MonsoonsTo explain the differences between the monsoon
periodsObjective:To develop knowledge of MonsoonsAim:
DefinitionMonsoonA seasonal windWinds change direction by 180 or
close to 180Generally with change of wind direction, one season
will be associated with heavier rainfall. (Wet summer, drier
winter)Short inter-monsoon period
Idealised planetary wind systemsTrade windsAssumptions?Earth
rotates about its axisSuns declination is zeroEarths surface is
uniform
Monsoon ExperienceAnywhere with large land masses close to the
ITCZNorth Indian Ocean, South East Asia & Western Pacific.West
Africa (failure of the monsoon leads to drought
conditions)AustraliaBrazilCentral & Eastern North America
(weak)
What happens to the ITCZ in July?
Jan to JulyITCZ moves NJuly to Jan ITCZ moves S
Cause of the Monsoons?Complete explanation is not yet
available!!Unequal heating and cooling of the earths surface: ie
land versus sea.Note topography complicates the monsoon circulation
and the distribution of rainfall disruption of the jet stream.
North East Monsoon (Nov ~ Mar)N of the Equator Wind: NE force 3
- 4 decreasing towards equator.Weather: fine & clearW
PacificWind: NE force 5 to 6 decreasing towards equator & more
northerly.Weather rain or drizzleNote Double ITCZ in Indian Ocean
(S of Equator).North Australia (NW monsoon)Wind: NW force 6
Weather: cloudy skies & heavy rain showersWeatherFor detailed
descriptions see Ocean Passages for the World
South West Monsoon (Jun ~ Sept)Associated weatherArabian
SeaWind: SW force 6 to 7Weather: extensive cloud & pptn
mod/poor visW PacificWind: SE to SW force 3 to 4.Weather: partial
cloud cover, occ showers or squalls (wind F7)North AustraliaWind:
SE trade windsFor detailed descriptions see Ocean Passages for the
World
Intermonsoon Periods (Apr ~ May & Oct)Conditions vary
greatlySST reaches 27CITCZ moving
