Fire in the Sky

  • Fire in the Sky
    26.11.2007 17:08

    While the weather is relatively quiet here in the UK, it is perhaps worth reflecting on lively  meteorological phenomena elsewhere.

    Let’s take a look at lightning, for instance. It is estimated that there are three million lightning strikes every day around the world – or 30 per second. The greatest frequency is in tropical and sub-tropical regions of the globe, and topping the list are: El Bagre, in Colombia (270 days per year with lightning); Tororo, in Uganda (251 days); and Bogor, in Java, Indonesia (223 days). Typically, these storms last for about two hours per day, with almost continual cloud-to-ground lightning and thunder.

    The most extraordinary electrical storm, however, is found in Venezuela, at the mouth of the Catatumbo river where it empties into Lake Maracaibo. This is the "Relámpago del Catatumbo" (“Catatumbo Lightning”). It can be seen during 140 to 160 nights of the year for as long as 10 hours per night and is comprised almost exclusively of eerily silent cloud-to-cloud lightning, arcing through the atmosphere at altitudes of five kilometres or more.

    The sky is illuminated by these flashes as often as 280 times per hour, amounting to over one million electrical discharges per year with an intensity of 100,000 to 400,000 amps each. The flashes are visible up to 40 kilometres away and have been used as a natural lighthouse for centuries; which is why this semi-permanent storm is also known as the “Faro de Maracaibo”, or "Maracaibo Beacon”.

    The confluence of cold winds pouring from the Andes and hot, humid air rising from Maracaibo’s marshlands is thought to be a major contributory factor to this unique display. Ionised gases ascend from the marshes, particularly methane from decaying vegetable matter. These feed the storms and produce spectacular displays of glowing red, orange, yellow and white incandescence.

    However, Angel Muñoz of the University of Zulia believes that a substance called kerogen (a mixture of organic compounds found in sedimentary rocks) might also play a rôle.

    "The substrata of the lake are rich in petroleum deposits,” he says, “and share with the river marshes the same geological history. The accumulation of methane in the atmosphere could be favoured by leaks of this gas through fissures in the rocky mantle and into the marshes and lagoons."

    This would at least explain the increase in the frequency and intensity of the Relámpago after nearby earthquakes, and its occasional disappearance.

    Whatever the reason, we can thank this violent but beautiful spectacle for helping to replenish ozone levels in the upper troposphere. It is thought to be the single greatest generator of ozone in the world, and there are calls for the region to be made a UNESCO protected zone.

    Each lightning bolt, it is said, could light all the bulbs in South America. Now, if only we could find a way to harness all that power.

    By: Stephen Davenport