Geography - Climate

CLIMATE

Q.1. Define: climate and weather.

 Or

        Differentiate between weather and climate.

Weather

a.       It refers to the state of the atmosphere over an area at any point of time.

b.      Weather conditions may vary a few hours or a few days.

c.       The elements of weather are temperature, wind, atmospheric pressure, humidity and precipitation.

Climate

a.       It refers to the sum total of weather conditions and variations over a area for a long period of time ( more than 30 years).

b.      Climate refers to average values of several elements of weather, relating to a period of more than 30 years.

c.       The elements of climate are temperature, wind, atmospheric pressure, humidity and precipitation.

           

Q.2. What are the elements of climate and weather?

Ans. The elements of climate and weather are temperature, atmospheric pressure, wind, humidity, and precipitation.

Q.3. How is the climate of India described as?

Ans. The climate of India is described as Monsoon type of climate.

Q4.What do you mean by Monsoon ?

 Ans.The word monsoon is derived from the Arabic word mausim , which means season .

       Monsoon refers to the seasonal reversal in the wind direction during a year .

       The climate of India is described as the monsoon .

       In Asia , this type of climate is found mainly in the south and the south east .

Q5.  Explain the variation in terms of climate from place to place and season to season that is observed in India.

                                                                  Or

 Describe the regional variations in the climatic conditions of India with the help of suitable examples.

Ans. . TEMPERATURE

(a) According to Seasons

- In summer, temperature occasionally rises to 50 C or more in some parts of Rajasthan. On the

other hand, it is around 20C in Pahalgam in Jammu and Kashmir.

- On a winter night, temperature at Drass in Jammu and Kashmir is as low as -45C at night.

-On the other hand, Thiruvanthapuram experience temperature of 20C.

(b) According to Day and Night

-Certain places have wide difference between day and night temperatures.

- In Rajasthan, the day temperature rises to 50  C and comes down to near freezing point the same night.

- On the other hand, there is hardly any difference in day and night temperatures in the Andaman

and Nicobar Islands.

 PRECIPITATION

(a) Forms and types of Precipitation

- Precipitation is mainly in the form of snowfall in the Himalayas.

- It is only in the form of water droplets over the rest of the country.

(b) Annual Variations in Rainfall

- Annual precipitation varies from over 400 cm in Meghalaya to less than 10cm in Ladakh and

Western Rajasthan.

- Most parts of the country receive rainfalls from June to September from advancing monsoons.

-Tamil Nadu coast get most of its rains during November and December from retreating

monsoons.

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                                                                   Climatic controls             

Q6. Explain the six major climatic controls with reference to India.

Ans. A. LATITUDE

Due to curvature of earth, the amount of solar energy received on the earth varies from latitude to latitude. This results in decrease of temperature from equator to poles.

Reference to India – Tropic of Cancer passing through India divides the country into tropical and subtropical zones. Hence, temperature remains high throughout the year in South India (tropical zone) while they are high in summer and low in winter in North India (sub-tropical zone).

B. ALTITUDE

With increase in altitudes, the atmosphere goes on becoming less dense and temperature goes on decreasing. .Hills are therefore cooler during Summers.

 Reference to India- though, Udagamandalam (Ooty) lies in low latitude area (tropical zone) but the climatic conditions are different from the adjoining regions because it is located at high altitude.

C. PRESSURE AND WINDS

The pressure and wind system exert influence on the climate of any place because they control the temperature and rainfall pattern.

Reference to India- Upper air circulation winds, western disturbances, tropical cyclones, monsoons etc.govern the climate and associated weather conditions in India.

D. DISTANCE FROM THE SEA

Sea exerts a moderating effect on climate. As the distance from  the sea increases, its moderating influence decreases and the people experiences extreme weather conditions .This condition is called Continentality.

Reference to India- temperature remains uniform at Mumbai throughout the year where as at Delhi winter and summer temperature vary from 50 C to 45 C.

