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Lisl Robertson, University of Cape Town, RSA with assistance from Stewart Bernard Christo Whittle GOOS AFRICA.

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Presentation on theme: "Lisl Robertson, University of Cape Town, RSA with assistance from Stewart Bernard Christo Whittle GOOS AFRICA."— Presentation transcript:

1 Lisl Robertson, University of Cape Town, RSA with assistance from Stewart Bernard Christo Whittle GOOS AFRICA

2 Preliminary Validation and Application of the Globcolour Products in the Benguela System HABs in the Southern Benguela: in situ and satellite monitoring activities Preliminary Qualitative Globcolour spectral validation Globcolour Regional experiments: Benguela System and Subtropical Convergence Marine Remote Sensing Unit: data provision to Africa

3 HABs and the Southern Benguela

4

5 BOB: HAB Monitoring Buoy Moorings: multi-sensor lightweight coastal buoys allowing high frequency point sampling with real time data on demand. Mooring system supplied real time data from January 2005 until April BOB Instrumentation Two hyperspectral radiometers 30 m digital thermistor chain Fluorometer ADCP Satellite Monitoring Satellites: Near real time reception of daily 1 km MERIS data directly from ESA via local DDS Archived reception of 250 m MERIS data on request Locally processed AVHRR sea surface temperature and MODIS data through UCT Remote Sensing Unit

6 A B C March 30 th : small Prorocentrum triestinum dominated assemblage April 2 nd : low biomass waters April 5 th : large Ceratium furca dominated assemblage Multi-Scale Observation of HAB Events: Summer 2005

7 Remote Sensing Reflectance Spectra: BOB vs Globcolour : high biomass diatoms, Chlorophyll a ~ : chlorophyll a estimated 5 – 10 Typical background signal in bloom season : massive dinoflagellate bloom, Chlorophyll a ~ : very odd spectrum…

8 Remote Sensing Reflectance Spectra: BOB vs Globcolour: focus on 531 nm band may be problematic in high biomass, but could also be sensitive to phycoerythrin peak – further investigation required

9 Remote Sensing Reflectance Spectra: BOB vs Globcolour: focus on 510 nm band Little mystery: one week in 2006 – 510 nm band failed. But look how well Globcolour performs in the blue …

10 Globcolour, BOB Remote Sensing Reflectance Comparisons 412 nm expected to perform worst 531 nm has some accurate matches but many outliers as has been seen Best performing bands at 620, 670 and 709 nm, with a slight general overestimation by Globcolour (also by MERIS). But Globcolour not fully normalised at 709 … unclear effect on RRS?

11 GlobColour Weighted Chl 1 SeaWiFS OC4 Chl GlobColour GSM Chl 1 GlobColour Experimental Benguela Chl GlobColour Comparative Products: Southern Africa and Southern Ocean

12 Analytical reflectance algorithms: size distributions of two layered spheres Chloroplast Cytoplasm The analytical reflectance algorithm is based on the representation of the optical properties of algal cells using two layered spheres, using Standard particle size distributions to simulate polydispersed natural algal populations. This allows better estimates of algal biomass (Chl a), and biomass independent assemblage descriptors: mean algal size (D eff ) and physiological/algal group proxies (fluorescence quantum yield). An analytical algorithm also allows analogous application to both buoy and satellite ocean colour measurements. Simulated effects of changing chlorophyll concentration, effective algal diameter, and assemblage type on the reflectance spectrum

13 Algal Fluorescence Line Height Non Algal BackscatteringAlgal Fluorescence Quantum Yield Algal Effective Diameter GSM Particulate Backscattering GlobColour Experimental Products: Southern Africa and Southern Ocean Experimental reflectance/fluorescence inversion algorithms Fluorescence line height and quantum yield products allow some assessment of algal biomass and physiological variability. Algal effective diameter is used to assess biomass specific assemblage variability e.g. HABs in the Benguela, carbon export in the sub-tropical convergence zone

14 Near Real Time: MODIS various MERIS various AVHRR SST MSG-2 SST Archive/Climate 10 yr colour, 15 yr altimetry, 20 yr+ winds, 20 yr+ temperature Higher Level Interoperable with other sites for integrated products New MRSU and GEO/GOOS ChloroGIN site to be launched November 2007 Marine Remote Sensing: Developing an Operational Capability

15 Validation and protocols for high biomass studies Algorithm validation and development Ecological use of Globcolour in regional systems


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