Tuesday, April 18, 2006

Twice in one week large chunks of ice have inexplicably fallen from the sky in California, leaving experts mystified.

In Loma Linda, Calif., Thursday a chunk of ice the size of a microwave oven came crashing through the roof of a recreation center, the San Francisco Chronicle reported. The ice then fragmented into several opaque, white chunks. No one was injured in the incident.

Unusually large hailstone a shrimp compared to ice falling in California.

"I've been in the fire service for 31 years. I've heard and read about these things, but I've never seen this in person,'' Rolland Crawford, division chief of the Loma Linda Fire Department, told the paper.

April 8 in Oakland a similar ice ball plunged to earth in a field at a park, making a 2-foot crater in the ground.

A typical explanation may involve ice falling from an airplane, but ice caused by leaks from a plane's lavatory is blue in color and these objects were white. Myriad other hypotheses have been offered, with one scientist even blaming global warming.

A spokesman with the Federal Aviation Administration told the Chronicle the incidents are being investigated as possibly being connected to aircraft, but it's difficult to accurately identify which commercial planes may have been responsible.

One theory is that the falling ice could have been built up on the outside of planes that were not protected by deicing equipment.

"I've talked to a lot of pilots who tell me there are places on airplanes where the deicing equipment doesn't cover," David Travis, a climatologist at the University of Wisconsin at Whitewater, told the San Franisco paper.

Jesus Martinez-Frias of the Planetary Geology Laboratory in Madrid cowrote in article with 11 colleagues that discusses 40 cases of falling ice – or "megacryometeors" – since 1999. He believes they could be caused by a process in the upper atmosphere similar to how hail is formed in which a formation of ice is repeatedly forced up into colder air, thus building up several layers.

According to the Chronicle report, Martinez-Frias suggests global warming has caused a new, steeper temperature difference between warm and cold air in the upper atmosphere that generates turbulent up-and-down winds, repeating the hail-formation process, even without a thunderstorm.