The evolution of microphysical and optical properties of an A380 contrail in the vortex phase

Abstract

Abstract.A contrail from a large-body A380 aircraft at cruise in the humid upper troposphere has been probed with in-situ instruments onboard the DLR research aircraft Falcon. The contrail was sampled during 700 s measurement time at contrail ages of about 1-4 min. The contrail was in the vortex regime during which the primary wake vortices were sinking 270 m below the A380 flight level while the secondary wake remained above. Contrail properties were sampled separately in the primary wake at 90 and 115 s contrail age and nearly continously in the secondary wake at contrail ages from 70 s to 220 s. The scattering phase functions of the contrail particles were measured with a polar nephelometer. The asymmetry parameter derived from these data is used to distinguish between quasi-spherical and aspherical ice particles. In the primary wake, quasi-spherical ice particles were found with concentrations up to 160 cm −3 , mean effective diameter D eff of 3.7 µm, maximum extinction of 7.0 km −1 , and ice water content (IWC) of 3 mg m −3 at slightly ice-subsaturated conditions. The secondary and primary wakes were separated by an almost particle-free wake vortex gap. The secondary wake contained clearly aspherical contrail ice particles with mean D eff of 4.8 µm, mean (maximum) concentration, extinction, and IWC of 80 (350) cm −3 , 1.6 (5.0) km −1 , and 2.5 (10) mg m −3 , respectively, at conditions apparently above ice-saturation. The asymmetry parameter in the secondary wake decreased with contrail age from 0.87 to 0.80 on average indicating a preferential aspherical ice crystal growth. A retrieval of ice particle habit and size with an inversion code shows that the number fraction of aspherical ice crystals increased from 2 % initially to 56 % at 4 min contrail age. The observed crystal size and habit differences in the primary and secondary wakes of an up to 4 min old contrail are of interest for understanding ice crystal growth in contrails and their climate impact. Aspherical contrail ice particles cause less radiative forcing than spherical ones.

The airborne mass spectrometer AIMS – Part 1: AIMS-H<sub>2</sub>O for UTLS water vapor measurements

“…In future, open questions regarding contrail microphysics Jeßberger et al, 2013;Schumann et al, 2013) and the persistence of contrails (Gayet et al, 2012;Kübbeler et al, 2011) will be addressed using ML-CIRRUS data from AIMS-H 2 O. In addition, we will perform a thorough intercomparison of the set of water vapor instruments operated on HALO to assess the quality of water vapor in situ measurements in the lower stratosphere in mid-latitudes.…”

Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

“…Assuming Mie scattering theory, additional binning into 15 size bins is employed to rule out ambiguities. Polarized backward-scattered light is detected to investigate the sphericity and phase of the particles (Baumgardner et al, 2005;Gayet et al, 2012;Järvi-nen et al, 2016). Number concentrations are derived using the probe air speed measured by the probe.…”

Aircraft type influence on contrail properties

“…Under ice supersaturated conditions the detrained ice particles grow further by uptake of ambient water vapour (Unterstrasser and Sölch, 2010). Ice crystal number densities and sizes can vary in the primary vortices and the secondary wake (Gayet et al, 2012). After the breakup of the vortex structures, initiated from small disturbances by the Crow instability or from ambient turbulence (Misaka et al, 2012), the contrail spreads out and disperses depending on atmospheric wind shear and turbulence (Jensen et al, 1998).…”