NCERT Class 9 Geography Chapter 4: Climate of India -Examrace | English | CBSE



Tom will start with yet another important topic in geography that's the climate of India now starting with the difference between the climate and the weather weather is something which is determined on a day to day basis however climate is a kind of year long average so I can say average conditions for 30 years or more would help you determine the climate of a place based on that I can say the region of Thera desert is a kind of arid climate because over the years the average and the phenomena has elaborated the concept or explain the thing that the climate is a kind of arid climate with less rainfall and high temperatures so you have climate which is a sum total of weather for 30 years or more however weather is at a given point of time now whenever we talk about weather or climate whatever it is there are a few parameters that we merged in most ever the first tells the temperature of the region the amount of rainfall the pressure conditions the wind flow and the humidity so these five are the primary things that you must look for to understand the climatic condition of a region now in India the most common climatic condition is attributed to the monsoons of India now this word monsoon was derived from the word nursing and this word was given by the Arab traders and the navigators when they landed into India and they felt there is some different phenomena then other countries that happen here and this word Muslim meant seasonal reversal in the wind direction so you have winds that flow in two different direction during the summers and the winter months India is predominantly a monsoon land being the monsoon land the rainfall is very pulsating and very even hundred phases from 100 to 120 days now if we talk about the climatic conditions there are extremes of climate that could be seen with Rajasthan at a high of 50 degree Celsius in contrast to Jammu Kashmir where you can reach as low as minus 45 degree Celsius then again you have extremes in rainfall that can be seen in the reason so you have rainfall in Meghalaya at 400 centimeters in contrast to lhasa which is a cold desert with merely 10 centimeters now samel nadu is known for the winter rains once when discuss this again as we move forward to understand broadly on the map of India I can say rainfall decreases as one moves from east to west so the westernmost region which is the region of Rajasthan is a desert region and the easternmost region is not the instant most of most of in one of the extremes of northeast you have maple air and this muharram is one of the places which has the highest rainfall again the coastal regions have less extreme temperatures as compared to the mainland so the coastal areas have kind of more moderate and more moderate temperatures because the pressure differences are not that extreme in the Minette way to understand how this works now there are various controls of climate first we see in latitude so from equator to poles the temperature decreases so equator being the voltage and poles getting cooler so you have temperature drop that is visible as you move on the latitude again if I move up on your ironing or fountain I will find a drop in temperature at higher areas the air is less dense er as compared to lower areas then the pressure and the wind pressure and wind depends on the latitude and the altitudes I the influence they influence the temperature and the rainfall of the region again the distance from the sea the higher container continentality is seen there is more exchange of pressure differences that are variables I can say this is a kind of extreme high pressure zone as compared to a low pressure zone that occurs in Australia other winds will move from high pressure then you have the ocean currents which are again classified as warm current and harm cool current then based on this you have the covalent circulations in the ocean water that could be seen now relief features artists barrier so in India the importance of Himalayas cannot be neglected because these Emmanuel's block the cold waves which can't come from the region of Central Asia and the mongol area so you have the cold fins that are blocked and again the monsoon winds that come here get collided with in himalayas and you have kind of abundant rainfall in the region so again this mounting acts as a barrier preventing the cold winds and leading to rainfall in the region now why are deserts predominantly located on the western margins in the subtropical region so what happens in the subtropical regions the prevailing wind direction of the tropical winds are easterly as a result the winds are originated from the east so you have kind of as they reach the westernmost edge they get dry so you have been that originated from East so you have the Eastern events that coming and as they reach towards the will begin crime since they can't dry the Western regions on the subtropical bed have desert type of climate that is mostly seen now as we talked about Latin altitude and latitude now let's come on to India this specific case we have already talked about the factors in general that affect the climate now coming on to India you have the role of Evalia that we already discussed and when we talk about the latitudinal extension you have the Tropic of Cancer which divides India into the tropical and subtropical region so you have the tropical region and the subtropical region and then the important thing that you must understand in climatology all climate as such is the direction of the phenomena of wind movement so we have covered this in details and we have found about the Coriolis force and the pressure gradient force the pgf now just a brief idea about that here now because of the Coriolis force what would happen is you would have the deflection towards the right in the North hemisphere and towards the left in the South hemisphere so you would have winds that were deployed towards right in