This paper analyzes the validity of various precipitation and temperature maps obtained by means of diverse interpolation methods. The study was carried out in an area where geographic differences and spatial climatic diversity are significant (the middle Ebro Valley in the northeast of Spain). Two variables, annual precipitation and temperature, and several interpolation methods were used in the climate mapping: global interpolators (trend surfaces and regression models), local interpolators (Thiessen polygons, inverse distance weighting, splines), geostatistical methods (simple kriging, ordinary kriging, block kriging, directional kriging, universal kriging and co-kriging) and mixed methods (combined global, local and geostatistical methods). The validity of the maps was checked through independent test weather stations (30% of the original stations). Different statistical accuracy measurements determined the quality of the models. The results show that some interpolation methods are very similar. Nevertheless, in the case of precipitation maps, we obtained the best results using geostatistical methods and a regression model formed by 4 geographic and topographic variables. The best results for temperature mapping were obtained using the regression-based method. The accuracy measurements obtained by the different interpolation methods change significantly depending on the climatic variable mapped. The validity of interpolation methods in the creation of climatic maps, useful for agricultural and hydrologic management, is discussed.

Abstract. This paper reviews multi-proxy paleoclimatic reconstructions with robust age-control derived from lacustrine, dendrochronological and geomorphological records and characterizes the main environmental changes that occurred in the Southern Pyrenees during the last millennium. Warmer and relatively arid conditions prevailed during the Medieval Climate Anomaly (MCA, ca. 900-1300 AD), with a significant development of xerophytes and Mediterranean vegetation and limited deciduous tree formations (mesophytes). The Little Ice Age (LIA, 1300-1800 AD) was generally colder and moister, with an expansion of deciduous taxa and cold-adapted montane conifers. Two major phases occurred within this period: (i) a transition MCA-LIA, characterized by fluctuating, moist conditions and relatively cold temperatures (ca. 1300 and 1600 AD); and (ii) a second period, characterized by the coldest and most humid conditions, coinciding with maximum (recent) glacier advances (ca. 1600-1800 AD). Glaciers retreated after the LIA when warmer and more arid conditions dominated, interrupted by a short-living cooling episode during the late 19th to early 20th centuries. Some records suggest a response to solar activity with colder and slightly moister conditions during solar minima. Centennial-scale hydrological fluctuations are in phase with reconstructions of NAO variability, which appears to be one of the main climate mechanisms influencing rainfall variations in the region during the last millennium.

Spatial patterns of the urban heat island (UHI) in Zaragoza (Spain) were determined by Principal Component Analysis (VARIMAX rotation) of air temperature in the city, and mapped using GIS. The 3 components extracted accounted for 92.9% of the total variance. Principal component (PC) 1 accounted for the most general patterns of UHI, PC2 showed a shift of warm areas to the SE and PC3 a shift to the NW. A rotated component matrix was used to identify correlations between each component and daily maps. The spatial patterns indicated by PC2 and PC3 were determined by surface wind direction. The displacement of warm areas to the SE (PC2) was greater during NW winds while the shift to the NW (PC3) was produced mainly by SE winds. KEY WORDS: Urban climate · Urban heat island · Spatial patterns · Principal component analysis · Surface wind · Zaragoza · SpainResale or republication not permitted without written consent of the publisher Clim Res 30: 61-69, 2005 wind direction. For these purposes we used urban transects, surface interpolation techniques and multivariate statistics of a Geographical Information System (GIS). STUDY AREAThe city of Zaragoza is located in NE Spain (Fig. 1) in the centre of the Ebro Valley (0°52' W, 41°38' N). It is the main industrial and commercial city of this region and occupies a plain of 159 km 2 ; in 2002 the city had a population of 620 000. It has a Mediterranean climate with a strong continental influence. The mean annual rainfall is just over 320 mm, with a maximum in May (38 mm) and minimum in August (21 mm). The mean annual temperature is 14.6°C, with cool winters (January: 6.2°C) and warm summers (July: 24.3°C). Winds are an important feature of the climate in the Ebro Valley. Two surrounding mountain ranges (the Pyrenees and the Iberian Range) isolate the valley from northerly and southerly flows, and winds are channeled in the valley in 4 dominant directions: WNW, NW, ESE, E. Westerly flows (W, WNW, NW, NNW) occur on 52% of the days, whereas ESE and E winds occur on 21% of the days.The UHI in Zaragoza has been studied by Cuadrat (1993), Cuadrat et al. (1993), De la Riva et al. (1997) and Saz et al. (2003). The absolute maximum difference in the temperature between the city and the outskirts is about 6°C, with a mean UHI intensity of 2.5 to 3.5°C. The UHI of Zaragoza shows a negative gradient from the city center to the outskirts, which is consistent with the findings of studies in other cities. Nevertheless, on many days the warm areas of Zaragoza present a marked shift to the NW or SE areas of the city. DATA AND METHODS Spatial variability of the UHI3.1.1. Data and quality control UHIs can be analyzed using urban-rural differences in the data from weather stations or groups of weather stations (i.e. Adeabayo 1987, Philandras et al. 1999; networks of fixed stations within and around the city (i.e. Kuttler et al. 1996, Morris et al. 2001; or, mainly, transects across an urban area (i.e. Moreno 1994, Saaroni et al. 2000, Unger et al. 2001.To determine the shape and tem...

RESUMENEn este trabajo se analiza la isla de calor y la isla de sequedad del verano del año 2015 a partir de la red de sensores de temperatura y humedad existentes en la ciudad y su entorno inmediato. Asimismo, se evalúa la incidencia de la ciudad sobre las temperaturas y la humedad durante la intensa ola de calor del mes de julio, y se caracteriza el régimen de confort a partir del índice de confort térmico THI, de Thom.Palabras clave, Isla de Calor, Ola de Calor, Índice termohigrométrico de confort (THI), Clima Urbano, Zaragoza. ABSTRACTThis paper analyzes both the heat island and the island of dryness of the summer of 2015 from the network of temperature and humidity sensors existing in the city and its surroundings. Furthermore, we evaluate the incidence of the city within the temperatures and humidity during the intense July heat wave. Finally, we characterized the thermal comfort index from the thermal comfort index THI, Thom.