Science

Weatherwatch: cloud 'x-rays' seek to reveal anatomy of a storm


Scientists have long used satellite cameras, such as the Geostationary Lightning Mapper (GLM), to count lightning flashes and monitor storms. Now Michael Petersen, of Los Alamos National Laboratory, is using the pulses of illumination to produce “fulminograms” showing clouds from inside.

“The output resembles an x-ray image of the storm,” Petersen says. “When light must penetrate thick convective cells, they stand out as dark spots in the image, while the brightest spots show us where lots of light can leak out of the cloud.”

GLM imagery of a convective storm over southern Brazil. The first image (a) shows optical energy measured by GLM; (b) shows the expected GLM energy distribution from idealised clouds; and the ratio of the measured-to-modelled energy in (c) highlights contrasts in cloud illumination that indicate cloud type and storm behaviour.



GLM imagery of a convective storm over southern Brazil. The first image (a) shows optical energy measured by GLM; (b) shows the expected GLM energy distribution from idealised clouds; and the ratio of the measured-to-modelled energy in (c) highlights contrasts in cloud illumination that indicate cloud type and storm behaviour.

Petersen’s work is described in a paper in the Journal of Geophysical Research: Atmospheres. The x-ray effect produces a map of the cloud density, giving an idea of the anatomy of the storm beneath its dark exterior. “Lightning measurements allow us to look through the anvil shield of intense thunderstorms to sense the dynamics at the heart of convection,” he says.

As well as giving close-up detail, the wide view from the GLM satellite means it should be possible to follow the progress of many storms simultaneously and provide weather warnings across a wide area. “We’re essentially trying to use lightning to create something akin to a simple weather radar for all thunderstorms across the Americas for now, and later across the globe,” Petersen says.



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