illuminated by low solar angles, this late 2016 Sentinel-3 OLCI image spectacularly features Greenland ice sheet undulations.
at a time when melting should be in full force and precipitation should perhaps be liquid that solid, Sentinel-3 OLCI provides views of a snow blanketed western Greenland ice sheet ablation area.
(above) 5 July, 2017 1458 UTC, we see surface meltwater lakes poking through fresh snow and even some snow on land (NW quadrant of image).
Field measurements are essential for testing the performance of new algorithms and validating satellite remote sensing products. Among the validation sites chosen for the project, Col du Lautaret, in the French Alps is an ideal validation site, as it offers easy access and a variety of conditions to test the performance and limits of our algorithms.
The site is located at approximately 2000 meters (6500 feet) a.s.l. , and is surrounded by high rugged mountains. At the col (mountain pass) itself, where a permanent automated weather station is located, the terrain consists of a (rather) flat plateau, surrounded by steeper slopes. Perfect for testing the complex terrain algorithms! Furthermore, the conditions of the alpine snowpack are in constant evolution over the winter season, which allow the team to test Sentinel 3 images for a wide range of snow types.
(above) The automated weather station at Col du Lautaret, French Alps. (Photo: M. Lamare)
During Spring 2017, the french team performed regular surface albedo measurements, coinciding with Sentinel 2 and 3 overpasses. Initially the data will be used to perform the characterisation of the validation site. Later in the project, the ground albedo measurements will be compared to the satellite acquisitions. Of course, more measurements will be taken… we just need to wait for the snow to return!
(above) Measuring the albedo of fresh snow, using Solalb, developped at IGE, Grenoble. (Photo: M. Lamare)
(above) Measuring the surface albedo of snow right until the end of the season. (Photo: M. Lamare)
(above) Sentinel 2 and 3 images over the validation site. 11/03/2017. Source: ESA, Copernicus.