Wind Shear Calculator

This calculator specifically needs two speed-and-height pairs because it solves for α = ln(speed2/speed1) / ln(height2/height1), which requires a ratio between two distinct points. With only one measurement you have no way to characterize how wind speed changes with height at your site — the best fallback is to enter a literature-based α (0.14 for open terrain) directly in the companion Tower Height Optimization calculator instead.

A negative α means your entered wind speed at the lower height was actually higher than at the greater height, which happens with measurement error, very short averaging periods, or unusual atmospheric conditions like a low-level jet or strong inversion. An unusually high α (above 0.4) usually points to one measurement being taken in a sheltered spot — behind a building or in a tree line — while the other was in open exposure. Recheck both readings before trusting the projected speed at your target height.

The calculator maps your derived α directly onto a five-point terrainClass scale: 1 for α at or below 0.10 (smooth water or ice), 2 for 0.10-0.16 (open terrain), 3 for 0.16-0.22 (rural or suburban), 4 for 0.22-0.30 (urban or forested), and 5 for anything higher (dense city-center canopy). It's a convenience label derived purely from your measured α, not an independent input — treat it as a sanity check on whether your two readings match the terrain you'd expect from that site.

If your two heights are identical, or either entered speed or height is zero, the formula for α involves dividing by zero or taking the logarithm of a non-positive number — both undefined operations. Rather than returning an error, the calculator substitutes the standard open-terrain default of 0.14 so the rest of the calculation still produces a usable (if generic) estimate; double-check your Height 1 and Height 2 inputs if you see this default appear unexpectedly.