Blick-Q & A: Are hailstones getting bigger?
Car windows blew out, tiled roofs shattered, and holes popped up in the walls. In June, hailstones hit the ground several times at a speed of up to 90 km/h and destroyed what hit them. Partially 7 cm or more in diameter, Meteoschweiz has also been reported. For comparison: it’s bigger than a tennis ball!
Should we expect more hail bombs in the future? And why are the pills so big? look clarifies.
How does cold happen?
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Hail always arises in thunderclouds. They form when there is a large difference in temperature between the air just above the ground and the atmosphere – this is especially the case in summer. Warm, moist air is carried upward by the processes of updating and changing from a gaseous state to a liquid state. In clouds, warm air sometimes meets very cold air. If the updraft is strong enough, the air will be pushed up even more, beyond the zero degree limit.
Water droplets turn into ice particles. If it is heavy enough, it retracts, collecting more water droplets. But since the upward current downward is still very strong, the ice grains are turned back, along with the accumulated water, which also freezes and makes the grains larger. This process repeats itself until the beans are too heavy to be pushed up. Then they fall to the ground like hail.
What is the size of hailstones?
Technically, ice crystals with a diameter of at least five millimeters are considered cold. Smaller grains of ice are known as frost. The largest hailstone to date was found in the USA in 2003. It landed in Nebraska, circumference 47.6 cm and weighing just under 758 grams, hitting the ground with a force three times the height of a rifle bullet. In 1986, a hailstone weighing more than one kilogram was reported in Bangladesh; There are even reports of 3.4 kg of hailstones in the Hyderabad region of India in 1939.
According to historical sources, the largest hailstone found in Switzerland fell from the sky on August 2, 1927 – about 13 cm in diameter. Meteoschweiz says that hailstones over 5 centimeters in diameter are fairly rare in Switzerland.
Are the hailstones getting bigger and bigger?
But in June of this year, the five-centimeter threshold was regularly crossed in Switzerland. It is very likely that this will be the case more frequently in the future because the zero degree boundary tends to move upwards. “Large hailstones tend to occur in severe thunderstorms, which we expect more often in the future,” says Olivia Romppainen-Martius of the Mobiliar Laboratory of Natural Hazards at the University of Bern. “Crown – Anzeiger”. “The hypothesis is that the distribution of hailstones will shift toward larger grains in the future because they do not dissolve on the longest way to Earth.”
However, there are many determining factors as to the size of a hail — and science still knows very little. Humidity plays as big a role as the zero degree limit rise or wind shear. “Science is currently trying to elucidate how these processes interact,” says Cornelia Schwierz, deputy head of climate division at Meteo Switzerland. It is still too early to have definitive answers.
How fast are hailstones?
This depends on the size. The heavier it is, the faster it falls and the higher its impact energy. A large hailstone falls 1 cm to the ground at a rate of 9 m/s (32.4 km/h). However, large hailstones can reach speeds of up to 60 m/s (216 km/h). Damage in planting should be expected from a size of 1.5 cm.
How often does a cold happen?
According to Meteoschweiz, there have been an average of 33 cold days per summer season in Switzerland since 2002. The number of cold days is very differently distributed. Especially in the southern region of Ticino, Emmental, Entelbuch and Napf, as well as along the Jura, there are areas where hail can often be expected. In some places in southern Ticino, hail occurs up to three times a year. Minimal cold days can be found in the interior alpine regions, where there has not been a single cold since 2002.
On average, at least one franking-sized (2 cm) hail event can be expected in Switzerland about 32 times per year, while events with golf-ball-size (4 cm) hail are expected about 29 times per year. Meteoswiss counts the days when the hailstone size was reached or exceeded and at the same time hail was expected across Switzerland over an area of at least 100 square kilometres.
Will there be more hailstorms in the future?
In Europe and Australia, yes, because global warming is likely to increase the water content in the atmosphere. In turn, the cold is expected to decrease in East Asia and North America. At least that’s what a study recently published in the journal says “nature” Posted and dated “Crown – Anzeiger” captured. However, the condition of the data is too poor to make accurate predictions. By the way, in China, the high level of air pollution is likely to be responsible for the fact that the hail will be less.
How bad are hailstorms?
Even if not every hailstorm is as devastating as the one in June that devastated Wolhusen LU, for example, closed a branch in Coop in Bulle FR and caused a rail depot to be breached, it rarely remains without consequences. According to a report by the Federal Council in 2016, the relative share of hail in damage from natural hazards in Switzerland is very high: at 31.1%, it is second only to floods (35.9%). And behind them was storm damage at 27.5 percent. On average, hailstorms in Switzerland cause building damage of up to 93 million Swiss francs each year. The damage to agricultural crops is about 65 million Swiss francs each year. It’s even worse in the United States, where hail causes an estimated $10 billion in damages each year.
Why does it actually only snow during the day?
What was noticeable about hailstorms in June was that they almost always occurred in the late afternoon or early evening. But at night, there was almost no hail. The explanation behind this: the floor that heats up during the day cools after sunset. This reduces the temperature difference between the layers of air on the ground and in the sky. The condition of thunderclouds slowly began to disappear.
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