1.1. Salient Features of Indian Climate

Following are the salient features of the Indian climate:

♤ Reversal of winds – the Indian climate is characterized by the complete reversal of wind system with the change of season in a year. During the winter season winds generally blow from north-east to south-west in the direction of trade winds. These winds are dry, devoid of moisture and are characterized by low temperature and high pressure conditions over the country. During summer season complete reversal in the direction of the winds is observed and these blow primarily from south-west to north-east.

♤ Formation of Alternatively High and Low pressure areas over the land – there is a change in the atmosphere pressure conditions with the change of season. During winter season due to low temperature conditions high pressure areas is formed over the northern part of the country. On the other hand the intense heating of the land during summer season leads to the formation of a thermally induced low pressure cell over the north-western part of the country. These pressure areas control the direction and intensity of wind.

♤ Seasonal and variable rainfall – In India over 80 per cent of annual rainfall is obtained in the latter part of the summer whose duration ranges from 1-5 months in different parts of the country. Since the rainfall is in the form of heavy downpour, it creates problems of floods and soil erosion. Sometimes there is continuous rain for many days and sometimes there is a long spell of dry period. Similarly, there is a spatial variation in the general distribution of rainfall. Cherrapunji has received in a single day an amount equal to 10 years of rainfall at Jaisalmer, Rajasthan.

In fact Indian climate is so varied and complex that it denotes climatic extremes and climatic varieties. While it provides enough heat to grow crops and carry on agricultural activities all over the country it also helps in the cultivation of a number of crops belonging to tropical, temperate as well as frigid1 areas.

♤ Plurality of seasons – the Indian climate is characterized by constantly changing weather conditions. There are three main seasons but on broader consideration their number goes to six a year (winter, fall of winter, spring, summer, rainy and autumn).

♤ Unity of Indian Climate – the Himalayas and the associated mountain ranges extend to the north of India from east to west. These tall mountain ranges prevent the cold northerly winds of Central Asia from entering into India. Therefore, even the parts of India extending

1 The Polar Regions have a very cold climate. These places are sometimes called the Frigid Zones.

north of the Tropic of Cancer experience a tropical climate. These ranges force the monsoon winds to cause rainfall over India and the entire country comes under the influence of the monsoon winds. In this manner the climate in the entire country becomes monsoon type.

♤ Diversity of Indian Climate – In spite of the unity of Indian climate, it is characterized by regional differences and variations. For example, while in the summer the mercury occasionally touches 55°C in the western Rajasthan, it drops down to as low as minus 45°C in winter around Leh. These differences are visible in terms of winds, temperature, rainfall, humidity and aridity etc. These are caused by differences in the location, altitude, distance from the sea, distance from mountains and general relief conditions at difference places.

♤ Characterized by natural calamities – Due to its peculiar weather conditions especially rainfall the Indian climate is characterized by natural calamities like floods, droughts, famines and even epidemics.