the North hemisphere and left in the South hemisphere now what would happen in the summers the summers would have a low-pressure in the central of India as it is in the winds from high pressure will move towards low pressure once we reach the regions of low pressure Damon risa saturation and finally they do drop down as ringing phone however in case of Southwest that happens in the case of southwest monsoon however in case of northeast monsoon you have high pressure over the mainland in Asia in compared to loop in Australia and whence flow from high pressure to low pressure so from India you have the northwest monsoon that goes and you have the northeast monsoon that goes here and both of these causes ways to retrain and hence they are the cause for the retreating monsoon or the winter rainfall in the coast of the bazaar that we saw now besides these the wind streams and the controls that we have talked about there are some other important controls the first is the upper air circulation this upper air circulation is comprised of two wins the tropical easterly jet stream and the westerly flow now easterly flows at 27 to 30 degrees north and it is also known as the subtropical destiny in India it runs south of Himalayas except for the summer season I it is the main cause for the Western disturbances in the region now in the summer the same westerly wind the westerly jet stream moves north of Himalayas then you have the easterly jet stream which is visible over the peninsula and mainly 14° not in the summers besides these you have the cyclonic disturbances that occur in winter so you have kind of low pressure zones that would be created and there would be cyclonic depressions you would have tropical cyclones that would occur in the month of monsoon odd because of the easterly flow you would have those in the month of October and them embarrassment so all these are other phenomena zahra per year phenomena that would affect the kind of climatic condition in a specific area now let us talk about monsoons in India monsoons is a phenomena that usually 20 degrees north and south you have mainly the equatorial sorry the tropical region that is affected by the monsoon winds in some areas as we saw you have the subtropical region the western sides of the continent where you have the desert kind of climate however monsoon is predominantly a tropical phenomena with differential heating of the land and sea so if both the bodies of land and water are at the same temperature there will be able to say no there is no differential heating they are at the same temperature there would be no of this movement of the wind that would affect certain phenomena of rainfall however when there is a difference in the temperature it would create differences in the pressure conditions once you have the pressure conditions that are different there would be wind movement and this fuel movement will determine if the winds are rolling from the sea they will bring in moisture and when they collide with Aldean's or there is a natural obstruction that comes into way they would drop down once they reach the saturation point and this would lead into rainfall so this is the basic process to understand how during fall occurs now because of the Southwest monsoons that comes and you big is mainly because you have India here and you have Africa here and this Africa has a continent of the country of where Alaska at Madagascar you have the high pressure zones that form which is when 20-degree sound and then again you have the heating of the Tibetan Plateau that occurs north of Indian mainland and because of this there is the kind of generation of winds phenomena from high pressure to low pitch to the rainfall into the Indian mainline now movement of the westerly jet stream in the Himalayas and easterly jet streams in the peninsula are also one of the causes for monsoon to occur now I have to understand monsoon again there is another phenomena which affects the monsoon to some extent which are known as Southern Oscillation are the Illinois effect or the La Nina effect now when we talk about southern oscillations I can say in the normal circumstances what happened you have Indian Ocean and Pacific Ocean Pacific Ocean remains at high pressure in comparison to Indian Ocean however there are phases of reversion every two to three years and what happens is you have a kind of hydration that builds up in the Indian Ocean as compared with the Pacific Ocean and this leads to southern oscillations so Southern Oscillation is the differences of the pressure conditions which could be seen in Tahiti Pacific and come back in comparison to Darwin in Australia in Indian Ocean and this would determine the intensity of the monsoon again if I say there is negative Southern Oscillation index that means there would be late monsoons or below average rainfall now what is El Nino Illinois Spanish term which means child or baby Chris Christ and this was the name given because Olivo starts to float during the month of Chris during the time there is Christmas coming up so what happens is instead of the routine cold current of the Peru the current becomes warm current every two to three and two to five years and because of this there are changes in the pressure conditions see which lead to the unli no Southern Oscillation southern oscillations we have already talked about and those certain oscillations are amplified by the impact of a lino this would lead to increase in the sea surface temperature and weakening of the trade winds again this Elina would lead to extremes of temperature so there would be kind of extreme poor monsoons in the region of India in comparison to America where you won't have ample of rainfall so you would have a kind of extreme differences between the Pacific and the Indian Ocean that would be visible because of our Nino and you have La Nina which is a kind of reverse phenomena of El Nino that is seen now what is the monsoon mechanism that works so let's say this is