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6 July, 2000

I've Looked at Clouds from Both Sides Now

Yesterday was a bad day for me. After talking to several scientists and staff members, I discovered that the way I was feeling was perfectly normal. Most were surprised that it occurred this late in my stint at Summit. Today I feel much better.

As I mentioned in many other journals, there's not much to look at here. Entertainment is isolated to the occasional Herk that ventures in our direction. This happens bi-weekly. The only other entertainment is looking at the clouds. Boring, right? Oh contraire. Yesterday was an exceptional day in cloud observation primarily because it was overcast. For almost my entire 4 weeks at Summit, we have had perfectly clear skies due to a high pressure system with an occasional passing cirrus cloud. Cirrus clouds are very high clouds consisting of ice crystals. The best way to describe them is they look like feathers or mare's tails. In the mid-latitudes where I am from (40 degrees N), cirrus clouds indicate an approaching warm front. After you view cirrus clouds, the sky begins to turn milky in color (altocirrus clouds) then to a darker color (stratus clouds) then usually nimbostratus (light rain clouds). When the clouds finally dissipate, warm air is upon us. This is not true in the high latitudes (66 degrees N +) or so I have discovered. Cirrus clouds are always present with high pressure.

One of my tasks at Summit is to take weather observations every 3 hours throughout the day. This consists of drawing the sky cover. After taking this observation, I code the type of clouds, cloud height, how much cloud cover is present, past and visual horizontal distance (which is difficult because I have lost my depth perception). With this data, I am correlating how much solar radiation has entered the atmosphere (radiation instruments that Koni has installed). Results are yet to be determined.

Yesterday was an unusual day in cloud observation. The cloud cover was almost complete throughout the day with a few blue patches showing periodically. Around noon, on the northern horizon, two mushroom shaped clouds appeared. At first, they looked like white glowing shafts of light but as time marched on, the white shaft of light took on a distinctive shape. I asked Jack Dibb what possibly could cause this phenomena to occur. I mentioned that if I didn't know any better, I could swear that I was observing the formation of a cumulus nimbus cloud (thunder cloud). I knew this was impossible because at Summit, the temperatures are too cold for the vertical development of a cumulus nimbus cloud. In order for a cumulus nimbus cloud to form, there needs to be a temperature gradient (large fluxes in temperature between the base and the top of the cloud). This does not happen here. Jack said that if I reported seeing a cumulus nimbus cloud, NSF would fly me home because I didn't know what I was talking about. With that, I just let my gut feeling slide. It was quite beautiful anyway.

Shortly after lunch, Dr. Omura was scurrying around camp taking pictures of the mushroom cloud. By this point, the cloud had developed into a large, single-celled monster. You could see the shearing top (very classic for a cumulus nimbus cloud) as well as several layers of lower clouds crossing the beast horizontally. Omura was very excited. He explained that this was indeed a cumulus nimbus cloud forming on the horizon. His hypothesis was that the warm temperatures from the coast (200 miles away) had caused a cumulus cloud to form. It was July and the temps at the coast were much warmer than at Summit. When the cloud reached the cold ice cap, a temperature gradient formed with cold temps on the surface and warm temps aloft(above). This caused the vertical development very classic of the cumulus nimbus cloud. The cloud remained on the horizon throughout the day and skirted by camp. This was an usual event, one that rarely occurs on the ice cap.

What's next in this winter wonderland? Would you believe a tornado? Actually we couldn't identify this weird cloud last night but it sure did look like a tornado moving on the horizon. I think we've all been here too long. Now we're beginning to see things.

Ciao, Cathi

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