Climate in Spain: Past, Present - Red TemÃ¡tica de CLIVAR-EspaÃ±a

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CLIVAR – SpainRegional ProjectionsTable 1: Seasonal changes (future climate (2071-2100) compared with present-day climate (1961-1990)) in temperature (in o C) and precipitation (relative change) for each of the PRUDENCE project regionalmodels, together with the ensemble of models. Additional simulations at higher resolution (25, 12 km) andforced by the ECHAM5 GCM are also shownECHTemperaturePrecipitationDJF MAM JJA SON DJF MAM JJA SONHIRHAM-50 3.13 3.46 5.38 4.12 -0.02 -0.28 -0.39 -0.17HIRHAM-25 3.05 3.34 5.27 3.98 -0.02 -0.28 -0.38 -0.17HIRHAM-12 3.05 3.36 5.19 3.96 -0.02 -0.27 -0.36 -0.16CHRM 2.46 3.05 4.90 3.48 -0.08 -0.39 -0.72 -0.26CLM 2.64 2.87 5.00 3.53 -0.04 -0.29 -0.46 -0.20HadRM3H 3.44 3.98 5.70 4.24 -0.08 -0.29 -0.44 -0.19RegCM 2.73 3.28 4.93 3.83 -0.01 -0.27 -0.39 -0.12RACMO 3.08 3.60 5.83 4.07 -0.05 -0.32 -0.60 -0.21REMO 3.12 3.43 5.42 4.18 -0.04 -0.31 -0.50 -0.23RCAO-50 3.06 3.35 5.73 3.96 -0.02 -0.28 -0.50 -0.17RCAO-25 3.09 3.41 5.59 4.00 -0.01 -0.29 -0.49 -0.16PROMES 3.05 3.73 5.82 4.21 -0.02 -0.28 -0.45 -0.16HadAM3H 3.59 4.09 6.30 4.41 -0.03 -0.31 -0.44 -0.20ARPEGE 3.05 3.61 4.78 3.88 -0.01 -0.24 -0.48 -0.25HIRHAM- 3.90 5.08 4.51 5.43 0.03 -0.26 -0.26 -0.25RCAO-ECH 4.15 5.99 7.83 5.54 -0.07 -0.50 -0.43 -0.33Ensemble 2.97 3.42 5.41 3.96 -0.04 -0.30 -0.48 -0.19Maximum and minimum daily temperatures show similar seasonal changes behaviour: largerincreases in summer than in winter and with the same spatial pattern for summer. However, an increase inmaximum temperatures around 1ºC higher than the minimum temperatures all along the year is obtained,particularly in summer, which would indicate an increase in the amplitude of daily temperature range[Sánchez et al., 2004]. Something similar occurs for the B2 scenario [Giorgi et al., 2004]. The timeseries forthe whole 21st century for the increase in maximum and minimum mean annual temperatures averaged for thewhole of the IP obtained by different regionalization methods (including the 10 RCMs of the PRUDENCEproject), different GCMs, and for several emissions scenarios (Fig. 1, [Brunet et al., 2008]), indicates a clearincrease in both temperatures. A greater increase in maximum temperatures compared with minimumtemperatures is projected from 2070.Figure 1: Timeseries of mean annual maximum and minimum temperature change for the wholeIP (Brunet et al., 2008) during the 21st century for A2 and B2 scenarios from the different regionalizationtechniques, GCMs and emissions scenarios related to the 1961-1990 mean value. The shaded arearepresents 1 deviation from the mean value (10-year running mean) represented by a continuous line.73
Climate in Spain: Past, Present and Future2.c.2.- PrecipitationThe changes in seasonal precipitation shown by several studies using individual models [Gibelin andDéqué, 2003; Giorgi et al., 2004; Räisänen et al., 2004; Sánchez et al., 2004; Rowell, 2005; Castro et al.,2007b; Giorgi and Lionello, 2008] show a decrease in summer for all the IP, presenting a north-southstructure in winter with slight increases in the northern half and decreases in the southern part. However, thediscrepancies among the results with the different models are larger than those obtained when comparingtemperatures. A decrease is also obtained in the total number of rainy days in all seasons and for the wholeregion [Sánchez et al., 2009b]. When the ensemble of RCMs forced by the same GCM from PRUDENCE isanalyzed (Table 1, [Christensen y Christensen, 2007]), a high degree of agreement among them is seen, with anegative change in relative precipitation average for the whole IP in all seasons, being maximum in summer (-0.48 on average for all the models, between -0.39 and -0.72) and minimum, almost negligible, in winter (-0.04) for the end of the 21st century under the A2 emissions