• Aires, F., A. Chédin, and J-P. Nadal, 2000: Independent component analysis of multivariate time series: Application to the tropical SST variability. J. Geophys. Res., 105 , 1743717456.

    • Search Google Scholar
    • Export Citation
  • Aires, F., W. B. Rossow, and A. Chédin, 2002: Rotation of EOFs by the independent component analysis: Toward a solution of the mixing problem in the decomposition of geophysical time series. J. Atmos. Sci., 59 , 111123.

    • Search Google Scholar
    • Export Citation
  • Akpo, L. E., and M. Grouzis, 1993: Etude comparée de la phénologie de la végétation herbacée sous et hors couvert ligneux en milieu sahélien. Webbia, 47 , 387401.

    • Search Google Scholar
    • Export Citation
  • Anyamba, A., and J. R. Eastman, 1996: Interannual variability of NDVI over Africa and its relation to El Niño/Southern Oscillation. Int. J. Remote Sens., 17 , 25332548.

    • Search Google Scholar
    • Export Citation
  • Anyamba, A., and C. Tucker, 2005: Analysis of Sahelian vegetation dynamics using NOAA-AVHRR NDVI data from 1981–2003. J. Arid Environ., 63 , 596614.

    • Search Google Scholar
    • Export Citation
  • Bader, J., and M. Latif, 2003: The impact of decadal-scale Indian Ocean sea surface temperature anomalies on Sahelian rainfall and the North Atlantic Oscillation. Geophys. Res. Lett., 30 .2169, doi:10.1029/2003GL018426.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., J. H. Ball, A. C. M. Beljaars, M. J. Miller, and P. A. Viterbo, 1996: The land surface–atmosphere interaction: A review based on observational and global modeling perspectives. J. Geophys. Res., 101 , 72097226.

    • Search Google Scholar
    • Export Citation
  • Bonan, G. B., 2002: Ecological Climatology: Concepts and Applications. Cambridge University Press, 678 pp.

  • Camberlin, P., and N. Philippon, 2002: The East African March–May rainy season: Associated atmospheric dynamics and predictability over the 1968–97 period. J. Climate, 15 , 10021019.

    • Search Google Scholar
    • Export Citation
  • Camberlin, P., and M. Diop, 2003: Application of daily rainfall principal component analysis to the assessment of the rainy season characteristics in Senegal. Climate Res., 23 , 159169.

    • Search Google Scholar
    • Export Citation
  • Camberlin, P., S. Janicot, and I. Poccard, 2001: Seasonality and atmospheric dynamics of the teleconnection between African rainfall and tropical sea-surface temperature: Atlantic vs. ENSO. Int. J. Climatol., 21 , 9731005.

    • Search Google Scholar
    • Export Citation
  • Charney, J. G., 1975: Dynamics of desert and drought in the Sahel. Quart. J. Roy. Meteor. Soc., 101 , 193202.

  • Crépeau, C., and Coauthors, 2003: Monitoring of dry land area vegetation using products derived from satellite images. Sécheresse,1E. [Available online at http://www.secheresse.info/article.php3?id_article=224#.].

  • Dai, A., P. J. Lamb, K. E. Trenberth, M. Hulme, P. Jones, and P. Xie, 2004: The recent Sahel drought is real. Int. J. Climatol., 24 , 13231331.

    • Search Google Scholar
    • Export Citation
  • de Bie, S., P. Ketner, M. Paasse, and C. Geerling, 1998: Woody plant phenology in the West Africa savanna. J. Biogeogr., 25 , 883900.

  • Dregne, H. E., and C. J. Tucker, 1988: Green biomass and rainfall in semi-arid sub-Saharan Africa. J. Arid Environ., 15 , 245252.

  • Eklundh, L., and L. Olsson, 2003: Vegetation index trends for the African Sahel 1982–1999. Geophys. Res. Lett., 30 .1430, doi:10.1029/2002GL016772.

    • Search Google Scholar
    • Export Citation
  • Eltahir, E. A. B., and C. Gong, 1996: Dynamics of wet and dry years in West Africa. J. Climate, 9 , 10301042.

  • Fontaine, B., and S. Janicot, 1996: Sea surface temperature fields associated with West African rainfall anomaly types. J. Climate, 9 , 29352940.

    • Search Google Scholar
    • Export Citation
  • Fontaine, B., S. Trzaska, and S. Janicot, 1998: Evolution of the relationship between near global and Atlantic SST modes and the rainy season in West Africa: Statistical analyses and sensitivity experiments. Climate Dyn., 14 , 353368.

    • Search Google Scholar
    • Export Citation
  • Fontès, J., J. P. Gastellu-Etchegorry, O. Amram, and G. Flouzat, 1995: A global phenological model of the African continent. Ambio, 24 , 297303.

