Guidelines for wind turbine and weather radar siting

Wind turbines can affect weather radars. To learn more about wind turbines and their effects please visit the overview of wind turbine interference with weather radar.

Recommended guidance for mitigation distances

Environment and Climate Change Canada's (ECCC) guidelines suggest siting distances around its S-Band weather radars to mitigate potential turbine-radar interference. These guidelines are based on guidance from:

• international groups such as:
  • World Meteorological Organization's publication No. 1064
  • European Meteorological Network's 2010 publication (PDF)
  • European Meteorological Network's 2022 publication (PDF), and
• our observations within our own radar data.

The distance between the wind turbine and the weather radar is one of the key factors when considering potential interference with the function of the radar. Additional factors that impact the weather radar include:

• the terrain
• the size and quantity of turbines
• the spacing between turbines and their orientation with respect to the radar, and
• the cumulative wind farm footprint taking into consideration nearby existing and other proposed turbines

A review of international guidance and collected radar data suggests that wind turbines erected within 60 km of a weather radar have the potential to interfere with the radar's function.  

The following guidance has been developed as a tool for wind farm proponents:

Range

0 to 10km (Definite impact zone)

• Potential impact: The wind turbine may completely or partially block the radar and can result in significant loss of data that cannot be recovered.
• ECCC guideline: Wind turbines should not be installed in this zone.

10 to 60km (Moderate impact zone)

• Potential impact: Multiple reflection and multi-path scattering can create false echoes and multiple elevations. Doppler velocity measurements may be compromised by rotating blades.
• ECCC guideline: Proponents should consult with ECCC to assess potential impacts at the earliest development stage possible and (if necessary) develop mitigation measures.

>60km (Low to Intermittent impact zone)

• Potential impact: Generally, no impact observed in the data, but can be visible in some conditions over 100 km.
• ECCC guideline: Proponents should notify ECCC, as in rare cases, impacts could be realized.

Most importantly, wind turbines located within 10 km of a weather radar risk degrading the data for a wide range of area covered by the radar. Thus, proponents should not site turbines within the definite impact zone (0–10 km) as this could severely impact ECCC's ability to gather critical weather information.

Moreover, proponents who plan to build a wind farm located in the moderate impact zone (10-60 km) should consult with ECCC and adhere to our case-by-case recommendations on wind turbine siting to enable the wind farm and the weather radar to co-exist.

While wind turbines located beyond 60 km generally do not pose negative impacts to the radar data, intermittent impacts could be possible in some atmospheric conditions. Therefore, wind farm proponents should still notify ECCC of all wind farm proposals in Canada at the earliest stage of planning (i.e. determining site location of wind farm).

Assessment process

Before undertaking any significant planning activities, wind farm proponents should contact ECCC about new wind farm development in writing, to: radarsmeteo-weatherradars@ec.gc.ca. Please submit the following information:

• project name
• coordinates for proposed locations of turbine(s), which may be in latitude and longitude coordinates given in decimal degrees format (or UTM coordinates with zone reference)
• number of turbines in proposal
• hub/nacelle height (tower itself only; not including the length of the blades)
• turbine blade sweep diameter (or length of the blades), and
• turbine base diameter (if known).

Reference image:

For each submission, our weather radar specialists will perform a preliminary analysis of the proposal in order to technically assess the likely impacts on the quality of products delivered by the Environment and Climate Change Canada radar network.

From this data, we determine if there is potential for the wind turbines to interfere with the function of the weather radar (i.e. whether the main radar beam will intersect any tower or turbine blade).

If the preliminary assessment concludes that the proposed wind farm is either within an area that is already blocked from the view of the radar, and/or it is far enough away from the radar and below the radar horizon, then we notify the proponent in writing that it has no concern.

If the development is visible to radar, ECCC considers the degree to which it will impinge on the radar beam at the various elevation and azimuth angles. This indicates the magnitude of negative contribution it will have on the radar data.

Once the impact has been determined, we notify the proponent and conduct further assessments of possible mitigation measures to eliminate or minimize the negative impacts.

In cases where mitigation is required to enable the wind farm and weather radar to co-exist, ECCC and the wind farm proponent should work to reach an agreement to develop and implement agreed upon mitigation measures.

Potential mitigation measures

Based on experience in Canada thus far, the vast majority of wind farm proposals assessed as having the potential to impact an ECCC weather radar have been accommodated with some design adjustments or changes in scale. Our goal is to avoid significant interference that would hinder the timely and accurate issuance of important weather warnings for populated areas or vulnerable infrastructure.

In cases where mitigation is required, typically, the most effective mitigation measures are to site the turbines:

• at our recommended siting distances away from the weather radar or
• behind existing stationary obstructions (i.e. mountains) and out of the Radar Line-Of-Site (RLOS).

Other mitigation methods vary in effectiveness, cost and scale, and could include:

• decreasing the overall height of the proposed turbines, so that the blade tips will be below the base of the main radar beam to reduce the resulting frequency and impact of clutter
• curtailing the use of the wind turbines during severe weather
• radar software to recover weather data in the contaminated wind turbine regions
• installing supplementary weather radar/instruments and/or
• requesting a Letter of Credit wherein wind farm proponents provide a security deposit of $5M for proposals that pose a significant radar interference risk.
  • These funds would be utilized as a last resort in situations where severe impacts of wind farm operations on ECCC radar data are observed.

Although these other mitigation methods could help reduce the negative impact of the wind turbines on the weather radar, they:

• have cost implications for proponents
• vary in effectiveness, and
• can be avoided by siting wind farms at the recommended distances away from a weather radar.

Contact information

For additional information on our Guidance for Wind Turbine and Weather Radar Siting, please email radarsmeteo-weatherradars@ec.gc.ca.

Related links

• Overview of wind turbine interference with weather radar - Canada.ca
• Canada radar visibility maps - Canada.ca
• Wind turbine interference with weather radar - Canada.ca