We describe a method to produce black carbon (BC) particles with a variable geometric mean diameter on the range 20-60 nm to simulate BC particles emitted by aircraft gas turbine engines. We show that the correlation between the BC mass concentration and smoke number is strongly dependent on the geometric mean of the particle size distribution. Current methods used to estimate aircraft BC emissions for the purposes of air quality and climate impact studies rely on an outdated correlation and underestimate by a factor of 2-3.