    • Search Google Scholar
    • Export Citation
  • Giannini, A., R. Saravanan, and P. Chang, 2003: Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science, 302 , 10271030.

    • Search Google Scholar
    • Export Citation
  • Grist, J., S. Nicholson, and A. Mpolokang, 1997: On the use of NDVI for estimating rainfall fields in the Kalahari of Bostwana. J. Arid Environ., 35 , 195214.

    • Search Google Scholar
    • Export Citation
  • Hanan, N. P., S. D. Prince, and B. N. Holben, 1995: Atmospheric correction of AVHRR data for biophysical remote sensing of the Sahel. Remote Sens. Environ., 51 , 306316.

    • Search Google Scholar
    • Export Citation
  • Hansen, M., R. DeFries, J. R. G. Townshend, M. Carroll, C. Dimiceli, and R. Sohlberg, 2002: Global percent tree cover at a spatial resolution of 500 meters: First results of the MODIS vegetation continuous fields algorithm. Earth Interactions,7. [Available online at http://EarthInteractions.org.].

  • Hiernaux, P. H. Y., M. I. Cissé, L. Diarra, and P. N. de Leeuw, 1994: Fluctuations saisonnières de la feuillaison des arbres et buissons sahéliens: Conséquences pour la quantification des ressources fourragères. Rev. Elev. Med. Vet. Pays Trop., 47 , 117125.

    • Search Google Scholar
    • Export Citation
  • Holben, B. N., and Coauthors, 2001: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET. J. Geophys. Res., 106 , 1206712097.

    • Search Google Scholar
    • Export Citation
  • Huete, A. R., and C. J. Tucker, 1991: Investigation of soil influences in AVHRR red and near-IR vegetation index imagery. Int. J. Remote Sens., 12 , 12231242.

    • Search Google Scholar
    • Export Citation
  • Hutjes, R. W. A., and Coauthors, 1998: Biospheric aspects of the hydrological cycle. J. Hydrol., 212–213 , 121.

  • Hyvarinen, A., and E. Oja, 2000: Independent component analysis: Algorithms and applications. Neural Networks, 13 , 411430.

  • Hyvarinen, A., J. Karhunen, and E. Oja, 2001: Independent Component Analysis. John Wiley and Sons, 481 pp.

  • Janicot, S., 1992: Spatiotemporal variability of West African rainfall. Part I: Regionalizations and typings. J. Climate, 5 , 489497.

  • Janicot, S., V. Moron, and B. Fontaine, 1996: Sahel droughts and ENSO dynamics. Geophys. Res. Lett., 23 , 515518.

  • Janicot, S., S. Trzaska, and I. Poccard, 2001: Summer Sahel-ENSO teleconnection and decadal time scale SST variations. Climate Dyn., 18 , 303320.

    • Search Google Scholar
    • Export Citation
  • Jarlan, L., Y. M. Tourre, E. Mougin, N. Philippon, and P. Mazzega, 2005: Dominant patterns of AVHRR NDVI interannual variability over the Sahel and linkages with key climate signals (1982–2003). Geophys. Res. Lett., 32 .L04701, doi:10.1029/2004GL021841.

    • Search Google Scholar
    • Export Citation
  • Justice, C. O., G. Dugdale, J. R. Townshend, A. S. Narracott, and M. Kumar, 1991: Synergism between NOAA-AVHRR and Meteosat data for studying vegetation development in semi-arid West Africa. Int. J. Remote Sens., 12 , 13491368.

    • Search Google Scholar
    • Export Citation
  • Le Barbé, L., T. Lebel, and D. Tapsoba, 2002: Rainfall variability in West Africa during the years 1950–90. J. Climate, 15 , 187202.

    • Search Google Scholar
    • Export Citation
  • Liebmann, B., and C. A. Smith, 1996: Description of a complete (interpolated) outgoing longwave radiation dataset. Bull. Amer. Meteor. Soc., 77 , 12751277.

    • Search Google Scholar
    • Export Citation
  • Los, S. O., G. J. Collatz, L. Bounoua, P. J. Sellers, and C. J. Tucker, 2001: Global interannual variations in sea surface temperature and land surface vegetation, air temperature, and precipitation. J. Climate, 14 , 15351549.

    • Search Google Scholar
    • Export Citation
  • Lotsch, A., M. A. Friedl, and J. E. Pinzon, 2003: Spatio-temporal deconvolution of NDVI image sequences using independent component analysis. IEEE Trans. Geosci. Remote Sens., 41 , 29382942.

