A Continuous-Flow Streamwise Thermal-Gradient CCN Chamber for Atmospheric Measurements

We have addressed the need for improved measurements of cloud condensation nuclei (CCN) by developing a continuous-flow instrument that provides in situ measurements of CCN. The design
presented in this article can operate between 0.1 and 3% supersaturation, at sampling rates sufficient for airborne operation. The design constitutes a cylindrical continuous-flow thermal-gradient
diffusion chamber employing a novel technique of generating a supersaturation: by establishing a constant streamwise temperature gradient so that the difference in water vapor and thermal diffusivity yield a quasi-uniform centerline supersaturation.

- G. C. Roberts1 and A. Nenes2