Has the aircraft type an impact on the microphysical parameters of young contrails?

Abstract

Modeling studies suggest an impact of the aircraft type on the microphysical and optical properties of young contrails. However, up to now, a low intercomparability of meteorological conditions has prevented a study on the aircraft effect on contrail properties using in-situ observations. Therefore, we analyze contrail observations from 3 different aircraft, a large A380, a medium sized A340 and a smaller A319, performed during the CONCERT2008 (CONtrail and Cirrus ExpeRimenT) campaign under similar meteorological conditions in terms of relative humidity over ice (RHi) and wind shear. The young contrails were probed on 19 November 2008 over Northern Germany with instruments onboard the DLR research aircraft Falcon. 1-min old contrails were sampled at an altitude of 10.6 km near ice saturation at temperatures of 217 to 218 K above a natural cirrus cloud layer. We find large differences in the 3 observed contrail optical depth distributions, while the aircraft impact is not as pronounced in the detected particle size spectra. In addition, we simulate the contrail properties from the 3 aircraft with two independent models, the Eulerian particle tracking EULAG-LCM model and the contrail and cirrus prediction tool CoCiP. The models generally confirm the observed trend, an increase in contrail optical depth with increasing aircraft size (or weight). However, the models show smaller contrail optical depths for all aircraft types than observations. These discrepancies are reduced assuming higher values for the ambient relative humidity.