Abstract
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.
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