Solar radiation over and under sea ice was measured by radiation station 2018R23, an autonomous platform, installed on land fast ice in the Lincoln Sea, Arctic Ocean during Alert_MAPLI18. The resulting time series describes radiation measurements as a function of place and time between 05 May 2018 and 25 May 2018 in sample intervals of 10 minutes. The radiation measurements have been performed with spectral radiometers. All data are given in full spectral resolution interpolated to 1.0 nm, and integrated over the entire wavelength range (broadband, total: 320 to 950 nm). Two radiometers measuring solar irradiance and upward reflected solar irradiance, were mounted on a platform about 1 m above the sea-ice surface. The third radiometer was mounted 0.5 m underneath the sea ice measuring the downward transmitted irradiance. All times are given in UTC.

The data set has been processed and contains quality flags for different kinds for erroneous data. Flag values are the sum of individual error codes. The value of 0 refers to no error. Quality flag, position: The geographic position is flagged +1 if the drift velocity, as derived from the GPS longitude and latitude, exceeds a threshold of 10 deg latitude or 50 deg longitude per time step; +2 if the position exceeds extreme values, such as longitude > 360 deg; +4 if the position is exactly 0.0. Quality flag, sun elevation: If the suns position is close to the horizon, the radiometers measure a very noisy signal. Radiometer measurements and variables which are computed from them are flagged +1 if the sun elevation is below 10 degrees; +2 if the broad band albedo exceeds the threshold 1.05.