Different Types of Lightning

eurosafesolutions eurosafesolutions.co.uk Different Types of Lightning Lightning is a sudden, electrostatic discharge - a spark or flash as charged regions in the atmosphere temporarily equalise themselves. It is the polarity of lightning discharge that can affect the way it spreads and branches in space and time. It is this, as well as its starting and ending points and direction of movement, that give rise to different 'types' of lightning. Lightning can strike the ground, the air or inside clouds, but there are roughly 5 to 10 times more cloud flashes than there are cloud-to-ground flashes. Examples + D B Different Types of Lightning - Key A Cloud-to-Cloud (CC) B Ground-to-Cloud (GC) c Cloud-to-Air (CA) D Cloud-to-Ground (CG) Positively and Negatively Charged Droplets Different Types of Lightning Cloud-to-Ground (CG) Lightning In this type of lightning, a channel of negative charge, called a stepped leader, will zigzag downward in a 'forked' pattern - which is why it is often referred to as forked lightning. This stepped leader is invisible to the human eye and travels to the ground in a millisecond. As it nears the ground, the negatively charged stepped leader is attracted to a channel of positive charge reaching up. This streamer normally passes through something tall, such as a tree, house or telephone pole. When the oppositely charged leader and streamer connect, a powerful electrical current begins flowing (hence why it is ill-advised to stand under a tall object during a thunderstorm!). A return stroke (the very bright visible flash that we see as lightning) travels at about 60,000 miles per second back towards the cloud, with one flash consisting of as many as 20 return strokes. Negative Cloud-to-Ground Lightning (-CG) The most regular CG flashes are initiated by a downward moving, negatively charged stepped leader, which is followed by an upward travelling return stroke. The net effect of this flash is to lower negative charge from the cloud to the ground. Negative CG lightning strikes can be recognised by their distinctive downward branching. + Positive Cloud-to-Ground Lightning (+CG) The less frequent CG flashes are started by a downward moving, positively charged stepped leader which is followed by an upward travelling return stroke that lowers the positive charge to earth. Such lightning is usually associated with supercell thunderstorms and trailing stratiform precipitation regions behind squall lines. Positive cloud-to-ground lightning strikes are typically very bright (relative to other lightning activity) and can be identified by their distinct lack of branching near the ground. Thunder from such lightning is very loud and may sound like a series of deep, low-frequency sonic booms. Cloud-to-Air (CA) Lightning A discharge that jumps from a cloud into clear air and terminates abruptly, CG lightning contains CA lightning via the branches that extend from the main channel into the mid-air. However, the most severe examples occur when long, bright lightning channels extend from the sides of cumulonimbus clouds. Ground-to-Cloud (GC) Lightning A discharge between cloud and ground caused by an upward-moving leader starting from an object on the ground. Ground-to-cloud lightning strikes - sometimes called upward-moving lightning - are common on tall towers and skyscrapers. GC lightning can also be either positive or negative in polarity. Lightning that demonstrates upward branching is a clear indication of a ground-to-cloud flash, though some upward-moving lightning is branchless below the cloud base. Intracloud (IC) Lightning This is the most common type of discharge and refers to lightning embedded within a single storm cloud, which jumps between different charge regions in the cloud. Cloud-to-Cloud (CC) Lightning Although infrequent, lightning can also travel from one cloud to another. Spider lightning refers to long, horizontal moving flashes often seen on the underside of stratiform clouds. Lightning Protection Testing EuroSafe Solution's extensive experience in working safely at height, combined with their knowledge in lightning protection, means they can offer a comprehensive nationwide lightning protection testing and inspection service. The ever-increasing reliance upon electronic systems in our everyday lives and the subsequent consequences of damage to these systems heightens the need to protect them from damage by lightning strike with lightning strike testing. For more details please visit www.eurosafesolutions.co.uk/service/test-inspection/lightning-protection Our Services Include: Roof Assessment & Evaluation Test & Inspection Plan of Action & Safety at Height Management System Programme of Requirements Training & Education Installation & Implementation Sheffield, UK eurosafesolutions Unit 51b Dorehouse Ind Est Orgreave Drive Sheffield, S13 9NR 0114 250 7411 eurosafesolutions.co.uk [email protected]