    • Search Google Scholar
    • Export Citation
  • Louvet, S., B. Fontaine, and P. Roucou, 2003: Active phases and pauses during the installation of the West African monsoon through 5-day CMAP rainfall data (1979–2001). Geophys. Res. Lett., 30 .2271, doi:10.1029/2003GL018058.

    • Search Google Scholar
    • Export Citation
  • Malo, A. R., and S. Nicholson, 1990: A study of the rainfall and vegetation dynamics in the African Sahel using the normalized difference vegetation index. J. Arid Environ., 19 , 124.

    • Search Google Scholar
    • Export Citation
  • Martiny, N., P. Camberlin, and Y. Richard, 2005: Interannual persistence effects in vegetation dynamics of semi-arid Africa. Geophys. Res. Lett., 32 .L24403, doi:10.1029/2005GL024634.

    • Search Google Scholar
    • Export Citation
  • Mayaux, P., E. Bartholomé, S. Fritz, and A. Beward, 2004: A new land-cover map of Africa for the year 2000. J. Biogeogr., 31 , 861877.

    • Search Google Scholar
    • Export Citation
  • Mitchell, T. D., T. R. Carter, P. D. Jones, M. Hulme, and M. G. New, 2004: A comprehensive set of high-resolution grids of monthly climate for Europe and the globe: The observed record (1901–2000) and 16 scenarios (2001–2100). Tyndall Center Working Paper 55, 30 pp.

  • Moulin, S., L. Kergoat, N. Viovy, and G. Dedieu, 1997: Global-scale assessment of vegetation phenology using NOAA/AVHRR satellite measurements. J. Climate, 10 , 11541170.

    • Search Google Scholar
    • Export Citation
  • Myneni, R. B., S. O. Los, and C. J. Tucker, 1996: Satellite-based identification of linked vegetation index and sea surface temperature anomaly areas from 1982–1990 for Africa, Australia and South America. Geophys. Res. Lett., 23 , 729732.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S., 2005: On the question of the “recovery” of the rains in the West African Sahel. J. Arid Environ., 63 , 615641.

  • Nicholson, S., M. Davenport, and A. R. Malo, 1990: A comparison of the vegetation response to rainfall in the Sahel and East Africa, using Normalized Difference Vegetation Index from NOAA AVHRR. Climatic Change, 17 , 209241.

    • Search Google Scholar
    • Export Citation
  • Nicholson, S., B. Some, and B. Kone, 2000: An analysis of recent rainfall conditions in West Africa, including the rainy seasons of the 1997 El Niño and the 1998 La Niña years. J. Climate, 13 , 26282640.

    • Search Google Scholar
    • Export Citation
  • Olsson, L., L. Eklundh, and J. Ardö, 2005: A recent greening of the Sahel—Trends, patterns and potential causes. J. Arid Environ., 63 , 556566.

    • Search Google Scholar
    • Export Citation
  • Philippon, N., and B. Fontaine, 2002: The relationship between the Sahelian and previous 2nd Guinean rainy seasons: A monsoon regulation by soil wetness? Ann. Geophys., 20 , 575582.

    • Search Google Scholar
    • Export Citation
  • Philippon, N., E. Mougin, L. Jarlan, and P-L. Frison, 2005: Analysis of the linkages between rainfall and land surface conditions in the West African monsoon through CMAP, ERS-WSC, and NOAA-AVHRR data. J. Geophys. Res., 110 .D24115, doi:10.1029/2005JD006394.

    • Search Google Scholar
    • Export Citation
  • Pinzon, J., M. E. Brown, and C. J. Tucker, 2004: Satellite time series correction of orbital drift artifacts using empirical mode decomposition. Hilbert-Huang Transform and Its Applications, N. E. Huang and S. S. P. Shen, Eds., World Scientific, 167–186.

  • Raicich, F., N. Pinardi, and A. Navarra, 2003: Teleconnections between Indian monsoon and Sahel rainfall and the Mediterranean. Int. J. Climatol., 23 , 173186.

    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent, and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108 .4407, doi:10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation
  • Rigina, O., and M. S. Rasmussen, 2003: Using trend line and principal component analysis to study vegetation changes in Senegal 1986–1999 from AVHRR NDVI 8 km data. Dan. J. Geogr., 103 , 3142.

    • Search Google Scholar
    • Export Citation
  • Rowell, D. P., 2001: Teleconnections between the tropical Pacific and the Sahel. Quart. J. Roy. Meteor. Soc., 127 , 16831706.

  • Rowell, D. P., 2003: The impact of Mediterranean SSTs on the Sahelian rainfall season. J. Climate, 16 , 849862.

  • Schwinning, S., and O. E. Sala, 2004: Hierarchy of responses to resource pulses in arid and semiarid ecosystems. Oecologia, 141 , 211220.

