Evaluation of MODIS chlorophyll algorithms in

Transcription

1 Evaluation of MODIS chlorophyll algorithms in Australian continental shelf waters: The IMOS match up data base Schroeder T, Lovell J,, Clementson L, King E, Brando V 9 July 2014 Australian Marine Science Association Conference, Canberra, Australia

2 Motivation No consistent national validation approach

3 Motivation No coherent algorithm validation on continental scale Global algorithms are biased towards northern hemisphere data

4 The Australian bio optical data desert

5 Motivation No coherent algorithm validation on continental scale Global algorithms are biased towards northern hemisphere data IMOS Ocean Colour Sub facility is addressing data gap Compilation of a national bio optical data base

6 IMOS data updates to NASA SeaBASS (since Jan 2014)

7 In situ HPLC chlorophyll IMOS data base N= p// / p /

8 Motivation No coherent algorithm validation on continental scale Global algorithms are biased towards northern hemisphere data IMOS Ocean Colour Sub facility is addressing data gap Compilation of a national bio optical data base Production and provision of Ocean Colour data

9 L2 re mapped d swath h L2 continental scale mosaics In future also via

10 Motivation No coherent algorithm validation on continental scale Global algorithms are biased towards northern hemisphere data IMOS Ocean Colour Sub facility is addressing data gap Compilation of a national bio optical data base Production and provision of Ocean Colour data Evaluation of algorithm accuracy: Combining coincident in situ chlorophyll and remote sensing measurements

11 Which chlorophyll product to choose? IMOS MODIS A repository based on SeaDAS v7.0 processing Empirical algorithms OC3 (MODIS standard algorithm) Clark Semi analytical algorithms GSM (Garver Siegel Maritorena model) Carder

12 IMOS in situ HPLC data coverage Time constrain to satellite overpasses ±1 day All HPLC data (N=1992) ±1 day (N=262)

13 IMOS in situ HPLC data coverage Time constrain to satellite overpasses p ±2 hours All HPLC data (N=1992) ±1 day (N=262) ±2 hours (N=34)

14 Data distribution NOMAD vs IMOS

15 Match up Methodology For each in situ Chl a data from IMOS data base identify matching satellite images within ±2 hours upto ±1 day Extract satellite derived CHL observations at in situ locations within a 5 km radius for open ocean waters, 3 km for coastal waters, calculate median and standard deviation Apply quality control flags Land, cloud, glint, Sun zenith < 60, view zenith < 60,... Calculate statistics (RMSE, % error, bias) of match up pairs Classify match up pairs according to Optical Water Type (OWT) 8 classes (Moore et al. 2009) Extra class for cocolithophore bloom

16 Optical Water Type (OWT) classification Moore et al. 2009

17 OC3 MODIS A) Satellite CHL (M In situ CHL

18 OC3 MODIS A) Satellite CHL (M In situ CHL

19 OC3 MODIS A) Satellite CHL (M In situ CHL

20 OC3 MODIS A) Satellite CHL (M In situ CHL

21 OC3 MODIS A) Satellite CHL (M In situ CHL

22 OC3 MODIS A) Satellite CHL (M In situ CHL

23 OC3 MODIS A) Satellite CHL (M In situ CHL

24

25

26 N=60 N=264 ±3 h ±1 day

27 Match up Statistics ±1 Day OC3 Clark Carder GSM N RMSE MAPE Bias ±3 hr OC3 Clark Carder GSM N RMSE MAPE Bias

28 Conclusions IMOS OC sub facility provides a useful platform for nationally consistent evaluation of ocean colour products All data freely available through the IMOS portal Ongoing effort (currently secured until 06/2015) Optical Water Types vital to constrain match up analysis exclude out of range conditions larger deviations OWT 7,8,9 In situ HPLC does not confirm presence of cocolithophore (OWT9) Reducing time window for match ups improves statistics (except Carder) Empirical algorithms perform better than semi analytical Performance ranking: OC3, Clark, Carder, GSM

29 The IMOS bio optical data base needs your data! The IMOS bio optical data base needs your data! It is a community effort.

30 Thank you question? Dr Thomas Schroeder, Brisbane Acknowledgements: SeaDAS Development Group and the OPBG at NASA GSFC for development, support and distribution of the SeaDAS software