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Global annual cycle

Explore the annual cycle and seasonal variations on Earth, including the impact of external forcing, inertia of oceans, zonal mean winds, monsoons, precipitation patterns, and the influence on different regions like the Mediterranean and Indian Monsoon. Understand the factors driving climate variability and the importance of the seasonal cycle in shaping Earth's climate.

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Global annual cycle

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  1. Global annual cycle F Kucharski Fred Kucharski, Abdus Salam ICTP, Earth System Physics Section, Climate Variability Group, Trieste, Italy

  2. http://www.windows2universe.org/earth/climate/cli_seasons.htmlhttp://www.windows2universe.org/earth/climate/cli_seasons.html

  3. External forcing Longitude average of Solar surface radiation In W/m^2 This clearly drives our seasons

  4. Of course, this translates Into seasonal variations of surface temperature (here in degrees C) However, note that the north- south excursions are much smaller……..and there is a 1-2 month shift -> Inertia of Oceans

  5. May be a more interesting field: Sea-level pressure (shown here in hPa) As you know, it rains where the pressure is low…

  6. But first have a look At the consequences For the zonal mean Winds [m/s]. Trades Interesting interruptions of trades: Monsoons! Extratropical westerlies

  7. And finally precipitation: The extratropical rainbelts The tropical ITCZ (precip in mm/day)

  8. Cool, why? Diff temp djf-jja

  9. Even the global men surface temperature has a seasonal cycle (due to heat capacity differences between ocean and land)

  10. Mediterranian Climates Subtropical monsoons Diff slp djf-jja

  11. Mediterranian Climates Subtropical monsoons Diff prec djf-jja

  12. Picture can be quite different if we zoom into specific regions: Indian Monsoon

  13. Seasonality of Indian Monsoon

  14. Mechanism 2 : Different heat capacity of land and sea (land-sea breeze)

  15. Mechanism 2 : Different heat capacity of land and sea (land-sea breeze)

  16. Zoom into Mediterranean

  17. Surface pressure: Azores high moving northwards

  18. Zoom into the Mediterranean

  19. Also Carbon Dioxide has a seasonal Cycle……..

  20. 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).

  21. THANK YOU!

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