Zero Order Glow and Virga

December 09, 2005


Provided and copyright by: Peg Zenko
Summary authors & editors: Peg Zenko

The above photo showing an isolated rain shower at sunset was taken in Green Bay, Wisconsin on October 27, 2005. Precipitation from this shower failed to reached the ground (virga). A layer of dry air between the clouds and the Earth's surface caused the drops to evaporate soon after leaving the clouds. Virga typically originates from clouds having an altitude between 7,000 to 15,000 feet. Especially noteworthy here is the color of the backlit drops. We're familiar with the phenomena of drops opposite the Sun producing a rainbow, but this photo illustrates that the setting Sun shining through rain can be just as beautiful. This sunlight diffusion is called "zero order glow." Whereas the raindrops of the primary rainbow reflect the sunlight once, and the fainter secondary bow is caused by two reflections, the zero order glow has zero reflections.

Related Links: