CLIMATE OF SOUTH ASIA : CLIMATE OF SOUTH ASIA Also referred as Indian Sub continent.
Does not have uniform climatic condition.
Great difference in R.F and Temperature.
Monsoon unifies the climate of sub continent.
India is regarded as ‘Geographical Laboratory’.
CLIMATE OF SOUTH ASIA : CLIMATE OF SOUTH ASIA Most of the part experiences Tropical climate.
Vast area comes under influence of Monsoon
(seasonal reversal of wind pattern).
Hence climate of Indian subcontinent is described as ‘TROPICAL MONSOON CLIMATE’.
CLIMATE OF SOUTH ASIA : CLIMATE OF SOUTH ASIA Factors affecting Climate of India:
Location.
Distance from sea.
Relief.
Monsoon winds.
Location:
Tropic of cancer roughly divides India into two equal halves.
Northern India (Temperate)
Southern India (Tropical).
CLIMATE OF SOUTH ASIA : CLIMATE OF SOUTH ASIA Distance from Sea:
Places north of Tropic of cancer (interior parts) experiences extreme climate.
Places south of Tropic of cancer, mainly coastal region experiences equable climate.
Relief:
Himalayas prevents cold winds from North.
Blocks monsoon winds & gives R.F.
Wn Ghats helps in heavy R.F in wind ward side.
Monsoon:
Derived from Arabic word Mausim.
Means seasonal reversal of wind pattern.
CLIMATIC SEASONS : CLIMATIC SEASONS Four distinct seasons according to IMD.
Hot dry season.
Rainy season
Retreating monsoon season.
Winter season.
CLIMATIC SEASONS : CLIMATIC SEASONS Hot Dry Season: March – May.
also known as Summer season.
Weather is hot, dry and sultry.
Temp increases towards north.
Low pressure prevails.
Max temp in may in Thar (up to 480).
Highest 49.40 @ Ganganagar (Rajasthan).
Temp in coastal area modified by sea.
CLIMATIC SEASONS : CLIMATIC SEASONS High mountains have low temp.
Convectional rain occurs in some regions.
Thunderstorms with strong wind occurs occasionally.
Known as Kalbaisakhi (W.B), Andhis in U.P, coffee blossom in Karnataka, Mango shower in Kerala.
Loo (hot dusty wind) are common in Nn plain.
CLIMATIC SEASONS : CLIMATIC SEASONS Characteristic features:
Marked by dry weather.
High temp in tropical India.
Range of temp is high in Interior parts and low in coastal areas.
Thunderstorms and dusty winds are common.
Brief spell of showers are experienced.
CLIMATIC SEASONS : CLIMATIC SEASONS Rainy Season: June to mid September.
Also known as S.W monsoon or Hot wet Season.
Moist wind blows from S.W towards land since L.P prevails in landmass.
These winds are known as S.W Monsoon.
Gives R.F to most of the regions.
Branches:
Arabian sea Branch.
Bay of Bengal Branch
CLIMATIC SEASONS : CLIMATIC SEASONS ARABIAN SEA BRANCH:
Blows from S.W, obstructed by Wn Ghats.
After crossing, it descend on eastern slopes.
Becomes dry, gives less R.F in leeward side known as Rain shadow region.
Part of Arabian sea branch is obstructed by Vindhyas, Satpuras and Central Mountains.
Rainfall decreases from W to E
Rainfall is Orographic in nature.
CLIMATIC SEASONS : CLIMATIC SEASONS BAY OF BENGAL BRANCH:
Gets sufficient moisture while blowing over Bay of Bengal.
Strikes hills of Meghalaya and Assam.
Causes heavy R.F.
Highest: Mawsynram 1147 cm.
Cherrapunji 1081cm.
Turns towards W and blows across N. India.
CLIMATIC SEASONS : CLIMATIC SEASONS R.F decreases towards W.
Gives little R.F when reaches Thar.
Andaman and Nicobar islands and Srilanka receives first rainfall through this branch.
Retreating Monsoon Season:
Mid September -November
Also known as N.E Monsoon.
Period of unsettled weather.
CLIMATIC SEASONS : CLIMATIC SEASONS Causes of occurrence:
Due to apparent movement of the sun, L.P is developed over the surrounding water body and H.P over landmass, the south west monsoon change their direction and moves as N.E winds.
These winds picks moisture from Bay of Bengal while retreating.
Owing to coriolis force, are deflected towards right.
CLIMATIC SEASONS : CLIMATIC SEASONS Reach Coramandal coast.
Give moderate R.F to Coast of T.N & A.P
Other parts do not receive R.F.
Tropical cyclones are common & frequent.
Causes heavy R.F and damage along their path.
Winter Season: early Dec to end of Feb
Chief characteristics:
low temperature,
clear sky,
low humidity.
CLIMATIC SEASONS : CLIMATIC SEASONS Light northerly wind prevails.
Temp increases from N to S.
Cool in N and quite warm in S.
January is the coldest month.
Hill areas of J&K and Himachal Pradesh record lowest temp.
Dras valley in Kashmir near Kargil has lowest temp.
High pressure in interior part
Little rainfall from depression of Mediterranean region
MECHANISM OF MONSOON : MECHANISM OF MONSOON Still not clearly known:
No explanation is satisfactory so far.
Earlier View:
In summer high temperature and Low Pressure in central Asia, Surrounding ocean had low temp and High Pressure.
Wind moved from sea to land during summer.
Vice a versa in winter.
MECHANISM OF MONSOON : MECHANISM OF MONSOON Modern Theory
Air mass theory :
N.E trade winds and S.E trade wind meet at equator.
This region is called ITCZ (Inter Tropical Convergence Zone.)
ITCZ shifts N of Equator in summer and S of Equator in winter.
While shifting N, S.E trade wind from Sn hemisphere cross equator and blow as S.W and gives R.F. This is known as S.W Monsoon.
MECHANISM OF MONSOON : MECHANISM OF MONSOON Jet Stream Theory :
Jet stream – Band of fast moving air found in mid latitudes in upper troposphere.
Westerly jet stream is located along Sn slope of Himalayas in winter.
Suddenly shifts N and flows over Tibetan plateau.
This periodic movement of sub tropical jet stream indicates arrival and withdrawal of monsoon.
MECHANISM OF MONSOON : MECHANISM OF MONSOON Recent observations reveals Inter connection between Intensity and duration of heating of Tibetan plateau and monsoon rain in India.
Higher the intensity and duration more the rainfall and vise a versa.
ANNUAL DISTRIBUTION OF RAIN FALL : ANNUAL DISTRIBUTION OF RAIN FALL Distribution of rain fall is uneven, uncertain, irregular.
Great variation in amount of rainfall in various parts.
Factors determining the distribution of rain fall are:
Direction of moist laden wind.
The relief features and
passage of cyclone.
ANNUAL DISTRUBUTION OF RAIN FALL : ANNUAL DISTRUBUTION OF RAIN FALL Rain fall Regions :
Areas of very high rainfall (>200 cm)
Southern slopes of En Himalayas, Assam hill regions, Wn slope of Wn Ghats.
Areas with high rainfall (100-200 cm)
Middle Ganga valley, Nn part of Andra Pradesh and Sn part of Tamil Nadu, Parts of Wn Ghats and En Maharastra.
ANNUAL DISTRUBUTION OF RAIN FALL : ANNUAL DISTRUBUTION OF RAIN FALL 3. Areas with Low Rain Fall (50-100 cm)
Upper Ganga valley, En Rajasthan, Sn Deccan comprising plateau region of Karnataka parts of Andhra Pradesh and Tamil Nadu.
Areas with very low Rain fall(<50 cm)
Wn Rajasthan, Sn Punjab, Nn most part of Kashmir, rain shadow regions of Wn Ghats.
CLIMATIC TYPE REGIONS OF SOUTH ASIA : CLIMATIC TYPE REGIONS OF SOUTH ASIA Srilanka type – Wet and Dry zone.
Tropical rain forest type – W. coastal plain and Assam.
Tropical Savanna – central and S. India, Bangladesh.
Tropical and subtropical steppe and semiarid – N.W India.
Hot desert of Karachi type.
Lahore type – Indian and Pakistani Punjab.
Himalayan type including Nepal, Bhutan.
CLIMATE - PAKISTAN : CLIMATE - PAKISTAN Lies in Temperate Zone:
Weather condition varies from humid coast, to dry, hot desert interior, to Icy mountains in North.
Four Seasons:
1. winter (Dec to Feb)
2. Hot – dry spring (March to May)
3. S.W Monsoon (June to Sept.)
4. N.E Monsoon (Oct to Nov.)
CLIMATE - PAKISTAN : CLIMATE - PAKISTAN In North and West rainy season occur during winter.
Arid condition prevails in most part.
Punjab has major fluctuations in monsoon rainfall.
Average rainfall 13 cm in Plains, 89 cm (high lands).
Hail storm is common.
Lofty mountains of N are permanently snow covered.
CLIMATE - BANGLADESH : CLIMATE - BANGLADESH Experiences 3 seasons viz.,
1. winter (Oct to early march),
2. Hot season (March to May),
3. Monsoon (May to September).
Has heavy average annual R.F 120 cm to 145 cm. 80% of rain fall in monsoon season.
Cyclones also occur during Oct-Nov.
Hail storm occur in monsoon season.
CLIMATE - NEPAL : CLIMATE - NEPAL Has 4 seasons:
1.Winter (Dec to Feb). Cold and clear with snow.
2. Spring (March to May) warm some showers.
3. Summer (June to August) Monsoon rain.
4. Autumn (Sept to Nov) cool and clear.
CLIMATE - NEPAL : CLIMATE - NEPAL Climate varies by altitude:
Above 1600 ft. below freezing point and permanent snow cover.
80% of rainfall from summer monsoon.
Rainfall ranges from < 25 to more than 600 cm.
CLIMATE - MYANMAR : CLIMATE - MYANMAR Average temperature 280C, dips below 00C. In mountains and 450C on central Plains.
Humidity 66% to 83%
3 seasons :
cool winter (Nov to Feb)
Hot season (Mar to April)
S.W monsoon (rainy season) May to Oct.
Average annual R.F. 500 cm. Frost and snow occur in high Mountains of North.
CLIMATE - AFGHANISTAN : CLIMATE - AFGHANISTAN Semi Arid to Arid climate:
Summers are hot and dry. Winter are bitterly cold.
Spare and irregular R.F.
Average rainfall 25 – 30 cm.
Humid air from Persian gulf produces summer showers and thunder storms in S.W.