Abstract

CAMPOS-ARANDA, Daniel Francisco. Quantification with SPEI of historical Droughts and under probable climatic change in the climatological station Zacatecas, Mexico. Tecnol. cienc. agua [online]. 2018, vol.9, n.2, pp.210-233.  Epub Nov 24, 2020. ISSN 2007-2422.  https://doi.org/10.24850/j-tyca-2018-02-09.

The SPEI (Standardized Precipitation-Evapotranspiration Index) is a variant of the widespread SPI (Standardized Precipitation Index), it has greater potential as drought index since it is sensitive to climate change because it uses a more realistic measure of the water availability: the climate balance. This measure is evaluated by the difference between monthly precipitation and potential evapotranspiration. This study describes in detail the calculation of SPEI and its application to the monthly historical records of precipitation and average temperature available in the climatological station Zacatecas, located in the capital of the state of Zacatecas, Mexico. The data covers 86 years in the period from 1930 to 2015. For historical droughts, the results of SPEI indicate in light, moderate, severe and extreme droughts, the following approximate values: 32.2%, 11.5%, 5.0% and 1.3%. For this particular location, three scenarios of climatic change were proposed; the first one accepts a progressive and linear reduction of 20% in annual precipitation, the second one adopts a progressive and linear increase of 4 °C in the average temperature and finally, the third one, superimposes the two effects mentioned; being therefore the most critical. For the three proposed scenarios, results suggest that light and extreme droughts increase scarcely in number or percentage, and that moderate and severe droughts decrease, also in a slight way. Results are condensed on graphs of SPEI evolution of duration 12 months, historical and the third scenario, in which the times of occurrence of drought periods are clearly displayed, as well as the specific differences in the value of SPEI exposed. Based on these analyzes, the systematic application of SPEI in the characterization of historical and future droughts is recommended, its application on future droughts would lead to results merely indicative.

Keywords : SPEI index; Log-Logistic distribution; probability weighted moments; potential evapotranspiration; statistical homogeneity; climate change.

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