Should the same wind-shear assumption be applied to every direction?

The short answer

One shear assumption may be adequate for a preliminary case, but it should not automatically represent every direction at a site with different terrain or roughness by sector. Direction-dependent treatment can be useful when supported by measurements or a suitable model and when it materially affects the project decision.

Identify why the sectors differ

Map the upwind land cover and terrain for relevant incoming directions. An open field, woodland edge and built area can present different exposure. Record how measurement positions and heights relate to those features rather than assigning parameters solely from a broad land-use label.

Review concurrent multi-height evidence where available. A difference between two sensors can include installation effects, so the geometry and data quality still need checking.

Avoid fitting more detail than the data support

Dividing a campaign into many sectors reduces the observations available in each group. Sparse or seasonally incomplete sectors may not support stable estimates. Use a method proportionate to coverage and retain uncertainty where evidence is weak.

Compare the resulting hub-height resource and energy estimate with a simpler documented treatment. If the added detail does not materially change the decision, report that finding rather than implying that a larger parameter table is automatically more accurate.

State how the result is transferred

Identify whether the sector treatment applies at the measurement location, the proposed turbine position or both. A horizontal move can change the relevant upwind exposure even when hub height remains the same.

Include sector definitions, valid paired coverage, parameter basis and sensitivity results in the assessment handover. This lets a buyer understand the resource estimate without turning a convenient default or a sparsely fitted directional model into a universal physical description of the site.