Daily PAR from the Arctic Ocean between 1998 and 2014

Instruments were calibrated by the manufacturer before each cruise. All instruments were cleaned on a regular basis and were recording PAR continuously (at 1 to 15 min intervals) throughout the field campaigns, providing detailed diurnal and seasonal variability of incoming light in Arctic. This dataset is used as a reference to evaluate the satellite-based irradiance estimation methods and to study its natural variability in the Arctic. To control the quality of the data, the daytime solar zenith angle (SZA) was plotted together with instant PAR measurements and a scatter plot of PAR vs SZA was examined to detect possible errors. For any given day, if two distinct curve shapes in SZA vs PAR were observed between sunrise and sunset, the daily PAR was flagged and further examined. Days containing gaps or obvious outliers were screened out. Trapezoid integration was performed to obtain daily measures.