Satellite microphysics retrievals rely on in situ measurements to tune and validate their algorithms. Particle imaging probes have been the most reliable in situ instruments for identifying the shapes of cloud particles, thereby distinguishing (non-spherical) ice particles from (spherical) water drops. However, improvements in the pixel resolution, number of gray-levels and software processing of the particle images are required to take these measurements to the next level. Here we describe a new optical probe that vastly improves the ability to automatically identify and classify ice particles and water drops in mixed-phase clouds. The Particle Phase Spectrometer that SPEC will design and test in the laboratory in Phase I will integrate three optical instruments into a single package: 1) a very high-resolution (1-μm pixel resolution) digital camera imaging system, 2) a 10-μm 2D-Gray optical array probe and 3) a forward scattering probe that sizes particles from 2 to 50 μm. The Particle Phase Spectrometer will provide unprecedented, high-resolution digital images that will be capable of distinguishing spherical from non-spherical cloud particles as small as 10 microns.
The Particle Phase Spectrometer will provide vastly improved ice particle and water drop size distributions in mixed-phase clouds, which constitute about 40% of clouds globally. The Particle Phase Spectrometer will also distinguish spherical from non-spherical particles in cirrus and sub-visible cirrus clouds. The improved microphysics retrievals from satellites will aid NASA in monitoring our changing climate.
The microphysical measurements will be used to validate satellite retrievals and improve calculations of radiative forcing by clouds, a critical factor in monitoring climate change. There will be a substantial benefit to both industry and society from an improved understanding of climate change.