Climate

C is correct. The retreating south-west monsoons travel over Bay of Bengal, and gain moisture. While exiting the sub-continent, these winds cross the peninsula in north-east to south-west direction. As they pass over Tamil Nadu, the discharge their moisture as winter rains.

A is incorrect. South West Monsoon causes heavy rainfall in Kerala during June-August months, as it is the harbinger of rainy season in the country. they do not pass over the West coast on arrival

B is incorrect. Temperate cyclones occur 35 degrees to 65 degrees north of equator, but Tamil Nadu lies under 20 degrees latitude.

D is incorrect. Local air circulation occurs close to the equator, but Tamil Nadu is too far from the equator to be affected by it.

As the monsoon bearing winds enter India from the south, they tend to lose their moisture by the time they reach the northern and western parts of the country. Consequently, the western part of the country receives less rainfall, usually under 75 cm a year.

Other options are incorrect.

D is false. The Southern part of the country is surrounded by seas. The proximity to huge water bodies exerts a moderating influence, and extreme seasonal conditions are not witnessed in the area.

A is true. This is due to the presence of water bodies in the vicinity.

B is true. The coastal winds maintain uniform temperature throughout the year

C is true. The proximity to equator ensures that the temperatures are generally high throughout the year.

When the sun shines over Tropic of Capricorn, the temperature of the air rises. Hot air expands, and lowers the pressure in the area. Consequently, North West India is at a higher pressure than the southern hemisphere. Thus, the air flows from this high pressure zone towards the Indian Ocean.

The mechanism of Indian weather is influenced by:

• Surface Pressure and Winds, which influence the weather in north India during winters.

• Jest Streams and Upper Air Circulation

• Cyclonic disturbances and tropical cyclonic depressions.

ITCZ refers to a narrow low-pressure zone located near the equator, where the trade winds from northern and southern hemisphere, converge. It forms a part of the surface wind systems, and shifts northwards during the summer season.

Breaking or Bursting of monsoons refers to the sudden arrival of south-west monsoon in the country. It is associated with violent thunder and lightning. It arrives along the western coast of Kerala in the first week of June.

Mawsynram, located on the Khasi hills, records the highest annual rainfall in the country.

A climatic region refers to an area characterised by similar climatic conditions all year round. This is primarily identified using Temperature and Rainfall data.

Koeppen uses the monthly values of temperature and precipitation to identify 5 major climatic zones, each of which has sub-zones.

Temperate cyclones originating over Mediterranean Sea, and travelling east-wards due to Jet Streams, cause rainfall in north-western India during winters.

These originate over Mediterranean Sea and gain moisture while passing over Caspian Sea and Persian Gulf.

Despite the large latitudinal extent of the country, monsoon winds exert a binding influence on the climate of the country. Since Indian farmers depend heavily on rainfall for irrigation, monsoons ties our cropping seasons together. In an agrarian country, this unification has important socio-economic consequences. While there are similar seasonal cycles across the country, with marked regional variations:

• In Rajasthan, summer temperatures might rise to 55 degrees, while it would be less than minus 45 degrees in Ladakh. (variation due to relief and altitude)

• Diurnal range of temperature is much lower in Kerala than in Rajasthan. (variation due to different distances from the sea)

• While it snows in Himalayas, it rains in the rest of the country.

• Rainfall might be as high as 400cm in Meghalaya, while it is below 10cm in Jaisalmer.

• Rainfall also occurs at different times. Kerala receives rainfall in June, whereas Tamil Nadu receives more rainfall during winter months.

This shows the great diversity in the weather conditions of India across the year.

The Indian Meteorological Department has identified the following seasons in the country:

• The Cold Weather Season

• The Hot Weather Season

• The South-West Monsoon

• The Retreating Monsoon

The Cold Weather Season:

• Arrival: The Cold Weather arrives in mid-November. December and January are the coldest months in the plains, with mean temperatures below 21 degrees.

• Cause: There are three primary causes for the cold wave in North India: (1) lack of moderating influence of sea, (2) snowfall in Himalayas and (3) Westerly winds from Caspian Seas

• Effects on Peninsular Region: There is no demarcated cold weather season due to the moderating influence of the seas.

• Rainfall: As the monsoon winds move from land to sea, they do not cause any rainfall. However, there is rainfall in some parts of the country: (1) North-western India experiences rainfall due to temperate cyclones of West Asia and (2) Tamil Nadu and southern Andhra Pradesh experiences rainfall due to north-east monsoon.