Host laboratory: Hydrogeology, Flood and Geotechnical Risk Assessment Section (BEHRIG)
Beginning of the thesis: October 2018
Student name: Hugues DELATTRE
IRSN and CSTB share a common interest in determining the impact of extreme and exceptional wind hazards on structures in metropolitan France. Wind design approaches for ordinary structures only consider synoptic events (low pressure storms) and do not include local meteorological events (storms, tornadoes, downbursts). Moreover, some particular structures (nuclear and chemical installations) are designed for accidental load cases not deduced from statistical approaches. It therefore appears necessary to have methods that make it possible to discriminate these hazards by identifying the phenomena at the origin of these winds and by proposing specific characterisation methods for each type. Moreover, it seems necessary to study the evolution of these hazards in relation to climate change.
The objective is to develop tools to :
- distinguish/classify the observed events according to a phenomenology which will be defined;
- characterize the extreme levels of the various identified windy phenomena, with statistical methods adapted to their specificities;
- study the evolution of the hazard levels of future climate predictions.
The approach will be to cross-reference observations at weather stations with data from re-analysis, satellite, radio soundings and/or climate model outputs; to carry out a search for statistical or other tools to distinguish exceptional events that deviate from conventional adjustments; to establish the definition of a methodology for classification by weather type; to implement and/or develop statistical methods adapted to evaluate rare hazard levels (5. 10-2/year) to very rare (< 10-2/year); to identify events "covered" by safety and sizing standards and regulations; to quantify uncertainties in climate models to represent high winds; to exploit event databases to determine whether they should be treated independently. If so, a specific methodology will be defined. If not, the existing statistical approach will be reviewed according to the latest scientific developments in the field; to identify the consequences of the impact of climate change on these hazards. These results will be made available for a revision of the extreme wind maps.