Mapping total suspended matter from geostationary satellites: a feasibility study with SEVIRI in the Southern North Sea

Abstract

Geostationary ocean colour sensors have not yet been launched into space, but are under consideration by a number of space agencies. This study provides a proof of concept for mapping of Total Suspended Matter (TSM) in turbid coastal waters from geostationary platforms with the existing SEVIRI (Spinning Enhanced Visible and InfraRed Imager) meteorological sensor on the METEOSAT Second Generation platform. Data are available in near real time every 15 minutes. SEVIRI lacks sufficient bands for chlorophyll remote sensing but its spectral resolution is sufficient for quantification of Total Suspended Matter (TSM) in turbid waters, using a single broad red band, combined with a suitable near infrared band. A test data set for mapping of TSM in the Southern North Sea was obtained covering 35 consecutive days from June 28 until July 31 2006. Atmospheric correction of SEVIRI images includes corrections for Rayleigh and aerosol scattering, absorption by atmospheric gases and atmospheric transmittances. The aerosol correction uses assumptions on the ratio of marine reflectances and aerosol reflectances in the red and near-infrared bands. A single band TSM retrieval algorithm, calibrated by non-linear regression of seaborne measurements of TSM and marine reflectance was applied. The effect of the above assumptions on the uncertainty of the marine reflectance and TSM products was analysed. Results show that (1) mapping of TSM in the Southern North Sea is feasible with SEVIRI for turbid waters, though with considerable uncertainties in clearer waters, (2) TSM maps are well correlated with TSM maps obtained from MODIS AQUA and (3) during cloud-free days, high frequency dynamics of TSM are detected.

Potential of High Spatial and Temporal Ocean Color Satellite Data to Study the Dynamics of Suspended Particles in a Micro-Tidal River Plume

“…MODIS sensors have 36 spectral bands with three spatial resolutions of 250 m, 500 m and 1 km, but only 5 bands are used for SPM retrieval: the two SWIR bands at 1240 and 2130 nm with a spatial resolution of 500 m (or NIR bands at 748, 869 nm with a spatial resolution of 1 km, depending of the selected atmospheric correction algorithm (e.g., [36])), the green band at 555 nm with a spatial resolution of 500 m and the red and NIR bands at 645 and 859 nm respectively with a spatial resolution of 250 m. SEVIRI provides data at a high temporal resolution with an image recorded every 15 min. Twelve spectral bands are available but only two can be used for SPM retrieval, the 635 nm spectral band (VIS0.6) used for SPM mapping and the 810 nm spectral band (VIS0.8) used for atmospheric corrections [19]. These spectral bands have a spatial resolution of 3ˆ3 km at the sub-satellite point, but due to the latitude of the study area the pixel are elongated to~3ˆ5 km.…”

“…SEVIRI L1.5 data were obtained from the EUMETSAT website (eumetsat.int) and cropped to the North Gulf of Lion region (127ˆ36 pixels). The water-leaving reflectance was obtained at the VIS0.6 band after correcting SEVIRI data for (1) atmospheric gas absorption; (2) Rayleigh scattering; (3) scattering by aerosols following the processing detailed in [19,20]. This atmospheric correction algorithm uses an approach similar to the MUMM correction [37] with the red (VIS0.6) and NIR (VIS0.8) bands of SEVIRI (called MUMM-S here after, see details in Table 1).…”

“…This atmospheric correction algorithm uses an approach similar to the MUMM correction [37] with the red (VIS0.6) and NIR (VIS0.8) bands of SEVIRI (called MUMM-S here after, see details in Table 1). [19] showed that this atmospheric correction is only valid for Rrs values lower than 0.02 sr´1 and 0.0038 sr´1 in the two red and NIR bands respectively. These limits are largely exceeded during the study period with Rrs values larger than 0.02 sr´1 in the SEVIRI red spectral band (see range of in situ radiometric data as shown by the SEVIRI red spectral band in Figures 4 and 5).…”

“…The SPOT (Satellite Pour l'Observation de la Terre) and Landsat high spatial resolution sensors have proved their capabilities in mapping concentrations of suspended solids in highly turbid waters [13,[16][17][18]. High temporal resolution satellite ocean color data acquired onboard geostationary satellite platforms has been demonstrated to provide valuable information in terms of SPM dynamics (e.g., [12,19,20]). A combination of these high temporal and high spatial resolution sensors should provide optimal remote sensing observations of surface SPM dynamics in coastal waters when operationally applied to data obtained by the next generation of (ocean-color) sensors: (i) MSI (MultiSpectral Instrument) and OLCI (Ocean and Land Color Instrument) onboard the Sentinel-2 and 3 (S-2 and S-3) polar-orbit platforms; and (ii) the Flexible Combined Imager (FCI) onboard the future Meteosat Third Generation (MTG) satellites.…”

Developments in Earth observation for the assessment and monitoring of inland, transitional, coastal and shelf-sea waters

“…SEVIRI is capable of imaging the hemisphere of the Earth every 15 minutes at a 3km resolution, while GOCI provides data at 500 m spatial resolution over a 625,000 km 2 area centred on the Korean Peninsula every 1 hour. SEVIRI was not designed primarily for applications over water but several studies have shown the feasibility of retrieving TSM in turbid waters (Neukermans et al, 2009;Neukermans et al, 2012). The GOCI sensor, however, is specifically designed for ocean colour applications and thus can be used to estimate Chl-a concentrations and at a spatial resolution that also allows data to be acquired for systems ranging in scale from shelf-seas to large lakes (Lyu et al, 2015).…”