Transport to ground of emissions in aircraft wakes. Part II: Effect on NOx concentrations in airport approaches

Predictions as to the transport of aircraft NOx emissions to ground level in the vicinity of an airport are made, taking account of the vortical dynamics of the aircraft wake. A model is used to calculate mean ground-level concentrations. It employs a kinematic approach, harnessing results from dynamical models in the literature. Two aircraft types are considered, a B737-300 (twin turbofan), taken as representative of short-range aircraft, and a B747-400, taken as representative of long-range aircraft. Airport and meteorological parameters are assigned values as holding in the case of Manchester Airport, UK, during a fortnight in May 1999 (prior to the opening of a second runway there). The airport operated at a capacity of about 45 aircraft movements per hour in the peak morning period, with frequencies in the middle of the day being about half this. Aircraft of maximum takeoff weight in excess of 120 tonnes accounted for some 6% of all movements. The simulations predict mean NOx concentrations of maximum 3 μg m−3 at the centre of the runway arising as a result of the vortex-mediated transport (as expressed on conversion of all NO to NO2), with concentrations on the order of 1 μg m−3 arising 0.5 km laterally from the runway.