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Presented byDEEPCHAND VDept. Of GeologyUniversity of [email protected]
Introduction
Monsoon rainfall is the life-blood of more than half the world’s population.
Most developing countries, live under the influence of monsoon-dominated climates.
Term “Monsoon” derived from an Arabic word “Mausim” means Season
“ monsoon is a seasonal change in the direction of the prevailing, or strongest, winds of a region”
Monsoons are controlled by Winds and most prominent through tropical atmosphere
wet and dry seasons
North American monsoon (NAM) North African monsoon (NAF), Indian monsoon (IND), East Asian monsoon (EAS), Western North Pacific monsoon (WNP), South American monsoon (SAM), South African monsoon (SAF), and the Australian monsoon (AUS).
Monsoon is the reversal of wind direction in every six month.Caused by the differential heating of land and ocean.
High pressure and low pressure area
Winter to Summer and Summer to Winter.
Heated air in equator release energy to atmosphere
Raised air from equatorial atmosphere moved towards subtropical low pressure region.
This cause increase pressure in subtropics and decrease in near equator.
Air from subtropics flows into equator to fill the space.
Thus forming a loop called Hadley Circulation.
Origin of Monsoon
Origin of Monsoon ITCZ -This is the low pressure area near equator with converging and then rising
winds.
Temperature Increases water vapor rise cools Condense clouds Rains near ITCZ
Hadley circulation is not same through out the year It changes with seasons This seasonal change in Hadley circulation cause World Monsoons
Wind flows towards equator turns Right in NH and turns Left in SH.
This turn is due to the Rotation of Earth Coriolis Effect
(Monsoons, Ocean Currents, Hurricane)
It was the spin of earth that caused the winds to turn as they blew towards the equator
Origin of Monsoon
Wind change through year
December SH Heats more than NH
So ITCZ lies below equator
Wind flows from NH to ITCZ in SH
June NH Heats more than SH
So ITCZ lies above equator
Wind flows from SH to ITCZ in NH
As the ITCZ changes location through the year winds, Rains, Location of Monsoon also change
Factors effecting Monsoon
Latitude
AltitudeWind direction
Physiography
Indian Monsoon
INDIAN MONSOON
largest and most powerful monsoon circulation
Also known as South Asian Monsoon.
Most prominent of the world’s monsoon systems
North-East Monsoon and South-West Monsoon
Reversal of wind from Indian ocean to Indian subcontinent
South West Monsoon
• June to September• 1 June coast of Kerala• At Indian subcontinent divide in to two
Arabian branch and bay of Bengal branch• Arabian branch western coast• Bay of Bengal branch eastern Ghats and
north eastern part• Meet at indo Gangatic plane • The ITCZ shifts northwards • Insolation over Northern India increases,
causing air to rise and creating low pressure• The humid unstable air results in rainfall.
Amounts are increased as air is forced aloft over the Himalayas and Western Ghats.
North East Monsoon
• Retreating
• September to December
• Start retreating June itself
• Winter air reach cost of Tamil nadu in middle of December
• Low temperatures over central Asia create areas of high pressure
• at the same time, the sub-tropical jet and ITCZ shift south.
• Air moving out from the area of high pressure is very dry and becomes drier as it crosses over the Himalayas
Theories of formation of Indian Monsoon• Thermal theory- Halley
• Flohn’s Theory migration of Thermally produced zones of pressure belts and planetary winds.
• Modern Theory
Role of Himalaya
Role of Tibet Platuo
Role of High pressure zone of East Madagascar
Role of El Niño
Southern Oscillation
East Asian Monsoon
East Asian Monsoon
carries moist air from the Indian Ocean and Pacific Ocean to East Asia.
It affects approximately one-third of the global population
driven by temperature differences between the Asian continent and the Pacific Ocean.
Warm and Wet Summer Monsoon
Dry and Cold Winter Monsoon(Loess plateau)
winds being southeasterly in late June, bringing significant rainfall to the KoreanPeninsula and Japan
In the winter, the winds are northeasterly and the monsoonal precipitation bands move back to the south, and intense precipitation occurs over southern China and Taiwan.
American Monsoon
North American Monsoon Monsoons are less pronounced over America than in other parts of the world.
Formed by a regional-scale circulation.
July through September
NAM is characterized by intense rainfall & thunderstorms in Mexico and South west USA.
The mechanism of formation of NAM is similar to that of Indian Monsoon
Summer daytime heating over the Sonoran Desert and Arizona forms large low-pressure cell over the region.
moist tropical air from the high pressure regions of Gulfs of California and Mexico move towards the land surface to fill the space
Also known as South West Monsoon, Arizona Monsoon and New Mexican Monsoon
South American Monsoon
The South American monsoon (SAM) receives moisture from the tropical Atlantic and Amazon River basin
In South America, the monsoon starts in the spring
Rainfall accumulations reach their maximum over eastern and southeastern region during the mature summer monsoon and then decrease during the monsoon retreat in autumn.
Large seasonal changes result in an increase of precipitation over the Amazon basin
plays an important role in distribution and duration of the rainy season manually over the South Western Amazonia, and the central west and southeast Brazil region
Australian Monsoon
Australian MonsoonAlso known as East Asian Winter Monsoon.
Alternates between two seasons linked to wind direction
In winter easterly winds bring dry condition
In summer westerly winds bring sustained rainy conditions.
In summer the sun heats the Australian land faster than the surrounding ocean
difference in heating produces a difference in pressure
Pressure lower over the land than the ocean
warm, moist air from the tropical ocean is drawn towards the lower pressure over the hot and dry north of Australia
increasing humidity development of deep clouds and storms sustained rains
simple monsoonal patterns size and compact shape
The north shore is subject to a clear-cut wind reversal between summer (November–April, northwesterly flow) and winter (May–September, southeasterly flow)
AFRICAN MONSOON
African Monsoon
West African Monsoon and East African Monsoon
WAM Northern Hemisphere Summer (June through September)
EAM rains during spring and autumn
Combined effect of Indo-pacific and Atlantic ocean
West African Monsoon• ITCZ Lies above equator • low level southwesterly flow from the Atlantic Ocean• Monsoon rainfall over West Africa( June-September)• primary northeast trade wind, which blows from the Sahara and the Sahel as a
deep stream of dry, often dusty air
African Monsoon
East African Monsoon • ITCZ Moved towards southern hemisphere• long rains prevail during spring and the short rains during
autumn• Thus the transition (equinox) seasons bring most rainfall to
East Africa • Abrupt decline in the long rains have resulted in droughts
over this region.
Advantages of Monsoon
Brings rain for cropsAllow rise to ripen and harvestRelief from heatVegetation Comes to lifePower productionEconomy
Disadvantages of Monsoon
FloodingDrought (If rain comes late)Durst storm Insects and reptilesDestruction