Why is lightning less frequent at sea than on land? Israel-led study clears the air

Big aerosol particles in sea spray cut ocean lightning by up to 90%, researchers in Israel, China and US find, in discovery that could help weather, climate, forecasts.

Heavy ocean storms feature a far lower incidence of lightning than those on land because of large particles in sea spray, research at Jerusalem’s Hebrew University has established.

Until now, the prevailing assumption had been that the dearth of lightning in sea storms was due to cleaner air over the ocean.

However, observations have already shown that, even when the air over the sea is polluted, lightning is still less frequent at sea than on land.

Now, research at the Hebrew University’s Institute of Earth Sciences, led by Prof. Daniel Rosenfeld and his doctoral student Zengxin Pan, has shown that it is the larger, coarse sea spray that reduces the amount of lightning by as much as 90 percent. Conversely, smaller aerosols — solid particles, or very small liquid droplets, suspended in the atmosphere — increase lightning.

The size of particles also affects rainfall, their research shows.

The researchers, collaborating with scientists at Wuhan and Nanjing Universities in China and the University of Washington, were able to use satellite imagery to track clouds over land and sea. This was combined with lightning measurements from the Worldwide Lightning Location Network (WLLN) and with data that provided information on aerosols in the clouds.

“The effect of aerosols on clouds has been underappreciated,” said Rosenfeld. “It needs to be incorporated into the models for better weather and climate prediction.”

The research was published in the peer-reviewed journal Nature Communications.

Additional researchers were Feiyue Mao, Yannian Zhu, Lin Zang, Xin Lu, Joel A. Thornton, Robert H. Holzworth, Jianhua Yin, Avichay Efraim, and Wei Gong.

Daniel Rosenfeld was the sole Israeli to serve on the team that produced the most recent United Nations report on global warming a year ago.

A lead author on the report’s chapter about changes in the water cycle, he told The Times of Israel that while there were no great surprises in the nearly 4,000 pages of the report’s text, “the most important thing is that we can declare without doubt that humanity is responsible for the warming of 1.09 degrees Celsius (1.9 degrees Fahrenheit) since the industrial revolution.”

Stressing that all views he expressed were as a private individual, Rosenfeld said: “The amount of global warming is proportional to the amount of carbon dioxide that we emit into the atmosphere, so the solution is reducing it – up to now the pace has been growing. We need to ensure that this is reversed.”