An Early Look into Boundary Layer-Wind Farm Interactions from the American Wake Experiment

Variations in the atmospheric boundary layer (ABL) due to onshore wind farms have been analyzed in the past, however, many questions remain unanswered since measuring wake properties and how they influence the ABL is a challenge. The American Wake Experiment (AWAKEN) is a field campaign aimed at observing and validating the potential effects of wind farms on the atmosphere. The role of the University of Oklahoma in AWAKEN has recently concluded with over a year of data collected in the U.S. Southern Great Plains. Here, we analyze this data from remote sensing instruments onboard the Collaborative Lower Atmospheric Mobile Profiling System (CLAMPS) deployed at two sites: one close enough to wind farms to be influenced by their collective wakes and a second in an undisturbed location far upwind of any wind farms. Preliminary findings from one of these instruments, the Halo Photonics Doppler Lidar, show that wind farms appear to enhance localized mixing (characterized as vertical velocity measurements) during both daytime and nighttime. Diurnally, updrafts and downdrafts consistently peak at deeper levels in the atmosphere than at the site upwind of the farms. Nocturnally, several cases have depicted an increase in vertical velocity intensity near heights encompassing wind farms (around 0-200 m) that are also not immediately present at the upwind site. Wind speed results indicate that the nocturnal low-level jet looks to be a factor in this nighttime intensity, mainly when the highest wind speeds occur near wind farms heights. Analysis has begun to classify types of nocturnal low-level jet conditions to determine those that aid in vertical velocity amplification. These results and those continuing to emerge could serve as valuable information as wind farms gradually increase throughout the United States and other countries, as well as provide valuable insights into how the relatively recent development of wind farms in this area may affect the long-term D OE climatological data collection at the Atmospheric Radiation Measurement Southern Great Plains (ARM SGP) site.