Validation of Offshore Winds in the ERA5 Reanalysis and NREL NOW-23 WRF Analysis Using Two Floating Lidars in the New York Bight

Abstract Low-level winds from two numerical weather prediction (NWP) model analyses are evaluated offshore at two floating lidars over the New York Bight (NYB) region. These analyses are often used to evaluate models and for offshore wind resource assessments, so it is important to understand the errors and the environmental conditions and flow patterns associated with these errors. Lidar winds in the lowest 20–200 m MSL are used to validate the fifth major global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) (ERA5) and the National Renewable Energy Laboratory’s 2023 National Offshore Wind (NOW-23) wind product. Validation is performed for different seasons, months, and times of day, as well as different marine atmospheric boundary layer (MABL) stabilities and for large wind speed error events during the warm season. Both the ERA5 and NOW-23 struggle to accurately predict the lower MABL winds (i.e., speed and speed shear), especially during the warm season, and they significantly differ in the sign of and temporal nature of wind speed errors. MABL stability and model depiction of MABL mixing are one of the most important factors influencing the magnitude and sign of wind errors. Stable MABLs are associated with significantly large model analysis underestimations in wind speed and vertical shear. ERA5 and NOW-23 tend to perform better under near-neutral to unstable conditions, but ERA5 can overestimate winds under these conditions. This work has implications for future offshore wind energy assessment and marine forecasting in the NYB. Significance Statement This work quantifies the wind speed errors for two different weather model analyses in the lowest 200 m MSL offshore in the New York Bight (NYB) and improves our understanding of the environmental conditions and flow patterns associated with these errors. This work has implications for future offshore wind energy assessment and forecasting in the NYB. Our findings demonstrate that model analyses struggle in accurately depicting the wind speed resource characteristics, especially in the warm season months. The vertical temperature profile and mixing in the MABL are important factors influencing the magnitude and sign of wind errors.