Class 9 Geography Chapter 4 Notes - Climate

Important Points To Remember

1. Mango showers

• Mango showers are pre-monsoon showers.
• This phenomenon is observed in Kerala and coastal Karnataka.
• The mango showers help in the early ripening of, mangoes.

Regions of Mango Shower and Kal Baisakh

2. Kalbaisakhi

• Kalbaisakhi means the violent black clouds of the month of Baisakh. 
• This is the name given to the north-westerly and northerly winds in Bengal and Assam. These winds cause very heavy rains and distraction.

3. Chennai receives more rain in winter

• The northeast winds pick up moisture while crossing Bay of Bengal. these winds are onshore in the winter season.
• In the summer Chennai lies in the rain-shadow of the Western Ghats, moreover the winds are offshore, therefore receives less rainfall.

4. Break or burst of the monsoon:

• The sudden approach of the moisture-laden winds is associated with violent thunder and lightning. 
• This is known as the “break” or “burst” of the monsoons. The first ‘break’ of monsoons on the southwest coast of India is around 1^st June.

5. Southern Oscillation

• The pressure systems of the Pacific and Indian Oceans are interrelated. 
• When the pressure is high in the Pacific, there is low pressure in the Indian Ocean. The winds move from high pressure to low pressure and vice-versa. 
• This causes the shifting of winds across the equator in different seasons. this is known as the southern oscillation.

6. EI Nino Southern Oscillations 

• A feature connected with Southern Oscillation is the EI Nino, a warm ocean current that flows past the Peruvian Coast, in place of the cold Peruvian current, every 2 to 5 years. 
• The changes in pressure conditions are connected to the EI Nino, the phenomenon is referred to as ENSO (EI Nino Southern Oscillations).

7. Mawsynram receives the highest rainfall in the world:

• Mawsynram is situated at the head of a funnel-shaped valley in the Khasi hills.
• Its unique topographical location together with wind direction is responsible for causing the heaviest rainfall in the world.

8. The rainfall decreases from South to North 

• The S.W. Monsoons originates from the Indian Ocean and divides into branches due to the shape of the Indian peninsular.
• Trivandrum gets above 200 cm.
• Whereas Delhi situated in the interior gets only about 50 cm.
• The Arabian Sea branch strikes the Western Ghats and causes heavy rainfall.
• Whereas another branch of the Arabian Sea monsoon blows parallel to the Aravallis. thus jodhpur gets less than 25cms of rain.

9. The Western Ghats receive more rain from the southwest monsoons than the Eastern Ghats because:

Map showing the position of Western and Eastern Ghats

• The Arabian Sea branch of the monsoon is onshore.
• These winds are forced to rise and cause heavy rains.
• By the time these winds reach the east coast, most of the moisture is lost.
• The winds are offshore, so they are given less rain.
• The Eastern Ghats lies on the leeward/rain-shadow area, hence it gets less rain.

Indian would have been an arid land or dessert if there had been no phenomena of monsoons :

• Indian receives 75 to 90% of the rainfall from the monsoons.
• These monsoons winds occur due to the uneven heating of land and sea.
• The mighty Himalayas check the two branches of southwest monsoons, the Arabian Sea branch and the Bay of Bengal branch. 
• These, cover the whole of India thus preventing it from becoming a desert.

Important Differences Between:  

1. Equable Climate & Extreme Climate

2. Rainfall and Precipitation