Operational ground-based measurements of snow water equivalent (SWE) do not adequately explain spatial variability in mountainous terrain. To address this problem, we combine satellite-based retrievals of fractional snow cover for the period 2000-2012 with spatially distributed energy balance calculations to reconstruct SWE values throughout each melt season in the Sierra Nevada of California. Modeled solar radiation, longwave radiation, and air temperature from NLDAS drive the snowmelt model. The modeled solar radiation compares well to ground observations, but modeled longwave radiation is slightly lower than observations. Validation of reconstructed SWE with snow courses and our own snow surveys shows that the model can accurately estimate SWE at the sampled locations in a variety of topographic settings for a range of wet to dry years. The relationships of SWE with elevation and latitude are significantly different for wet, mean and dry years as well as between drainages. In all the basins studied, the relationship between remaining SWE and snow-covered area (SCA) becomes increasingly correlated from March to July as expected because SCA is an important model input. Though the SWE is calculated retrospectively SCA observations are available in near-real time and combined with historical reconstructions may be sufficient for estimating SWE with more confidence as the melt season progresses.

No abstract

Our work explores the prospect of bringing the temporal production profile of solar photovoltaics (PV) into better correlation with typical electricity consumption patterns in the midlatitudes. To do so, we quantify the potential of three choices for PV installations that increase production during the winter months when electricity is most needed. These are placements that favor (i) high winter irradiance, (ii) high ground-reflected radiation, and (iii) steeper-than-usual panel tilt angles. In addition to spatial estimates of the production potential, we compare the performance of different PV placement scenarios in urban and mountain environments for the country of Switzerland. The results show that the energy deficit in a future fully renewable production from wind power, hydropower, and geothermal power could be significantly reduced when solar PV is installed at high elevations. Because the temporal production patterns match the typical demand more closely than the production in urban environments, electricity production could be shifted from summer to winter without reducing the annual total production. Such mountain installations require significantly less surface area and, combined with steeper panel tilt angles, up to 50% of the winter deficit in electricity production can be mediated.

Using data from two measurement networks, we analyse the following aspects of wind speeds over Switzerland to assess the possibility of high wind power penetration: spatial correlation, persistent low wind power conditions and the diurnal and seasonal wind speed patterns. We show that correlation amongst speeds as a function of distance is significantly lower compared to values found in literature. This can be attributed to the complex terrain of the Alps, which has a profound influence on meteorological parameters. Secondly, using extreme value analysis we calculate return levels for low wind power periods. Large differences are found, with return levels ranging from 29 to 1017 hours of no power production for a return period of 10 years. No clear spatial pattern was found that can account for these values. However, the length of no-production periods decreases with increasing elevation. Next, we investigate diurnal and seasonal wind speed patterns and show how the different patterns and their intra-annual variation can be explained by local topography. We also find that with increasing elevation mean wind speeds and power production increase, even when accounting for lower air density. Wind speeds are on average higher in winter, and at elevation the relative increase in winter compared to summer is higher. Notable exceptions are explained from topography and carry implications for wind power development. In view of Switzerland's electricity shortage in winter, these findings make a strong claim for wind power development, especially at higher elevations.