Study of contrail microphysics in the vortex phase with a Lagrangian particle tracking model (vol 10, pg 10003, 2010)

Abstract

Crystal sublimation/loss is a dominant feature of the contrail evolutionduring the vortex phase and has a substantial impact on the latercontrail-to-cirrus transition. Previous studies showed that the fractionof crystals surviving the vortex phase depends primarily on relativehumidity, temperature and the aircraft type. An existing model forcontrail vortex phase simulations (with a 2-moment bulk microphysicsscheme) was upgraded with a newly developed state-of-the-artmicrophysics module (LCM) which uses Lagrangian particle tracking. Thisallows for explicit process-oriented modelling of the ice crystal sizedistribution in contrast to the bulk approach. We show that it is ofgreat importance to employ an advanced microphysics scheme to determinethe crystal loss during the vortex phase. The LCM-model shows evenlarger sensitivities to the above mentioned key parameters thanpreviously estimated with the bulk model. The impact of the initialcrystal number is studied and for the first time also the initial widthof the crystal size distribution. Both are shown to be relevant. Thiscorroborates the need for a realistic representation of microphysicalprocesses and knowledge of the ice phase characteristics. cirrusproperties. Thus, in a first step Large Eddy Simulation models (LES)should be used to better understand the contrail-to-cirrus transitionand quantify the dominant atmospheric and aircraft parameters affectingit. Recently, the transition of single contrails into a contrail-cirruswas extensively studied with a high resolution numerical model(Unterstrasser and Gierens, 2010a,b). Among other things thesesimulations revealed that the early contrail evolution during the jetand vortex phase affects the optical properties and the lifetime of thecontrail-cirrus even hours later, emphasising the need for realisticvortex phase simulations.