NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-12-1493-2012 Spatial and temporal variability of precipitation and drought in Portugal Martins D. S. 1 Raziei T. 1 2 Paulo A. A. 1 3 Pereira L. S. 1 CEER-Biosystems Engineering, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Portugal Soil Conservation and Watershed Management Research Institute, Tehran, Iran Escola Superior Agrária de Santarém, Portugal 16 05 2012 12 5 1493 1501 Copyright: © 2012 D. S. Martins et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/articles/12/1493/2012/nhess-12-1493-2012.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/12/1493/2012/nhess-12-1493-2012.pdf

The spatial variability of precipitation and drought are investigated for Portugal using monthly precipitation from 74 stations and minimum and maximum temperature from 27 stations, covering the common period of 1941–2006. Seasonal precipitation and the corresponding percentages in the year, as well as the precipitation concentration index (PCI), was computed for all 74 stations and then used as an input matrix for an R-mode principal component analysis to identify the precipitation patterns. The standardized precipitation index at 3 and 12 month time scales were computed for all stations, whereas the Palmer Drought Severity Index (PDSI) and the modified PDSI for Mediterranean conditions (MedPDSI) were computed for the stations with temperature data. The spatial patterns of drought over Portugal were identified by applying the S-mode principal component analysis coupled with varimax rotation to the drought indices matrices. The result revealed two distinct sub-regions in the country relative to both precipitation regimes and drought variability. The analysis of time variability of the PC scores of all drought indices allowed verifying that there is no linear trend indicating drought aggravation or decrease. In addition, the analysis shows that results for SPI-3, SPI-12, PDSI and MedPDSI are coherent among them.

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