THE CLIMATE OF INDIA

FACTORS THAT AFFECT

Total Area : 32,87,263 Sq. km Latitude : 8o 4’ N to 37o 6’ N Longitude : 68o 7’ E to 97o 25’ E North to South : 3,214 km East to West : 2,933 km Main land Coastline : 6,100 km Total Coastline : 7,516 km Land Frontier : 15,200 km Northern-most Point : Indira Col near

Karakoram Pass Southern-most Point : Indira point, (Great

Nicobar , Andaman and Nicobar Island) Western-most Point : West of Ghuav Mota

Gujarat Eastern-most Point : Kibithu (Arunachal

Pradesh) Highest Altitude: Kanchenjunga Lowest Altitude : Kuttanand (Kerala) Territorial Sea : 12 nm Contiguous Zone : 24 nm Exclusive Economic Zone : 200 nm

INDIA : GEOGRAPHICAL FACTS

10 FACTORS THAT AFFECT THE . CLIMATE Location and Latitudinal Extent Distance from the Sea The Northern Mountain Ranges Physiography Monsoon Winds Upper Air Circulation Tropical Cyclones and Western Disturbances El-Nino La Nina Southern Oscillation

Location and Latitudinal Extent

Areas south of the Tropic of Cancer are closer to the equator and experience high temperature throughout the year .The northern parts on the other hand lie in the warm temperature zone. Hence they experience comparatively low temperatures. Some places record considerably low temperatures particularly in winter. Water bodies comprising the Arabian Sea and the Bay of Bengal surround the peninsular India and make climatic conditions mild along the coastal areas.

Distance from the Sea The sea affects the climate of

a place. Areas near the coast have equable or marline climate Coastal areas are cooler and wetter than inland areas. Clouds form when warm air from inland areas meets cool air from the sea. The center of continents are subject to a large range of temperatures. In the summer, temperatures can be very hot and dry as moisture from the sea evaporates before it reaches the center of the land mass.

The Northern Mountain Ranges

India is separated from the rest of Asia by the impenetrable wall of the Himalayan mountain ranges. These ranges protect India from the bitterly cold and dry winds of Central Asia during winter. Further, these mountain ranges act as an effective physical barrier for rain bearing south-west monsoon winds to cross the northern frontiers of India. Thus, the Himalayan mountain ranges act as a climatic divide between the Indian Sub-continent and Central Asia.

Physiography Physiography of India has a great

bearing on major elements of climate such as temperature, atmospheric pressure, direction of winds and the amount of rainfall. In fact, physical map of India is very closely related to the climatic conditions of the country. Places located at higher altitude have cool climate even though they are located in the peninsular India,eg.Ooty. The greatest control of physiography in the peninsular India is seen in the distribution of rainfall. The south-west monsoon winds from the Arabian sea strike almost perpendicular at the Western Ghats and cause copious rainfall in the Western Coastal plain and the western slopes of the Western Ghats.

Monsoon Winds The most dominating factor of the

Indian climate is the ‘monsoon winds’ as a result of which we receive the rainy season. The complete reversal of the monsoon winds brings about a sudden change in the seasons and the harsh summer season suddenly giving way to eagerly awaited monsoon season .The south-west summer monsoons from the Arabian Sea and the Bay of Bengal bring rainfall to the entire country. The north-eastern winter monsoon travel from land to sea and do not cause much rainfall except along the Caromandel coast after getting moisture from the Bay of Bengal.

Upper Air Circulation The changes in the upper air circulation over

Indian landmass influence the climate of India to a great extent. Jet streams in the upper air system influence the Indian climate in the following ways:

Westerly Jet Stream:Westerly jet stream blows at a very high speed during winter over the sub-tropical zone. This jet stream is bifurcated by the Himalayan ranges. The northern branch of this jet stream blows along the northern edge of this barrier. The southern branch blows eastwards south of the Himalayan ranges along 25° north latitude. This help in the sudden onset of the south-west monsoons. Easterly Jet:Reversal in upper air circulation takes place in summer due to the apparent shift of the sun’s vertical rays in the northern hemisphere. The westerly jet stream as replaced by the easterly jet stream which owes its origin to the heating of the Tibet plateau. This leads to the development of an easterly cold jet stream centered around 15°N latitude and blowing over peninsular India. This help in the sudden onset of the retreating monsoons.

Tropical Cyclones and Western Disturbances

Tropical cyclones originate in the Bay of Bengal and Arabian Sea and the influence large parts of the peninsular India. Majority of the cyclones originate in the Bay of Bengal and influence the weather conditions during the south-west monsoon season. Some cyclones are born during the retreating monsoon season(in October and November) and influence the weather conditions along the eastern coast of India.

A Western Disturbance is an extra tropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent. It is a non-monsoonal precipitation pattern driven by the westerlies. The moisture in these storms usually originates over the Mediterranean Sea and the Atlantic Ocean. Extra tropical storms are a global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere. In the case of the subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.

El-Nino Effect El Niño is the warm phase of the El Niño

Southern Oscillation (commonly called ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (between approximately the International Date Line and 120°W), including off the Pacific coast of South America. El Niño Southern Oscillation refers to the cycle of warm and cold temperatures, as measured by sea surface temperature, SST, of the tropical central and eastern Pacific Ocean. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected. In American Spanish, the capitalized term "El Niño" refers to "the little boy", so named because the pool of warm water in the Pacific near South America is often at its warmest around Christmas.

La Nina Effect La Niña is a coupled ocean-

atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño–Southern Oscillation climate pattern. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5 °C. A La Niña often, though not always, follows an El Niño. A La Nina also marks an active hurricane season. But in India, the presence of La Nina portends exceptionally good news. It is the harbinger of heavy monsoon showers in India.

Southern Oscillation There is a strange linkage of

meteorological changes often observed between the Indian and the Pacific Oceans. It has been noticed that whenever the surface level pressure is high over the Indian Ocean, there is low pressure over the Pacific Ocean and vice-versa .This inter relation of high and low pressure over the Pacific and the Indian Ocean is called Southern Oscillation. When the winter pressure is high over the Pacific Ocean and low over the Indian Ocean, the south-west monsoons in India tend to be stronger. In the reverse case, the monsoons are most likely to be weaker.

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