The \u201cbombshell\u201d study showing \u201cpotentially serious consequences for agriculture\u201d is in fact a computer simulation designed to test how turbines<\/a> influence surface temperatures and soil moisture in central Europe.<\/p>\n It does include some scary numbers, but with a careful proviso that the scenarios it\u2019s testing are not possible in the real world.<\/p>\n What climate and energy engineer Sampath Weerappulli found was that under the right circumstances a small turbine with a 57m hub height could cause as much as 0.73\u00baC of surface warming and a small drying effect in the top layer of soil.<\/p>\n But that was an extreme outlier; the next highest figure was 0.34\u00baC, with two measurements showing cooling. <\/p>\n The highest soil moisture change was 0.002316 per cent.<\/p>\n \u201cOur study does not demonstrate that wind farms cause long-term drying of agricultural land,\u201d Weerappulli said in an email to Renew Economy.<\/p>\n \u201cThe changes in soil moisture that we observed were very small and, in my view, are not large enough to give cause for concern about substantial additional drying.\u201d<\/p>\n Weerappulli said he would also be \u201ccautious\u201d about mapping the results directly onto dry regions such as southern Australia, or applying them to much larger modern turbines which are now the norm for southern hemisphere wind projects.\u00a0<\/p>\n \u201cAssessing potential effects under drought conditions would require simulations with different soil-moisture states, realistic Australian meteorology, soils, and vegetation, and substantially longer simulation periods,\u201d he says.\u00a0<\/p>\n Unfortunately, there is no local data to feed into Weerappulli\u2019s model.<\/p>\n Juan Zaracho, a research fellow at James Cook University in Queensland, says the German study is \u201clegitimate, careful science\u201d but there\u2019s no Australian data to anchor it either way.<\/p>\n \u201cYour question about Australian data. I quickly looked, and I think there\u2019s essentially none,\u201d he told Renew Economy.<\/p>\n \u201cI couldn\u2019t find a published Australian field or satellite study on this\u2026 nobody on either side can point to Australian measurements.\u201d<\/p>\n Zaracho says Australia\u2019s wind farms are mostly on windy ridges and coasts where natural turbulence is already high and turbine-added mixing matters less. Inland cropping country with still, clear nights is where he\u2019d most expect to see a change, if it happened.\u00a0<\/p>\n Warmer nights, cooler days<\/p>\n Weerappulli set out to uncover how the turbulent air that eddies from turbines alters microclimates close to the ground and soil moisture.\u00a0<\/p>\n There is already a small amount of observational research in China, Europe and the US showing turbines sometimes create a small warming effect at night and a small cooling effect during the day, as blades mix colder surface air with warmer layers higher up.\u00a0<\/p>\n The bigger the wind farm, the bigger the effect, but the change is measured in tiny increments \u2013 0.72 per cent over a decade at one large wind farm in Texas<\/a>, and just 0.07-0.1\u00baC over grasslands and crops in China<\/a>.\u00a0<\/p>\n To smooth out a lack of European field data and to compare identical scenarios, Weerappulli\u2019s paper used a computer model to simulate ideal conditions over a fixed 4.5 hour period.<\/p>\n The model looked at nine atmospheric conditions, from strongly unstable through to neutral and strongly stable.\u00a0<\/p>\n It was under strongly stable \u2013 no wind, no mixing of air layers \u2013 night time conditions that the model predicted a small but measurable drying effect in the top millimetres of soil.\u00a0<\/p>\n The model showed that a simulation of a 5\u00d75 array of 25 turbines on perfectly flat, uniform European farmland over a 4.5 hour period, could \u2013 under the right circumstances \u2013 cause as much as 0.76\u00baC of surface warming and a small drying effect in the top layer of soil.<\/p>\n The results came with the proviso that \u201csuch stationary conditions do not occur in nature\u201d \u2013 scary numbers that amount to snapshots from an idealised model.<\/p>\n The data also shows turbines can also cause a colder microclimate or create no measurable change at all.<\/p>\n \u201cAlthough these effects may appear small on average, even subtle shifts in microclimatic conditions can influence plant growth, frost risks, and soil water retention factors critical to sustainable agricultural productivity,\u201d Weerappulli wrote in the paper, published in the journal Boundary-Layer Meteorology in late July.<\/p>\n But strongly stable is \u201ca rather extreme\u201d scenario, Weerappulli says. It\u2019s not a condition that would occur at every moment all night long, for example.\u00a0<\/p>\n In a real-world scenario, there is likely to be some wind, which lends itself to smaller surface temperature changes and soil moisture effects.\u00a0<\/p>\n \u201cIn real conditions, where atmospheric stability and wind direction continuously change, these effects would not necessarily persist in the same direction or over the same location,\u201d he says.<\/p>\n \u201cChanging wind directions would also distribute any potential long-term effects over a larger area, making them less pronounced locally.\u00a0<\/p>\n \u201cOverall, one of the key takeaways from our study is that although wind turbines can measurably modify near-surface turbulent exchanges, the resulting soil-moisture effects were very small and did not indicate a significant risk of increased drying of agricultural land.\u201d<\/p>\n The Australia question<\/p>\n Although the study was designed to look specifically at central Europe, Weerappulli says Australia\u2019s dry climate makes the soil moisture question \u201cparticularly interesting\u201d.<\/p>\n \u201cOur simulations showed that turbine-generated turbulence can modify latent heat flux and therefore soil moisture loss,\u201d he says.<\/p>\n \u201cFor Australian wind farms, the frequency of the relevant stability regimes would\u2026 be just as important as turbine size.\u201d<\/p>\n And could turbines exacerbate a drought? Weerappulli says no.<\/p>\n Extra atmospheric mixing can\u2019t strip out moisture that isn\u2019t there.\u00a0<\/p>\n But looking into surface temperatures during drought is one direction Weerappulli\u2019s work may go next.<\/p>\n Turbine-maxxing<\/p>\n Developers in Australia have been turbine-maxxing for years, building bigger and bigger machines to capture stronger winds higher above the earth.<\/p>\n But bigger turbines, that interact with more atmospheric layers, don\u2019t necessarily mean hotter eddies or bigger surface effects.\u00a0\u00a0<\/p>\n \u201cI would not assume that a larger turbine automatically produces proportionally greater effects at the surface,\u201d Weerappulli says.\u00a0<\/p>\n \u201cHub height, rotor diameter, atmospheric boundary layer depth, the strength of the nighttime temperature inversion, wind shear, turbine spacing, and land-surface conditions would also matter.\u00a0<\/p>\n \u201cOther than that, due to changing wind directions, the same area is not continuously affected by turbine wakes. As a result, any long-term effects are distributed over a larger area and are therefore likely to be weaker at any specific location.\u201d<\/p>\n Extrapolating any of these results to Australia, be it from a model designed for Europe or satellite images from China, is fraught because there isn\u2019t any similar data here.<\/p>\n It\u2019s not possible to scale up the effect of a turbine on temperature or soil moisture by scaling up a turbine, says Zaracho.\u00a0<\/p>\n \u201cThe near-surface effect depends on whether the rotor actually reaches down into the shallow, cold, stable layer near the ground,\u201d he told Renew Economy.\u00a0<\/p>\n \u201cSo [a computer model based on a smaller turbine] genuinely can\u2019t tell you what a 140m machine does. If anything, that\u2019s a reason to be sceptical of anyone using a 57m-hub German simulation to predict effects for the much taller turbines built here.\u201d<\/p>\n
![](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/05\/RachelWilliamson-July2020-11-e1707446545797.jpg\"\/)
<\/p>\n