Are there temperature inversions?
Previous research (Shaw, 2001) reconfirmed by these authors, shows strong night-time radiative temperature inversions during periods when wind machines might be used, both below and above the Niagara Escarpment. At 20 m (66 ft) above ground it can be 5 to 10°C warmer (9 to 18°F) than at 0.625 m (2 ft) above ground at vine level. Temperature inversions are strong when temperature differences are at least 3°C (5.5°F) warmer (Figure 5). Figure 5. Air temperatures high above ground can be much warmer than near the ground during inversions as shown in the authors’ research data above. The authors have shown wind speeds must be less than about 6 km/h (4 mph) in Niagara for temperature inversions to occur (Ker et al, 2007). If air temperatures near the crop are expected to be in the critical range and there is a strong temperature inversion, wind machines should help prevent cold injury. There is anecdotal evidence that on the very rare nights when it is calm, but with little to no temperatur
