Tesis doctoral de Joan Pons Claret
The presented dissertation pursues several objectives, all of them aimed to better understand the electromagnetic emission of the sea surface. This knowledge can be applied to better explain the diverse contributions to the sea surface brightness temperatures emissions that lead to the final and most relevant derived parameter, the wind vector (wind speed and direction). although there are several methods to measure the wind vector, like anemometers placed on buoys, it is quite complex to obtain a global map with a dense grid, implying world wide buoys allocation at a small distance. The alternative is the remote measurement of those parameters by means of active (radar) or passive (radiometer) radiofrequency devices. one of the main goals of this dissertation is to design, develop, and test a state of the art radiometer capable of measuring the electromagnetic emission of the sea surface remotely. The frequency of operation is one of the key parameters, and is chosen to match one of the windsat satellite (18,7 ghz), launched early 2003, as a proof of concept mission to remotely retrieve the wind vector. The developed instrument must be robust enough to efficiently operate not only in a controlled environment but also in a remote location with adverse weather conditions. once the construction of the radiometer is completed, this has to be calibrated using the latest and most innovative calibration standards, which in turn, will provide accurate measurements. This calibration process will allow extensive testing and tweaking of the radiometer in a controlled environment, mainly indoors in a laboratory. once the radiometer has satisfactorily covered the testing stage, this will be deployed in a field experiment, to gather data in a real scenario. The goal is to leave the instrument operating standalone during a long period of time (around one month) measuring the emissivity of the sea surface from various incidence and azimuth angles. the measured raw data is then processed and analyzed. To remove all the non desired effects, like downwelling brightness temperature, platform heading, or tilting, that can alter the real brightness temperatures signatures laying beneath the raw measurements. The processed empirical data will be compared with several different emissivity theoretical models. this dissertation focuses on the first layer products, ie. Brightness temperatures at four different polarizations. Even tough the final desired product is the wind vector over the sea surface, this would require a suite of different instruments operating at several different frequencies and polarizations and measuring simultaneously the same scene, which is not feasible with the use of only one radiometer. Windsat satellite for example, consists of several receivers operating at different frequencies which allow deriving brightness temperatures and wind speed and direction. to illustrate a possibility to convert brightness temperatures measurements to wind speed and vector outputs, several theoretical algorithms are presented. The accuracy of these algorithms is tested with empirical data obtained from the satellite ssm/i. The objective is to present a tool that merges all the diverse components of the raw data, providing a meaningful measurement of the desired outcome.
Datos académicos de la tesis doctoral «Wind vector retrieval over the ocean by means of microwave radiometry«
- Título de la tesis: Wind vector retrieval over the ocean by means of microwave radiometry
- Autor: Joan Pons Claret
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 03/12/2000
Dirección y tribunal
- Director de la tesis
- Nuria Duffo Ubeda
- Tribunal
- Presidente del tribunal: ignasi Corbella sanahuja
- ramón Villarino villarino (vocal)
- pedro Antonio De paco sánchez (vocal)
- Antonio ramon Lázaro guillén (vocal)