Retrieval of Snow Properties from the Sentinel-3 Ocean and Land Colour Instrument

Abstract

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.

The Determination of Snow Albedo from Satellite Measurements Using Fast Atmospheric Correction Technique

“…Satellite measurements, of particular importance for studies of polar environment [4], are usually performed with a fixed observation geometry. Therefore, special procedures are needed to convert satellite-measured reflectance to a plane albedo [5,6]. The broadband plane albedo (BBA) can be derived using various parameterizations or by integration of the spectral plane albedo with account for the spectral snow irradiance at the snow surface [7].…”

“…While the algorithm is easily portable to other multi-spectral instruments observing the cryosphere from space, we present an application to data from the Ocean and Land Colour Instrument (OLCI) on board the European Union Copernicus Sentinel-3A satellite. The theoretical modeling of spectral snow reflectance is performed as in [6]. The earlier atmospheric correction used in [6], which appears in OLCI Snow Properties module incorporated in the European Space Agency (ESA) SeNtinel Application Platform (SNAP), can be biased in case of strong atmospheric pollution episodes (arctic haze, etc.)…”

Glacier algae foster ice-albedo feedback in the European Alps

“…While field spectroscopy data are fundamental for assessing the local impact of glacier algae on the optical properties of ice 24 , remotely sensed data can provide a synoptic view of the phenomenon. In particular, the launch of new satellite missions such as Sentinel-2 and Sentinel-3, from the European Space Agency (ESA) Copernicus program, has created new opportunities for the study of the cryosphere from space 42,43 . The spatial, spectral and temporal resolution of these missions allows the monitoring of changes in both alpine and polar glaciers.…”

“…The spatial, spectral and temporal resolution of these missions allows the monitoring of changes in both alpine and polar glaciers. Sentinel-2 is particularly suited for mapping spatial and temporal variability of the cryosphere at fine scale 44 , while Sentinel-3 allows a broader perspective 43 . Some studies have already exploited these data for mapping algae distribution in Maritime Antarctica 33 and Southwest Greenland 25,35 .…”

Quantification of the radiative impact of light-absorbing particles during two contrasted snow seasons at Col du Lautaret (2058 m a.s.l., French Alps)

“…Di Mauro 30 et al, 2015) or satellites (e.g. Kokhanovsky et al, 2019). Recently, a method was proposed to estimate AECs of homogeneous snow layers in depth from vertical profiles of spectral irradiance (Tuzet et al, 2019).…”