E. OCEAN CURRENTS

Ocean currents along with on-shore winds influence climate of coastal regions.

Reference to India- warm currents along the coastal region of India influence the climate of the

adjoining areas.

F. RELIEF

Relief (physiography) plays a major role in determining the climate of a place. High mountain act as barriers for cold or hot winds , they may cause precipitation if they are high enough and lie in the path of rain bearing winds .

Reference to India- Himalayas do not allow the cold winds from Central Asia to enter India, neither allows monsoon winds to cross India. Also, relief also helps in orographic rainfall in many parts of the country.

Q.7. What is Continentality?

Ans. As the distance from the sea increases, people experience extreme weather conditions, i.e., very hot during summers and very cold during winters. This condition is known as Continentality.

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                                                            Factors affecting India,s climate

Q8. Explain the factors affecting India’s climate.

a)Location

- Tropic of cancer passes through the middle of the country from the Rann of Kuchhh in the west to Mizoram in east, divides India into sub-tropical and tropical zones.

b)Relief

- Due to the triangular shape of the Indian plateau, the moderating influence of the sea is felt in the coastal areas and in the plains in the north experience continental climate.

-The Himalayas in the north act as a climate divide by protecting the northern plains from the cold winds from the Central Asia.

b)Pressure and winds:

-In the winter season, cold dry North east trade winds  originate from the north west India and blow southwards.  So winters are cold and dry in the northern plains and rainy in the eastern coastal plains

whereas during summer there is complete reversal in direction of winds with the change of atmospheric pressure.

-The rain bearing winds blow from sea to land bringing widespread rains in the country.

c)Upper air circulation:

-The upper air circulation of this region is dominated by a westerly flow which is called jet stream, located approximately over 27-30* north latitude.

-The western cyclonic disturbances experienced in the north and north-west parts of the country are brought in by this westerly flow.

Q9.What are jet streams and how do they affect the climate of India?

a.       Jet streams are a narrow belt of high altitude (above 12,000m) westerly winds in the troposphere.  Their speed varies from about 110 km/hr in summer to about 184km/hr in winter.

b.      As these winds are located approximately over 27*-30* north latitude they are known as sub-tropical westerly jet streams.

c.       Over India, these jet streams blow south of the Himalayas, all through the year except in summer.

d.      The western cyclonic disturbances experienced in the north and north-western parts of the country are brought in by this westerly flow.

e.       In summer, the sub-tropical westerly jet streams moves north of the Himalayas with the apparent movement of the sun.

Q10. What is Coriolis force?

Ans. An apparent force caused by the earth’s rotation responsible for deflecting winds towards the right in the northern hemisphere and towards the left in the southern hemisphere. This is also known as Ferrel’s law.

Eg. South-east winds become south-west winds.

                                                            The Indian Monsoon

Q11. Discuss the mechanism of monsoons.

Ans. The monsoons are experience in the tropical area roughly between   between 20 degree  n and 20 degree south . The mechanism of monsoon can be understood from the following facts:

 (a) The different rates of heating and cooling of land and water : At the end of May, due to high temperature, low pressure is created on the landmass of India while seas around experience  high pressure.       

 (b) The shift of the position of Inter Tropical Convergence Zone (ITCZ) : ln summer, over the Ganga plain, low pressure trough is positioned.

 (c) The presence of high pressure area, east of madagascar at 20° South  over the Indian ocean

 (d) The Tibetan Plateau gets intensely heated during  summer which results in strong vertical air currents .

  (e) The movement of the westerly jet streams to the north of the Himalayas and the presence of the tropical  easterly jet streams over the Indian Peninsula during summer.

Q12 What is El Nino?

Ans . It is a warm ocean current that blows past the Peruvian coast in place of the cold Peruvian current every 2 to 5 years.  The presence of the El Nino leads to an increase in sea surface  temperatures and weakening of the trade winds in the regions.

