Designing and Testing a Camera System for Capturing Hail in Natural Free Fall

The fall behavior of hailstones is a particularly difficult topic to study, partly due to the hazardous environmental conditions in which hailstones fall, the fast motion of falling hailstones, and the often low-light nature of the environment. The understanding of hailstone fall behavior has implications towards radar-based hail identification, hailstone growth understanding, and microphysical cloud modeling. It has been approximately 40 years since the last efforts to photograph hail in natural free fall and both camera and lightning technologies have progressed extensively since those previous efforts, lending credence to a renewed effort to photograph hail in natural free fall.

A camera system was designed by CIMMS and NSSL, and deployed during the 2019 spring Central Plains storm season. The system consisted of two camera systems contained within a single protective enclosure, which was powered by LiPo batteries. The camera was typically aimed at a flat black backdrop, but was occasionally deployed without the backdrop to speed up deployments. The backdrop for a few initial deployments had two light panels extending from the backdrop towards the camera. Each side panel implemented 5, 4-foot strips of LEDs, resulting in 1,300 lumens per foot. Additional forward lightning was provided by a 100W LED spotlight, powered by LiPo batteries, mounted above the camera that provided 14,000 lumens of light. The side panels were not used for a majority of deployments due to time requirements setting up the panels, which included a battery box to operate the lights.

A cursory review of the captured images revealed that very clean images of falling hailstones was possible, especially when the backdrop was present. Surprisingly, the images revealed that the camera system was capable of clearly rendering even the very small drops and captured many instances of drop/hailstone collisions, with several drop breakups captured. Detailed discussion of deployments, highlights of images captured, design for the next iteration of the camera, and future plans for deployment of the current and future camera systems will be discussed.