A year ago the National Oceanic and Atmospheric Administration (NOAA) conducted a series of experiments in the Arctic Circle. The program, called the Aerosol, Radiation and Cloud Processes affecting Arctic Climate (ARCPAC), was conceived to measure changes in the Arctic atmosphere. ARCPAC scientists also studied how radiation, cloud formation and airborne aerosols are affecting climate. For the experiments, the NOAA fitted a Lockheed WP-3D Orion aircraft's fuselage and wings with cloud probes, aerosol spectrometers and other sophisticated equipment. In this image, the WP-3D is preparing to takeoff from an airfield in Fairbanks, Alaska.

Photo credit: NOAA