Saturday, May 19, 2007
First windy day
Our first 2 weeks at Summit have been beautiful. Every day has been bright and sunny, with only a few minor high cirrus clouds. The plot above shows UV levels I measured over the past few days. You can see how the it has been very few clouds. Today the winds have gotten up to 20 miles per hour, so we have some blowing snow, which has reduced our visibility.
Here is a photo from the Total Sky Imager (TSI) that is used to calculate the percent cloud cover. You can not see any clouds in this photo, but you may be able to see the halo (or sun dog) around the Sun. This is caused by ice crystals in the atmosphere which are hexagonal in shape. The ice crystals could be in high level cirrus clouds or right at the surface in diamond dust (ice fog). Last night we had diamond dust forming, but since it is so windy today, these ice crystals are from cirrus.
There is a photo of the Big House last night around 0100 as Sun is low on the horizon and diamond dust was forming in an ice fog. It may not seem like much, but we were all excited that weather is changing some. The reactions we are studying are driven by sunlight, and we observed our most interesting results during blowing snow conditions. Now that all the instruments are more or less working we are hoping that the weather cooperates and brings us a few days of high winds and white out conditions over the next 4 weeks.
Posted by Barry Lefer at 8:27 AM