Snow Monsters, Juhyou, Frost-covered Trees

The selective inverted sink prevents frost by drawing cold air from the ground and blowing it up through a chimney. It was originally developed to prevent frost damage to citrus fruits in Uruguay.
In New Zealand, helicopters are used in a similar function, especially in the vineyard regions like Marlborough. By dragging down warmer air from the inversion layers, and preventing the ponding of colder air on the ground, the low-flying helicopters prevent damage to the fruit buds. As the operations are conducted at night, and have in the past involved up to 130 aircraft per night in one region, safety rules are strict.