EESS talk on "The fascinating katabatic winds in Antarctica: a come back to the ‘home of the blizzard"
Event details
| Date | 12.05.2020 |
| Hour | 12:15 › 13:00 |
| Speaker | Dr Etienne Vignon, Remote Sensing Laboratory, IIE, EPFL |
| Location | |
| Category | Conferences - Seminars |
Abstract:
The margin of East Antarctica is a region of great meteorological interest particularly due to the so-called ‘katabatic winds’ that fascinated and severely tested the pioneering scientific expeditions in the far south. The cold, dense and fierce katabatic winds that flow over the sloping surfaces of the ice sheet can attain very high speeds in confluence regions like Adélie Land. This region exhibits the most intense sustained surface winds on Earth and was immortalized in Douglas Mawson’s 1915 book ‘The Home of the Blizzard’. From a climatological perspective, the offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of deep ocean waters. Strong but also dry, katabatic winds significantly diminish the precipitation amount that actually falls onto the ice sheet by sublimating the snowflakes before they reach the ground surface.
In this seminar, we will first briefly review our knowledge of the Antarctic katabatic winds and present recent advances in our comprehension of their vertical structure.
We will then 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 surface or is completely sublimated in the katabatic layer.
In a third part, we will focus on the offshore extent of the intense katabatic flows and more precisely on the dynamical transition they experience at the coast. By combining satellite images, remotely-sensed measurements and numerical simulations, we will evidence the formation of a ‘katabatic jump’ that 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 reveals that katabatic jumps and low-level gravity waves frequently occur over coastal Adélie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics.
Short biography:
Dr 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 Institute of Environmental Geosciences in Grenoble, France. His current research focuses on the study of atmospheric processes in the polar atmosphere. He also spends time in trying to improve the representation of those processes in climate models.
The margin of East Antarctica is a region of great meteorological interest particularly due to the so-called ‘katabatic winds’ that fascinated and severely tested the pioneering scientific expeditions in the far south. The cold, dense and fierce katabatic winds that flow over the sloping surfaces of the ice sheet can attain very high speeds in confluence regions like Adélie Land. This region exhibits the most intense sustained surface winds on Earth and was immortalized in Douglas Mawson’s 1915 book ‘The Home of the Blizzard’. From a climatological perspective, the offshore extent of Antarctic katabatic winds exerts a strong control on the production of sea ice and the formation of deep ocean waters. Strong but also dry, katabatic winds significantly diminish the precipitation amount that actually falls onto the ice sheet by sublimating the snowflakes before they reach the ground surface.
In this seminar, we will first briefly review our knowledge of the Antarctic katabatic winds and present recent advances in our comprehension of their vertical structure.
We will then 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 surface or is completely sublimated in the katabatic layer.
In a third part, we will focus on the offshore extent of the intense katabatic flows and more precisely on the dynamical transition they experience at the coast. By combining satellite images, remotely-sensed measurements and numerical simulations, we will evidence the formation of a ‘katabatic jump’ that 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 reveals that katabatic jumps and low-level gravity waves frequently occur over coastal Adélie Land. It emphasizes the important role of such phenomena in the coastal Antarctic dynamics.
Short biography:
Dr 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 Institute of Environmental Geosciences in Grenoble, France. His current research focuses on the study of atmospheric processes in the polar atmosphere. He also spends time in trying to improve the representation of those processes in climate models.
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Alexis Berne, LTE