Wind speed trends over the contiguous United States

Abstract

[1] A comprehensive intercomparison of historical wind speed trends over the contiguous United States is presented based on two observational data sets, four reanalysis data sets, and output from two regional climate models (RCMs). This research thus contributes to detection, quantification, and attribution of temporal trends in wind speeds within the historical/contemporary climate and provides an evaluation of the RCMs being used to develop future wind speed scenarios. Under the assumption that changes in wind climates are partly driven by variability and evolution of the global climate system, such changes should be manifest in direct observations, reanalysis products, and RCMs. However, there are substantial differences in temporal trends derived from observational wind speed data, reanalysis products, and RCMs. The two observational data sets both exhibit an overwhelming dominance of trends toward declining values of the 50th and 90th percentile and annual mean wind speeds, which is also the case for simulations conducted using MM5 with NCEP-2 boundary conditions. However, converse trends are seen in output from the North American Regional Reanalysis, other global reanalyses (NCEP-1 and ERA-40), and the Regional Spectral Model. Equally, the relationship between changing annual mean wind speed and interannual variability is not consistent among the different data sets. NCEP-1 and NARR exhibit some tendency toward declining (increasing) annual mean wind speeds being associated with decreased (increased) interannual variability, but this is not the case for the other data sets considered. Possible causes of the differences in temporal trends from the eight data sources analyzed are provided. Motivation and Objectives[2] Wind speed time series have been subject to far fewer trend analyses than temperature and precipitation records [Gower, 2002;Keimig and Bradley, 2002;McAvaney et al., 2001;McVicar et al., 2008; Tomasin, 1999, 2003;Pryor and Barthelmie, 2003;Tuller, 2004;Brazdil et al., 2009], in part because of data homogeneity issues [Thomas et al., 2008;Tuller, 2004;DeGaetano, 1998]. However, understanding how evolution of the global climate system has been manifest as changes in near-surface wind regimes in the past and how near-surface wind speed regimes might alter in the future is of great relevance to the insurance industry [Changnon et al., 1999;Thornes, 1991], the construction and maritime industries [Ambrose and Vergun, 1997;Caires and Sterl, 2005;Caires et al., 2006], surface energy balance estimation [Rayner, 2007], the community charged with mitigating coastal erosion [Bijl, 1997;Viles and Goudie, 2003], the agricultural industry [O'Neal et al., 2005], forest and infrastructure protection communities [Jungo et al., 2002], and the burgeoning wind energy industry [Pryor et al., 2006b]. With respect to the latter, it is worth noting that during 2005-2008 over 18,000 MW of wind energy developments came online in the continental United States, increasing installed capacity to over 25 GW (AWEA wind ene...

Wind speed trends over China: quantifying the magnitude and assessing causality

“…For example, in the analysis of daily mean wind speed data over Australia, measurements from terrestrial anemometers showed declines (a 'stilling') of −0.13 m s -1 /decade when averaged over the entire country, but two gridded wind speed datasets (including the NCEP/NCAR reanalysis output) did not exhibit temporal tendencies (McVicar et al, 2008). Further, comparisons of 10-m wind speeds from observational data sets, reanalysis products and Regional Climate Model (RCM) simulations over North America showed trends in reanalysis data sets and RCM output were generally of lesser magnitude, and frequently of opposite sign, to those manifest in observational data sets (Pryor et al, 2009). Smits et al (2005) also reported that the apparent decrease in storminess over the Netherlands based on station data was inconsistent with that based on reanalysis data, which suggested increased storminess during the same 41-years period.…”

“…For example, model simulations over Eurasia using MM5 suggested that the recent increase in surface roughness (due to landover change) explained 25-60% of the reported decline in 10-m wind speeds (Vautard et al, 2010). Since landsurface characteristics are not variable with year in the reanalysis data sets, changes in roughness length would not be characterized by the boundary data sets used within the reanalysis systems (Pryor et al, 2009). This mechanism, if confirmed, would also account for the discrepancy between temporal trends over land and water surfaces.…”

“…The lack of correspondence between observational and reanalysis data sets and between observational data sets may derive from differences in time-series duration (and the short time-series of wind speed that are available for analysis), changes in station location, measurement height, data recording procedures and instrumentation deployed, in addition to difficulties in developing homogeneous observed records of near-surface wind speed (Pryor et al, 2009;Fu et al, 2011;Wan et al, 2010). Further, mid-latitude wind speeds exhibited high variability at interannual to interdecadal time scales linked to seasonal variation of the atmospheric circulation and internal modes of climate variability (Enloe et al, 2004;Pryor et al, 2005, Park et al, 2010Pryor and Ledolter, 2010) which further confounds identification of robust trends and attribution thereof.…”

“…A number of recent studies have reported declines in near-surface observed wind speeds during the past 30-50 years over parts of North America (Klink, 1999;Tuller, 2004;Pryor et al, 2009;Pryor and Ledolter, 2010), China (Xu et al, 2006;Jiang et al, 2010), regions of Europe (Pirazzoli and Tomasin, 2003;Brazdil et al, 2009) and Australia (McVicar et al, 2008). However, converse trends toward increasing wind speeds have been reported over the global oceans (Young et al, 2011).…”

Spatial and temporal variations of global frictional torque during the period 1948–2011

“…A decline of near-surface wind speed in recent years has been observed in China, the Czech Republic, the United States, and Australia (McVicar et al, 2008;Brázdil et al, 2009;Pryor et al, 2009;Yang et al, 2012). It has been reported that wind speed declined by 5%-15% in the midlatitudes of the NH between 1979 and 2008 (Vautard et al, 2010).…”