In situ observations and model calculations of black carbon emission by aircraft at cruise altitude

The exhaust aerosol of two aircraft at cruise was extensively characterized in the size range from 0.003 to 2 mu m for plume ages less than or equal t o 2 s. The black carbon (BC) exhaust aerosol of an older technology engine (Rolls-Royce/Snecma M45H Mk501) consisted of a primary BC mode with a modal diameter of 0.035 mu m and a mode of coagulated BC particles with a peak n ear 0.15 - 0.16 mu m in diameter. The total number density at the nozzle ex it plane was 3x10(7) cm(-3) In contrast, a modern technology engine (CFM In ternational CFM56-3B1) emitted far smaller BC particles with a primary mode at 0.025 mu m and a coagulated mode at 0.15 mu m, as well as fewer particl es by number with a concentration of 9x10(6) cm(-3) The single-scattering a lbedo of the jet exhaust aerosol was 0.035 +/- 0.02 inside the plume, indic ating a dominant contribution of ultrafine (D < 0.1 mu m) BC particles to l ight extinction. Black carbon number emission indices EI(N) varied from 3.5 x10(14) (CFM56-3B1) to 1.7x10(15) kg(-1) (M45H Mk501) with corresponding ma ss emission indices EI(BC) of 0.011 and 0.1 g kg(-1) (M45H Mk501) with corr esponding mass emission indices EI(BC) of 0.011 and 0.1 g kg(-1). Previousl y reported corresponding values for a CF6-80C2A2 engine were 6x10(14) kg(-1 ) and 0.023 g kg(-1), respectively. A comparison between EI(BC) values calc ulated by a new correlation method and measured data shows an excellent agr eement, with deviations < 10% at cruise conditions. By extending the EI(BC) calculation method to a globally operating aircraft fleet, a fleet-average d emission index EI(BC) = 0.038 g kg(-1) is calculated.