. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. a lot more going on than meets the eye, scientists say. Inside that cloud, a complicated chain of events is in the works. And it's about to create the first bolt of lightning. Vin Saxena, a physical meteorologist at North Carolina State University, ex- plains how lightning forms. Even in fair weather, there is an elec- trical field spread over the Earth, Sax- ena says. For example, from your waist down, you are continually being bombarded with about 120 volts per meter of elec- tricity—an amount similar to
. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. a lot more going on than meets the eye, scientists say. Inside that cloud, a complicated chain of events is in the works. And it's about to create the first bolt of lightning. Vin Saxena, a physical meteorologist at North Carolina State University, ex- plains how lightning forms. Even in fair weather, there is an elec- trical field spread over the Earth, Sax- ena says. For example, from your waist down, you are continually being bombarded with about 120 volts per meter of elec- tricity—an amount similar to that in an electrical outlet. In industrial areas, the electrical field can be as much as 360 volts per meter, Saxena says. But in a thunderstorm, the electrical field becomes exaggerated. When hot and cold air masses mix, a thunderstorm starts brewing. The top of the thunderstorm cloud becomes posi- tively charged, and the bottom nega- tively charged. Down below, the positively charged surface of the Earth reacts to that law of nature that says opposites attract. The more negative the base of the cloud becomes, the more positive the Earth's surface becomes. The air between the two acts as an insulator until the voltage difference reaches 3 million volts per meter. At this point, the insulation breaks and lightning begins to form. A line of current races from the base of the cloud toward the Earth, search- ing for the quickest way to the ground. It finds the tallest point—a tree, a radio tower, a church steeple. The positive charge of the target leaps up to meet the negative charge from the cloud, creating a connection between the two and a blinding flash of Photo from National Oceanic and Atmospheric Administration This is called the return stroke. And contrary to the popular belief that the flash moves from cloud to ground, it's the return stroke that's actually visible. With the return stroke, the air becomes super heated, raising the temperature instantly to 30
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Keywords: ., bookcentury1900, bookcollectionunclibra, booksubjectoceanography
