Climatology and trends of reference evapotranspiration in Spain

Abstract

This study presents a climatology and trend analysis of reference crop evapotranspiration (ET o) over continental Spain and the Balearic Islands. Geographic features of the study region play a substantial role in the climatology of ET o. The highest values (in excess of 1,200 mm y −1) are found at lower elevations in the south, while the lowest values (less than 900 mm y −1) are found in the highest elevations in the north. A deep analysis reveals: (a) a low interannual variability; (b) summer accumulates more than 50% of annual values; and (c) the radiative component contribution is higher than 50%. A positive long-term trend (1961-2014) has been detected for most of the study area, but showing contrasting situations when shorter periods (20-30 years) are analysed. A short initial period of negative trend was followed by a longer period of a positive trend. We argue that global dimming/brightening played a role in this process, as these two contrasting periods are clearly guided by the radiative component. A seasonal analysis of the trends reveals that spring and summer are the seasons showing the long-term positive trends. Interestingly, a monthly analysis shows that spring trends are guided by March and April and summer trends are mostly guided by June, which is the month showing the highest relative changes. This could have important consequences for agriculture and natural ecosystems since this month represents the start of the summer (dry) period.

Flash Drought Response to Precipitation and Atmospheric Evaporative Demand in Spain

“…In addition to the markedly seasonal character indicating the role of AED in the development of flash droughts, we also found a strong spatial component determining the role of AED in these events in Spain. The AED shows strong spatial differences in Spain, with a clear north-south gradient between the humid regions of the north and the drier regions of southern and central Spain [36,39]. Several studies suggested that the contribution of AED is much higher in dry regions than in humid ones, since its role is only important during periods of low precipitation or limited soil moisture [9,17].…”

“…Several studies showed the high occurrence of severe droughts episodes in Spain through historical [28][29][30] and instrumental records [31]. Spain has strong climatic contrasts with marked spatial and seasonal differences in precipitation [32][33][34][35] and AED [36][37][38][39]. Northern Spain is characterized by its humid oceanic climate with abundant precipitation over the year, while northeastern and southeastern regions are mainly characterized by semiarid conditions with annual precipitation generally below 300 mm [40].…”

Evapotranspiration Response to Climate Change in Semi-Arid Areas: Using Random Forest as Multi-Model Ensemble Method

“…According to the values obtained for the F statistics in the different seasons, the highest increments of ET 0 are observed for spring, while the lowest variation has been obtained for summer. Tomas-Burguera et al [107] analyzed the evolution of the ET 0 in Spain for the period 1961-2014, and they also obtain the highest increments of ET 0 for the study area in spring. The results obtained in both works for that season may have or may be already having repercussions in water resources availability, these repercussions should be analyzed in future studies.…”

Directions and Extent of Flows Changes in Warta River Basin (Poland) in the Context of the Efficiency of Run-of-River Hydropower Plants and the Perspectives for Their Future Development

“…Because the calculations with the WBS methods showed the occurrence of numerous breakpoints in the analysed indicators of flow changes within individual rivers and corresponding indicators within all rivers, multitemporal trend analysis was applied. Following McCabe and Wolock [49] and Tomas-Burguera et al [50], the Mann-Kendall and Sen test statistics were calculated for every possible combination of start and end years in 1951-2020 for DL7, YM, TBQ50, TBQ90 and TQ5090%. This involved performing 1327 calculations for each flow indicator.…”