asperitas clouds over dekalb, il
09 november 2022

at 15:16z (9:16 am cst) on 09 november 2022, the sky over dekalb, il took on an unusual and striking appearance. rolling, wave-like cloud formations covered the sky—almost as if the atmosphere was stirred like water. this rare formation is known as asperitas.

asperitas clouds form when there are ripples in the atmosphere—called gravity waves—that move through a layer of clouds. these waves are often caused by earlier thunderstorms, cold fronts, or changes in wind direction. when they pass through a flat layer of mid-level clouds, like stratocumulus, they distort the cloud base into these wavy, uneven shapes.

that morning, dekalb was likely under the influence of stable air behind a weak cold front or convective system. the sunlight, still low in the sky, helped highlight the sharp texture of the cloud base, making the waves especially visible.

although they may appear dramatic, asperitas clouds are not associated with severe weather. they are relatively rare and tend to appear only under very specific atmospheric conditions. in fact, asperitas was only officially added as a recognized cloud type in 2017 by the world meteorological organization—making it one of the newest entries in modern cloud classification.