Coronavirus, aviation and astromonical seeing

[starbrush]

Dear all,
[I just did a search in hope I wasn't duplicating an existing topic; sorry if I missed one after all]
After 9/11, as I recall, after just a few days of almost no air traffic over the US, the daily peak temperature range (lowest night-time, highest daytime temperatures) expanded dramatically, due perhaps to reduced aviation contrails, pollution etc. I guess this also improved the clarity of the atmosphere for ground-based astronomical observers.
Is this happening with the now global reduction in aviation and, indeed, terrestrial transport and industrial activity? It would be fascinating to know whether, say, a 3rd magnitude star is now appearing to be a slightly lower magnitude thanks to any improved atmospheric clarity.
In England I've started to notice a gorgeous, intense cobalt blue hue to the sky between fluffy cumulus clouds which may themselves have taken on a whiter shade of pale! Then again, a lot of us are savouring features of our surroundings with renewed acuity and I may be seeing more with my brain than with my optics.
So, how's the sky changing for the Oobservatories among us?
All the best.

[neufer]

After 9/11, as I recall, after just a few days of almost no air traffic over the US, the daily peak temperature range (lowest night-time, highest daytime temperatures) expanded dramatically, due perhaps to reduced aviation contrails, pollution etc. I guess this also improved the clarity of the atmosphere for ground-based astronomical observers.
Is this happening with the now global reduction in aviation and, indeed, terrestrial transport and industrial activity? It would be fascinating to know whether, say, a 3rd magnitude star is now appearing to be a slightly lower magnitude thanks to any improved atmospheric clarity.
In England I've started to notice a gorgeous, intense cobalt blue hue to the sky between fluffy cumulus clouds which may themselves have taken on a whiter shade of pale! Then again, a lot of us are savouring features of our surroundings with renewed acuity and I may be seeing more with my brain than with my optics.
So, how's the sky changing for the Oobservatories among us?

It should prove to be an interesting experiment especially when using a long run of improved weather & climate satellites.

<<The grounding of planes for three days in the United States after September 11, 2001, provided a rare opportunity for scientists to study the effects of contrails on climate forcing. Measurements showed that without contrails, the local diurnal temperature range (difference of day and night temperatures) was about 1 °C higher than immediately before; however, it has also been suggested that this was due to unusually clear weather during the period.

Condensation trails have been suspected of causing "regional-scale surface temperature" changes for some time. Researcher David J. Travis, an atmospheric scientist at the University of Wisconsin-Whitewater, wrote in the science journal Nature that the effect of the change in aircraft contrail formation during the three days after the September 11 attacks was observed in surface temperature change, measured across over 4,000 reporting stations in the continental United States. His research documented an "anomalous increase in the average diurnal temperature change". The diurnal temperature range (DTR) is the difference in the day's highs and lows at any weather reporting station. Travis observed a 1.8 °C departure from the two adjacent three-day periods to 11–14 September. This increase was the largest recorded in 30 years, more than "2 standard deviations away from the mean DTR".

The September 2001 air closures are deeply unusual in the modern world, but similar effects have provisionally been identified from World War II records, when flying was more tightly controlled. A 2011 study of climate records in the vicinity of large groups of airbases found a case where contrails appeared to induce a statistically significant change in local climate, with a temperature variance around 0.8 °C, suggesting that examination of historic weather data could help study these effects.>>

[BDanielMayfield]

Interesting question starbrush. This global slowdown event is and will be much longer than what happened after 9/11, although the 9/11 slowdown was deeper than what we are now experiencing.

Reduced air pollution is a good thing, but the cost to achieve it this way is horrible. But good on you starbrush for looking for a silver lining to this disaster.

Bruce

[Bobinius]

I am really wondering if there will be a rebound after the economic activity resumes. It will be progressive, but later in the year I am afraid that all of this could be surpassed by an even more intense pollution. People will want to recover. However, the impact on plane traffic will be durable, since the restriction on people circulation will be only slowly tapered.

[starbrush]

Hi all -
In the context of pollution (or its reduction), I've been wondering whether you can take a ground-based stellar spectrograph for a star, and then 'subtract' spaceborne readings for the same star, to give you an indication of our own atmosphere's intervening pollutants/gases and their likely quantities.
Can anyone offer tips for keywords to use in a search - or to an article that addresses this?
Thanks. Keep well.