CLIMATE STD IX GEOGRAPHY
IMPORTANT TERMS
Climate: The sum total of weather conditions and variations over a large area for a long period of time (more than thirty years) is called climate. Weather: The state of the atmosphere over an area at any point of time is called weather. Monsoon: This type of climate is mainly found in the south and Southeast Asia. The climate of India is of monsoon type. The seasonal reversal in wind direction during a year is called monsoon. Coriolis Force: An apparent force cause The winds are deflected towards right in the northern hemisphere and towards the left in d by the earth s rotation is called Coriolis Force. theJet southernStream: hemisphereFast flowing dueand to narrow this force. air currents This is also are known called jetas Ferrel sstreams. Law . The streams flow at high altitudes (about 12,000 feet) in the troposphere. Their speed varies from about 110 km/h in summer to 184 km/h in winter. Western Cyclonic Disturbance: The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region. They usually influence the weather of the north and north-western regions of India. Inter Tropical Convergence Zone (ITCZ): The Inter Tropical Convergence Zone (ITCZ,) is a broad trough of low pressure in equatorial latitudes. The northeast and the southeast trade winds converge in this zone. This zone lies more or less parallel to the equator. It moves north or south with the apparent movement of the sun. Pressure and Winds: The Indian subcontinent lies in the region of north-easterly winds. These winds originate from the subtropical high-pressure belt of the northern hemisphere. After that, these winds blow towards south. They get deflected to the right due to the Coriolis force and then move towards the low pressure area near the equator. The north-easterly winds originate and blow over the land and hence they carry very little moisture. India should have been an arid land because of these winds but that is not the case. There is high-pressure area towards the north of the Himalayas. Cold winds from this region blow to the low pressure areas over the oceans in the south. During summer, low-pressure area develops over interior Asia and also over northwestern India. This results in a complete reversal of the direction of winds during summer. Air; from the high-pressure area moves over the southern Indian Ocean in a south- easterly direction. It crosses the equator and turns right towards the low-pressure areas over the Indian subcontinent. These winds are known as the Southwest Monsoon wind. They collect moisture from the warm oceans and bring widespread rainfall over the mainland of India. The upper air circulation in this region is dominated by a westerly flow. Jet stream is an important component of this flow. These jet streams are called subtropical westerly jet streams because they are located approximately over 27°-30° north latitude. El Niño is an abnormal weather pattern that is caused by the warming of the Pacific Ocean near the equator, off the coast of South America. This occurs when the normal trade winds weaken (or even reverse), which lets the warm water that is usually found in the western Pacific flow instead towards the east. This warm water displaces the cooler water that is normally found near the surface of the eastern Pacific, setting off atmospheric changes that affect weather patterns in many parts of the world.
Water temperature of the Pacific Ocean during El Nino
A temperature increase of least 0.9 F (0.5 C) needs to occur in the waters of the eastern Pacific Ocean near the equator for it to be considered an El Niño year. Although El Niño does not occur in a perfectly regular pattern, it seems to happen every 2 to 7 years. Following an El Niño, an opposite phenomenon occurs, called La Niña. During La Niña, the eastern Pacific Ocean experiences cooler than normal temperatures around the equator. Effects The effects of El Niño are strong and can wreak havoc on weather systems around the world. The changes vary drastically around the globe. Storms Along the Pacific coast of the Americas, El Niño can cause severe storms and flooding. Peru and Ecuador usually receive the brunt of the force of El Niño. During the months of April- October, this area experiences increased rain fall. El Niño's effects are not only felt through rain. In normal years, along the coast of Peru, cool nutrient-rich water is pushed up from the deep waters off the Pacific coast, and this nutrient-rich water is a food source for marine life. However, during an El Niño year, this cold water is replaced by warmer water that lacks those important nutrients. The nutrient-deficient water starves the bottom of the food chain and the effects cause a die-off of larger fish. El Niño is not all bad in the Americas, though. Away from the Pacific coast, North America actually tends to have milder winters during El Niño years, and it is even thought that El Niño reduces the number and intensity of hurricanes in the Atlantic.
CLIMATE STD IX GEOGRAPHY
QUESTION BANK
Q1. Describe how the Himalayas affect the climate of India.
Q2. Explain the major factor affecting the climate of India
Q3. Why does the rainfall decrease from east to west in northern part of India?
Q4.Q5. WhatDefine are monsoon. western Differentiate disturbances? between How do Burst they affectof monsoon the climate and Breakof India? of monsoon .
Q6. Give an account of weather conditions and characteristics of the cold season. Q7. Give the characteristics and effects of the monsoon rainfall in India.
Q9.Q8. What is SouthernCoriolis force? Oscillation? State the Ferrel s law.
Q10. Why are the parts of Rajasthan, Gujarat and the leeward side of the Western Ghats drought prone?
Q11. Why does seasonal reversal of wind direction take place over the Indian subcontinent?
Q12. Why does Mawsynram receive the highest rainfall in the world?
Q13. Give examples of regional variation affecting the Indian climate.
Q14. Differentiate between S.W (southwest) and N.W (northwest) monsoon.
CLIMATE STD IX GEOGRAPHY
PRACTICE MAP WORKSHEET
On a given outline map of India locate the regions receiving (a) Heavy rainfall, (b) moderate rainfall, (c) low rainfall, (d) scanty rainfall .