![]() ![]() To do that, a team of researchers from China, Israel and the U.S. Although this mechanism for dampening lightning at sea has been suggested before, evidence for it had not yet been found in global weather observations. When large, water-absorbent particles of sea salt-abundant in ocean spray-are present, however, the tiny droplets that typically condense on microscopic dust and soot to form clouds grow much more rapidly, becoming heavy enough to fall as rain well before the cloud can grow tall enough to charge up. When the charge difference grows big enough, lightning strikes. Over time, this separation generates an electrical field between the cloud’s positively charged top and negatively charged bottom. The positively charged ice crystals are so light that updrafts of air bring them to the top of the cloud, whereas heavier graupel tend to sink. As these icy particles bump into one another, they transfer electrical charges: the larger graupel tend to become negatively charged, whereas the smaller ice crystals end up with a positive charge. ![]() Thick clouds that form overhead during storms can become electrified when upward-moving air helps them grow tall enough that the upper parts of the cloud freeze into a mixture of granular, rounded pellets of snow called graupel, and microscopic ice crystals. A new study published on Tuesday in Nature Communications suggests salt spray could be getting in the way of clouds charging up for a lightning strike. Although most rain on Earth falls over the oceans, lightning at sea is rarer than expected-and for decades, scientists were not sure why.
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