WP-3D Cloud Physics

The primary cloud physics instruments on the WP-3D are the 2D-C (0.005 mm resolution) and 2D-P (0.15 mm resolution) PMS probes for sampling the sizes of raindrops and ice crystals. The data from the 2D-imaging probes were recorded on 9-track tapes prior to 1992 and on DAT since 1992. Small ice columns are detected directly on a FORMVAR replicator. Cloud water is measured by both JW and King Probes.

Electric fields are measured by 4 shutter type mills mounted normal to the aircraft skin, up, down, left, and right. The horizontal mills are symmetrically mounted about midway between the door and the trailing edge of the wings. The vertical mills are mounted near the trailing edge of the wings, but their vertical location differs by 0.6 m and the top mill is mounted on a 0.3 m aluminum pylon. Relative enhancements were measured by charging the aircraft in cloud-free flight.

Cloud Physics Parameters Instrumentation Range
Small cloud droplet spectrum FSSP forward scattering probe 0.005-0.047 mm
Cloud droplet spectrum PMS 2-D Gray and/or mono probes 0.03-1.92 mm
Hydrometeor size spectrum PMS 2-D Gray and/or mono probes 0.15-9.6 mm
Cloud liquid water Johnson-Williams hot wire <0.04 mm
Total liquid water PMS King probe <0.1 mm
Cloud particle replication Formvar Replicator-DRI 0.05-1.3 mm
Cloud particle charge Particle charge probe-DRI >2 pC
Two components of electric field Field Mills-DRI 2-120 kVA/m
Icing rate Rosemount


Jorgensen, D., and P. Willis, 1982: A Z-R relationship for hurricanes. J. Appl. Meteor., 21, 356-366.

Willis, P., J. Hallett, R. Black, and W. Hendricks, 1994: An aircraft study of rapid precipitation development and electrification in a growing convective cloud. J. Atmos. Res., 33, 1-24.

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Updated August 28, 2001