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PRODID:-//Memento EPFL//
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SUMMARY:EESS talk on "The fascinating katabatic winds in Antarctica: a com
 e back to the ‘home of the blizzard"
DTSTART:20200512T121500
DTEND:20200512T130000
DTSTAMP:20260929T040040Z
UID:f8846f0f342992217518bdf0f934f1d04f307f1c6f624299470d2f9d
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Etienne Vignon\, Remote Sensing Laboratory\, IIE\, EPFL\nAb
 stract:\nThe margin of East Antarctica is a region of great meteorological
  interest particularly due to the so-called ‘katabatic winds’ that fas
 cinated and severely tested the pioneering scientific expeditions in the f
 ar south. The cold\, dense and fierce katabatic winds that flow over the s
 loping surfaces of the ice sheet can attain very high speeds in confluence
  regions like Adélie Land. This region exhibits the most intense sustaine
 d surface winds on Earth and was immortalized in Douglas Mawson’s 1915 b
 ook ‘The Home of the Blizzard’. From a climatological perspective\, th
 e offshore extent of Antarctic katabatic winds exerts a strong control on 
 the production of sea ice and the formation of deep ocean waters. Strong b
 ut also dry\, katabatic winds significantly diminish the precipitation amo
 unt that actually falls onto the ice sheet by sublimating the snowflakes b
 efore they reach the ground surface.\nIn this seminar\, we will first brie
 fly review our knowledge of the Antarctic katabatic winds and present rece
 nt advances in our comprehension of their vertical structure.\n\nWe will t
 hen decipher the complex interplay between katabatic winds and the weather
  systems transiting over the Austral Ocean and that transport moisture and
  precipitation towards the ice sheet. By tracking the pathway of moisture 
 from the ocean to its condensation and sedimentation onto the ice sheet\, 
 we will explain in which synoptic conditions snowfall either reaches the s
 urface or is completely sublimated in the katabatic layer.\nIn a third par
 t\, we will focus on the offshore extent of the intense katabatic flows an
 d more precisely on the dynamical transition they experience at the coast.
  By combining satellite images\, remotely-sensed measurements and numerica
 l simulations\, we will evidence the formation of a ‘katabatic jump’ t
 hat manifests as a turbulent ‘wall’ of blowing snow. The wall reaches 
 heights above 1000 m and horizontally extends over more than 400 km along 
 the coast. The jump then favors the trapping of a gravity wave train that 
 develops within a few hours. A statistical analysis of observations reveal
 s that katabatic jumps and low-level gravity waves frequently occur over c
 oastal Adélie Land. It emphasizes the important role of such phenomena in
  the coastal Antarctic dynamics.\n\nShort biography:\nDr Etienne Vignon is
  a post-doctoral researcher at the Environmental Remote Sensing Laboratory
 \, EPFL. He graduated in Geophysics at École Normale Supérieure in Paris
  and then obtained a PhD in atmospheric boundary-layer dynamics at the Ins
 titute of Environmental Geosciences in Grenoble\, France. His current rese
 arch focuses on the study of atmospheric processes in the polar atmosphere
 . He also spends time in trying to improve the representation of those pro
 cesses in climate models.\n 
LOCATION:Join ZOOM - ID 92723305112 https://epfl.zoom.us/j/92723305112
STATUS:CONFIRMED
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