scenario. In contrast to what happens withtemperature, the RCMs show an important bias for present-day climate that can double the climate changeresponse. However, the all RCM precipitation projections have a similar behaviour for the A2 emissionsscenario, slightly different from the GCM, meanwhile systematic biases are more scattered [Déqué et al.,2005]. The percentage change in annual precipitation by degree of increase in temperature in the global modelranges between -9.7 and -3.1 K -1 , which is the largest for the whole of Europe. This result is important, evenfrom a political point of view, in relation to the proposed possible stabilization scenarios based on certaintemperature thresholds (2, 3 or 4 degrees centigrades). The probability distribution functions of changes inannual precipitation indicate a decrease between 18 and 0.4% for the 1 and 99 percentiles [Ekström et al.,2007, Hingray et al., 2007]. The daily precipitation distribution function points towards a decrease of lightprecipitation amounts (up to 15 mm/day) [Boberg et al., 2009]. The strength (peak in the standard frequencyspectrum) of the annual precipitation cycle in the north-west region of the IP appears to increase for all RCMs,which could be related to changes in frontal activity in that area [Tapiador and Sánchez, 2008]. This resultcould be related to a northward move of the low pressure winter systems obtained in the global modelprojections (IPCC 2007, Chapter 10 [Meehl et al., 2007]), and also the north-eastward displacement of theprincipal low frequency variability patterns [Rodríguez-Fonseca et al., 2005]. Regarding more specificregions in the IP, a maximum decrease is obtained over the Ebro basin in summer, with much smallerchanges, and even slight increases for some models in winter [Blenkinsop and Fowler, 2007]. Over thePyrenees area, the models project a decrease of 10 and 15% in annual precipitation for B2 and A2 scenarios,respectively, being the maximum decrease in summer [López-Moreno et al., 2008a].2.d.- Projected changes in other climatic magnitudes and processesOther aspects of climate change projected by the RCMs over the IP show an intensification of thetypical summer thermal lows in the centre of the IP and an increase in sea breezes for the 2071-2100 period[Hoinka et al., 2007], corresponding to an increase in annual turbulent kinetic energy (as a measurement ofturbulent activity in the lower layers of the atmosphere), mainly in summer and in the centre of the Peninsula.The Bowen ratio (ratio of sensible to latent heat fluxes over a surface) shows a change for the end of the 21stcentury whose spatial pattern presents a north-south gradient, being maximum on the southern part, that wouldpoint to an increased aridity and a tendency towards the desertification of that area [Sánchez et al., 2007a,b].A significative jump of an important fraction of points towards more arid climates is obtained over theIP in respect of present-day climate (top figures) both if the climate change projections are analysed (bottomleft figure) or if the change climate signal is added to the observed climatology (bottom right figure) [Castroet al., 2007a]. Although winter precipitation variability patterns are related to large scale mechanisms, andtheir change for future climate conditions is similar, with a north-eastward displacement in these structuresboth for the GCM and the RCM, the more regional modes show discrepancies in their projected change forthe 21st century [Rodríguez-Fonseca et al., 2005]. There is also evidence that the magnitude of the projectedchanges has an important effect on the evolution of the snow mantle [López-Moreno et al, 2008b].The construction of climate types in the Köppen-Trewartha classification from the 10 RCMs of thePRUDENCE project and their changes for future climate conditions is shown in Fig. 2.74
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