Satellite photo shows odd cloud phenomenon

GREENBELT, Md., Nov. 20 (UPI) -- NASA says its Terra Earth observation satellite has captured a striking image of an atmospheric phenomenon knows as "cloud streets" over Canada's Hudson Bay.

Cloud streets are long parallel bands of cumulus clouds that form when cold air blows over warmer waters, while a warmer air layer -- or temperature inversion -- rests over the top of both, the space agency said.

As the comparatively warm water gives up heat and moisture to the cold air above, columns of heated air called thermals naturally rise through the atmosphere until they reach the inversion layer which acts as a lid.

The rising thermals hit this "lid," roll over and loop back on themselves to create "streets" of parallel cylinders of rolling air.

This creates flat-bottomed, fluffy-topped cumulus clouds that line up parallel to the prevailing wind, NASA said.

If the land or water surface underneath is uniform, as in Canada's huge Hudson Bay, cloud streets can stretch for hundreds of miles, the agency said.

The Terra satellite obtained the image on Nov. 13.