Microphysics and heterogeneous chemistry in aircraft plumes - high sensitivity on local meteorology and atmospheric composition

[摘要] An aircraft plume model has been developed on the basis of two coupledtrajectory box models. Two boxes, one for plume and one for backgroundconditions, are coupled by means of a mixing parameterizationbased on turbulence theory.The model considers comprehensive gas phase chemistry for thetropopause region including acetone, ethane and their oxidation products.Heterogeneous halogen, N₂O₅ and HO_x chemistry on varioustypes of background and aircraft-induced aerosols (liquid and ice)is considered,usingstate-of-the-artsolubility dependent uptake coefficients for liquid phase reactions.The microphysical scheme allows for coagulation, gas-diffusive particlegrowth and evaporation, so that the particle development from1s after emission to several days can be simulated.Model results are shown, studying emissions into the upper troposphere as well asinto the lowermost stratosphere for contrail and non-contrail conditions.We show the microphysical and chemical evolution of spreading plumes anduse the concept of mean plume encounter time, t_l,to defineeffective emission and perturbation indices (EEIs and EPIs)for the North Atlantic Flight Corridor (NAFC) showingEEI(NO_y) and EPI(O₃) for various backgroundconditions, such as relative humidity, local time of emission, andseasonal variations.Our results show a high sensitivity of EEI and EPIs on the exact conditionsunder which emissions take place.The difference of EEIs with and without considering plume processesindicates that these processes cannot be neglected.

[学科分类] 大气科学