Theory for Radar Reflecting Clouds

An explanation for a strange property of noctilucent clouds - thin, wispy clouds hovering at the edge of space at 85 km altitude - has been proposed by an experimental plasma physicist at the California Institute of Technology (Caltech), possibly laying to rest a decades-long mystery.

Noctilucent clouds, also known as night-shining clouds, were first described in 1885, two years after the massive eruption of Krakatoa, a volcanic island in Indonesia, sent up a plume of ash and debris up to 80 km into Earth's atmosphere. The eruption affected global climate and weather for years and may have produced the first noctilucent clouds.

Twenty-five years ago, researchers at Poker Flat, Alaska, discovered that the clouds were highly reflective to radar. This unusual property has long puzzled scientists.

Dr Paul Bellan, reporting in the August issue of the Journal of Geophysical Research-Atmospheres, now has an explanation: the ice grains in noctilucent clouds are coated with a thin film of metal, made of sodium and iron. The metal film causes radar waves to reflect off ripples in the cloud in a manner analogous to how X-rays reflect from a crystal lattice.

It raises the question: Could Radio Amateurs reflect signals off these clouds for DX Microwave contacts ?

The full press release can be read at 'Caltech Scientist Proposes Explanation for Puzzling Property of Night-Shining Clouds at the Edge of Space'