imgNo sudden, sharp boundary marks the passage of day into night in this gorgeous view of ocean and clouds over our fair planet Earth. Instead, the shadow line or terminator is diffuse and shows the gradual transition to darkness we experience as twilight.

With the Sun illuminating the scene from the right, the cloud tops reflect gently reddened sunlight filtered through the dusty troposphere, the lowest layer of the planet's nurturing atmosphere. A clear high altitude layer, visible along the dayside's upper edge, scatters blue sunlight and fades into the blackness of space. Learn more.

This picture was taken in June of 2001 from the International Space Station orbiting at an altitude of 211 nautical miles.

Credit: Astronomy Picture of the Day. Click to enlarge.



Today's Weather Activity

Welcome to JetStream, the National Weather Service Online Weather School. This site is designed to help educators, emergency managers, or anyone interested in learning about weather and weather safety.

The information contained in JetStream is arranged by subject; beginning with global and large scale weather patterns followed by lessons on air masses, wind patterns, cloud formations, thunderstorms, lightning, hail, damaging winds, tornados, tropical storms, cyclones and flooding. Interspersed in JetStream are "Learning Lessons" which can be used to enhance the educational experience.

You are free to use the materials in any manner you wish. We welcome your feedback on this project. Your input will greatly assist others in teaching the "hows" and "whys" of weather. Not sure where to begin? Click to see all topics in JetStream in the Topic Matrix. Contact Us:

Steven Cooper Steven.Cooper@noaa.gov
Deputy Regional Director, NWS Southern Region Headquarters, Fort Worth, Texas

Dennis Cain Dennis.Cain@noaa.gov
a.k.a. "Professor Weather", NWS Fort Worth, Texas