Estimation of dynamics from multiscale image assimilation. Application to : Rain nowcasting from ground radar images
The forecast of precipitation takes a special place, in view of their direct economic impact.
These forecasts allow, on the one hand, to anticipate environmental constraints and optimise, for example, the management of water resources, and, on the other hand, to anticipate flood risks. The aim of this study is to improve the nowcasting of precipitation rate of the Rain Nowcast (RN) algorithm that previously provides relevant forecasts for a time horizon of 30 minutes.
A multi-scale approach is suggested to merge two types of radar data, with different spatial resolutions, in order to increase the time horizon of the forecast while ensuring a forecast of quality in terms of both location and quantity of precipitation. We propose two multi-scales algorithms, the first one is sequential "Sequential Motion RN" : a global estimation with regional data to guide a local estimation with local data. The second is parallel "Parallel Motion RN": using both local and regional data simultaneously.
Two other methods dedicated to forecast have been proposed: geostrophic wind hypothesis, which involves correcting the underestimation motion intensity for low contrast structures in radar images. The second method: histogram correction, which involves correcting the smoothing effect caused by the numerical scheme by using a widely described technique in literature, to correct raingauge measurements estimated from radar images.
Defence : 06/11/2020 - 09h - Visioconférence Jury members : Mme. Bernadette Dorizzi, Professeur , Telecom SudParis [Rapporteur]
M. Laurent Barthes, Maître de conférences, UVSQ [Rapporteur]
Mme. Isabelle Herlin , Professeur, Inria
M. Dominique Béréziat, Maître de conférences, Sorbonne Université
M. Emmanuel Buisson, Experte, Weather Measures
Mme. Sylvie Thiria, Professeur, Sorbonne Université
M. Lionel Lacassagne, Professeur, Sorbonne Université
M. Étienne Huot, Maître de conférences, UVSQ
A. Zébiri, D. Béréziat, E. Huot, I. Herlin, E. Buisson : “Prévision multi-échelles des précipitations”, GRETSI 2019 - XXVIIème Colloque francophone de traitement du signal et des images, Lille, France, pp. 4 p. (2019)