THEORETICAL DESIGN AND PRELIMINARY TESTS OF 2 NEW PARTICLE SPECTROMETERS FOR CLOUD MICROPHYSICS RESEARCH

Reliable cloud microphysical measurements can lead to a better understanding of the development of precipitation and cloud radiation. However, imaging of cloud particles with sizes < similar to 200 mu m has been limited to small (collected) samples of high-quality photographs or large quantities of poor-quality digital images. Here we introduce two new instruments with demonstrated abilities for improved measurements of cloud drop spectra, liquid water content and digital imaging of the size and shape of small ice crystals. The first instrument uses digital holography to increase the sample volume over that possible with in-focus imaging of small particles. The digital holograms can be processed automatically and are expected to reveal the size and shape of small ice crystals, and the three-dimensional concentration, spacing and liquid water content of cloud drops. The second instrument measures cloud drop spectra and liquid water content from high-resolution measurements of forward-scattered light from an ensemble of drops. This eliminates inherent problems of coincidence and the small sample volume associated with single-drop measurements of drops. The theory of measurement and results from tests of both instruments are presented.