Wind Drought Index: a proposal to assess low wind speed events over the Iberian Peninsula

Near-surface wind speed (SWS) has been the forgotten part of the climate system, compared with other viables as temperature or precipitation, due to poor quality of observational data and the challenges in the homogenization process. During the last two decades the interest in long-term SWS variability and trends has increased and two main phenomena were discovered using observational data: the first one is termed “stilling” (decline until the 2010s), followed by the “reversal” (increase since then) of SWS. For a complete characterization of SWS changes, extremes also need to be evaluated as they have wide socioeconomic and environmental implications. The majority of the studies dealing with wind extremes are focused on high wind speeds associated with extratropical cyclones, hurricanes, tornados, storms, etc., which represent a threat for human lives and cause large damages. However, low wind speed events (known as “wind droughts”) have received less attention, representing a research gap in climate studies, and they are crucial due to the strong impacts on, for example, wind power generation a key motor of decarbonization. The main objective of this study is to define a Wind Drought Index (WDI) to identify and quantify the magnitude and extend of low wind speed events over the Iberian Peninsula. Our analyses are based on quality controlled and homogenized observational data series from 86 stations over Spain and Portugal for 1961-2022. Here we present for the first time the long-term and spatio-temporal changes in the occurrence and intensity of wind drought events over the study region.