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Wednesday, April 8, 2015

map of highest incidence of lightning .... and looping lightning !!!

Sometimes when it rains, you get to hear the thunderstorms and see lightning. Lightning is the transient passage of electrical current between a cloud and either the surface of the earth, or another cloud, etc.  Lightning is one of the most beautiful displays in nature. It is also one of the most deadly natural phenomena known to man. With bolt temperatures hotter than the surface of the sun and shockwaves beaming out in all directions, lightning is a lesson in physical science and humility.  It is common knowledge that lightning is generated in electrically charged storm systems, but the method of cloud charging still remains elusive.

For an Insurer, Lightning is a peril and cause loss or damage. In India, the Standard Fire & Special Perils policy ~ a named Perils policy has ‘lightning’ included in the listed perils and hence loss or damage caused  by lightning is indemnifiable.

'Looping lightning' shows bolts travelling upwards  before striking the Earth - but the phenomenon is probably an optical illusion.  Lightning is caused when positive and negative charges build up in a cloud to a level where one leaps to the other. As a result lightning has been seen striking the ground from a cloud and vice versa, and can move between clouds.

MailOnline reports that a bolt of lightning has been spotted soaring from the top of a cloud before looping back on itself and striking the ground in Australia. The image was captured over Jaibru in Australia by an off-duty emergency services officer who dubbed the phenomenon 'looping lightning'. Upwards lightning is possible, but is very rare - with current estimates suggesting less than one per cent of lightning strikes travelling in an ‘upwards’ direction.  And storm chaser Dan Robinson believes 'looped lightning' is simply a trick of perspective, based on where the viewer is stood, meaning it appears to rise and loop even though it is not.

Typically lightning is seen from a distance, or from the side, and it is rare to capture an image almost directly beneath a bolt.  As a result, this can skew its perspective. In particular, if the bolt is travelling straight at the viewer - so they are almost looking up the length of the bolt -  it can make it appear as if it is curving because of its forked nature.

There are places where lightning strikes regularly - Africa is the lightning capital of the world, according to map that tracked every  bolt of lightning to hit the earth for 18 years.  A Nasa map has revealed which parts of the world experience the most flashes of lightning ever year.  According to the satellite observations, lightning occurs more often over land than it does over oceans; lightning seems to happen more often closer to the equator, owing to the hotter temperatures .... Democratic Republic of Congo and Lake Maracaibo in northwestern Venezuela experienced the most.

The amazing map of NASA reveals average yearly counts of lightning flashes per square kilometre from 1995 to 2013.  The  results show that the highest amounts of lightning flashes occur in the far eastern Democratic Republic of Congo and Lake Maracaibo in northwestern Venezuela.  In the map, areas with the fewest number of flashes each year are grey and purple; areas with the largest number of lightning flashes - as many as 150 per year per square kilometer (0.4 square miles) - are bright pink. The Democratic Republic of Congo was found to have the most over the period.

The map was created using data from Nasa’s Tropical Rainfall Measuring Mission satellite, and the Orbview-1/Microlab satellite. The higher frequency over land is because solid earth absorbs sunlight and heats up faster than water, so there is greater atmospheric instability - leading to the formation of storms.

And Nasa’s Dr Daniel Cecil, a member of the Global Hydrology and Climate Centre’s lightning team, said the data also shows interesting trends.  Researchers have found that regardless of where you are in the world, lightning bolts are at their most powerful at 8am. This is because there are fewer particles in the atmosphere overnight, so it takes a more powerful charge to overcome the extra distance between these particles and release the bolt of power.

With regards – S. Sampathkumar
8th Apr 2015

Photos and news source :  //www.dailymail.co.uk/sciencetech/

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