Numerical simulations of contrail-to-cirrus transition - Part 1: An extensive parametric study

Abstract

Simulations of contrail-to-cirrus transition over up to 6 h wereperformed using a LES-model. The sensitivity of microphysical, opticaland geometric contrail properties to relative humidity RH(i),temperature T and vertical wind shear s was investigated in an extensiveparametric study. The dominant parameter for contrail evolution isrelative humidity. Substantial spreading is only visible for RH(i)greater than or similar to 120%. Vertical wind shear has a smallereffect on optical properties than human observers might expect from thevisual impression. Our model shows that after a few hours the watervapour removed by falling ice crystals from the contrail layer can beseveral times higher than the ice mass that is actually present in thecontrail at any instance.