Also, they just looked at 2 years, so there could be cherry picking. Jet stream is affected by el nino. 1979 was weak el nino, 2020 was moderate la nina.
Why do you say that? Just looking at the plots in Prosser et al (2023) it is obvious they had a lot more years than just two.
If you actually read the short paper you'll find they actually used reanalysis data sampled at a rate of every three hours across 42 years to compute their statistics:
> Global ERA5 reanalysis data (Hersbach et al., 2020) [...] were extracted on the 197 hPa pressure level with 0.25° horizontal resolution at three hourly intervals from 1 January 1979 to 31 December 2020. To allow the computation of CAT diagnostics that require vertical derivatives, fields on the 188 and 206 hPa levels were also extracted. The 21 turbulence diagnostics were then calculated from the extracted reanalysis fields every three hours.
How you go from that to "they just looked at 2 years" is beyond me.
Right, and those two years are generationally distant. Another question I have is if pilots have a stable mechanism (that is, an unchanged objective sensor or something) that records the CAT or if it’s recorded by pilots, whose sensitivity to CAT might differ over time. Didn’t mention in the article how it’s measured.
CATs are recorded in pilot reports using terms like "light", "moderate", "severe", and "extreme" which each have a definition. I.e. severe is "Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. Food service and walking are impossible." I think only severe and extreme turbulence need mandatory reports and the lower two levels are a bit more subjective ("Food service and walking are difficult")
Newer planes have sensors to measure eddy dissipation rates which are an objective measure of turbulence but I don't know how widespread those systems are and whether they get reported anywhere. They're mostly used for long distance transoceanic flights.
Unsecured objects being tossed around has no real meaning, it’s about controllability of the aircraft.
I’m a pilot and it’s been a while since I went over PIREPS but generally severe is rarely used, severe means the turbulence is so bad you can no longer control the aircraft. What most passengers imagine as severe is probably light turbulence. Most of the time it’s not even reported. As a side note if you’re ever on an aircraft and not secured at all times, you’re making a huge mistake.
Have there been any reports of true severe clear air turbulence (where the pilot cannot control the plane) or are all of these cases not technically severe because the pilots were in control the entire time and it was just a bumpy ride?
Another question I have is what do you do in that scenario if you can't control it? Just ride it out and hope for the best?
You don't have to live in fear of turbulence when flying, just keep your seatbelt on when you're seated. Turbulence is fairly rare but it's still a numbers game. The probability that you experience it the 99% of the time you're seated is much higher than the probability of experiencing turbulence while standing, especially since pilots proactively turn on the seatbelt sign when turbulence is expected.
If you actually read the short paper you'll find they actually used reanalysis data sampled at a rate of every three hours across 42 years to compute their statistics:
> Global ERA5 reanalysis data (Hersbach et al., 2020) [...] were extracted on the 197 hPa pressure level with 0.25° horizontal resolution at three hourly intervals from 1 January 1979 to 31 December 2020. To allow the computation of CAT diagnostics that require vertical derivatives, fields on the 188 and 206 hPa levels were also extracted. The 21 turbulence diagnostics were then calculated from the extracted reanalysis fields every three hours.
How you go from that to "they just looked at 2 years" is beyond me.