1. Comparison of Green Vegetation Fraction Retrievals from SPOT-VEGETATION and MSG-SEVIRI Sensors Bernard LACAZE (1) and Aydin ERTÜRK (2) CNRS UMR 8586 PRODIG Pôle de Recherche pour l’Organisation et la Diffusion de l’Information Géographique, Paris, France Turkish State Meteorological Service, Remote Sensing Division, Ankara, Turkey 1

3. SPOT-VEGETATION : deriving Green Vegetation Fraction (GVF) from scaled NDVI

4. MSG-SEVIRI : deriving GVF from spectral unmixing or scaled NDVI

5. Results : Comparison of dekadal NDVI and GVF data (MSG-SEVIRI and SPOT-VEGETATION)

6. ConclusionIGARSS 2011 24-29 July, Vancouver, Canada 2

7. SPOT-VEGETATION sensor (since 1998) SPOT-4 and SPOT-5 sun synchronous orbit altitude 822 km return interval 1 day swath width 2250km IGARSS 2011 24-29 July, Vancouver, Canada 3

8. SPOT-VEGETATION 10-daily NDVI S10 :Maximum Value Compositing IGARSS 2011 24-29 July, Vancouver, Canada 4

9. SPOT-VEGETATION 10-daily NDVI NDVI data : HDF format, 1 byte/pixel Real NDVI = 0.004 * Digital Number -0.1 Status map : HDF format, 1 byte /pixel IGARSS 2011 24-29 July, Vancouver, Canada 5

10. MSG-SEVIRI sensor (since 2004) MSG-1 and MSG-2 SEVIRI one image every 15mn Spinning Enhanced Visible and Infrared Imager resolution at nadir 3km (1km for channel 12) IGARSS 2011 24-29 July, Vancouver, Canada 6

12. daily NDVI derived from LSA-SAF spectral albedos is available from AMMASAT data base (area= West Africa, spatial resolution 0.05°, daily since september 2005)

13. daily experimental NDVI data available from EUMETSAT, since February 2011 (+ pre-operational data from 2010 : 176 days, elaborated with Turkish State Metorological Service)IGARSS 2011 24-29 July, Vancouver, Canada 7

15. resolution 0.05°  1000 samples x 500 lines

16. daily data since septembre 2005

17. NDVI calculatedfrom spectral albedosproduced by LSA-SAF (BRDF model Roujeanet al., 1992, k0parameter), model fitted over 5 days)

18. NetCDF format, integer, NDVI*10000, NDVI≥0, -1 = ocean8

19. MSG – SEVIRI NDVI monthly synthesis january 2010 AMMASAT database 9

21. MSG native projection  3712 samples x 3712 lines

22. 176 days (February-August 2010)

23. NDVI calculatedfrom top of atmospherereflectances, with BRDF correction (dailymean, maximum and minimum NDVI, number of obervations)

24. HDF5 format, byte, NDVI*100, NDVI≥010

25. MSG-SEVIRI NDVI 10-daily synthesis 0 0.7 Maximum NDVI 20-30 March 2010 IGARSS 2011 24-29 July Vancouver, Canada 11

26. MSG-SEVIRI NDVI 10-daily synthesis 21-31 May 2007 0 0.7 Maximum NDVI 20-30 March 2010 IGARSS 2011 24-29 July Vancouver, Canada 12

28. MSG native projection  3712 samples x 3712 lines

29. daily data sinceFebruary 2011

30. NDVI calculatedfrom top of atmospherereflectances, with BRDF correction

31. HDF5 format, with 899 bytes header13

32. MSG – SEVIRI NDVI daily data Eumetsat experimental data (2011) surface type = IGBP land cover classification 14

33. From NDVI to Green Vegetation Fraction GVF is the fraction of green vegetation covering a unit area of horizontal soil, varying from 0 (bare soil) to 1 (full cover) GVF is independent of leaf and soil optical properties although it is defined with reference to green elements It is generally close to FAPAR (varying from 0 to 0.95) with the advantage of being defined independently of illumination conditions, making it an intrinsic canopy attribute for these reasons, GVF is a very good candidate for substitution of classical vegetation indices like NDVI IGARSS 2011 24-29 July, Vancouver, Canada 15

34. Availability of Green Vegetation Fraction data SPOT-VEGETATION : GVF is named fCover and available since October 2009 from Geoland 2 BIOPAR products database (archived data to be available end of 2011) ; Geoland2 is carried out in the context of GMES, a initiative of the European Commission, which aims to build up a European capacity for Global Monitoring of Environment and Security; other sites for obtaining or disseminating data : GEOSUCCESS, VGT4Africa, EUMETCAST, DevCoCast MSG-SEVIRI: daily GVF (named FVC Fraction of Vegetation Cover) is an operational product since March 2007 available from LSA SAF archive http://landsaf.meteo.pt/ IGARSS 2011 24-29 July, Vancouver, Canada 16

35. Deriving Green Vegetation Fraction (Fcover) from SPOT-VEGETATION data scaled NDVI BioPar Product User Manual (2010) IGARSS 2011 24-29 July, Vancouver, Canada 17

36. Deriving Green Vegetation Fraction (Fcover) from SPOT-VEGETATION data NDVIsoil = min (NDVImin, 0.14) NDVImax = 0.85 BioPar Product User Manual (2009) IGARSS 2011 24-29 July, Vancouver, Canada 18

37. Green Vegetation Fraction (FCover) from SPOT-VEGETATION data Fcover : 30-days composite, updated every 10 days using a sliding window ADDITIONAL DATA: FCover-ERR (estimated uncertainty) SMB (Status Map or Quality Flag) NMOD (number of clear observations) LMK (Land cover map = GLC 2000 Global Land Cover Map) BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada 19

