Preliminary laboratory studies of the optical scattering properties of the crystal clouds

Abstract. Ice crystal clouds have an influence on the radiative budget of the earth; however, the exact size and nature of this influence has yet to be determined. A laboratory cloud chamber experiment has been set up to provide data on the optical scattering behaviour of ice crystals at a visible wavelength in order to gain information which can be used in climate models concerning the radiative characteristics of cirrus clouds. A PMS grey-scale probe is used to monitor simulta-neously the cloud microphysical properties in order to correlate these closely with the observed radiative properties. Preliminary results show that ice crystals scatter considerably more at 90 ° than do water droplets, and that the halo eects are visible in a laboratory-generated cloud when the ice crystal concentration is suciently small to prevent masking from multiple scattering. Key words. Meteorology and atmosphere dynamics á Climatology á Radiative process á Atmospheric composition and structure á Cloud physics and chemistry