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

2 thoughts on “Week 1: Flight Relief – No Contrails

  1. I live in North Oxfordshire. We had beautiful blue skies when the planes stopped flying..the best I have seen for years. Since then you have to get up at 6.am to see blue skies. Thereafter the planes start crisscrossing from London and the midlands and, before you know it, it is a cloudy day.
    Such is the effect that I have been totally put off flying. I also wonder to what extent forecasters get our weather wrong because they fail to take the contrail effect into account?
    Kind regards
    Mary Groves

  2. I concur with Ms Groves. I live near Swindon (south England) and during the volcanic ash saga, I too noticed the increased brilliance of the blue skies. What induced me to write this message was that this morning at about 9am; a ‘clear and cloudless’ day, I stopped counting aircraft contrails at 20. The sky was criss-crossed in all directions.

    As a once frequent flier, I too question the sustainability of jet aircraft use and certainly believe that short haul domestic flights should be replaced by surface travel.

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