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UID:20250731T061914EDT-1352xiuhSh@132.216.98.100
DTSTAMP:20250731T101914Z
DESCRIPTION:Please join us as we welcome Dr. Francesco Pausata\, a Research
 er in the Department of Meteorology (MISU) at Stockholm University for a s
 eminar titled 'The impacts of Sahara greening on the West African Monsoon 
 and its teleconnections to ENSO variability and storm activity during the 
 African Humid Period.' Coffee will be served.\n\nAbstract\n\nOne of the mo
 st dramatic changes in the West African Monsoon (WAM) occurred between 150
 00–5000 yr BP\, when increased summer rainfall led to the so-called “Green
  Sahara” and to a reduction in dust emissions from the region. However\, m
 odel experiments are unable to fully reproduce the intensification and geo
 graphical expansion of the WAM and the reduced El Nino-Southern Oscillatio
 n (ENSO) variability during this period. Here\, we use a fully coupled sim
 ulation for 6000 yr BP (mid Holocene) in which prescribed Saharan vegetati
 on and dust concentrations are changed in turn. A close agreement with pro
 xy records is obtained only when both the Saharan vegetation changes and d
 ust decrease are taken into account. The dust reduction strengthens the ve
 getation–albedo feedback\, extending the monsoon’s limit approximately 500
  km further north than the vegetation-change case only (to about 30°N). Ac
 counting for a vegetated and less dusty Sahara also has teleconnections fa
 r afield. We show that the strengthening of the WAM is able to affect ENSO
  variability\, reducing it by 25%\, more than twice the decrease obtained 
 using orbital forcing alone (10%). We identify changes in tropical Atlanti
 c mean state and variability as fundamental agents driving ENSO variations
 . The momentous strengthening of the West Africa Monsoon (WAM) simulated u
 nder vegetated Sahara leads to an Atlantic Niño-like mean state and a redu
 ction of its variability (46%). These changes in the equatorial Atlantic\,
  in turn\, affect the ENSO behaviour over the Pacific through changes in t
 he Walker circulation.  The above-mentioned changes in the large-scale cir
 culation\, and the thermodynamical and kinetic state of the atmosphere hav
 e also strong impacts on tropical cyclone (TC) development worldwide. Our 
 results show that the greening of the Sahara and its associated reduction 
 in dust emissions leads to an increase of TC activity in both hemispheres\
 , particularly over the Caribbean Sea\, Gulf of Mexico and east coast of N
 orth America.  Overall\, our studies highlight the importance of Saharan v
 egetation and dust emission in altering not only the intensity of the WAM\
 , but also ENSO variability and the potential intensity and genesis of TCs
 .\n
DTSTART:20161108T203000Z
DTEND:20161108T213000Z
LOCATION:Room 934\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Seminar: Dr. Francesco Pausata
URL:/meteo/channels/event/seminar-dr-francesco-pausata
 -263736
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