Characterizing cloud droplets and ice crystals in clouds with the digital holographic airborne instrument, HOLODEC and HALOHOLO

Jacob P. Fugal

Institute for Atmospheric Physics, University of Mainz and the Max Planck Institute for Chemistry

Clouds play an essential role in the Earth's water cycle and atmospheric energy

budget, and by extension also life on earth. Measurements of Earth's clouds are done via

satellite, radar, and in-situ with aircraft, balloon and drop-sonde platforms, yielding

measurements such as liquid and ice water content (grams of liquid water/ice per cubic

meter of cloud), droplet and ice crystal size distributions and number concentrations,

radar reflectivities, and various radiative properties and chemistry measurements. The

HOLODEC instrument (Holographic Detector for Clouds) built for the NSF/NCAR G-V

aircraft, and the HALOHolo instrument (HALO Holographic instrument) being built for

the German G-550 HALO Aircraft, make unique measurements of cloud ice and water

particles. For the particles appearing in a localized sample volume of size order 1x1x10

cm^3, they yield the three-dimensional position, shape, size, and particle number

concentrations. Using these measurements, one can see for the first time the local

structure or spatial distribution of cloud particles. First results from the HOLODEC

instrument aboard the NCAR C-130 in the IDEAS 4 field campaign in Oct-Nov 2011 over

Colorado and Wyoming will be presented. Some of the limitations of holographic

measurements will also be discussed.