This fall, the ARM-Unmanned Aerospace Vehicle Program—specifically, the Proteus aircraft—is participating in the Mixed-Phase Arctic Cloud Experiment (M-PACE) in Alaska. However, several of the aircraft’s onboard instruments have been modified since its last deployment in November 2002. To verify instrument operation and calibration prior deployment as part of M-PACE, in late September 2004, ARM researchers flew the Proteus from Mohave, California, out over the Pacific Ocean to collect radiometric, remote sensing, and in situ data for analysis. The aircraft flew over low marine cloud cover and clear skies over the ocean, also taking observations within and above cirrus clouds.

Researchers plan to conduct one or two more test flights before sending the aircraft to Alaska for participation in M-PACE. Of specific interest in the Proteus payload is the 95 GHz cloud radar (equipped with a new transmitter) and the short-wave broadband irradiance radiometers (with new preamplifiers and digitizers). Data recorded during the flight tests will be reviewed for quality, then made available to interested reviewers, and added to the ARM Climate Research Facility Data Archive as well. Data quality and instrument performance will continue to be assessed throughout the experiment.

The primary research objective for the M-PACE is to collect a focused set of data needed to advance the understanding of dynamic processes in arctic mixed-phase clouds, including cloud microphysical processes and radiative transfer through clouds. These data sets can then be used in computer models that simulate the arctic climate. As one of two aircraft equipped with downward looking sensors during the experiment, the Proteus will fly between four ground stations, obtaining data to complement the surface based measurements. Combined, these observations will document the full breadth of cloud and radiative transfer processes in mixed-phase arctic clouds in the study area.