India - Environment
India is a country of great diversity with a wide range of landform types, including major mountain ranges, deserts, rich agricultural plains, and hilly jungle regions. Indeed, the term Indian subcontinent aptly describes the enormous extent of the earth's surface that India occupies, and any attempt to generalize about its physiography is inaccurate. Diversity is also evident in the geographical distribution of India's ethnic and linguistic groups. In ancient times, the major river valleys of the Indo-Gangetic Plain of South Asia were among the great cradles of civilization in Asia, as were the valleys of the Tigris and Euphrates rivers in West Asia and the Huang He (Yellow River) in East Asia. As a result of thousands of years of cultural and political expansion and amalgamation, contemporary India has come to include many different natural and cultural regions.
The Himalayas (and the nations of Nepal and Bhutan) form India's northern frontier with China. Pakistan borders India to the west and Bangladesh (formerly East Pakistan) to the east.
When the 1991 national census was taken, India's population was approximately 846.3 million. The annual population growth rate from 1981 to 1991 was 2 percent. Accounting for only 2.4 percent of the world's landmass, India is home to 16 percent of the world's population. Every sixth person in the world in the early 1990s was an Indian. It is generally assumed that India's population will surpass the 1 billion mark some time before the next census in 2001. In July 1995, the population was estimated at 936.5 million.
India's total land mass is 2,973,190 square kilometers and is divided into three main geological regions: the Indo-Gangetic Plain, the Himalayas, and the Peninsula region. The Indo-Gangetic Plain and those portions of the Himalayas within India are collectively known as North India. South India consists of the peninsular region, often termed simply the Peninsula. On the basis of its physiography, India is divided into ten regions: the Indo-Gangetic Plain, the northern mountains of the Himalayas, the Central Highlands, the Deccan or Peninsular Plateau, the East Coast (Coromandel Coast in the south), the West Coast (Konkan, Kankara, and Malabar coasts), the Great Indian Desert (a geographic feature known as the Thar Desert in Pakistan) and the Rann of Kutch, the valley of the Brahmaputra in Assam, the northeastern hill ranges surrounding the Assam Valley, and the islands of the Arabian Sea and the Bay of Bengal.
Climate
The Himalayas isolate South Asia from the rest of Asia. South of these mountains, the climate, like the terrain, is highly diverse, but some geographers give it an overall, one-word characterization--violent. What geographers have in mind is the abruptness of change and the intensity of effect when change occurs--the onset of the monsoon rains, sudden flooding, rapid erosion, extremes of temperature, tropical storms, and unpredictable fluctuations in rainfall. Broadly speaking, agriculture in India is constantly challenged by weather uncertainty.
It is possible to identify seasons, although these do not occur uniformly throughout South Asia. The Indian Meteorological Service divides the year into four seasons: the relatively dry, cool winter from December through February; the dry, hot summer from March through May; the southwest monsoon from June through September when the predominating southwest maritime winds bring rains to most of the country; and the northeast, or retreating, monsoon of October and November.
The southwest monsoon blows in from sea to land. The southwest monsoon usually breaks on the west coast early in June and reaches most of South Asia by the first week in July. Because of the critical importance of monsoon rainfall to agricultural production, predictions of the monsoon's arrival date are eagerly watched by government planners and agronomists who need to determine the optimal dates for plantings.
Theories about why monsoons occur vary. Conventionally, scientists have attributed monsoons to thermal changes in the Asian landmass. Contemporary theory cites other factors--the barrier of the Himalayas and the sun's northward tilt (which shifts the jet stream north). The hot air that rises over South Asia during April and May creates low-pressure areas into which the cooler, moisture-bearing winds from the Indian Ocean flow.These circumstances set off a rush of moisture-rich air from the southern seas over South Asia.
The southwest monsoon occurs in two branches. After breaking on the southern part of the Peninsula in early June, the branch known as the Arabian Sea monsoon reaches Bombay around June 10, and it has settled over most of South Asia by late June, bringing cooler but more humid weather. The other branch, known as the Bay of Bengal monsoon, moves northward in the Bay of Bengal and spreads over most of Assam by the first week of June. On encountering the barrier of the Great Himalayan Range, it is deflected westward along the Indo-Gangetic Plain toward New Delhi. Thereafter the two branches merge as a single current bringing rains to the remaining parts of North India in July.
The withdrawal of the monsoon is a far more gradual process than its onset. It usually withdraws from northwest India by the beginning of October and from the remaining parts of the country by the end of November. During this period, the northeast winds contribute to the formation of the northeast monsoon over the southern half of the Peninsula in October. It is also known as the retreating monsoon because it follows in the wake of the southwest monsoon. The states of Tamil Nadu, Karnataka, and Kerala receive most of their rainfall from the northeast monsoon during November and December. However, 80 percent of the country receives most of its rainfall from the southwest monsoon from June to September.
South Asia is subject to a wide range of climates--from the subfreezing Himalayan winters to the tropical climate of the Coromandel Coast and from the damp, rainy climate in the states of Assam and West Bengal to the arid Great Indian Desert. Based on precipitation and temperature, experts define seven climatic regions: the Himalayas, Assam and West Bengal, the Indo-Gangetic Plain, the Western Ghats and coast, the Deccan (the interior of the Peninsula south of the Narmada River), and the Eastern Ghats and coast.
In the Himalayan region, climate varies with altitude. At about 2,000 meters, the average summer temperature is near 18°C; at 4,500 meters, it is rarely above 0°C. In the valleys, summer temperatures reach between 32°C and 38°C. The eastern Himalayas receive as much as 1,000 to 2,000 millimeters more precipitation than do the Western Himalayas, and floods are common.
Assam and West Bengal are extremely wet and humid. The southeastern part of the state of Meghalaya has the world's highest average annual rainfall, some 10,900 millimeters.
The Indo-Gangetic Plain has a varied climatic pattern. Rainfall and temperature ranges vary significantly between the eastern and western extremes. In the Peninsula region, the Western Ghats and the adjoining coast receive heavy rains during the southwest monsoon. Rainfall in the peninsular interior averages about 650 millimeters a year, although there is considerable variation in different localities and from year to year. The Eastern Ghats receive less rainfall than the western coast. Rainfall there ranges between 900 and 1,300 millimeters annually.
The northern Deccan region, bounded by the Western Ghats, the Vindhya Range and the Narmada River to the north, and the Eastern Ghats, receives most of its annual rainfall during the summer monsoon season. The southern Deccan area is in a "rain shadow" and receives only fifty to 1,000 millimeters of rainfall a year. Temperature ranges are wide--from some 15°C to 38°C--making this one of India's most comfortable climatic areas.
Throughout most of non-Himalayan India, the heat can be oppressive and sometimes, such as was experienced in 1994 and 1995, literally can be a killer. Hot, relatively dry weather is the norm before the southwest monsoons, which, along with heavy rains and high humidity, bring cloud cover that lowers temperatures slightly. Temperatures reach the upper 30s°C and can reach as high as 48°C during the day in the premonsoon months.
