Detect Icing with Polarization Experiment (DIPOLE)

The Detect Icing with Polarization Experiment (DIPOLE) is funded by the Federal Aviation Administration to investigate the detection of hazardous icing conditions using advanced radar techniques. It extends the work begun under the WISP experiment.

Icing is blamed for an average of 40 fatalities per year in airplane crashes. Dangerous accretion of ice on wings and tails occurs as an airplane flies through supercooled cloud water droplets and/or supercooled drizzle or rain. The key to detecting icing conditions and warning pilots to avoid them, lies in detecting regions of hazardous supercooled water drops and distinguishing them from regions of benign ice crystals in clouds and precipitation.

One promising approach involves the use of dual-polarization radar measurements which can reveal distinct and theoretically predictable differences between the depolarizing behavior of the nearly spherical water droplets and the non- spherical crystals. DIPOLE collected data using ETL's NOAA/K millimeter-wave cloud radar in early 1998 to investigate new transmitted polarization configurations, controlled by a rotating, phase- retarding plate (photo inset), to optimize the droplet/crystal discrimination capability. An ETL vertically-pointing microwave radiometer was also used in the project. Icing monitoring from ground-based radars at airports is one potential application of this research, but millimeter-wave radars can also be light-weight, low-power systems suitable for airborne use to avoid icing hazards in-route.