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Accueil du site → Doctorat → Mexique → Variabilidad de la sequía meteorológica de largo plazo en la parte mexicana de la Cuenca del Río Bravo

Universidad Autónoma de Nuevo León (2013)

Variabilidad de la sequía meteorológica de largo plazo en la parte mexicana de la Cuenca del Río Bravo

Núñez López, Daniel

Titre : Variabilidad de la sequía meteorológica de largo plazo en la parte mexicana de la Cuenca del Río Bravo.

Auteur : Núñez López, Daniel

Université de soutenance : Universidad Autónoma de Nuevo León

Grade : Doctor en Ciencias con especialidad en Manejos de Recursos Naturales UANL, 2013

Résumé
In this study were conducted retrospective analyses of climatic indicators in order to assess the variability of drought events occurred in medium and long term over the Mexican territory of the Rio Bravo Basin (CRBM). The first phase of the study was analyze monthly rainfall data from 201 weather stations in order to evaluate the influence of the topographic, geographic and continentality variables on the spatial distribution of mean monthly precipitation. Multiple regression models were fitted to predict the spatial distribution of the PMM as a function of elevation, complexity of the topography, coast proximity and geographic location of weather stations. The results show that the spatial variability of precipitation that occurs during the wet period could be explained between 70 and 82% by the predictive variables. Validation tests revealed that the models from May to August were the best predictions. The calibration of the models significantly improved the reliability of the interpolations of every month, obtaining reliable geographical coverages of PMM with high spatial resolution that could be used as input variables in models that assess hydrological processes in the CRBM.
In a next phase, standardized precipitation index (SPI) values were calculated from instrumental records to identify meteorological drought during the period of 1970 2008. The study confirmed that the most intense, persistent and severe drought events from the analyzed period were occurred at mid-nineties and early twenty first century. Integrated difference curves showed since the mid-nineties, downward trends indicating the presence of a dry period, that seems to end in 2005. However, SPI values reconstructions performed with dendrochronological series distributed in the mountain zone of the of the CRBM, revealed that the drought severity of the late twentieth and early twenty-first century was not higher than of the droughts identified at mid-twentieth century (1948 to 1957), at the nineteenth century (1866-1877) and at the eighteenth century (1780-1787), and none of the above was comparable with the mega-drought of the sixteenth century (1525-1550). Integrated difference curves derived with SPI values reconstructed, allowed to identify, cyclic behavior characterized by curves with upward and downward trends that indicated the establishment of multidecadal wet and dry periods. The amplitude of the cycles observed from the last three centuries, seems to correspond chronologically in the reconstructed series, so if this oscillatory behavior is maintained, it can be expected that drought period observed from late twentieth and early twenty-first, could continue for the next decades. Finally, the influence of ocean-atmospheric indicators was evaluated and we found that long term trends toward the warm phase from the North Atlantic Ocean and toward the cold phase from the Pacific Ocean determine the occurrence of winter–spring droughts in the CRBM.

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Page publiée le 17 novembre 2016, mise à jour le 16 août 2017