In gallery: Photos of the month (2004)
Related photos: Miscellaneous
Ice & frost
This is a macro photo of the cross-section of a large hailstone. On October 5, a rare one-in-a-century hailstorm occured over Socorro, New Mexico (USA). Stones fell as big as 8 cm (3") causing lots of damage in property. The frame above extends 3 cm in length (1 1/4"), clearly showing the several growth rings of the hail. The opaque white rings are caused by accretion of ice crystals and little graupel particles when the hail is high in the storm; the more clear ice is grown when the stone is in the liquid-water part of the cloud. Big stones as these where cycled through the storm up to 5 or more times before falling out. Since such stones fall at terminal velocities up to 150 km/h (90 mph), and they are being suspended by the updraft in the storm until they grow too large, this gives an idea of the extreme updraft velocities that can occur in severe storms.
Imaged with Nikon D100 digital camera, fitted with extension rings and 50mm/1.4 Nikkor lens set at f/16. Shutter speed was 4 seconds at 200 ISO sensitivity. The whole setup was mounted on a tripod. The hailstone slice was created by melting a stone halfway through on a hot plate, then reversing and melting the other side until a few mm thick slice (about 1/8") was obtained.