Joan A. Lopez-Bustins

Homogenization and Assessment of Observed Near-Surface Wind Speed Trends over Spain and Portugal, 1961–2011*

Near-surfacewindspeedtrendsrecordedat67land-basedstationsacrossSpainandPortugalfor1961–2011, alsofocusingonthe1979–2008subperiod,wereanalyzed.Windspeedseriesweresubjectedtoqualitycontrol, reconstruction, and homogenization using a novel procedure that incorporated the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)-simulated seriesasreference.Theresultantseriesshowaslightdownwardtrendforboth1961–2011(20.016ms 21 decade 21 ) and 1979–2008 (20.010ms 21 decade 21 ). However, differences between seasons with declining values in winter and spring, and increasing trends in summer and autumn, were observed. Even though wind stilling affected 77.8% of the stations in winter and 66.7% in spring, only roughly 40% of the declining trends were statistically significant at the p , 0.10 level. On the contrary, increasing trends appeared in 51.9% of the stationsinsummerand57.4%inautumn,withalsoaround40%ofthepositivetrendsstatisticallysignificantat the p , 0.10 level. In this article, the authors also investigated (i) the possible impact of three atmospheric indices on the observed trends and (ii) the role played by the urbanization growth in the observed decline. An accurate homogenization and assessment of the long-term trends of wind speed is crucial for many fields such as wind energy (e.g., power generation) and agriculture–hydrology (e.g., evaporative demand).

Impacts of climate change on water resources in the Mediterranean Basin: a case study in Catalonia, Spain

Abstract Most climate change projections show important decreases in water availability in the Mediterranean region by the end of this century. We assess those main climate change impacts on water resources in three medium-sized catchments with varying climatic conditions in northeastern Spain. A combination of hydrological modelling and climate projections with B1 and A2 IPCC emission scenarios is performed to infer future streamflows. The largest reduction (34%) in mean streamflows (for 2076–2100) is expected in the headwaters of the two wettest catchments, while lower decreases (25% of mean value for 2076–2100) are expected in the drier one. In all three catchments, autumn and summer are the seasons with the most notable projected decreases in streamflow, of 50% and 30%, respectively. Thus, ecological flows in the study area might be noticeably influenced by climate change, especially in the headwaters of the wet catchments.

Future variability of droughts in three Mediterranean catchments

In the present study, we analyze the magnitude and frequency of long-term droughts throughout the present century in Catalonia in the north-eastern Iberian Peninsula (Spain). In fact, this western Mediterranean region has recently suffered one of the most extreme dry episodes (2006–2008) in the last decades. This calls for further study of future perspectives of drought variability at the local scale. We selected three medium-sized catchments on the Catalan littoral: Fluvià, Tordera and Siurana. We employed both instrumental and simulated temperature and rainfall data to calculate two multi-scalar drought indices: the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Instrumental data consisted of several weather stations for a recent period: 1984–2008. Future projections covering the 2001–2100 period were extracted from a dynamical downscaling procedure at a 15-km horizontal grid resolution, nesting the mesoscale model MM5 into the atmosphere–ocean coupled model ECHAM5/MPI-OM, performed by the Meteorological Service of Catalonia. We calculated 24-month SPI and SPEI values for the instrumental and simulated periods, and no changes were found in drought variability for the early twenty-first century. For the mid-century, high climatic variability was detected, as extremely dry and wet periods might alternate according to the SPI values. At the end of the present century, we generally detected, particularly in the dry catchment of southern Catalonia, Siurana, more severe and longer droughts than the last extreme drought (2006–2008). There is a need to implement appropriate and specific adaptation strategies for water management of each catchment over the next decades to reduce the risk of the forecasted drought conditions.

Observed Changes in Daily Precipitation Extremes at Annual Timescale Over the Eastern Mediterranean During 1961–2012

The Eastern Mediterranean is one of the most prominent hot spots of climate change in the world and extreme climatic phenomena in this region such as drought or extreme rainfall events are expected to become more frequent and intense. In this study climate extreme indices recommended by the joint World Meteorological Organization Expert Team on Climate Change Detection and Indices are calculated for daily precipitation data in 70 weather stations during 1961–2012. Observed trends and changes in daily precipitation extremes over the EM basin were analysed using the RClimDex package, which was developed by the Climate Research Branch of the Meteorological Service of Canada. Extreme and heavy precipitation events showed globally a statistically significant decrease in the Eastern Mediterranean and, in the southern parts, a significant decrease in total precipitation. The overall analysis of extreme precipitation indices reveals that decreasing trends are generally more frequent than increasing trends. We found statistically significant decreasing trends (reaching 74% of stations for extremely wet days) and increasing trends (reaching 36% of stations for number of very heavy precipitation days). Finally, most of the extreme precipitation indices have a statistically significant positive correlation with annual precipitation, particularly the number of heavy and very heavy precipitation days.