by Sharon Hill
Too often, perhaps, scientists tend to avoid research into a seemingly common but rather anomalous occurrence that interests the average person. That’s why a recent news article in Science caught my attention. The journal’s August 2, 2002 issue contains a report by a researcher in Spain regarding large ice balls that landed on the Andalusian region over several days.
Soon after a two kilogram chunk of ice smashed a windshield in Tocina, Spain in January 2000, planetary geologist Jesus Martinez-Frias collected the object for study. Additional objects were also retrieved over the next few days but no one could conceive of an adequate explanation for their appearance. A team was formed to figure out what mechanism could have spawned these objects from a cloudless sky.
By definition, hailstones are balls of ice accumulated by strong updrafts in cumulonimbus clouds – associated with thunderstorms. Two problems with the Spanish ice balls were as follows: 1.) There were no clouds at the time, and 2.) The ice balls were larger than known hailstones. The largest confirmed hailstone in the United States was a substantial grapefruit-sized chunk that fell on Kansas in 1970 and weighed in at 0.75 kg. One kilogram hailstones were reported in Nepal (year unknown). Greater size is obtained by the amount of time the material is kept aloft within the cloud – layers accrete as the hailstone falls and ascends repeatedly before becoming heavy enough to overcome the updrafts and fall to earth. A hailstone has a characteristic “onion-like” layering when dissected.
Any liquid or ice precipitation that falls is known as hydrometeors. Martinez-Frias designates these particular ice balls megacryometeors (large, icy atmospheric phenomena). He maintains a website with additional data (partially in Spanish) on the occurrence of megacryometeors. (http://tierra.rediris.es/megacryometeors/index2.html)
Anomalous icefalls are exceedingly rare but they are not unknown. They are reported from many regions around the world from the past to the present. William Corliss runs The Sourcebook Project in which the goal is to catalog anomalous natural phenomena with the intent of providing fodder for scientific investigation. (See references below for his website.) The Martinez-Frias website intends to do the same - citing recent reports of icefalls. Past reports of huge ice chunks have also been associated with clear skies. In some cases, the pieces are much larger than those that were under investigation in Spain – measured in feet instead of inches.
There are some similarities in historic reports of icefalls but also variance. Pieces may be round, knobby, angular or irregular. Some may resemble hail coalesced into a larger mass. Ice balls may be layered like a normal hailstone. Falling pieces may be associated with a peal of thunder, flash of lightning or a “whooshing” sound. Conversely, observers may be only aware of the object because of the resulting crash on impact. The material may be transparent, opaque due to air bubbles or have incorporated solid material. From the pieces that have been analyzed, various constituents include tea, coffee, detergent, salt, metal ions, gravel, bacteria, sand, and even small animals (an incredibly rare event apparently associated with the organisms entrained in the updraft and quick frozen at high altitudes).
The most common and obvious explanation for ice falling from the sky sans clouds is aircraft. Perhaps rainwater froze against the fuselage or moisture condensed on the wings which subsequently peeled off at high altitudes. However, aircraft rarely builds up ice during flight. Discarded waste from aircraft has also been proposed. However, commercial aircraft do not normally jettison their material while in the air. Plus, commercial aircraft toilet liquid is an obvious blue color due to the added disinfectant. In many cases, flight patterns at the time of icefalls can be checked. While this is not conclusive, planes flying overhead can generally be ruled out in certain instances.
Are the large chunks visitors from space? We know that comets and some space debris are made of dirty ice. Have some made it through our atmosphere to the ground? Possibly. But, again, study of some fallen ice material shows it does not have the chemical signature designating a space origin.
One explanation we must always consider is the human one. Did someone intentionally perpetrate an act of vandalism or a downright hoax? “Phony” ice balls were noticed associated with the Spanish ice balls in 2000. However, the chemical properties were obviously different than the natural ones. Hoaxing or observation error are most often the simplest explanation for anomaly cases but with the prolific reports by trained professional observers (scientists), there is little doubt that some downright weird phenomena truly does occur.
The investigation undertaken by the Spanish researchers revealed some curious physical scenarios that could account for the sunny day hailstones. First, it was discovered that no aircraft flyovers corresponded to all the megacryometeor appearances. The ice balls were found to contain air bubbles, layering, ammonia, silica and specific isotopes – all of which were characteristic of hailstones matching the composition of rainwater.
From meteorological data, they discovered low levels of ozone in the days prior to the icefalls. This condition subsequently led to temperature differences between layers of the atmosphere and caused associated wind shear. With a noted moist stratosphere, an ice crystal could accumulate additional layers when passing through. To form the initial crystals, a nucleus is needed. The researchers suggest that aircraft contrails may have provided the nuclei for the crystals to grow. Contrails (condensation trails) are artificial cirrus clouds formed from the emission of water droplets from jet exhaust at high altitude. They condense immediately upon release because the temperature of upper layers of the troposphere is below freezing (32 degrees Fahrenheit). Long lasting contrails are a sign of high moisture levels.
Since there were limited nuclei, there were few megacryometeors that formed and fell over Spain in January of 2000.
The Spanish scientists say their explanation is speculation. More testing needs to be performed in order to substantiate this idea. However, Science noted that in preparation for the article they contacted experts on hail formation who were cold to this idea of natural megacryometeor formation. In fact, at least one fell back on the icy plane scenario. From the article, it was clear that a few researchers are serious about looking beyond the clouds to explain this odd weather phenomenon while some still have their heads stuck in them. Hopefully, more researchers will take up the task of investigating anomalous natural phenomena and fresh ideas based on the new information will result.
References
Bosch, Xavier. “Great Balls of Ice”, Science 297, no. 5582 (2002): 765.
Corliss, William R. Handbook of Unusual Natural Phenomena, Glen Arm, Md.: Sourcebook Project, 1977. Reprint, Gramercy Books, 1995.
Simons, Paul. Weird Weather, London, U.K.: Little, Brown and Company, 1996.
“Science-Frontiers Online”, http://www.science-frontiers.com/sfonline.htm , Accessed August 24, 2002.
“Weather And Then Some: Hailstorms”, http://weather.andthensome.com/severeweather/hail.htm , Accessed August 24, 2002.
Last updated August 25,
2002.
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