Geographical Information, Remote Sensing, and Climatology
Résumé
Research carried out in the field of climatology is based on weather observations that are recorded in a certain number of climatological stations. These observations can sometimes be recorded over a very long period of time, as is the case in China (where rainfall records date back to the Middle Ages), and in England where rainfall records date back to the 18th century. In his thesis, “Climate history since the year 1000”, the historian E. Leroy Ladurie proved the usefulness of written or iconographic documents for the study of past climates. Different climate events have also strongly influenced history, for example, during wars. However, our knowledge of the Earth's climate is not only used for strategic purposes. It is, above all, the agricultural industry that depends on climatic conditions and, in some cases, the local climate can be seen as a useful resource or as a constraint. This means that climate does not play a neutral role in space or in the world of geographical reasoning: it is one of the elements that influences the land that is used by humans. Different societies function in different ways and this depends on a particular country's level of development, on a society's knowledge of different climate factors, and on the methods that it has available so that it can protect itself from harmful climatic events. Since the 1970s satellite observation of the Earth's atmosphere has greatly transformed and improved our knowledge of how different climate mechanisms function. From a very early point in the 1970s climatologists have understood the importance and significance of satellite data for their research: this can be seen in pioneering research and the success of Barrett's manual. Other pioneering work carried out in this field include the contents of Satellites et Climatologie the 3rd Conference held by the International Association of Climatology as well as the many theses written in France or in Brazil, where data produced by remote sensing proved to be extremely useful. More recently, the initiative created by the Research group of the French national center for scientific research, and Meteosat Second Generation has meant more collaboration between different geographers in order to produce and process Meteosat Second Generation images. The aim of this chapter is to analyze the use of satellites, which have greatly improved our knowledge of the spatialization of climate data over the past 30 years. An explanation will be given as to why satellite data plays a decisive role when it comes to increasing the density of geographical information for research that is carried out in regions in which there are not many conventional climatological stations available. For example, in Mato Grosso the rapid expansion of crops has led to an increasing demand on the climate. After an overview of the available satellite data, we will use examples of cases where geostationary data are used to estimate rainfall levels, and where SPOT-vegetation satellite data are used to estimate the extension of vegetation and crop cover.