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Universidade de Lisboa (2016)

Cartografia da perigosidade e suscetibilidade de ocorrência de seca em Cabo Verde a partir de informação obtida por detecção remota

Santos, Carlos Albertino Borges dos

Titre : Cartografia da perigosidade e suscetibilidade de ocorrência de seca em Cabo Verde a partir de informação obtida por detecção remota

Auteur : Santos, Carlos Albertino Borges dos

Université de soutenance : Universidade de Lisboa

Grade : Mestrado em Sistemas de Informação Geográfica e Modelação Territorial Aplicados ao Ordenamento 2016

Résumé
This dissertation was developed in the scope of the project “Comprehensive Hazard Assessment and Mapping in Cape Verde. Drought Risk Assessment”, financed by the United Nations Development Programme (UNDP) and aims to contribute to the enrichment of scientific knowledge of droughts in the archipelago of Cape Verde. The archipelago is located in a vast zone of arid and semi-arid climate under the influence of the trade winds, crossing the African continent from the Atlantic Ocean to the Red Sea. Depending on the time of the year, the Cape Verde archipelago is influenced by the Azores high or the Intertropical Convergence Zone, which mean has a climate marked by high temperatures throughout the year and rainfall concentrated between July and November, although droughts are a recurrent phenomenon. Meteorological drought may be defined as the negative deviation of precipitation in relation to its normal values and is usually characterized by its duration, severity and frequency and has usually negative impact on different sectors such as agriculture, energy, tourism and transport. The drought phenomenon is related to risk management and food security and thus its monitoring is essential in this region. Despite the uncertainties of climate change projections, some models point out to an increase of the number of drought events during the current century making its analysis even more relevant. The gaps in rainfall data series and the poor spatial coverage of weather stations do not allow a detailed spatial analysis. The methodology presented in this research is based on traditional methods of drought identification, such as the Standardized Precipitation Index (SPI), combined with a new approach that uses other variables, such as the Normalized Difference Vegetation Index (NDVI), the geographical position of the archipelago, the altitude and the exposure to the trade winds. To assess the susceptibility of the islands to these events, several tests based on regression techniques were taken to verify the degree of association between precipitation and NDVI. The SPI calculations for the period between 1962 and 2013 allowed the identifications of 209 drought episodes, of which 114 were moderate, 43 severe and 53 extreme. Chronologically, the crisis of the 1970s, occasional episodes recorded at the beginning of the 1980s and 90s and a succession of normal and wet years in the twenty-first century were identified. The susceptibility evaluation led to the conclusion that about 80% of the archipelago’s territory has a high susceptibility to drought.

Mots clés  : Sistemas de informação geográfica - SIG Cartografia - Cabo Verde Detecção remota Seca - Cabo Verde Teses de mestrado - 2016

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