Q13. What is Southern Oscillation?

Ans. Changes in the pressure conditions over the Southern ocean also effect monsoons. Normally, when   the tropical eastern South Pacific ocean experience high pressure, the tropical eastern South Indian Ocean experience low pressure.

 But, in certain years, the usually prevailing pressure conditions are reversed; it results in low pressure on the eastern pacific ocean, in comparison to the eastern Indian Ocean. This periodic change in pressure conditions are known as Southern Oscillation or SO.

Q 14. What do you understand by ITCZ?

Ans.  Inter-tropical Convergence Zone or ITCZ, is a broad trough of low pressure in equatorial latitudes.

This is the area where northeast and southeast trade winds converge.This convergence zone lies  more or less parallel to the equator but moves northwards or  southwards with the movement of the sun.

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The onset of the Monsoon and With drawal

Q15. What do you understand by the terms burst of monsoons ?

Ans. Burst of monsoons: the phenomena when the normal rainfall increases suddenly and continues constantly for several days are known as burst of the monsoons.

Q16.What do you understand by “break” of the monsoon?

a. Monsoon ‘break’ refers to the happening of wet and dry spells during the rainy season.

b.The monsoon rains take place only for a few days at a time.

c. They are interspread with rainless intervals.

17. Explain the route followed by the monsoon winds over the Indian landmass.

Ans. ONSET OF THE MONSOON

-Monsoon winds are pulsating in nature.

-The monsoon arrives at the southern tip of the Indian peninsula

generally by the first week of June.

-From here, it divides itself into two – the Arabian sea branch and the Bay of Bengal Branch.

-The Arabian Sea Branch reaches Mumbai about ten days later on 10 June.

- The Bay of Bengal branch also advances rapidly and arrives in Assam in the first week of June. On reaching the Eastern Himalayas, it is deflected towards the west over the Ganga plains.

 -By mid June, The Arabian Sea branch of the monsoon arrives over the Saurashtra-Kutch region and the Central part of the country.

-The Arabian Sea branch and the Bay of Bengal branches of the monsoon merge over the north-western part of the Ganga plains.

RETREAT OF THE MONSOON

-Withdrawal or retreat of the monsoon is a more gradual process than the onset.

- It begins in the western parts of northwestern states of India by early September.

 -Withdrawal from the southern half of the country is fairly rapid.

- By early December, withdrawal of the monsoon has taken place from the rest of the country.

Q18. Why the climate of India is described both as tropical as well as sub-tropical?

Ans. The tropic of cancer passes through the middle of the country. Almost half of the country, lying south of the Tropic of Cancer belongs to the tropical area and the remaining area, north of tropics lies in sub-tropics. Therefore,climate of India has the characteristics of tropical as well as sub-tropical climate.

Q19. How western disturbances are important for the agriculture of India?

Ans. The western disturbances during the winters are of immense importance for the cultivation of rabi crop which is extensively done over the North-western part of the country.

                                                                        The Season

Q20. Give an account of weather conditions and characteristics of the cold season.

a.       The cold weather season begins from mid-November in northern India and stays till February.  December and January are the coldest months in northern part of India.

b.      Temperature decreases from south to the north.  Days are warm and nights are cold.  Frost is common in the north and the higher slopes of the Himalayas experience snowfall.

c.       During this season, the north-east trade winds prevail over the country which blow from land to the sea and therefore, for most part of the country, it is a dry season.

d.      The weather is normally marked by clear sky, low temperature and low humidity and feeble, variable winds.

e.       A characteristic feature of the cold weather season over the northern plains is the inflow of cyclonic disturbances from the west and the northwest.

f.       A low pressure system originate over the Mediterranean Sea and western Asia and move into India, along with the westerly flow.  They cause the much needed winter rains over the plains and snowfall in the mountains.

