European Facility For Airborne Research

Sample arm has heated dry air blowing OUT of it into airstream. Location of flow stagnation plane within intake determines minimum aerodynamic size of particles that can enter. Liquid or ice cloud particles enter intake, where water evaporates leaving cloud drop residual and water vapour.

three parts:COPAS (two channel condensation nuclei counter) Lyman-a water vapour instrument TDL to measure nitric acid HNO3 This is a particular inlet, which permits the passage only of particles having a kinetic energy larger a given value, thus having a diameter larger than a critical one, generating a dynamical blocking through a couterflow of known and controlled air. The particles that are able to pass this dynamic barrier are heated, because of the barrier, and evaporate.

<u>Alternative techniques :</u> determine the nunber concentration and condensed water content of tropical cirrus cloud elements larger then approximately 2mm radius; and determine the concentration of nitric acid (HNO3) associated with the condensed phase material in tropical cirrus clouds.

MISU, Stockholm University of Mainz, GermanyIEQ-CNR, IFA-CNR, IROE-CNR, Italy Free University of Berlin, Germany