Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations

Abstract

Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.

Statistics of sea-effect snowfall along the Finnish coastline based on regional climate model data

“…When the threshold for 10 m wind speed was kept at 7 m s −1 , there were 33 favorable days (Sect. 3.2.1) with a well-known sea-effect snowfall case detected in January 2006 (Savijärvi, 2012). When the threshold value for 10 m wind speed was increased to 10 m s −1 , the number of detected favorable days decreased to 15.…”

“…In addition, wintertime precipitation amounts are expected to increase (IPCC, 2019), yet at the same time a smaller share of snowfall compared to rainfall is expected in a warming climate Luomaranta et al, 2019). However, since easterly and northerly wind directions might become less frequent in the autumn and winter over the future Baltic sea (Ruosteenoja et al, 2019), the large-scale conditions might become less favorable for snow bands. Based on simple physical reasoning it is therefore difficult to predict the future evolution of sea-effect snowfall, but careful analysis of climate model data is needed.…”

“…During the cold season, vigorous boundary layer convection can develop when cold continental air masses are advected over an open and relatively warm body of water, like the Great Lakes of North America (e.g., Hjelmfelt and Braham, 1983), the English Channel and the Irish Sea (e.g., Norris et al, 2012), the Japan Sea (e.g., Ohtake et al, 2009) and the Baltic Sea in northern Europe (Savijärvi, 2012;Mazon et al, 2015;Jeworrek et al, 2017;Olsson et al, 2018). Intense snowfall may occur when significant amounts of heat and moisture fluxes from the water destabilize the overlying air.…”

“…These criteria were adopted from previous works by Laird et al (2003), Niziol et al (1995, Andersson and Nilsson (1990), Niziol (1987), and Holroyd (1971. Case studies and idealized simulations of snow bands over the Gulf of Finland have been conducted in the past (Savijärvi, 2012;Mazon et al, 2015). However, no statistics of the frequency and intensity of the snow bands affecting the Finnish coast have been published to our knowledge.…”

Projections of future climate for Europe, Uruguay and China with implications on forestry

“…These are related to changes in forest management practices. The projections of future climate indicate only quite modest changes in extreme wind speeds for northern Europe (Figure 2.10; Ruosteenoja et al, 2019). Nevertheless, decreasing soil frost may increase wind damage risk (section 2.3.3).…”