MERIS for Case 2 Waters

Transcription

1 MERIS for Case 2 Waters Roland Doerffer &Helmut Schiller GKSS Forschungszentrum Institute for Coastal Research doerffer@gkss.de

2 Case 2 water reflectance spectra North Sea

3 Dissolved and suspended matter in coastal water water molecules hydrocarbons, aminoacids humic acids clay-humic-metal -complexes viruses colloid range bacteria terrigenous sm eroded mud and sand fly-ash fecal pellets phytoplankton desert-dust macroflocs zooplankton colonies 0.1 nm 1 nm 10 nm 100 nm 1 µm 10 µm 100 µm 1 mm 1 cm dissolved 0.45 µm suspended

4 Case 2 Water Algorithm COASTLOOC COLORS MAPP MAPP Bio-optical measurements a(λ), a(λ), b (λ), (λ), Pig, Pig, TSM, TSM, C, C, Y Lu/Ed(λ,z), RLw RLw Bio-optical Model Model Incl. Incl. variability Set Set up up radiance transfer model model Monte Monte Carlo, Carlo, Hydrolight fann, fann, bann bann MERIS MERIS Processor 3 angles 8 RLw ann Simulation of of RLw(λ,θ v,θ v,θ s,φ s,φ vs vs > Spectra Training and and Test Test of of ann ann TSM Pig Gelb Conf. Flag MERIS MERIS Product

5 Scheme of a bio-optical model: optical components for MERIS Water sample In situ AC-9 BB-4 particle particle scattering scattering backscattering backscattering TSM Gelbstoff yellow substance particle total absorption Absorption Absorption of of Total Total --bleached bleached fraction fraction = phytoplankton phytoplankton absorption absorption Absorption Absorption of of bleached bleached fraction Absorption fraction Absorption of of = spm spmabsorption bleached bleached Fraction Fraction + gelbstoff gelbstoff gelbstoff gelbstoff absorption absorptionspectrum = spectrum total total gelbstoff gelbstoff spectral spectralexponent exponent Optical properties at 442 nm Chlor Gelb

6 COLORS Helgoland Gelbstoff absorption all stations 1.2 COLORS Helgoland Gelbstoff absorption all stations absorption a (m -1 ) wavelength (nm)

7 Pigment absorption spectra H187, Norway different locations Norway all stations a (m -1 )) norm a (m -1 )) norm wavelength (nm) wavelength (nm)

8 Bio-optical model Based on: MAVT North Sea / German Bight (GKSS), Norwegian waters (NIVA, Uni Oslo, NERSC), Baltic Sea (IOW), Recommendation by M. Babin Gelbstoff absorption exponent: Bleached particle absorption exponent: Particle scattering exponent: White particles scattering exponent: 0.0 Phytoplankton pigment absorption: > 200 spectra from different areas and seasons Gelbstoff absorption ays(443): m-1 Particle scattering bp(443): m-1 White particle scattering: m-1 Phytoplankton pigment abs. apig(443): m-1 Minimum particle scattering bp(443): 0.25*a_pig(443) Bleached particle absorption abp(443): 0.1*bp(443)+ran_gauss*0.03*bp(443)

9 The actual MERIS case II water algorithm r, r log of reflectances c log of concentrations g geometry information q quality indicator NN input NN output r r invnn q q g g c forwnn r c c If RLw < , RLw = Flag q true if sum (r(i) / r (i)) > 4.0

10 NN sensitivity test, all cases 10 2 case 2 water chlorophyll retrieval with NN nn-derived µg/l model chlorophyll µg/l

11 NN sensitivity, typical North Sea water 10 2 Pigment in North Sea Water (gelb < 0.2 m-1, MSM < 5 mg/l) nn µg/l model µg/l

