Installation site: Pic du Midi and surrounding plains
Discipline: Meteorology
Research field: Physics of severe thunderstorms
Context
Study of the frequency and structure of hail at high altitude.
Installation method and operation
A hail meter is installed outside the buildings and operated by Observatory staff. This passive measuring device consists of a specially-treated polystyrene panel (plate) positioned horizontally to the falling hail and sleet. After a hailstone fall, the staff document the hailstone impact on the back of the panel (time, duration, specific observations) and place a new panel in position. The plates are analysed at ANELFA’s Technical Centre to determine the dimensional distribution of the hailstones, as well as various integrated parameters such as hail mass per square metre and total kinetic energy of the hailstones…
Expected results
Hail climatology has become a very important research topic in meteorology, mainly because the phenomenon is expected to increase with global warming. Hail measurement networks operate in various parts of the world, but none are located at altitude. The effect of altitude is decisive both for the convection that ensures hail formation and for the melting of hailstones as they fall into the part of the atmosphere with a positive temperature. The Pic du Midi is currently the highest point in the world for measuring hail. After ten years of measurements, it has already proved that of all the measuring stations installed in the Midi-Pyrénées region, this is the place where the frequency of hail falls is highest, the total number of hailstones in a fall is maximum, but the average diameter of the hailstones is smaller than that measured in the plains.
Laboratories and partners involved
- Laboratoire d’Aérologie
- Association Nationale d’Etudes et de Lutte contre les Fléaux Atmosphériques (ANELFA)
