A Systematic Attempt to Measure Air Traffic Levels and Trails

[Mick West]

In a very detailed article, Andrew Johnson recounts his attempt to correlate the frequency of air traffic over various parts of the UK with the frequency of persistent contrails observed in those locations.
http://www.checktheevidence.co.uk/c..._content&task=view&id=393&Itemid=50#_ftnref20

This research used a collection of software and hardware to receive and decode ADS-B messages from aircraft as well as photograph the sky at 1-minute intervals. The software ran on several Raspberry Pi computers stationed at up to 6 different locations in the UK. The objective was to count the number of aircraft detected at a given location and compare these counts, both on an hourly and a daily basis, when the skies were clear enough to have seen persistent jet trails or “chemtrails”. Time-stamped time-lapse videos were generated for images taken between sunrise and sunset each day. These were inspected to count the number of trails observed in each 30-min period of daylight. Trail counts and aircraft counts were collated into a Microsoft Access Database. SQL Queries were then developed to allow comparison of aircraft counts during periods when trails were observed and clear periods when no trails were observed.

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After much analysis, the conclusion of the report was what you would expect:

From all the data gathered so far, it seems there is no large difference in “ADS-B detectable” aircraft on days of high trailing than there are on days of no trailing. The data here does not establish a clear link between levels of aircraft and levels of trailing.

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While there are various methodological objections that could be raised about this study, the primary problem is the ignoring of what 100 years of science tells us is the reason for persistent contrails: the weather.

Contrails persist in regions of air that are ice-supersaturated. Regions of ice-supersaturated air (sometimes referred to as Ice Super-Saturated Regions, or ISSR) are essentially invisible clouds. The plane passing through them makes them visible by temporarily raising the humidity. ISSRs vary in almost exactly the same way that clouds vary. So just like the sky can one day be clear, and the next day be cloudy, you can also have one day with no ISSRs, and the next day with lots, or a few broken ones (giving broken persistent contrails). And like clouds, ISSRs occur in layers, so planes flying at slightly different altitudes leave very different contrails.

None of this should be controversial. It's backed by science and observation dating as far back as the first observations of persistent contrails in the 1920s, and by discussions about contrails in over 70 years worth of weather books:

And this has been well discussed in the scientific literature for a similar length of time:
http://www.pa.op.dlr.de/issr/Cha1.html

The existence of cloud free air masses in the state of supersaturation with respect to ice was proven almost 60 years ago. E. Glückauf (1945) found from hygrometer data obtained over southern England that (very high) supersaturation with respect to ice occurs very frequently in the upper troposphere. H.Weickmann concluded in his 1945 review paper on "Shapes and formation of atmospheric ice crystals" (Weickmann 1945) that ice crystals in the atmosphere, i.e. cirrus clouds, form mainly via the water phase and not as soon as ice saturation is reached. He characterized the ice forming regions in the upper troposphere and the (lowermost) stratosphere as regions of high ice-supersaturation but with small absolute humidity.
...
A good marker of ISSRs is persistent condensation trails (contrails) when the sky is otherwise free of clouds. Since the mixing process in an aircraft exhaust plume can create very high degrees of supersaturation even in dry ambient air, the formation of contrails does not require as high ambient humidity as the formation of natural cirrus. Contrails can therefore decorate the sky when no cirrus clouds are around. Contrail persistence however requires at least ice saturation. A sky full of contrails but without cirrus therefore shows that there must be an ISSR.

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So while I applaud Andrew's hard work, and the database created might even have some interesting data in it, it seems like he was looking at the wrong thing. Nobody had ever claimed that days with more contrails were the result of more air traffic. It's always been about the weather, at 28,000 to 40,000 feet.

 

[deirdre]

he should use those doohickey's to count the planes on persistent contrail days and compare them to the number of recorded passenger flights. granted, military planes may make some persistent contrails (in chemtrail photos) but I imagine, way more often then not, his counts on PC days would show only ordinary passenger filled airlines making trails.

and passenger filled airline planes cannot hold enough 'chemical weight' to produce 'chemtrails'.

 

[Jazzy]

So while I applaud Andrew's hard work, and the database created might even have some interesting data in it, it seems like he was looking at the wrong thing. Nobody had ever claimed that days with more contrails were the result of more air traffic. It's always been about the weather, at 28,000 to 40,000 feet.

I've had a run in with him before. First and foremost he "knows" what's happening but can't find convincing proof. If you disagree you're in the "wrong" camp, and furthermore you're only before him to trick him. He certainly spent some time with life- (and death-ray) affirming Dr. Judy Wood. He has a sort of dyslexia with perspective with observed trails* apparently uncorrected by having also observed railway tracks converging to a point.

I suppose I shall have to watch this.

Edit: Read this. Copious. Reminds me of a SF story called "Prott". The Borrowash version, hoping for blue skies in one of the world's cloudiest regions. You can't fault him for effort. But otherwise… …you can.

Conclusions
8.1 Detected Air Traffic Levels and Trailing
From all the data gathered so far, it seems there is no large difference in “ADS-B detectable” aircraft on days of high trailing than there are on days of no trailing. The data here does not establish a clear link between levels of aircraft and levels of trailing. Looking at some figures in isolation, it could be argued that there is a lower amount of aircraft on days of trailing. This result, therefore would tend to disprove a general statement that trailing is seen because of increased levels of air traffic – if that is the case, then it is air traffic which is not detectable in the same way as “regular” air traffic.
Perhaps a better detector is needed, although this is unlikely – as a range of 20 miles should be sufficient to “detect planes and see trails” with this sort of equipment. For example, if one examines the charts, most of them have an unbroken line of travel for the planes, which means enough of the messages were picked up, while the plane was in range, to plot the path of the plane.

8.2 Identification of Flights Leaving Trails and Formation of Grids
It was sometimes quite difficult to identify which flights left trails – perhaps because only a maximum of about 50% of the flights could have their latitude and longitude decoded. Without this information, it was impossible to know if the flight was precisely overhead, or whether it was 100 miles away. The “percentage located” figure showed no appreciable variation between days of trailing and no trailing.
The study from 25 Nov 2013 of the WA6 tracker shows that it is was not possible, using ADS-B data, to identify all of the flights which made the grids. Though, looking at some of the charts, the potential for grids to form can be seen, these were not seen “in the right place” and not enough flights were detected to prove, from this data, that civilian air traffic is responsible for forming these grids. So they remain a mystery.
A study of data from the DE72 tracker seemed also to show that flights that were travelling in a NorthóSouth Direction were rarely seen on charts – and if they were, it was over the far west of Derby – about 20 miles from where the tracker was sighted. Further attempts at identifying “trailing flights” could be undertaken, even with the existing data.

8.3 Days of Trails or No Trails?
No obvious reason could be observed why trails were seen on some days and not others. Again, taking the 25 Nov 2013 time-lapse video, it can easily be seen that there are persistent and non-persistent trails appearing in the same periods of time and the same part of the sky. So this remains unexplained.

8.4 Weather Anomalies
The tracker with the best view did seem to observe some kind of weather anomalies on some days – why would cloud formations remain in the same place above the ground, whilst “other weather” drifts past? Why would this happen the clouds both at lower and higher altitudes? What is the cause of linear weather fronts?

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What is atmospheric science, indeed?

* He needs to see Mick's work on this.