Margen
It goes off every 7 seconds and nobody has ever shown that it does anything at all. It is a sonic cannon, a tube that fires a shockwave of air upwards to break up the cloud before the hail falls. There are at least 10 of them on the Lleida plain.
The mayor of Torrebesses said so on television in July 2023, in Catalan, "cada set segons espetega" — every seven seconds it cracks — and people have had enough. That noise gets on my nerves. And even so, the noise is the least of it.
There is not a single piece of evidence that they work, and that is not me talking. It is AEMET, the Spanish state weather agency, on its own blog, in April 2023, in an article signed by 7 people from the agency. What they wrote is that hail cannons are «a very old technique that lacks any plausible basis to justify their usefulness». Which means they have been around for a century and nobody has found a reason why they should work. They say so after going through the studies there are, one by one, without finding a single one that backs them up.
Very old, genuinely. AEMET illustrates that article with an engraving of the 1901 Lyon congress, where people were already arguing about how to shoot at hail. That was 125 years ago, and AEMET still writes it the same way.
Here the cannons arrived as an alternative to seeding the clouds with silver iodide, a salt you fire into the core of the storm so the ice shares itself out into many small stones instead of a few big ones. Nobody has ever measured the cannons. That is why several town councils and the farmers’ union Unió de Pagesos asked the regional government to have IRTA, the public agricultural research institute, study whether they work. Néstor Serra, from the union, put it in one line: in dry-farming country, where the fields drink only what falls on them, and with the climate changing on top, a cannon whose job is breaking up clouds makes no sense.
What does stop hail is a net stretched over the tree. No mystery there. The stones hit the mesh and not the pear. And that is exactly what almost nobody has. According to the regional agriculture department, only 6 % of Lleida’s fruit trees have hail netting, and putting it up costs around 30,000 euros a hectare.