On the following subject:
"Identification and detection of transient phenomena in low signal-to-noise ratio radar measurements. Joint applications to oceanographic and atmospheric problems".
Under the supervision of Mr Charles-Antoine GUERIN, University Professor, University of Toulon and Mr Julien MARMAIN, Degreane Horizon, thesis co-supervisor.
before a jury made up of
Alexandre BAUSSARD, University Professor, Troyes University of Technology, Rapporteur
René GARELLO, Professor Emeritus, IMT Atlantique, Rapporteur
Ms Anne MOLCARD, University Professor, University of Toulon, Examiner
Ms Marie LOTHON, CNRS Research Fellow, OMP - Observatoire Midi-Pyrénées de Toulouse, Examiner
Mr Julien MARMAIN, Doctor, Degreane Horizon, Co-supervisor
Charles-Antoine GUERIN, University Professor, University of Toulon, Director
Abstract
Radar remote sensing can be used to observe the dynamics of the atmosphere and ocean surface. In both cases, the usual approach is to numerically calculate the Doppler spectrum of the time echoes received using a discrete Fourier transform. Although satisfactory for most applications, this method is not suitable for observing transient phenomena, which are shorter than the integration time required for radar observation. We use an alternative technique, based on an autoregressive representation of the radar time series and associated with the maximum entropy method. This approach is applied to the measurement of surface currents by coastal radar in the high-frequency band, and then to the measurement of wind in the lower atmosphere by L-band radar. In both situations, we show using numerical simulations, comparisons with other instruments and case studies that the proposed approach leads to reliable estimates of geophysical quantities (marine currents and wind speeds) for short integration times, where the conventional method fails.
Key words: remote sensing, oceanographic radars, wind profilers, ocean currents, space radars, tsunami, turbulence, autoregressive models, maximum entropy method.