Monthly Archives: December 2011
How do snowflakes grow?
A snowflake can be an individual ice crystal or an aggregate of ice crystals. Ice crystals can grow by water vapor deposition on the crystal or by collisions with other cloud particles.
An ice crystal can grow if the air around it has a relative humidity near 100 percent. The ice particle grows by water vapor deposition. Growth by deposition is generally slow. If you find nicely shaped snowflakes, they likely were produced by vapor deposition. Continue reading
When is the Winter Solstice?
The winter solstice (from the Latin sol, or “sun,” and stice, or “come to a stop”) is the day of the year with the fewest hours of daylight. This year, this occurs for the Northern Hemisphere at 11:30 pm Wednesday. Continue reading
Why does the moon look red during a lunar eclipse?
A total lunar eclipse could be seen in cloud-free regions across most of the United States and Canada on Saturday morning, Dec. 10. In a total lunar eclipse the sun, Earth and moon line up and the Earth casts its shadow on the moon. The moon is always a full moon and it never goes completely dark during a total lunar eclipse. It appears reddish for the same reason that sunsets and sunrises often have a red tint. Continue reading
What is the outlook for Wisconsin’s winter?
The National Oceanic and Atmospheric Administration’s Climate Prediction Center issues seasonal climate outlook maps for the nation. The organization’s forecast for Wisconsin’s 2011-12 meteorological winter (which started Thursday and runs through Feb. 29) is for below-normal temperatures and above-normal precipitation. Continue reading