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An inverse Case 2 water algorithm applied to the North Sea and the White Sea. A. Folkestad 1 , A. Korosov 2 , D. Pozdnyakov 2 , L. H. Pettersson 1 , and K. Sørensen 3 1) Nansen Environmental and Remote Sensing Center (NERSC) Bergen, Norway
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An inverse Case 2 water algorithm applied to the North Sea and the White Sea A. Folkestad1, A. Korosov2, D. Pozdnyakov2, L. H. Pettersson1, and K. Sørensen3 1) Nansen Environmental and Remote Sensing Center (NERSC) Bergen, Norway 2) Nansen International Environm. and Remote Sensing Center (NIERSC) St. Petersburg, Russia 3) Norwegian Institute for Water Research (NIVA) Oslo, Norway MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Outline • Inverse retrieval algorithm developed at NIERSC and NERSC • applicable to any OC sensor and water body • Algorithm validation in the Skagerrak (North Sea) by Ship of Opportunity • Seasonal variations in water constituents investigated for Skagerrak (MERIS) and White Sea (MODIS/SeaWiFS) MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Inverse algorithmfor retrieval of CPA concentrations from ocean colour data • Remote sensing sub-surface reflectance • S(i) satellite retrieved • Rrsw (i) model simulated SIOPs a*CHL(i) bb*CHL(i) a*TSM(i) bb*TSM(i) a*YS(i) S(i) IOPs • Pixel by pixel • Simulate Rrsw • Iterative • Minimize f (C) • Levenberg-Marquardt multivariate optimiz. procedure a(i) bb(i) Rrsw (i) (1) CHL TSM aYS(443) (2) CPA Forward bio-optical model: (1a) a(i)= aw(i) + CHL·a*CHL(i) + TSM·a*TSM(i)+ aYS(443)·a*YS(i) Levenberg (1944) Marquardt (1963) Bukata et al. (1995) Jerome et al. (1996) (1b) bb(i)= bbw(i) + CHL·bb*CHL(i) + TSM· bb*TSM(i) (2) Rrsw(i)= k1 + k2 [bb(i)/a(i)] + k3 [bb(i)/a(i)]2 MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
(Specific) Inherent Optical Properties White Sea bb*sm [m2 g-1] bb_w [m-1] a *sm [m2 g-1] a*doc [m2 gC-1] a_w [m-1] bb*chl [m2 mg-1] a *chl [m2 mg-1] Skagerrak bb*TSM [m2 g-1] bb_w [m-1] a *chl [m2 mg-1] a *TSM [m2 g-1] bb*chl [m2 mg-1] a*YS [-] a_w [m-1] MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Validation of satellite retrievals by Ship of Opportunity MERIS MS Color Festival Algal 1 (Chl a) Ferrybox Satellite Temp. Salinity YS Chl Chl TSM Turb. MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Chl a SOOP & MERIS (2nd repr) [mg m-3] TSM and turbidity June 06 2003 [g m-3] [FNU] Black: Standard algor. Grey: L-M inverse algor. Red: SOOP observ. YS and Salinity [m-1] [PSU] MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Chl a SOOP & MERIS (2nd repr) [mg m-3] TSM and turbidity June 20 2003 [g m-3] [FNU] Black: Standard algor. Grey: L-M inverse algor. Red: SOOP observ. YS and Salinity [m-1] [PSU] MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Skagerrak: Monthly median by L-M inverse algorithm Chl a [mg m-3] TSM[g m-3] YS[m-1] Feb Mar MERIS 2005 MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Skagerrak: Monthly median by L-M inverse algorithm Chl a [mg m-3] TSM[g m-3] YS[m-1] Apr May MERIS 2005 MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Skagerrak: Monthly median by L-M inverse algorithm Chl a [mg m-3] TSM[g m-3] YS[m-1] Jun MERIS 2005 MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
White Sea: Monthly median by L-M inverse algorithm Chl a [mg m-3] SM[g m-3] DOC[gC m-3] May Jun MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005 MODIS/SeaWiFS 1998-2004
White Sea: Monthly median by L-M inverse algorithm Chl a [mg m-3] SM[g m-3] DOC[gC m-3] Jul Aug MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005 MODIS/SeaWiFS 1998-2004
White Sea: Monthly median by L-M inverse algorithm Chl a [mg m-3] SM[g m-3] DOC[gC m-3] Sep MODIS/SeaWiFS 1998-2004 MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005
Summary An analytical inverse Case 2 water algorithm utilizing the MERIS spectral reflectance in the visible is developed. The algorithm is applicable to any OC sensor and water body, provided that area-specific sets of the spectral concentration specific inherent optical properties exist. Concentrations of water constituents are accurately retrieved from MERIS data, when compared to SOOP observations. Cases of low quality algorithm performance will be investigated to identify the causes. The algorithm has been implemented for various OC sensor systems (MERIS, MODIS, SeaWiFS). Seasonal variations of water constituents are analyzed for different water bodies (Skagerrak and White Sea) after the algorithm has been applied to a large number of OC scenes. MERIS - (A)ATSR workshop, Frascati, 26-30 September 2005