Optical particle probes have been used on research aircraft to measure the microphysical properties of cloud particles since the 1960’s. However, significant (and sometimes unquantifiable) uncertainties have haunted the measurements since their inception. In particular, optical imaging probes have been plagued by slow response times and uncertainties in the optical depth of field for small (< 100 micron) particles. This talk addresses these issues and introduces measurements from an instrument that appears to reduce measurement uncertainties compared with older technologies. The measurements are framed in terms of laboratory tests and comparisons with other instruments during recent field campaigns (e.g., RICO, NAMMA, TC4, ICE-L).

Shattering of large particles on optical probe inlets, producing small particle artifacts, is another type of measurement uncertainty that has been the subject of much recent attention. Particle shattering is considered using the arrival times of individual particles to eliminate those that are closely spaced. Measurements from various optical cloud probes, including scattering and imaging probes, are compared and discussed.

During the course of the talk, some sidebars showing various microphysical cloud parameters, such as particle concentration, extinction and ice water content in anvil and cirrus clouds are presented and discussed. For example, measurements by the NASA DC-8 in a maritime anvil reveal a 20 m/s updraft at 36,000 ft (-47 C), 30 per cc ice particles (including graupel) and an ice water content of 2 g per cubic meter. Microphysical parameters of these magnitudes at this altitude have never been measured before in maritime convection, which suggests that numerical models of maritime convection may need to be reexamined.

Finally, some new instrumentation measurement concepts are briefly introduced and discussed.