An Assessment of the Need for Parameterizing the Effects of Wind Farms within the HRRR for Operational and Research Applications

The 3-km convection-allowing High-Resolution Rapid Refresh (HRRR) is an hourly-updating forecast model that supports short-range forecasting for renewable energy needs within the contiguous United States. During the second installment of the Wind Forecast Improvement Project (WFIP 2), the HRRR has been targeted for the improvement of low-level wind forecasts in the Columbia River Basin (CRB). Many wind profiling and scanning instruments have been deployed in the CRB for WFIP 2; some of them have been placed adjacent to wind farms. When using this data to validate model forecasts, an important question arises as to whether or not the observations contain wake-structures from these nearby wind farms. If so, model validation using this data may be inappropriate, since the current HRRR does not include the effects of extra drag and turbulence produced by wind farms.  

The current operational and experimental versions of the HRRR use the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary layer (PBL) scheme, which can be coupled to the wind farm parameterization (WFP) of Fitch et al. (2012, MWR).  This study explores the impact of including the effects of the WFP within an experimental version of the HRRR, which includes an embedded 750-m nest over the CRB.  Case studies have been selected, which represent a variety of weather regimes, to estimate the length, depth, magnitude and temporal variability of wakes from nearby wind farms that may extend over the location of the wind profiling/scanning instruments.  We will assess which weather conditions can produce wakes over instrument sites and, by evaluating and comparing how the model forecast errors change during these periods with and without the WFP, we will additionally determine the level of need for WFP inclusion within the HRRR and its 750-m nest.