Lightning protection - HUBER+SUHNER - #10

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40 60 60 60 40 140 20 10 5 1 10 60 80 30 140 180 5 180 10 10 5 5 20 40 40 40 10 5 1 80 80 40 40 60 100 10 60 40 20 100 60 60 100 140 60 80 60 120 80 40 40 100 5 20 5 40 20 10 10 5 140 100 10 5 1 100 80 5 40 120 60 60 50 40 20 10 5 1 10 20 6 HUBER+SUHNER The electrical charge of a lightning stroke may exceed 100 As. It is discharged to the earth within 10 to 100 ms. The temperatures created in the lightning channel are higher than those on the sun’s surface. The air is heated so quickly that it expands with the force of an explosion. The resulting sound waves can be heard as «thunder» as far away as 20 km. Lightning flashes may be as long as 50 km, but are only a few millimeters thick. Lightning variants Thunderstorms occur most frequently in the tropical and subtropical belts surrounding the earth, where the temperatures and the air humidity are very high. At any given time, almost 2000 thunderstorms are in progress on earth, and every 1/100 second or 6000 times a minute a bolt of lightning strikes the earth. For many reasons the world is mapped concerning thunderstorm days – or the ground flash density (GFD) maps – and number of hits per area (square miles, square km, etc.). Also satellite flash event maps are available. GFD map of the USA In the USA alone, lightning strikes 40 million times each year. Its occurrence in the USA is greatest within a 100-kilometer-wide strip crossing the state of Florida, called «lightning alley». In this area, thunderstorms can be observed on 90 days every year. World map of isokeraunic level (annual number of days when thunder is heard)