12 Pigment absorption Chl. a, H Heincke187 a443 pigment n=95 chlorophyll a [mg/l] a(443) (m -1 )) Conversions: Chl. a [mg m-3] = 21 * a_pig_442 ^1.04 TSM [ g m-3] = 1.72 * b_tsm_442

13 MEGS 7.2 algal_1 / algal_2=21*a_pig^1.04 Red dots indicate pixels localized in the map (next pages), these dots have been selected by hand, because they form a second cloud in the scatter plot. As seen in the map they belong mainly to case 2 water. The regression line was also determined by hand only for the upper data cloud (case 1 water) Algal_2=21*a_pig^1.04

14 MEGS 7.2 relationship, log ref. input Red line: alg1=21*apig^1.04 MEGS 7.3 coefficients

15 World map of MERIS data of MEGS 7.2 processing, red dots indicate data which form a second cloud in the scatter plot Algal_2 computed

16 MERIS algal_2,

17 MERIS, TSM,

18 MERIS, Gelbstoff,

19 Red Tide German Bight , MERIS FR

20 North Sea Red Tide of Myrionecta rubra

21 Chlorophyll Distribution Northsea March 2003 (MERIS) Chlorophyll] mg/m³ L3-Product: Monthly Median MERIS-Algal2 March 2003, 37 scenes, GKSS-ESA-Algorithm

22 comparison transect Cuxhaven -> Helgoland ca. 60 km from highly turbid waters to average North-Sea water

23 comparison concentrations Meris <-> in-situ along track Cuxhaven-Helgoland match-up

24 comparison concentrations Meris <-> in-situ along track Cuxhaven-Helgoland match-up

25 Algal 1 and 2 Mean algal_1_mean algal_2_mean 1.E+02 1.E+01 1.E+00 mg/m³ 1.E-01 1.E-02 1.E product id

26 MEGS 7.3, lin refl. Input Histogram 8000 Histogram log(alg2) MEGS7.3 (linnn) Histogram log(alg1) MEGS7.3 (linnn) logn(algal_1) logn(algal_2)

27 MERIS Case 2 algorithm test against IOCCG simulated data set 10 1 a_tot sun TSM scatter a_tot_442 NN GKSS [m -1 ] b_tot_442 NN GKSS [m -1 ] a_tot_442 test_case [m -1 ] bb_tot_442 test_case [m -1 ] Total absorption at 442 nm Total scattering at 442 nm

28 High suspended matter concentrations in the German Bight MERIS FR Helgoland Bight Section 160 km

29 Strange Spectra producing negative reflectances MERIS FR RL_toa RL_tosa RL_path RLw_bread 0.04 RL [sr -1 ] wavelength [nm]

30 SPM distribution Helgoland Bay MERIS FR North Sea Elbe estuary mg/l

31 Summary and Conclusions Primary output of MERIS Case 2 water algorithm are the inherent optical properties: (1) scattering b of all particles, (2) absorption a_y of dissolved gelbstoff + absorption of bleached particles, (3) absorption of phytoplankton pigments, all at MERIS band 2 (442 nm) Variability of bio-optical variables as well as expected errors are included in the training of the NN Using a combination of a backward and forward NN the input reflectance spectrum (i.e. after atmospheric correction) is tested if this spectrum is within the range of the training data set, a flag is set if deviation is too high Accuracy of results may change pixel by pixel, depends on concentration mixture and scope of the bio-optical model MERIS Case 2 water algorithm as implemented in MEGS 7.4 for reprocessing is more robust than pre-launch version: Improved bio-optical model based on more data Using cut-off reflectance more robust against error in atmospheric correction Further test are needed world wide

32 Algal 1 and 2 Stdev algal_1_stddev algal_2_stddev 1.E+02 1.E+01 1.E+00 mg/m³ 1.E-01 1.E-02 1.E product id

33 MEGS 7.3, lin reflectance input mean values of scenes 10 2 Mean of algal_2, YS, TSM with LinNN algal_2 ys tsm 10 1 mean concentration product id