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Germany - Hail cannons prevent hail damage but still no rain

The prolonged heat and dryness caused gardens, meadows and fields to wither this year. The German Weather Service reports an all-time high precipitation deficit in Germany. Meteorologists see the cause in a blocking, high-pressure area, which has created a stable weather situation with warm and dry air from the south east since April. Apart from this exceptional situation, severe risks for Ostland Dürrweitz AG are formed by thunderstorms and hail in particular. Hailstones can destroy considerable portions of the fruit harvest within a few minutes.

Hail cannon
To reduce this risk, to avoid possible economic damage and safeguard the jobs of the more than 380 employees from the region over the long term,
more than 10 years ago Obstland Dürrweitzschen AG decided to purchase six hail protection guns. “After the last severe hail storms we were no longer able to market up to 60% of the harvest from the affected plantations,” says Tina Hellmann, press liaison for Obstland Dürrweitzschen AG. The invention of the hail protection cannon dates back to the 19th century. Today it is mainly used by winemakers and fruit growers in southern Germany, Austria, France, South Tyrol, Spain, Holland and Belgium.

Hail occurs when evaporated water rises with the warm air. The water vapour cools and forms into droplets and clouds are formed. The water attaches to particles that are already present in the air. Together they rise to very high altitudes, where ice crystals are formed. Through gravity, they sink back down, all the while collecting more water droplets. The interplay between air currents and gravity leads to a circulation of ice crystals, in which they keep on growing.

Vertical pressure waves
The hail protection cannon interrupts this cycle by vertical pressure waves at
15 second-intervals. These pressure waves are generated by the explosion of an acetylene-oxygen mixture. As a result, water droplets cannot form into ice or hailstones so that they fall to the ground as rain or wet snow. For this principle to work, the hail protection cannons must be activated in time. Therefore, the fruit farmers are warned from approaching bad weather by a weather service. On the basis of radar images and through many years of experience, those responsible can tell whether it is a threatening thunderstorm front or a pure rain cell and in which direction the cells will probably go. Only when there is a serious danger to the fruit on the trees, the hail protection cannons are put into operation. 

“We are an agricultural company. Every euro we spend must be earned outside in the plantation. That’s why we think very carefully about which measures make sense,” the spokeswoman explains. Once the danger is over, the mission is terminated. Evidence of the effect of the hail protection cannons can be seen in the radar images. The effect of the hail protection cannons does not only extend to the orchards of Obstland Dürrweitzschen AG. Other farmers in the region, as well as the greenhouses, roofs and cars of neighbouring residents benefit from this protection measure.
Support of rainwater formation
The accusation that the use of hail protection cannons prevents the clouds from raining down, is invalidated by Dr. Armin Raabe from the Institute of Meteorology of the University of Leipzig. He says -from his scientific perspective: “From this point of view, the generated sound field would be more likely to support rainwater production, regardless of whether or not there was an effect on hail suppression.”

The spokeswoman emphasizes that rain is of immense importance for the agricultural company: “We manage more than 1,300 hectares of fruit acreage between Grimma, Döbeln and Oschatz. We only irrigate strawberries and a part of the pears. That’s less than 10 percent of the acreage. All other crops, such as apples, currants or plums, rely on naturally occurring precipitation and root-accessible water supplies in the soil.” 

Modern corporate network
Together with the parent company there are e
leven more subsidiaries that form Obstland Dürrweitzschen AG. The group of companies operates with around 380 employees in the fields of agriculture, trade and services. The group is known particularly for the production, processing and distribution of domestic fruits under the brand name “Sachsenobst”. This business division comprises six agricultural-oriented subsidiaries, Kelterei Sachsenobst GmbH and Sachsenobst Vermarktungsgesellschaft mbH. 

Since 2003, fruit farm Dürrweitzschen AG cultivated land through ecologically certified cultivation. In addition to this, the group is active in construction, electrical engineering, energy and building technology as well as in housing management. Deeply rooted in the “Saxon fruit country”, regional responsibility at Obstland Dürrweitzschen AG is seen as a matter of the heart. In-house environmental management ensures the continuous improvement of environmental protection.
Source – http://www.freshplaza.com

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