Q21.Explain the weather conditions and characteristics of the hot weather season.

a.       The global heat belt shifts northward during the hot weather season which lasts from March to May.

b.      In May, temperature of 45*C is common in the north-western parts of the country whereas in Peninsular India, temperature remains lower due to the moderating influence of the oceans.

c.       Rising temperature and falling air pressure is observed in the country during this period.

d.      An elongated low pressure area is developed in the region extending from the Thar Desert in the north-west to Patna and Chotanagpur plateau in the east and south-east.  Circulation of air begins to set around this trough.

e.       Strong, hot and dry winds called ‘Loo’ blow over northern and north western India during day time.  In May, dust storms occur in the evening to bring some relief as they cool the weather with breeze and light rain.

f.       Pre-monsoon showers mark the close of this season particularly in Kerala and Karnataka.

Q22. Distinguish between South-west and north-east monsoon.

South-West monsoon

a.       They blow in summer from June to September

b.      They blow from high pressure to low pressure land.

c.       They are moisture bearing winds.

d.      They blow in 2 branches: Arabian sea branch and Bay of Bengal , & give bulk of rainfall to India from 75% to 90%.        

e.       Rainy days, soothing winds and overcast skies are the characteristic features.

            North- East Monsoon

a.       They blow in winter from December to February.

b.      They blow from high pressure land to low pressure area.

c.       These are dry winds.

d.      While crossing the Bay of Bengal, they pick up moisture and give rainfall to the Coromandel coast.

e.       Clear skies, low temperature, gentle breeze and rainless fine weather.

Q23.Describe the main features of the retreating monsoon season in India.

a.    During October- November the monsoon trough becomes weaker and is replaced by a high pressure system .  The south-west monsoon winds starts withdrawing gradually.

b.  The months of October and November are a period of change from the hot rainy season to dry winter conditions.  The land is moist, the sky is clear and the temperature rises but the nights are cool and pleasant.

c.    Owing to high temperature and humidity, the heat becomes oppressive during day time and it is called ‘October heat.’ (What is October heat? Ans: a,b,c)

d.         The low pressure conditions get transferred over the Bay of Bengal by the beginning of November.  This shift is associated with the occurrence of cyclonic depression, which develops over the Andaman sea.  These cyclones cross the eastern coast and cause heavy rainfall.

e.    These tropical cyclones are destructive and the deltas of Godavari, Krishna and Kaveri are often struck by cyclones which cause great damage to life and property.

Q24. Explain the characteristics of the monsoon rainfall in India.

a. The duration of the monsoon is between 100-120 days from early June to mid-September.  Around the time of its arrival, the normal rainfall increases suddenly and continues constantly for several days which is known as the ‘burst’ of the monsoon.

b.The monsoon arrives at the southern tip of the Indian peninsula generally by the first week of June.  It proceeds into two – the Arabian Sea branch and the Bay of Bengal branch.

c. The Arabian sea branch reaches Mumbai about 10^th of June.  The Bay of Bengal branch arrives in Assam in the first week of June.

d.      By mid-June the Arabian sea branch of the monsoon arrives over the central part of the country.  It merges with the Bay of Bengal branches of the monsoon over the north western part of the Ganga plains.

e.  By mid-July, the monsoon reaches Himachal Pradesh and the rest of the country.  The islands receive the very first monsoon showers from the last week of April to the first week of May.

Q25. Give reason. Why parts of Rajasthan, Gujarat and the leeward side of the Western ghats are drought prone?

a. Parts of Rajasthan, Gujarat and the leeward side of the western Ghats depend on the Arabian sea branch of the south west monsoons for the rainfall.

b.The Arabian Sea branch strikes the western Ghats and sheds most of its moisture on the windward side of the western Ghats and when it reaches the Leeward side it has shed most of its moisture and the Leeward side becomes drought prone.

c. By the time the Arabian sea branch reaches Gujarat, it has shed most of its moisture on the way causing scanty rainfall.

d.      When it reaches Rajasthan, it blows parallel to the Aravalli hills.  Due to high temperatures its capacity to retain moisture increases, hence both Gujarat and Rajasthan receive scanty rainfall and are drought prone.

