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
Therefore?
Monsoon activity today?SPECIAL DAILY WEATHER REPORT
Progress of Monsoon
Synoptic chartSurface winds
http://en.wikipedia.org/wiki/Image:India_southwest_summer_monsoon_onset_map_en.svg
Rainfall Chart(cm)http://www.imd.gov.in/section/climate/jan-feb-rainfall.htm
http://www.imd.gov.in/section/climate/jun-sep-rainfall.htmRainfall Chart(cm)