S20 - Session O3 - An evaluation of the temperature inversion conditions to determine the usefulness of wind machines for frost protection in Mendoza, Argentina

Authors: Mark Battany *

Spring frosts can cause significant damage to wine grapes and other sensitive crops in many areas of the world. Various active protection measures are used to prevent damage, including wind machines, sprinklers, and the burning of various fuels. These methods each have their own limitations, respectively being the high initial cost of wind machines, the need for large amounts of water for sprinklers, and the high fuel/labor costs and pollution concerns with burning fuels. Given these limitations, some areas forego any active protection measures and may suffer otherwise preventable crop losses. The purpose of this study was to determine if the temperature inversion conditions on frost nights in the Mendoza region of Argentina would enable wind machines to provide beneficial warming to reduce frost risk. Temperature inversion conditions were measured with ten towers each having temperature sensors at 1.5 m and 10.7 m heights taking readings every 15 minutes. The towers were operated continuously from September 2019 until December 2020, encompassing two consecutive spring frost seasons. Nights with below-freezing temperatures that occurred from September 2019 to May 2020 and from September 2020 to December 2020 were included in the assessment. Inversion conditions were observed on each of the 33 cold nights evaluated during this period; the temperature difference between the two tower heights had a mean value of 2.18 °C with a standard deviation 0.47 °C. Prior research has shown that the operation of wind machines can be expected to increase the crop-level air temperatures by about half of the temperature difference between these measurement heights; therefore the expected temperature gain at crop level by operating wind machines in this region has a mean value of 1.09 °C with a standard deviation of 0.24 °C. These results support the use of wind machines for frost protection in this region.