Improving the Mapping and Prediction of Offshore Wind Resources
With few weather observations over the coastal Atlantic Ocean, atmospheric models are an essential bridge to map offshore wind resources and forecast wind power potential, up to hours or days in advance. Unfortunately, these models have large wind speed uncertainties over the ocean, especially at wind turbine height a few hundred feet above the ocean.
IMPOWR, a three-year field project, is improving atmospheric modeling of low-level wind fields with a combination of aircraft and in situ tower observations, namely by using ensemble modeling to provide a comprehensive planetary boundary layer (PBL) verification over southern New England coastal waters, as well as possible improvements to PBL parameterizations. IMPOWR includes the region surrounding Nantucket Sound, offshore from Massachusetts.
IMPOWR observations suggest that:
- Weather Research and Forecasting (WRF) model diurnally forced low-level jets are too weak during the warm season.
- WRF is too cool near the surface.
- PBL is too shallow near the coast (e.g., not enough mixing).
- WRF PBL parameterizations consistently underpredict wind speeds at Cape Wind tower at all levels.
- WRF near-surface temperature at Nantucket Sound buoy is too warm during the cool season and too cool during the warm season.
- Cape Wind Tower, 60-m tower within Nantucket Sound (from 2003-2011).
- 23-m Air-Sea Interaction Tower (ASIT), located just south of Martha's Vineyard and owned by the University of Connecticut
- 25-m Buzzard's Bay tower, operated by the National Oceanic and Atmospheric Administration
- Instrumented Long-EZ aircraft (20-25 flights), operated by Ultra-Pure Inc.
- AIMMS-20 instrument collected temperature, up to 40 Hz measurements of three-dimensional winds, pressure, and relative humidity data at a frequency of 20 times per second, profiling the lower atmosphere from about 30 to 1500 m above the ocean's surface.
Sampling included a variety of wind and temperature regimes from cool onshore (easterly) flows to warmer, more turbulent southwesterly cases.
Cole BA, MJ Sienkiewicz, CL Archer, and D Veron. 2015. "The IMPOWR (Improving the Mapping and Prediction of Offshore Wind Resources) Project: Evaluation of WRF PBL Schemes." In North American Wind Energy Academy 2015 Symposium (NAWEA 2015). June 09-11, 2015, Blacksburg, Virginia. Available online at: http://vtechworks.lib.vt.edu/handle/10919/54701.