Integration of NEXRAD, marine radar, sodar and conventional anemometry for avian risk assessment

Wind energy permitting often requires intensive monitoring of bird and bat activity in conjunction with meteorological conditions. A community wind project in rural Albany county, NYS, conducted studies of bird and bat activity which entailed the integration of multiple sources of data including an on-site X-band marine radar for tracking avian passage rates, Doppler SoDAR profiling, a 50-m meteorological tower, acoustic monitoring for bats, and NEXRAD data. The SoDAR allowed the determination of wind speed and direction as well as turbulence intensity to a height of 200 m.

Community members and students played an active role in the assessment of migratory bird and bat activity; more than 25 individuals were trained in the use of the marine radar for making avian counts.

Migratory bird activity was tracked with X-band marine radar at site as well as (regional) NexRad. Three migration seasons of NEXRAD data were collected, 2 of them concurrent with onsite X-band marine radar. The X-band marine radar screens were captured so that a digital record of each night's “voyage” was kept. The marine radar was operated in a “vertical” mode so that bird migration could be tied to particular heights above the ground. The movement of individual birds was tracked, allowing correlation between the meteorological conditions and rate of movement of the birds.

Night-migrating birds took flight within a short period of time after sunset, and returned to ground shortly before sunrise. The bulk of night-migrating birds were found to be at least 300 m above the ground, well above the top of the rotor sweep of utility-scale wind turbines.

The KENX NEXRAD radar was useful for the detection of general trends in migratory bird activity in the region. The reflectivity at the 13 km range gate, corresponding to the community wind site, was best correlated with bird counts at 300 m height above the ground.

One daytime case is included for the purpose of determining raptor migration activity near the site. Data for that case included Doppler sodar measurements and onsite marine radar as well as the measurements at the 50-m met. tower.

The study represents an unusual integration of multiple sources and scales of meteorological and biological data of importance for environmental permitting of wind energy.