‘Season’, on account of deeply affecting the seasons of the particular region.

Two types of barometers are used for measuring pressure, e.g. Fortin’s Barometer and Aneroid Barometer. The main difference is that Fortin’s Barometer is filled with mercury, while the Aneroid Barometer is without any liquid. Fortin’s Barometer consists of a long narrow tube filled with mercury, while Aneroid is in the round shape like a watch.

Due to the low pressure created in the Northern Indian subcontinent and high-pressure center located in the Indian ocean, the Monsoons start to blow from the ocean to the Indian landmass taking a direction from southwest to northeast in summer seasons.

The name of the cyclones is different in different parts of the world on the basis of the local languages e.g. hurricanes in America, typhoons in China, and Japan, meaning the destructive horrible cyclonic winds.

Chinook in North America blowing eastwards from the Rockies slopes make the climate of Central Plains ideal for animal rearing and agriculture.
Foehn: winds descending down from the Alps makes the agriculture successful in PO basin and
Mistral: from the Alps along with France towards the Mediterranean sea brings the temperature suddenly down instead of bright sunshine.

Doldrums is a low-pressure belt along the equator from 5°N to 5°S. In this belt due to a high amount of evaporation, the atmosphere is very calm and quiet due to no circulation of winds and continuous rising air mass creating a hollow like condition in this belt. In spite of air pushed towards the equator, it is immediately deflected to right and left, creating a vacuum-like condition resulting in a belt of calm named as ‘Doldrums’

In tropical regions, the air is greatly humid due to excess of evaporation creating low-pressure conditions, while the cold regions with less humidity are high-pressure areas. So, the humid air is lighter than dry air.

When the temperature increases and the air start to rise upwards. creating a low-pressure area, but when the temperature decreases, the air starts to sink downwards creating a high-pressure area on the land surface. So, the temperature and pressure are inversely related to one another.

Mediterranean lands come along the belt of Westerlies along 30°S in place of 40°N in winter. So, the Mediterranean countries along 30°N get ample rainfall. Similarly in the Southern Hemisphere the Westerlies blow along 30°S, in winter, so, the southern Mediterranean countries get winter rainfall.

As the air becomes thinner with increasing height, so, the air pressure also decreased. The rate of decrease is 100 millibars per 1000 meters of height gained. So mountain hikers take an oxygen cylinder with them to compensate the air inhaled.

In the Southern Hemisphere, there is an open ocean for free movement along the belt of Westerlies. These blow with a roaring sound and great speed along 40°S. and are known as ‘Roaring Forties’.