Latest Publications

Week 1: Flight Relief – No Contrails

As you’re all well aware, the ash cloud from the erupting Icelandic volcano has meant a suspension of many European flights over the last week. This has been the only major grounding of planes since the post-9/11 grounding in the US, and as such I make Saturday 17 April 2010 the first day in my lifetime in which I saw no atmospheric condensation of any sort – be it clouds or contrails.

Contrails are such a common thing these days that you can barely ever look up at blue skies and not see one. In fact, as I am writing I can see three or four short lived contrails criss-crossing the skies above campus. With 28,000 commercial flights departing Europe daily, and a similar number for the US – should we be worried about the impact of these “artificial clouds” on our atmosphere?

In the right conditions contrails can spread and last for days. Whilst they are high, they still have a radiative impact, blocking sunlight during the day and trapping longwave emission at night. This would mean decreased maximum temperatures and increased minimum temperatures. Remember to account for these in the Weather Game. A study (Travis et al, Nature, 2002) in 2002 showed exactly this; that the grounding of flights in the aftermath of 9/11 lead to days with a larger daily temperature range than average, using data from 4,000 US synoptic stations.

Change in Daily Temperature Range (DTR) from the 1971-2000 average for 3 3-day periods in September 2001

Whilst this result and it’s attribution to contrails have both been strongly disputed in the literature (see Hong et al, GRL, 2008) the potential climatic importance of contrails is obvious, if hard to quantify.

Looking a little closer to home, at the data from the atmospheric observatory, you can see an increase in the temperature range during the period of the recent plane grounding. How much of this is as a result of contrails will be hard to say, how much is a result of weather variability within the high pressure, and what impact does the volcanic ash have on radiation? It looks like this discussion might continue for some time. Feel free to continue it and add you thoughts by using the comments section…

Fieldsite temperature trace for the last 12 days

Volcanic ash observations from the ground and air

Robin Hogan and others have been putting together some very nice material looking at observations of the Ash cloud from satellite and ground based instruments, particularly those in Chilbolton, which you can see here (powerpoint presentation)

Particularly interesting are the apparent signatures of volcanic products at the ground. Robin will be updating the presentation as more analysis becomes available. Expect to see some of this analysis on Friday at WCD.

Also see some images of the ash collected at Lerwick on Thursday here showing the irregular shapes of the crystals (thanks to Chris Westbrook)

Giles Harrison and others have also been trying to measure the plume in-situ, early results available in a Met Office press release here

Eyjafjallajökull eruption and ash plume

An early post on the volcanic plume currently causing severe disruption to air travel over northern Europe. I’ve collected together some of the links already sent to met social by Keith which has lots of new images and the EUMETSAT front page from David which has some nice animations.

For those who want a journal reference as a jumping off point for thinking about ash plumes and their impact on aviation, you could do worse than the recent review by Pete Webley who was a PhD student in ESSC (click through the Science Direct link). Please add comments and other links below.

Come along to WCD next week for the latest update and to see if I’ve learned how to pronounce the name of the volcano!

Summer Term

Welcome to the new WCD blog. We hope this test run will help us to see how useful a blogging service will be and how we might make best use of this technology. This term there will be 10 guest bloggers, who will write a blog about WCD each week. The schedule for the summer term is below. If you would like to be a guest blogger and you aren’t on the list please contact Andrew Charlton-Perez. You can also subscribe to the blog using your favourite rss feed reader

  • Week 1 (April 23rd) Andy Barrett
  • Week 2 (April 30th) Jeff Chagnon
  • Week 3 (May 7th) Jon Shonk
  • Week 4 (May 14th) Leon Hermanson
  • Week 5 (May 21st) Amanda Maycock
  • Week 6 (May 28th) Rob Thompson
  • Week 7 (June 4th) John Lawson
  • Week 8 (June 11th)
  • Week 9 (June 18th) Ed Hawkins
  • Week 10 (June 25th) Kathy Maskell