Precipitation reduction during Hurricane Harvey with simulated offshore wind farms

Abstract

Hurricane Harvey brought to the Texas coast possibly the heaviest rain ever recorded in US history, which then caused flooding at unprecedented levels. Previous studies have shown that large arrays of hypothetical offshore wind farms can extract kinetic energy from a hurricane and thus reduce the wind and storm surge. This study quantitatively tests whether the hypothetical offshore turbines may also affect precipitation patterns. The Weather Research Forecast model is employed to model Harvey and the offshore wind farms are parameterized as elevated drag and turbulent kinetic energy sources. Model results indicate that the offshore wind farms have a strong impact on the distribution of accumulated precipitation, with an obvious decrease onshore downstream of the wind farms, and an increase in offshore areas, upstream of or within the wind farms. Compared with the control case with no wind turbines, increased horizontal wind divergence and lower vertical velocity are found where precipitation is reduced onshore, whereas increased horizontal wind convergence and higher vertical velocity occur upstream of or within the offshore wind farms. The sensitivity to the size of the offshore array, inter-turbine spacing, and the details of the wind farm parameterization are assessed. The results suggest that large arrays of offshore wind turbines can effectively protect the coast from heavy rain during hurricanes and that smart layouts with fewer turbines over smaller areas can be almost as effective as those with more turbines over larger areas.