SoRPIC (short for Solar Radiation and Phase Discrimination of Arctic Clouds) is a scientific project to investigate the effects of mixed-phase clouds on the energy budget of the Earth's atmosphere in the Arctic. Similar to greenhouse gases, they interact with solar and terrestrial (thermal infrared) radiation. Generally and annually averaged, Arctic boundary-layer clouds tend to have a warming effect: While the clouds reflect solar energy back into space, they also keep terrestrial (thermal) radiation from escaping into space. The resulting impact, however, is in detail highly variable and depends on various properties of the clouds and of the underlying surface. Furthermore, the long periods of polar day and polar night makes the estimation of the overall effect even more complicated. The Arctic boundary-layer mixed-phase clouds are particularly difficult to include in climate models, but play a crucial role in the predictions. The SoRPIC participants have performed airborne measurements of the microphysical and radiative properties of clouds in the Norwegian Arctic (based in the town of Longyearbyen on the Svalbard archipelago) in April and May 2010.Warning! All files are very big. Do not open with your browser, use right click to save file to disk.Find further documention of calibration routines at hdl:10013/calibration.1000