The isothermal haze chamber with discontinuous flow: a new experimental device for CCN measurements at low supersaturation

An isothermal haze chamber (IHC) has been designed, incorporating results from the tests of earlier instruments held at the 1981 Reno (NV) workshop. This instrument, named isothermal haze chamber with discontinuous flow (IHCDF), periodically discontinues the flow through the haze chamber in order to form a well-defined region of 100% RH in the center of the chamber. Indeed, tests performed with our conventional continuous flow IHC showed a poorly defined 100% RH field in the chamber, mainly due to an unsteady laminar air flow through the chamber during measurement. ments with polydispersed NaCl aerosol showed that a supersaturation spectrum could be obtained within a growth time of 300 s, over a supersaturation range of 0.01–0.1%. strument is suitable for field use. It is contained in a package 1.4 m high and weighs 5 kg. Three minutes is required to collect the air sample and 5 min for drop growth, thus permitting the analysis of seven samples per hour.