Validation of remotely sensed snow liquid water content on the Greenland ice sheet at the PROMICE weather station sites

• Main Author: Aaslyng Dall, Maja
• Format: Dataset
• Language: unknown
• Published: GEUS Dataverse 2020
• Subjects: Greenland; Ice Sheet
• Online Access: https://dx.doi.org/10.22008/fk2/hqaew3; https://dataverse01.geus.dk/citation?persistentId=doi:10.22008/FK2/HQAEW3

Surface melt on the Greenland Ice Sheet has been estimated using L-band radiometer data measured by the SMOS satellite. This data has previously been validated with the focus of correct binary detection of melt. In this thesis, the validation will extend to correct detection of the magnitude of snow liquid water content as well. It will be validated by comparing the data from the SMOS satellite to data from the PROMICE automatic weather stations along the margin of the Greenland Ice Sheet. The SMOS satellite data has contamination issues along the margin of the Ice Sheet, where land or rock is near, as the resolution of the antenna on the SMOS satellite is 40 km. The contaminated data mainly shows low values of snow liquid water content with no clear peaks or onsets of melt and has therefore been discarded. When comparing data from the PROMICE Automatic weather stations along the margin of the Greenland Ice Sheet to data the SMOS satellite further in on the Ice Sheet, the SMOS satellite data shows a later onset of melt. This is not an issue with automatic weather station less than 20 km away. Moreover, the penetration depth of the L-band is depending on the snow liquid water content. This is clear as the SMOS satellite has higher snow liquid water content values than the PROMICE automatic weather stations, when the snow liquid water content is low, and lower value when the content is high. The penetration depth is estimated to at least 1.8 m in snow with 1% snow liquid water content, and higher in dry snow. Based on this, the penetration depth is assumed 1.8 m in this thesis, though results indicate that it should be less, which is reasonable as the snow liquid water content often is higher than 1% in the ablation season.