In many countries wind turbines are rapidly growing in numbers as the demandfor energy from renewable sources increases. The continued deployment of windturbines can, however, be problematic for many radar systems, which areeasily disturbed by turbines located in the radar line of sight. Windturbines situated in the vicinity of Doppler weather radars can lead toerroneous precipitation estimates as well as to inaccurate wind andturbulence measurements. This paper presents a quantitative analysis of theimpact of a wind farm, located in southeastern Sweden, on measurements froma nearby Doppler weather radar. The analysis is based on 6 years ofoperational radar data. In order to evaluate the impact of the wind farm,average values of all three spectral moments (the radar reflectivity factor,absolute radial velocity, and spectrum width) of the nearby Doppler weatherradar were calculated, using data before and after the construction of thewind farm. It is shown that all spectral moments, from a large area at anddownrange from the wind farm, were impacted by the wind turbines. It was alsofound that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. It is shown that this in part canbe explained by detection by the radar sidelobes and by scattering offincreased levels of dust and turbulence. In a detailed analysis, using datafrom a single radar cell, frequency distributions of all spectral momentswere used to study the competition between the weather signal and windturbine clutter. It is shown that, when weather echoes give rise to higherreflectivity values than those of the wind farm, the negative impact of thewind turbines is greatly reduced for all spectral moments.
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