Spatio-Temporal Variability of Surface Air Temperature in Northeastern Spain
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2012 39 Ahmed Mohammed Hussain El Kenawy El Sayed Spatio-temporal variability of surface air temperature in northeastern Spain Departamento Geografía y Ordenación del Territorio Director/es Vicente Serrano, Sergio Martín López Moreno, Juan Ignacio Tesis Doctoral Autor Director/es UNIVERSIDAD DE ZARAGOZA Repositorio de la Universidad de Zaragoza – Zaguan http://zaguan.unizar.es Departamento Director/es Tesis Doctoral SPATIO-TEMPORAL VARIABILITY OF SURFACE AIR TEMPERATURE IN NORTHEASTERN SPAIN Autor Ahmed Mohammed Hussain El Kenawy El Sayed Director/es Vicente Serrano, Sergio Martín López Moreno, Juan Ignacio UNIVERSIDAD DE ZARAGOZA Geografía y Ordenación del Territorio 2012 Repositorio de la Universidad de Zaragoza – Zaguan http://zaguan.unizar.es Departamento Director/es Tesis Doctoral Autor Director/es UNIVERSIDAD DE ZARAGOZA Repositorio de la Universidad de Zaragoza – Zaguan http://zaguan.unizar.es SPATIO‐TEMPORAL VARIABILITY OF SURFACE AIR TEMPERATURE IN NORTHEASTERN SPAIN A Dissertation submitted for the Degree of Doctor in Philosophy in the Department of Geography and Land Management University of Zaragoza Presented by Ahmed Mohammed Hussain El Kenawy El Sayed MSc in Environmental Informatics, University of Leicester, UK (2007) Supervisor Dr. Sergio Martin Vicente‐Serrano Instituto Pirenaico de Ecologia, Consejo Superior de Investigaciones Cientificas (CSIC), Zaragoza Co‐Supervisor Dr. Juan Ignacio López Moreno Instituto Pirenaico de Ecologia, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza Summer 2012 gÉ My little kid Kareem “If you cannot do great things, do small things in a great way.” Napoleon Hill (1883-1970) American writer Sergio Martín Vicente Serrano y Juan Ignacio López Moreno, científicos titulares del Departamento de Procesos Geoambientales y Cambio Global del Instituto Pirenaico de Ecologia (Consejo Superior de Investigaciones Científicas) CERTIFICAN: Que Don Ahmed Mohammed Hussain El Kenawy El Sayed ha realizado bajo nuestra dirección el trabajo que, para optar al grado de Doctor en Geografía, presenta con el título: “Spatio‐temporal variability of surface air temperature in northeastern Spain”, y Que el trabajo se ajusta a los objetivos establecidos en el proyecto de Tesis Doctoral aprobado el 16 noviembre de 2009, por el Departamento de geografía y Ordenación del Territorio y ratificado por la Comisión de Doctorado. Y para que así conste, firmamos la presente Certificación en Zaragoza a 25 de Mayo de 2012 para los efectos que sean oportunos. Fdo. Sergio M. Vicente Serrano Fdo. Juan I. López-Moreno ACKNOWLEDGMENTS My thanks go to all the people who have supported, accompanied and guided me throughout my PhD. First of all I would like to acknowledge Dr. Sergio Martin Vicente-Serrano for giving me the opportunity to continue my postgraduate studies in his research group. I also acknowledge my second supervisor, Dr. Juan Ignacio Lopez-Moreno, for his inspiring discussions. Both have been great motivators, given me their endless support, extensive insights and fruitful guidance throughout my work. They gave me the opportunity to live in Zaragoza for more than four years, a city which I admire very much. I would also like to thank Dr. Nathaniel Brunsell from the Atmospheric Research Group at the University of Kansas for his support during my academic visit to the USA. Also, I am greatly indebted to Dr. Petr Stepanek from the Czech Hydrometeorological Institute for his very useful advice in general and his ProClim software in particular. I am also very grateful to all my colleagues in Instituto Pirenaico de Ecologia for the very pleasant working atmosphere for the duration of this study. I specially thank to Arben, Yacine, Javier, Marta, Hugo, Jorge and Edmond for their invaluable help in all the aspects of this study. Many thanks also due to all the administrative and technical people including: Cecilia, Trinidad, and Jose Manuel. I extend sincere gratitude to Consejo Superior de Investigaciones Cientificas (CSIC) for the financial support of this work through the JAE scholarship program. My wife, thank you for believing in me. Many thanks for your support, motivation and inspiration. You provided me the balance during hard times. I This work has been supported by the research projects CGL2011-27574-CO2-02, and CGL2011-27536 financed by the Spanish Commission of Science and Technology and FEDER, ACQWA (FP7-ENV-2007-1- 212250) financed by the VII Framework Programme of the European Commission, “Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés” financed by “Obra Social La Caixa” and the Aragón Government and Influencia del cambio climático en el turismo de nieve, CTTP01/10, Financed