Noctilucent Clouds Above Durham, England
September 16, 2007
The photo above shows a particularly intense noctilucent cloud display above Durham, England. Noctilucent or "night shining" clouds can be seen when the Sun is between 6 and 16 degrees below the horizon -- during the summer months in the United Kingdom. They're typically observed a couple of hours either side of sunrise or sunset. These clouds form at much higher altitudes than normal clouds and seem to have appeared more frequently in the past 20 years or so. This photo was taken at 3:00 a.m. local time on June 23, 2006. See also tomorrow's Earth Science Picture of the Day.