Zusammenfassung der Ressource
Climate of India
- Introduction
- climate of a country includes temperature, rainfall, atmospheric pressure &
direction & velocity of winds over a long period of time
- in the north Indian sub-continent is separated from rest of
asia by the Himalayan ranges
- so cold air masses from central
Asia cannot enter India
- so whole of India South of Himalayas
treated as a tropical country
- although its norther part is situated in temperate belt
- the Arabian sea & Bay of Bengal in the south of Indian
coast give it a typical tropical monsoon climate
- Diversity in the Unity of
Indian Monsoon climate
- the climate of India has many regional
variations expressed in
- winds, temperature, rainfall, rhythm of
seasons & degree of wetness or dryness
- these climatic differences are due to
- location
- altitude
- distance from sea
- relief
- Factors Influencing the climate of India
- influenced by largely geographical factors
- Location & Longitudinal Extent
- Distance from the Sea
- coasts experience equable climate
- interiors experience extreme continental climate
- The Northern Mountain ranges
- Himalayas act as a climatic divide between
Indian Sub continent & central Asia
- Physiography
- physical map of India is closely related to
climatic conditions of the country
- Monsoon Winds
- most dominating factor of Indian Climate -
so called Monsoon climate
- Upper Air Circulation - Jet Streams
- Westerly Jet Stream
- Easterly Jet Stream
- Tropical Cyclones & Western Disturbances
- El-Nino Effect
- La Nina
- Southern Oscillation
- The Monsoon Winds
- Mechanism of the Monsoons
- Classical Theory
- summer monsoon
- winter monsoon
- Halley - explained the monsoon as resulting from
thermal contrasts between continents & oceans due to
their differential heating
- Modern Theories
- Air mass theory
- due to the seasonal shift of ITCZ
- Flohn's model
- Jet Stream Theory
- the Periodic movements of the jet stream are often indicators
of the onset & subsequent withdrawal of the monsoon
- In winter the western jet stream flows along the southern slopes of the
Himalayas but in summer it shifts northwards, rather dramatically, &
flows along the northern edge of the Tibet plateau
- Yin model
- the burst of monsoon depends upon the upper air circulation
- the intensity & duration of heating of tibet
plateau has a direct bearing on the amount of
rainfall in India by the monsoons
- when the summer temperature of air over tibet remains
high for a sufficiently long time, it helps in strengthening
the easterly jet & results in heavy rainfall in India.
- Besides differential heating, the development of
monsoon is influenced by the shape of the
continents, topography, the condition of upper
air circulation etc.
- Meteorological Teleconnections
- Southern Oscillations
- Sea-saw pattern of meteorological changes
observed between Pacific & Indian Oceans
- the pattern of low & high pressures over Indian & Pacific oceans give
rise to vertical circulation along the equator - Walker Circulation
- low pressure over Indian Ocean in winter months - good for monsoon
- shifting east wards from its normal position in ElNino
Years reduces monsoon rainfall in India
- due to close association b/w ElNino & SO - jointly referred as ENSO event
- Southern oscillation index SOI is
used to measure the intensity of SO
- this is the difference in pressure between Tahiti
representing Pacific ocean & port Darwin in
northern Australia representing pacific ocean
- Positive SOI - HP over east pacific Tahiti & Low Pressure over
Indian ocean - low rainfall over eastern pacific & good
monsoon rain over India & Indian ocean
- HP in Indian Ocean & LP over East pacific - poor monsoon over
India & higher then usual rain over east pacific
- El Nino
- narrow warm current, which appears off the coast of Peru in dec.
- The Child Christ
- influence Indian monsoon
- when surface temp goes up in southern pacific
ocean - India receives deficient rainfall & conversely
- term monsoon derived from the Arabic Mausam meaning season
- seasonal winds which reverses their direction
of flow with the change of season
- they flow from sea to land during the summers
& from land to sea during winters
- called as double system of seasonal winds -
the sum of summer & winter winds
- Seasonal Rhythm
- The cold Weather season or Winter Season
- from NOV to MAR
- clear sky, pleasant weather, low temperature & humidity etc.
- Temperature
- Pressure & winds
- Western disturbances & Tropical Cyclones
- the spell of fine weather is often broken due to
inflow of depressions from the west
- the low pressure depressions are called
western disturbances
- they originate in the
Mediterranean sea & enter India
- intensify over NW India & reach
upto Arunachal Pradesh
- lowers temperatures
by 5 - 10 degree C
- jet streams play important role in bringing these
- season of least tropical cyclone activity - due to low sea
surface temp & location of ITCZ farthest south
- The Summer Season
- March - June - High temp & low humidity
- Pre-monsoon period
- temperature
- the diurnal range of temp is very high
- the temp are lower in southern parts due to moderating effect of the sea
- the temp of west coast are comparatively lower than those
prevailing on the east coast due to prevailing westerly winds
- Northern & central part experience heat waves i.e. 6-8° more than
normal - because of their location far away from the sea.
- the strong north westerly winds check the onward sea breeze over eastern
coastal belt & create heat wave conditions over coastal A.P & Orissa
- Pressure & Winds
- Low pressure - high temp
- during may june - high temp in NW India builds - hot,
dust laden & strong wind known as loo blows
- strong dust storms - Andhis - thunderstorms from NW
bring small showers - give relief from scorching heat
- the strong westerly winds or western disturbances in upper troposphere lead to thunderstorms in east &
north-eastern part of the country - they normally originate over chota nagpur plateau & carried eastwards by
westerly winds - known as Norwesters - some times hailstones - cause heavy damage to crops - mainly occur
during mid March - Mid April - of Vaisakh month - locally known as Kalabaisakhis - black storms
- western disturbances still prevails with their frequency & intensity gradually decreasing -
these cause change in weather conditions, bringing cloudiness & convective activity
- few tropical cyclones originate in Bay of Bengal & Arabian sea
- Precipitation
- 1% of annual rainfall receive during this season
- Norwesters bring rainfall of about 50 cm in NE India
- also known as spring storm showers
- there will be some mango showers in A.P & T.N