by the Comisión de Trabajo de los Pirineos. II III IV ABSTRACT From the climatological point of view, northeast Spain is an area of large interest due its varied geographical, topographical and climatic characteristics. In this work, a spatially and temporarily high-resolution daily dataset of temperature was developed for northeastern Spain. Data derived from a high number of observatories (1583) spanning some period between 1900 and 2006 was tested for internal and external consistency to check data quality. To improve data completeness, a linear regression model was then utilized to infill gaps in the daily temperature series using the best correlated data from nearby sites. Discontinuities in the reconstructed series were then determined by combining the results of three homogeneity relative tests: the Standard Normal Homogeneity Test (SNHT), the Easterling and Peterson two- phased regression method, and the Vincent test. The newly complied dataset seems to be more robust and reveals more coherent spatial and temporal patterns of temperature compared with the original dataset. This finding was confirmed by means of a suite of statistics (e.g., semivariance models and L-moment statistics). From the temporal and spatial perspectives, the new dataset comprises the most complete register of temperature in northeast Spain (1900-2006), with a reasonably spatial coverage. Therefore, this database provides a more reliable base for studying temperature changes and variability in the region. This thesis analyzed the surface air temperature variability and trends over the study domain for the 20th century based on the new compiled dataset. An assessment of long-term change and variability of temperature was provided using a dataset of 19 observatories from 1920 to 2006. In addition, a more detailed analysis of the spatial and temporal variability of maximum, minimum, and mean temperatures, and the V diurnal temperature range (DTR) was also carried out employing 128 observatories spanning the period from 1960 to 2006. In general, maximum, minimum, and mean temperatures increased significantly, mostly from contributions in the late decades of the 20st century. At the seasonal scale, the analysis revealed that the weakest trends (mostly insignificant at the 95% level [p<0.05]) were observed during autumn, while the strongest warming rates were found during summer and spring. Spatially, the observed warming was more robust in the coastal portions compared with mainland observatories. Spatial and temporal characteristics of extreme temperature events were also investigated. A total of 21 indices were used to assess changes in the cold and warm tails of the daily temperature distribution, calculated at the annual timescale. The presence of trends in temperature extremes was assessed by means of the Mann- Kendall statistic. However, prior to assessing trends, the autocorrelation function (ACF) and bootstrap methodologies were used to account for the influence of serial correlation and cross-correlation on the trend assessment. In general, the observed changes were more prevalent in warm extremes than in cold extremes. The results indicated a significant increase in the frequency and intensity of most of warm extremes. An increase in warm nights (TN90p: 3.3 days decade-1), warm days (TX90p: 2.7 days decade-1), tropical nights (TR20: 0.6 days decade-1) and the annual high maximum temperature (TXx: 0.27ºC decade-1) was detected in the 47-year period (1960-2006). In contrast, majority of the indices related to cold extremes (e.g., cold days [TX10p], cold nights [TN10p], very cold days [TN1p], and frost days [FD0]) demonstrated a decreasing but statistically insignificant trend. Spatially, similar to temperature means, the coastal areas along the Mediterranean Sea and the Cantabrian Sea experienced stronger warming compared with mainland areas. VI In this thesis, a procedure for classifying daily temperature extremes into homogenous regions was also presented and evaluated. This procedure employed characteristics of temperature extremes calculated for summer (JJA), including temperature frequency (e.g., warm days), intensity (e.g., warmest day), and duration (e.g., maximum length of warm spell). Following the results of the principal components analysis (PCA) and the Ward´s method of clustering, the study area was divided into four homogenous sub-regions: the Mediterranean region, the mainland and the Cantabrian region, the moderately elevated areas westward and southward, and the mountainous region. The quality of this clustering was evaluated and ensured by means of an internal cluster validation measure (Silhouette width). Overall, the delineated sub-regions were proved as homogenous in terms of both the geographic and climatic meanings. The temporal