Spatial and Temporal Variations of Wind Energy in Long Bay of the Carolinas: Numeric Modeling Estimates for the Year 2009-2010

In Long Bay of the Carolinas, wind energy varies greatly in space and time. Natural variations of winds make it challenging to select the best location of wind farms. The Palmetto Wind Research Project is designed to physically measure and numerically model the variations of wind field within Long Bay. Particular focus is on resolving the gradient of the cross-shore wind profile and the areas where the most energetic winds 100 m above sea surface can be found closest to the coast. As a modeling part of this collaborative Project, a three-dimensional Weather Research and Forecasting (WRF) model (Version 3.2) was used to investigate the variability of wind field in this area. A 12-month simulation was focused on the period of July 2009 to June 2010. Model initial and boundary conditions were from the final analysis dataset (1 degree resolution, every 6 hours) of National Centers for Environmental Prediction (NCEP). Three model domains and twenty-seven vertical grid layers were used. The parent domain (3-km resolution) covered the entire land-sea boundary of Long Bay from Cape Fear, NC to Cape Romain, SC, and two high-resolution (1-km) domains were one-way nested in the parent domain offshore of North Myrtle Beach and Winyah Bay mouth, respectively. Another atmosphere-ocean coupled model also was used to study the air-sea interaction in this area, and the differences between the results from the coupled model and these from WRF alone were relatively small under fare-weather conditions. Under storm conditions, however, the coupled model produced better wind field. Wind speeds at 3m, 10m and 100m above the surface were calculated from the pressure-based three-dimensional WRF grids. The 12-month WRF modeling results were validated by six observational buoys deployed (at 3 m elevation) by this Project as well as three nearby metrological stations (at 10 m elevation) maintained by National Data Buoy Center (NDBC). Modeling results indicate that wind energy increases dramatically from the coastal line to 10-20 km offshore, beyond which winds become more stable. The most energetic winds are in the months of December 2009- February 2010. Dominant wind direction is shore-parallel, either from northeast or southwest, although the direction changes month by month. The land-sea boundary can become very unstable during storm seasons, generating highly-variable winds along the coast. In order to better model land-sea boundary in the future, higher-resolution topographic (such as LIDAR), oceanographic, and atmospheric observations are urgently needed.