SCIENCE LAB STRIKES : LIGHTNING

 

A Strike Suppressant

To avoid lightning go heavy on the salt.

One of nature's most intense spectacles can be tamed with humble sea salt, the same stuff that graces some dinner tables.

Researchers recently found that the frequency of lightning decreases by up to 90 percent in the presence of salty sea spray. That makes sense based on how electric fields build up within clouds, the team proposes.

These new results, reported in the journal Nature Communications, help explain why thunderstorms occur much less frequently over the ocean than over land.

Compared with the lightning that recorded over the continents, only about one-tenth as many strikes occur at sea. Why exactly has long remained a mystery.

To dig into this enigma, Zenggxin Pan, an atmospheric scientist at the Hebrew University of Jerusalem, and his colleagues mined data from over 75,000 lightning storms.

The goal was to trace how convective clouds - the birthplace of lightning - evolved over time in different atmospheric conditions, said Daniel Rosenfeld, co-author of the study who is also at the Hebrew University of Jerusalem.

Dr. Pan and his collaborators showed that the effects of sea spray were substantial : Storms exposed to high levels of sea salt aerosols produce up to 90 percent less lightning than storms with very low levels of sea salt aerosols.

Thunderstorms are therefore less common over the ocean than over land for two reasons.

The fine airborne particles that promote lightning are more prevalent over land, close to more pollution sources. And larger sea salt aerosols - which suppress lightning- are naturally found near or over open water. [ Katherine Kornei ]