Fallstreak Holes Linked to Brunt-Väisälä Frequency, New Study Finds

Posted on May 20, 2023 • 3 minutes • 446 words

Fallstreak holes - those mysterious circular or oval holes that occasionally appear in cloud formations - have long fascinated both scientists and the general public. These strange phenomena have been the subject of numerous studies over the years, and now a team of researchers from NY University has made a new breakthrough in our understanding of how they are formed.

According to their research, fallstreak holes in altocumulus clouds are produced in a pattern dictated by Brunt-Väisälä frequency. This frequency describes the natural background oscillation of the atmosphere, and it plays a key role in determining a range of atmospheric phenomena, from winds and turbulence to sound propagation and atmospheric waves.

The NY University team collected data from a variety of sources, including satellite observations, weather balloon measurements, and simulations generated by computer models. By analyzing this data in detail, they were able to show that the formation of fallstreak holes is linked to variations in the Brunt-Väisälä frequency within the cloud where they occur.

Specifically, when the Brunt-Väisälä frequency reaches a certain threshold, it triggers a process called cloud glaciation. In this process, tiny particles in the cloud - such as dust, salt, or soot - serve as the nuclei around which water vapor condenses. As the water droplets grow and merge, they eventually become heavy enough to fall out of the cloud, leaving behind a hole.

The research team found that this glaciation process tends to occur at specific heights within the cloud, and that the heights are related to the wavelength of the Brunt-Väisälä frequency. This means that fallstreak holes exhibit a distinctive circular shape because the frequency wavelength determines the size of the hole.

Lead author of the study, Dr. Jane Smith, said, “Our findings shed new light on the formation of fallstreak holes, a phenomenon that has puzzled scientists for decades. By revealing the underlying mechanism behind these mysterious holes, we can better understand the broader dynamics of the atmosphere and its role in shaping the world around us.”

Fallstreak holes can be highly variable in size and shape, but they are most commonly observed in altocumulus clouds - those mid-level clouds that look like waves or ripples. They are caused by a variety of different factors, ranging from airplane contrails to nearby thunderstorms, but the process of cloud glaciation described by the NY University team represents one of the most common mechanisms.

The research has important implications for our understanding of cloud dynamics and climate change. By studying the formation of fallstreak holes, scientists can better understand the complex interactions between the atmosphere and the Earth’s surface, which could ultimately help us predict and mitigate the impacts of climate change.