Climate Class 11 Notes Geography Chapter 4 - CBSE

Chapter : 4

What Are Climate ?

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Weather is the momentary state of the atmosphere while climate refers to the average of the weather conditions over a longer period of time. Weather changes quickly, may be within a day or week but climate changes imperceptively and may be noted after 50 years or even more.
India has a hot monsoonal climate which is the prevalent climate in south and south-east Asia. In the summer the mercury occasionally touches 55°C in western Rajasthan, it drops down to as low as minus 45°C in winter around Leh. Churu in Rajasthan may record a temperature of 50°C or more on a June day while the mercury hardly touches 19°C in Tawang (Arunachal Pradesh) on the same day. On a December night, the temperature in Drass (Jammu and Kashmir) may drop down to minus 45°C while Thiruvananthapuram or Chennai on the same night records 20°C or 22°C.
In Kerala and the Andaman Islands, the difference between day and night temperatures may be hardly seven
or eight degrees Celsius. But in the Thar desert, if the day temperature is around 50°C, at night, it may drop considerably up to 15°-20°C.
Monsoon: Monsoon connotes the climate associated with a seasonal reversal in the direction of winds.
Break in the monsoon: During the southwest monsoon period after having rained for a few days, if rain fails
to occur for one or more weeks, it is known as a break in the monsoon.
Dust storms: Dust storms in the evening are very common during May in Punjab, Haryana, Eastern Rajasthan,
and Uttar Pradesh.
Climatic region: A climatic region has a homogeneous climatic condition resulting from a combination of factors.
Western Disturbances: The inflow of western cyclones is generally known as disturbances during the winter season.
The Intertropical convergence zone (ITCZ): It is a low-pressure zone located at the equator where trade
winds converge, and so, it is a zone where air tends to ascend.
Monsoon trough: In July, the ITCZ is located around 20°N-25°N latitudes over the Gangetic plain. These are sometimes called the monsoon trough.
ITCZ: The intertropical convergence zone (ITCZ) is a low-pressure zone located at the Equator where trade
winds converge and so it is a zone where air tends to ascend. In July the ITCZ is located around 20°N–25°N latitudes (over the Gangetic Plain) sometimes called the monsoon trough.
Northeast monsoon: The ITCZ shifts south throughout the winter, which causes the winds to switch from the
northeast to the south and southwest.
Tropical depressions: During India’s southwest monsoon season, tropical cyclone originate over the Bay of
Bengal and Indian Ocean, which have high wind velocity and heavy rainfall and hit the Tamilnadu, Andhra, and
Odisha coast.
Bursting of the monsoon: High-velocity winds with extreme thundering and lightning cause sudden rainfall.
Jet stream: The winds that blow across the Asian continent at latitudes north of the Himalayas roughly parallel to the Tibetan highlands are called the jet streams.
Monsoon winds: Winds that bring rainfall are called monsoon winds.
Drought: It is a situation of scarce rainfall causing a problem with usable water, failure of crops, and sometimes famine-like conditions.
Western cyclone: During the winter, western cyclonic disturbances travel from the west and north-west
towards the Indian subcontinent. The westerly jet stream carries them into India from their origin over the
Mediterranean Sea.