Unravelling the secrets of the wind at the ocean’s surface using scanning LiDAR

The aim? To measure the wind as close as possible to the water’s surface, within the first few metres above the waves. This measurement is made possible by scanning LiDARs capable of scanning the horizon several kilometres from the shore.

Belle-Île-en-Mer was not chosen at random. The island benefits from direct exposure to the Atlantic, a long stretch of open water where the wind can build up fully, as well as strong and consistent winds – ideal conditions for this type of measurement. The cliff at Pointe du Talut offers an unobstructed view of the sea and a wave-gauge buoy that continuously measures sea conditions.
 
The installation was a success. The data collected will provide a better understanding of the interactions between wind and waves, particularly in the presence of large waves, a key issue for climate modelling and the development of offshore wind power.
  The sensors at the Pointe du Talut (2 scanning LiDARs, 1 profiling LiDAR, 1 weather mast with 1 3D wind sensor and 3 temperature sensors).

Start of the test campaign for the PRAMAG project

This new test campaign forms part of the PRAMAG project, funded by the French National Research Agency (ANR) and the Defence Innovation Agency (AID). The aim of this project is to observe the interactions between wind and waves, and in particular the transfer of energy from waves to the wind. Indeed, whilst generally speaking wind blowing over the sea creates swells, sometimes, even when the wind stops, the swells continue and can have a feedback effect on the atmosphere. The objective of this measurement campaign is to observe this phenomenon.
 
This is a dual-purpose project, meaning it has both civilian and military objectives.

    Civilian: to improve our understanding of physics, enhance climate forecasting, and better understand the impact of rough seas on floating wind turbines.
    Military: to improve estimates of radar range. 

An initial trial campaign took place in 2023 using a single LiDAR scanner as part of the CARNOT MERS ExplOr project. See the article on ‘ExplOr 2023’.

3 partners, 3 complementary measurement methods

PRAMAG is a collaborative project, in partnership with research organisations that use complementary measurement methods.

• The LiDARs installed by the DAUC team at the Laboratory for Research in Hydrodynamics, Energy and the Atmospheric Environment (LHÉEA – Centrale Nantes/CNRS) measure the mean and turbulence profiles of the wind between the surface and 150 m above sea level.
• The small floats (2x2 m) deployed by the Mediterranean Institute (MIO – AMU/CNRS/IRD/UTLN) measure energy and heat exchange at the sea surface.
• The quadcopter drones (4 rotors) from the National Centre for Meteorological Research (CNRM – Météo France/CNRS) measure the temperature and humidity profile in the first few tens of metres above the surface.