Global annual cycle F Kucharski Fred Kucharski Abdus
Global annual cycle F Kucharski Fred Kucharski, Abdus Salam ICTP, Earth System Physics Section, Climate Variability Group, Trieste, Italy
http: //www. windows 2 universe. org/earth/climate/cli_seasons. html
External forcing Longitude average of Solar surface radiation In W/m^2 This clearly drives our seasons
Of course, this translates Into seasonal variations of surface temperature (here in degrees C) However, note that the northsouth excursions are much smaller……. . and there is a 1 -2 month shift -> Inertia of Oceans
May be a more interesting field: Sea-level pressure (shown here in h. Pa) As you know, it rains where the pressure is low…
But first have a look At the consequences For the zonal mean Winds [m/s]. Trades Interesting interruptions of trades: Monsoons! Extratropical westerlies
And finally precipitation: The extratropical rainbelts The tropical ITCZ (precip in mm/day)
Cool, why? Diff temp djf-jja
Even the global men surface temperature has a seasonal cycle (due to heat capacity differences between ocean and land)
Mediterranian Climates Diff slp djf-jja Subtropical monsoons
Mediterranian Climates Diff prec djf-jja Subtropical monsoons
Picture can be quite different if we zoom into specific regions: Indian Monsoon
Seasonality of Indian Monsoon
Mechanism 2 : Different heat capacity of land sea (land-sea breeze)
Mechanism 2 : Different heat capacity of land sea (land-sea breeze)
Zoom into Mediterranean
Surface pressure: Azores high moving northwards
Zoom into the Mediterranean
Also Carbon Dioxide has a seasonal Cycle……. .
SUMMARY • The annual cycle is the largest climate variation on Earth. • It is forced by the Earth axis tilt with respect to the rotation axis around the sun. • The surface temperature reacts to this forcing with some delay, depending on the total heat capacity (land/ocean). • The responses of other climatic fields, such as surface pressure, winds and rainfall, is also very clear, but more complicated. • Usually the annual cycle is stronger in high latitudes than in low latitudes, particularly for temperature. • The climate in the mediterranean region is strongly influenced by the seasonal cycle, but also the climate in monsoon regions (i. e. Indian Monsoon).
THANK YOU!
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