Effect of climate change on regional surface layer winds

Boundary layer winds and climate variability are inextricably intertwined. The magnitude and direction of these winds are crucial for pollutant dispersion modeling, accurate site assessments for wind energy generation, and estimating the magnitude of surface evapotranspiration.

Preliminary analysis indicates a general decrease in boundary layer wind speeds throughout much of the United States. However, wind speeds above the boundary layer show the opposite trend. Whether this is a natural fluctuation, a result of changes in surface roughness, or a consequence of long-term trends related to global climate change is still an open question. Recent studies using Global Climate Models (GCMs) for several climate change scenarios are inconclusive as to the sign of the change in surface wind speeds. Some regions may experience a net increase in boundary layer winds, while other areas observe a decrease. Areas within the U.S. that are most susceptible to climate change also contain substantial wind resources (for example, California and the Great Plains). The next few decades under a changing climate may also see greater variation in seasonal and annual wind speeds, making long-term planning for air quality and wind energy purposes problematic. Thus, the purpose of this presentation is to show preliminary results from a regional-scale study focusing on the effects of climate change on wind in the boundary layer.

Under the sponsorship of the California Energy Commission (CEC) and the Lawrence Livermore National Laboratory (LLNL), simulations of future-climate (2040-2060) wind speeds in the surface layer were performed in in order to estimate affects upon wind power production under the IPCC A2 greenhouse gas emissions scenario. Output from high-resolution (50 km) global climate simulations conducted at LLNL for the Department of Energy (DOE) National Science Foundation (NSF)-funded North American Regional Climate Change Prediction Project (NARCCAP) was used to initialize AWS Truewind's Mesoscale Atmospheric Simulation System (MASS) model. Simulations covering the entire state of California, with a grid size of 15 km, and “inner nests” with finer resolution (4.0 km) in the Tehachapi Pass and other wind energy production regions were performed. We present the results of these simulations and will discuss the implications for future wind energy resource assessment, air dispersion applications, and energy balance consequences.