A Laser Trapping-Spectroscopy Study on Mass Transfer Processes Across a Single Micro-Droplet/Air Interface

Abstract

Clouds regulate the earth's energy balance by reflecting and scattering solar radiation and by absorbing the earth's infrared radiation. The fundamental knowledge about mass transfer processes across a micro-droplet/air interface is very important to give mathematical equations that describe the growth process of clouds for climate models. So far, experimental studies on the condensation growth of water droplets have been conducted by using either an aerosol flow tube or a vibrating orifice aerosol generator. However, the mass accommodation coefficients evaluated by such techniques are very scattered and, therefore, the detailed mechanisms of condensation growth of micrometer-sized water droplets are still controversial. The primary reason for this is difficulties in observing the growth processes of single water droplets in air. In this study, we demonstrate a novel approach for in situ observation of the evaporation and condensation processes of single water droplets levitated in air by means of a laser trapping technique.