One exciting thing from over the holidays is that the Int'l Civil Aviation Organization (@ICAO) and aircraft engine manufacturers for the first time publicly released quantitative emissions indices for particle # and mass emitted per unit fuel burn! 🧵 1/

https://t.co/zXuFN66SWe

Up until now, certification data for aircraft engine particle emissions have been reported in terms of a "smoke number", which is derived from the change in reflectance of a Whatman 4 filter after collecting 16.2 kg/m² exhaust. 2/

https://t.co/6fa9Kkdupr

One challenge with the smoke number measurement is that the filter doesn't capture all of the particles -- especially small ones. Is the decrease in smoke number over time because we are trading a few large soot particles for many more smaller soot particles? 3/

While smoke numbers are not particularly helpful for quantitatively assessing particle emissions impacts on air quality & upper tropospheric composition, they have been a huge success in motivating the reduction of unsightly exhaust plumes! 4/

Photo credit: flickr/dsleeter_2000

The new EI data are much more useful for #AirQuality and #Climate modeling efforts seeking to understand the environmental impacts of aviation. Since they're collected at ground conditions, the data are most relevant to AQ, but maybe can be extrapolated to cruise conditions? 5/