ao2019_optical.nc: 
data from OptiCAL (Optical Chain And Logger) that was deployed as an autonomous ice-tethered observatory (ITO) for measuring the underwater light climate.

ao2019_heimdall.nc: 
For comparison with OptiCAL data three surface irradiance datasets, solar and lunar zenith angles were modelled using the HEIMDALL radiative transfer model (Connan-McGinty et al., 2022). One for constant clear sky, one for constant cloud covered skies, and one with varying local cloud conditions predicted by ERA5 cloud data (Hersbach et al., 2018).