A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers

Abstract

Abstract. Transformation of the mass flux towards the particle from the kinetic regime to the continuum regime is often described by the Fuchs-Sutugin coefficient. Kinetic regime can be obtained as a limiting case when only one term of the expansion of the Fuchs-Sutugin coefficient at small 1/Kn is considered. Here we take into account the two first terms, and get the mass flux which agrees well with the full mass flux up to Kn ∼ 0.5. This procedure allows to obtain an analytical solution of the condensation equation valid for the range of intermediate Knudsen numbers. The expansion is further applied 5 to calculate analytically the condensation sink. The formula for the condensation sink is tested against field observations. The relative contribution of different aerosol modes to the condensation sink is discussed. Furthermore, we present a simple model describing a coupled dynamics of the condensing vapour and the condensation sink. The model gives reasonable predictions of the condensation sink dynamics during the periods of the aerosol modes growth by condensation in the atmosphere.

Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

“…The condensation sink, being proportional to the surface area of an aerosol population, is one of the major parameters controlling NPF. A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers was developed to describe the coupled dynamics of the condensing vapour and the condensation sink (Ezhova et al, 2018a). The model gives reasonable predictions of condensation sink dynamics during periods of particle growth by condensation in the atmosphere.…”