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The increasing use of wind and solar power requires interventions to balance the associated variability in energy production. One option to reduce the costly interventions is to exploit the natural de-correlation of wind and irradiance. This study characterises the balancing potential of the natual variability in wind and photovoltaic energy production within and across eleven European countries. We use 20 years of highly resolved meteorological data from a post-processed regional reanalysis with a 6 km horizontal grid to calculate daily photovoltaic and wind power. Our results suggest a country-dependent reduction of the day-to-day variability in energy production by 29%–42% due to installing both PV and wind power capacities, compared to wind power only. The optimized photovoltaic to photovoltaic plus wind power generation ratios are 45–57% for maximizing balancing effects associated with the changing weather. We further identify on less than 10% of the days a simultaneous occurrence of extremes in photovoltaic and wind power across European countries. The cross-border balancing potentials for the extremes in renewable energy production are therefore high due to the spatio-temporal differences of the local weather.

Most air quality stations in Spain exceeded the European Union's daily PM10 limit due to the February 2016 Saharan dust outbreak, which resulted from two successive dust storms in Northwest Africa. This study identifies the meso-β/meso-γ-scale dynamical processes responsible for developing these dust storms using observations and high-resolution Weather Research and Forecasting model coupled with Chemistry simulations. The results revealed that the first dust storm was associated with a strong barrier jet (BJ). The BJ formed on the southeastern foothills of the Saharan Atlas Mountains (SAM) when an easterly-northeasterly low-level Mediterranean flow was blocked by a stably stratified layer close to the SAM. The BJ intensified just after sunrise on 20 February and the associated near-surface peak winds organized the first dust storm. The second dust storm was linked to a mesoscale gravity wave (MGW) and hydraulic jumps. A long-lived westward propagating MGW was triggered by a downslope flow interacting with the stable layer near the northeastern edge of the Tinrhert Plateau in eastern Algeria. When this MGW crossed the Tademait Plateau, hydraulic jumps formed on its lee side. The strong winds accompanying these hydraulic jumps formed the second dust storm on 21 February. The lifted dust extended over a depth of 2–3 km in the growing daytime boundary layer and was advected poleward by the southerly/southeasterly mid-tropospheric winds. Our results underline the importance of resolving terrain-induced mesoscale processes to understand dust storm dynamics, which are difficult to represent in coarse-resolution numerical models.

The analysis of three extreme African dust outbreaks over the Iberian Peninsula (IP) shows that a double Rossby wave breaking (RWB) process in the polar jet (PJ) creates the conditions for dust storm formation over subtropical deserts in North Africa and the restructuring of upper-level air flows critical for the dust transport poleward after ablation. Two consecutive anticyclonic RWBs initiate over the IP and the adjacent Atlantic, the first commencing 10 days before dust reaches the IP and the second three to five days later. The first RWB becomes quasi-stationary over the eastern Mediterranean when the second RWB develops. In turn, the first RWB blocks downstream propagation of the second, which is amplified by energy reflection poleward from the first break causing vortex intensification and equatorward propagation over the Atlas as well as a strengthening and coupling of the subtropical jet (STJ) to circulations in the ITCZ. Zonal flows are blocked and sustained low-level northeasterlies/easterlies are induced across northwest Africa. The three events present substantial differences in the location and geometry of key upper- and low-level subsynoptic features that organize the dust storms over the Sahara following the second break. Dust lifted by either the cold outflow from convective downdrafts or by orographic gravity waves interacts with terrain-induced and larger scale circulations and is transported to the IP. The location of the cyclonic large scale signal from the second RWB to the west or over the Atlas and the blocking of zonal flows are key for the poleward dust transport.