38. Green Vegetation Fraction (FCover) from SPOT-VEGETATION data 10° x 10° tiles GVF data available since oct. 2009; archived data available end of 2011 BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada 20

39. Green Vegetation Fraction (FCover) from SPOT-VEGETATION : West Africa, July 1-10, 2010 DN 0-250 = FVC*250 DN=255 : Invalid Example of SPOT-VEGETATION 10-daily GVF BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada 21

41. The algorithm relies on an optimised Spectral Mixture Analysis (SMA) technique. In a first step, an exhaustive training set for the soil and vegetation components is defined. Second, a Gaussian Mixture Model is fit to the training data. Third, a Bayesian model selection is used to compute the relative likelihood of membership in each soil/vegetation single-model. FVC is then estimated using a linear-weighted combination single-model estimateIGARSS 2011 24-29 July, Vancouver, Canada 22

42. Daily Green Vegetation Fraction (FVC) from MSG-SEVIRI data EUMETSAT 4 sub-images HDF5 format IGARSS 2011 24-29 July, Vancouver, Canada 23

44. Maximum of 10 daily NDVI values, MSG-SEVIRI experimental product, resampled at 0.025° resolution (daily mean of n available data during each day)IGARSS 2011 24-29 July, Vancouver, Canada 24

45. Results : SPOT-VEGETATION NDVI S10 Example : 10-day NDVI (1-10 July 2010), West Africa area DN Cloud contaminated pixels IGARSS 2011 24-29 July, Vancouver, Canada 25

46. Results : SPOT-VEGETATION NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area cloudy pixels (from status map) in white DN IGARSS 2011 24-29 July, Vancouver, Canada 26

47. Results : MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area maximum of 10 daily mean values NDVI x NDVI x 100 IGARSS 2011 24-29 July, Vancouver, Canada 27

48. Comparison of SPOT-VEG and MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area Histograms of NDVI values (cloud-free pixels only) SPOT-VEG MSG-SEVIRI IGARSS 2011 24-29 July, Vancouver, Canada 28

49. Comparison of SPOT-VEG and MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area cloud-free pixels only MSG SPOT-VEG IGARSS 2011 24-29 July, Vancouver, Canada 29

51. Mean of 10 daily MSG-SEVIRI operational product FVC (LSA-SAF) , resampled at 0.025° resolution

52. Mean of 10 daily MSG-SEVIRI scaled NDVI, using threshold values NDVImin = 0.098 and NDVI max = 0.71 ( values proposed by NOAA-NESDIS, Bob YU pers. comm.)IGARSS 2011 24-29 July, Vancouver, Canada 30

53. Results : SPOT-VEG GVF (scaled NDVI) Example : 10-day FCOVER (1-10 July 2010), West Africa area grey= no vegetation cover (GVF = 0) ; white = invalid data BioPar Product FCover GVF (%) BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada 31

54. Results : MSG-SEVIRI GVF (LSA SAF FVC) mean of daily FCOVER (1-10 July 2010), West Africa area Grey= no vegetation cover (GVF=0) GVF (%) derived from FVC product IGARSS 2011 24-29 July, Vancouver, Canada 32

55. Comparison of SPOT-VEG and MSG GVF Example : 10-day GVF 1-10 July 2010), West Africa area Cloud-free pixels with GVF>0 only GVFmsg = 0.85 * GVFspot-veg + 10.49 r2 = 0.86 IGARSS 2011 24-29 July, Vancouver, Canada 33

56. Comparison of SPOT-VEG and MSG GVF Example : all Africa, years 2008,2009 IGARSS 2011 24-29 July, Vancouver, Canada 34

57. Results: MSG-SEVIRI GVF(scaled NDVI) mean of daily GVF (1-10 July 2010), West Africa area Grey= no vegetation cover GVF (%) GVF (%) NDVImin = 0.098; NDVImax = 0.71 (NOAA-NESDIS, 2011) IGARSS 2011 24-29 July, Vancouver, Canada 35

58. Comparison of SPOT-VEG and MSG FVC Example : 10-day GVF 1-10 July 2010), West Africa area Cloud-free pixels with GVF>0 only MSG GVFmsg = 0.71 * GVFspot-veg + 17.88 r2 = 0.67 SPOT-VEG IGARSS 2011 24-29 July, Vancouver, Canada 36

59. Comparison SPOT-VEG vs MSG GVF Example : desert pixels (GVF = 0) yellow : GVF = 0 for both data sources orange : only GVF SPOT-VEG=0 SPOT-VEG and MSG (FVC from LSA-SAF) SPOT-VEG and MSG (GVF from scaled NDVI) IGARSS 2011 24-29 July, Vancouver, Canada 37

61. Both SPOT-VEGETATION (10-daily) and MSG-SEVIRI (daily) GVF data can be obtained on a near real-time basis: status of products = operational

62. MSG-SEVIRI has lower spatial resolution than SPOT-VEG, but provides a higher number of available observations in regions with high cloud occurrence, and can be used for high temporal resolution monitoring (1 to 5 days)IGARSS 2011 24-29 July, Vancouver, Canada 38

64. Discrepancies between GVF results from MSG and SPOT-VEG are observed, mainly overestimation of GVF in arid areas when using MSG data

65. Further research is needed to validate FVC estimations and to ensure intercomparability of results between MSG, SPOT-VEG, MODIS, METOP,… using preferably the same preprocessing/ processing methods to derive GVFIGARSS 2011 24-29 July, Vancouver, Canada 39

66. Thank you for your attention lacaze.bernard@gmail.com Télédétection peer-reviewed electronic open-access journal http://www.teledetection.net IGARSS 2011 24-29 July, Vancouver, Canada 40