How Changing Weather Conditions Make Contrails Show Up


Senior Member.
On a recent walk in the hills my day started like thisDSC_0717.JPG

The relative humidity chart from shows around 50% RH at 300mb. The red dot is my approximate location.


By the end of my walk the skies looked like this


The relative humidity chart from shows greater than 90% RH at 300mb.



Senior Member.
i been waiting to show this in other threads i will see if can show it here

But to my frustration SQ297 seem not to follow the same flight path each day and can travel over head 1000 clicks north of me or as today just beyond my sight yet for a few days over 2 weeks it went right over head



Senior Member.
well it took sometime for the atmosphere conditions and flight SQ297 to go over my head but today it all came together..

well will ya look at that out my window 6/2/18 at 615 am today SQ297 almost right over head & no trails


chugging along nicely 37000FL I still wonder why/how the same flight can go 1000 clicks to my north yet still aim at fuel efficiently at Christchurch,,, ? upper jet stream winds im suspecting

because its too dang dry at 35000


Staff member
It is a false colour plot of backscatter (colour scale) against time (X axis) and vertical range ( Y axis) as clouds/aerosols/contrails etc. advect (with the wind) over a Met Office lidar ( in this case for Eskdalemuir). The cloud base is marked in black and the colour is an indication of the amount of backscatter in (relatively) arbitary units, as in the case of these lidars, which operate in the IR, there is virtually no air backscatter to use as a reference value. The light blue, in this case, near the ground is aerosol backscatter in the boundary layer, and the rest is cloud/contrails of various sorts. The black dots higher up are probably contrails which pass through the laser beam in a relatively short time. I should add that the signal to noise decreases with height as 1/(range squared), so it runs out of steam higher up, although it can still see the denser clouds (but not aerosols).
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