a kind of pulsating behavior that occurs and it happens every hundred to 120 days from the month of June to September initially there is a burst of monsoon so you have the island regions here the module first appears on to the island and the month of April to me but it touches the mainland by the 1st of June when the first on choke it touches the southernmost tip of India as it moves it bifurcates into two branches one branch go towards the Ganga I merge by June and the other is the one which goes towards Bay off I go on and brings rainfall to the region of northeast and finally comes up and joins the main stream here again in the Ganga Plains so this branch and this branch they again kind of and the Northern Plains causing kind of ample rainfall in the the other things of the gonca plains of India however in the month of September there is a gradual retreat that starts from the northwest of India so you have September retreat and it retreats from the eastern coast India by the month of October and November and this retreating monsoon brings about winter rainfall in Tamil Nadu which are good for certain crops here and you call it cherry columns there now there are four seasons which we do market based on the Indian climate the first is the cold weather you have been Thurman's from the moment to February it's snow and frost in the north and northeast you have drive-ins you have been to reinforce in Tamil Nadu this winter rainfall if it is in a small quantity is good and it is known as Mohammed it is good for the Rabi crops in the region hot weather is mainly from March to May is the main region of the north where you have the hotbed you have our local languages known as Lou in India that flows which is dry gusty and it leads to localized storms like Carl basic in West Bengal between the hot winter season on a monsoon season you have a kind of pre monsoon showers and these pre monsoon showers are good for ripening of mangoes specifically in Kerala and Karnataka they are known as mango showers then you have the advancing monsoons which is the Southwest monsoons you have a windward side the side towards the waist which receives most of the rainfall and then you have the levered sign which receives less rainfall on the Western cards this advancing monsoon is maximum in the northeast of India so you have back in the northeast India there are definitely breaks so you have very dry spell mighty spirit dry spell there is not a kind of continuous 100 days or 200 days of rainfall then you have my syrup which is the place with highest rainfall this region is also known Falls talgamite sand sand besides caves then finally you have the retreating monsoon which causes winter rainfall in Tamil are you have the temperature that is starts to rise with clear skies in the month of October the region also known as October heat because you have high temperature and humidity in today and this leads to cyclonic depression in the region of Andaman Sea and finally from the Andaman it retreats by the month of December and January so from the main line we say retreat a retreat of monsoon is by the month of October a number but if we incorporate the region of islands it's the month of December and January now this map shows the onset of monsoon and this map shows the withdrawal of monsoon so as you can see you have the onset of monsoon that it starts with first June in the southernmost India so you have the 1st June which is this then you have the 5th June and finally 15 July you touch the northwest of the region now this region you have the retreat which it starts from 1st September so as you can see you have minimum period of rainfall towards the western most region and as a result it is one of the driest region then you have the retreat that's 15 September and finally 1 December by November and you have 1 December by the southernmost region and finally as I said you have the islands you retreat there you have retreat by the end of December now definitely monsoons act as a unifying thing they have a kind of unifying bond because they bring in lot of Agriculture waters to the river since there are ample waters there would be less conflicts less ethnic and kind of less conflicts between various tribal groups and the various regions you would have a kind of rhythmatic cycle of seasons that would occur there would be less extremes in the temperature variations that would be seen if there is good rainfall and ambleve on schools that occur and finally you have Himalayas which protect from the north winds north wind and they kind of exert the mean they are the main cause for the phenomena of monsoon in India however Peninsula do exert some influence but not as a kind of moderate influence on the climatic conditions of India in general so with this we cover the fourth chapter we will be covering two more remaining chapters for class 9 and upcoming lectures have a good day




Comments
  1. Its really helped me a lot tommoew is my final exam of class 9 and I dont yet studies anything but after all vedios of you I get all chapter clearly in mind😭😭😭❤ thanks guys ❤❤❤👍👍

  2. Very helpful ma'am u explain each and every imp point of the book not like others who just try to finish ch in easy language and leave main main points. I must have watched 2-3 videos just to understand that pressure and wind topic but they all were only telling about high pressure and low pressure. Thanks once again this video was quite helpful for me 😊

  3. Ma'am I was not able to understand just by studying the chapter but when you explained my each and every doubt was clear. It helped me a lot for my test. And your drawings are perfect.

  4. Mam pressure and temperature are inversely proportional to each other in most cases but it would not happen in case of high altitude why?

  5. Very nice mam …. I like it very much.. Yoy are inspiration for us thabjs man for uploaded thus video.. Mam plz take history also..thanku!!!!!

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