Q26.Why does Mawsynram receives the highest rainfall in the world?

a. Mawsynram, lies in the Khasi hills in Meghalaya, receives the heaviest rainfall in the world due to its topographic location.

b.  It is on the windward side of the Meghalaya hills which is the first barrier for the Bay of Bengal branch of South-west Monsoons.

c. Striking against the north eastern hills they bring heavy rainfall in this area, especially in Mawsynram.

Q27.Tamil Nadu coast receives rainfall during winter. Give reason.

a. Winter rains in Tamil Nadu are caused by the north-east trade winds (north-east monsoon).

b.In winter, there is a high pressure area in the north of the Himalayas and the cold dry winds blow from this region to the low pressure area over the oceans.

c. When these winds blow over the Bay of Bengal, these pick up moisture and becomes moisture laden. These winds are on-shore along the Tamil Nadu coast and give heavy rainfall in the winter season.

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                        Monsoon as a unifying bond and distribution of rainfall

Q28.Why is monsoon considered a unifying bond?

a. The Indian landscape, its animal and plant life , its entire agricultural calendar and the life of the people, including their festivals, revolve around this phenomena.

b.The seasonal alternation of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons that binds the whole country.

c. Year after year, people of India from north to south and from east to west, eagerly await the arrival of the monsoon.

d.      These monsoon winds bind the whole country by providing water to set the agriculture activities in motion.

e. The river valleys which carry this water also unite as a single river valley unit.

Q29.Explain the regional variations in the  distribution of rainfall in India.

a. Parts of western coast and northeastern India receive over about 400cm of rainfall annually.

b.It is less than 60cm in western Rajasthan and adjoining parts of Gujarat, Haryana and Punjab. Rainfall is equally low in the interior of the Deccan plateau, and east of the Sahyadris.

c.   A third area of low precipitation is around Leh in Jammu and Kashmir.

d.      The rest of the country receives moderate rainfall.

e. Snowfall is restricted to the Himalayan region.

Q30.Which part of India experiences the highest diurnal range of temperature and why?

a. Dirunal range of temperature is the difference between maximum and minimum temperature of a day.

b.Dirunal range of temperature is high in desert regions like Rajasthan, Thar desert and interior parts of Rann of Kachch.

c. In these sandy areas the day temperature may rise to 50*C and drop down to near freezing point the same night.

d.      It is because the sand absorbs heat very fast during day and loses very fast at night. 

Q31.Which wind account for rainfall along the Malabar coast and the Coromandel coast ? Explain.

a. The Arabian sea branch of the south-west monsoons strikes the Western Ghats in June and gives heavy rainfall to the Malabar coast.

b.Since it is the first region to receive rainfall, Malabar coast experiences heavy rains in the month of June-July.

c. Coromandel coast is on the eastern strip , it hardly gets rain from the Arabian sea branch of the south west monsoons, because by the time it reaches Coromandel coast, it has shed most of its moisture.

d.      Coromandel Coast gets moist of its rainfall from the north-east monsoons in November- December, when the north-east monsoons pick up moisture from the Bay of Bengal  and give rainfall to the Coromandel Coast.

e. Here, the bulk of rainfall is caused by depression and cyclones.

Q32.“India would have been an arid land or desert if there had been no phenomena of Monsoons.”Explain by giving three examples.

a. India receives 75% to 90% of the rainfall from the monsoons.

b.The lofty Himalayas prevents the South-West monsoon to cross over to Tibet.

c. The peninsular shape sub-divides the South-West monsoons into two branches.- the Arabian Sea branch and the Bay of Bengal branch.

d.      Thus, it covers the whole of India and prevents it from becoming a desert.

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