2009.02.13
The sun and its dog go for an evening walk
A visit to the Roanoke Times roof garden earlier this evening resulted in an unexpected treat. The late-day sun, out of view to my left, was refracting through high ice-crystal clouds known as cirrus, creating a phenomenon known as a sun dog. A sun dog almost looks like a second sun, with a slight rainbow effect as light rays are scattered by ice crystals. So the photo at left may look like the sun itself somewhat obscured by clouds near the horizon, but fact, it is the sun's light some distance north of the setting sun. (full-size version of photo linked here)
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Brandon and Kevin, in your comments yesterday you two were talking about ice on the wings of airplanes. My wife Nancy was an eyewitness to the Air Florida crash into the Potomac River on the D.C.-Virginia border in 1982 (I believe it was February). That plane was only airborne for about a minute from National Airport and could not attain lift because of severe icing on the wings. It has certainly been the most famous case of an airplane crash caused by icing in my lifetime. That crash spurred research into improving the de-icing capabilities of airplanes. Buffalo crash last night was probably caused by a malfunctioning de-icing system, despite the fact that the pilot confirmed that the cockpit gauge indicated that the system was turned on.
Comment by Doug Griggs — February 13, 2009 @ 10:21 pm
I just watched TWC's Weekly Planner and it indicates snow showers for us on Monday, and rain/snow for both Wednesday and Thursday. What sayeth thou, KM? Are we -- RRA -- finally going to see our first inch within 24 hours?? I bet not, at least for any of these three days.
Comment by Doug Griggs — February 13, 2009 @ 10:25 pm
There is a graphic on the front page of today's Roanoke Times that depicts effects of icing on wings ... it states that icing only the width of a compact disc reduces a plane's lift ability by 25 percent. For those of you too young to remember ... the 1982 crash Doug refers was into a largely frozen Potomac River, and there is a famous news video of a bystander jumping into the river and swimming out to save a woman who was hypothermic in the icy river ... large jetliner crashes were much more frequent in the 1980s and early 1990s ... aside from 9/11, we haven't had a large domestic flight jetliner crash in the U.S. killing more than 100 people since the ValuJet crash in the Florida Everglades on May 11, 1996. (There was a crash in Queens, NY, in November 2001 of an American Airlines jetliner headed to the Dominican Republic, killing more than 200.) Amazing when you stop to think how many planes are flying every day!
As for this week's weather ... Sunday-Monday's system looks like it will develop too late to do very much, maybe some sprinkles or light snow (could be a little of that in some areas tonight with a weak disturbance), while the midweek system will likely be too far north, but it could be intense and lead to a large-scale pattern shift that will return us to unseasonably cold weather for several days afterward. I will digest it a little more and post later this evening.
Comment by kevinmyatt — February 14, 2009 @ 1:13 pm
Kevin, you're right about how remarkable it is that so many flights occur daily without problems. This website...http://flightaware.com/live/... displays current air traffic. For example, right now there are 4728 aircraft aloft. Check out the animation of a 24 hour period from 2005.
Comment by Jim D — February 14, 2009 @ 2:06 pm
Jim D.: thanks for the post. I am not a global warming advocate at all, but I do acknowledge that at least up until roughly a year ago, there has been an overall significant warming trend worldwide, and extremely signif. in places like the American and Canadian Rockies. If this trend were to continue for another 25-30 years, THEN I would believe all the articles and claims -- assuming I am alive and not senile. And there are three things that I would acknowlecge that probably contributed to warming. First, the elimination of mind-boggling numbers of trees in the Brazilian rain forest; 2: the growth of cities and concrete and steel -- I do acknowledge that cities are heat islands; and 3. the immense increase in the numbers of airplane flights!! I have never heard of any research on this little theory of mine, but all that consumed jet fuel might have contributed quite a bit to a warming of the atmosphere. 4700+ flights in progress at one time!!! That's a heckuva lot of jet fuel being burned.
Comment by Doug Griggs — February 14, 2009 @ 5:33 pm
Doug: Jet planes use a lot of fuel with carbon emisssions, but they also leave jet trails that can form clouds which (1) hold temperatures up at night by inhibiting radiational cooling and (2) block sunlight in the day, reducing temperatures. There was a study done in the days after 9/11 ... when commercial air traffic was halted ... that detected a slight increase in daily temperature range, which would be consistent with less atmospheric moisture condensation from jet trails. Here is a CNN summary of that study:
http://archives.cnn.com/2002/TECH/science/08/07/contrails.climate/index.html
Comment by kevinmyatt — February 14, 2009 @ 6:36 pm
There was an interesting program on Nova last year about the possible impact of both contrails and air pollution on climate. Essentially, air pollution may ironically be reflecting enough sunlight to somewhat dampen global warming.
http://www.pbs.org/wgbh/nova/sun/
Comment by KevinL — February 15, 2009 @ 3:34 pm