    • Search Google Scholar
    • Export Citation
  • Schwinning, S., O. E. Sala, M. E. Loik, and J. R. Ehleringer, 2004: Thresholds, memory and seasonality: Understanding pulse dynamics in arid/semi-arid ecosystems. Oecologia, 141 , 191193.

    • Search Google Scholar
    • Export Citation
  • Servain, J., 1991: Simple climatic indices for the tropical Atlantic Ocean and some applications. J. Geophys. Res., 96 , 1513715146.

  • Shinoda, M., 1995: Seasonal phase lag between rainfall and vegetation activity in tropical Africa as revealed by NOAA satellite data. Int. J. Climatol., 15 , 639656.

    • Search Google Scholar
    • Export Citation
  • Shinoda, M., and Y. Yamaguchi, 2003: Influence of soil moisture anomaly on temperature in the Sahel: A comparison between wet and dry decades. J. Hydrometeor., 4 , 437447.

    • Search Google Scholar
    • Export Citation
  • Sultan, B., and S. Janicot, 2000: Abrupt shift of the ITCZ over West Africa and intra-seasonal variability. Geophys. Res. Lett., 27 , 33533356.

    • Search Google Scholar
    • Export Citation
  • Tanré, D., B. N. Holben, and Y. F. Kaufman, 1992: Atmospheric correction algorithm for NOAAAVHRR products: Theory and applications. IEEE Trans. Geosci. Remote Sens., 30 , 231248.

    • Search Google Scholar
    • Export Citation
  • Tateishi, R., and M. Ebata, 2004: Analysis of phenological change patterns using 1982–2000 Advanced Very High Resolution Radiometer (AVHRR) data. Int. J. Remote Sens., 25 , 22872300.

    • Search Google Scholar
    • Export Citation
  • Townshend, J. R., and C. O. Justice, 1986: Analysis of the dynamics of African vegetation using the normalized difference vegetation index. Int. J. Remote Sens., 7 , 14351445.

    • Search Google Scholar
    • Export Citation
  • Tucker, C. J., 1979: Red and photographic infrared linear combinations for monitoring vegetation. Remote Sens. Environ., 8 , 127150.

  • Tucker, C. J., 2005: An extended AVHRR 8-km NDVI data set compatible with MODIS and SPOT vegetation NDVI data. Int. J. Remote Sens., 26 , 14611471.

    • Search Google Scholar
    • Export Citation
  • Vizy, E. K., and K. H. Cook, 2001: Mechanisms by which Gulf of Guinea and eastern North Atlantic sea surface temperature anomalies can influence African rainfall. J. Climate, 14 , 795821.

    • Search Google Scholar
    • Export Citation
  • Von Storch, H., and F. W. Zwiers, 1999: Statistical Analysis in Climate Research. Cambridge University Press, 484 pp.

  • Wang, G., and E. A. B. Eltahir, 2000a: Role of vegetation dynamics in enhancing the low-frequency variability of the Sahel rainfall. Water Resour. Res., 36 , 10131021.

    • Search Google Scholar
    • Export Citation
  • Wang, G., and E. A. B. Eltahir, 2000b: Ecosystem dynamics and the Sahel drought. Geophys. Res. Lett., 27 , 795798.

  • Wilks, D. S., 2006: Statistical Methods in the Atmospheric Sciences. 2d ed. Academic Press, 627 pp.

  • Xie, P., and P. Arkin, 1997: Global precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78 , 25392558.

    • Search Google Scholar
    • Export Citation
  • Xue, Y., 1997: Biosphere feedback on regional climate in tropical North Africa. Quart. J. Roy. Meteor. Soc., 123 , 14831515.

  • Zeng, N. J., J. D. Neelin, K. M. Lau, and C. Tucker, 1999: Enhancement of interdecadal climate variability in the Sahel by vegetation interaction. Science, 286 , 15371540.

    • Search Google Scholar
    • Export Citation
  • Zhang, X., M. A. Friedl, C. B. Schaaf, A. H. Strahler, and Z. Liu, 2005: Monitoring the response of vegetation phenology to precipitation in Africa by coupling MODIS and TRMM instruments. J. Geophys. Res., 110 .D12103, doi:10.1029/2004JD005263.

    • Search Google Scholar
    • Export Citation
  • Zheng, X., and E. A. B. Eltahir, 1998: The role of vegetation in the dynamics of West African monsoons. J. Climate, 11 , 20782096.

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Characterization of the Interannual and Intraseasonal Variability of West African Vegetation between 1982 and 2002 by Means of NOAA AVHRR NDVI Data

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  • 1 Centre de Recherches de Climatologie, UMR5210 CNRS, University of Burgundy, Dijon, France
  • | 2 Centre d’Etudes Spatiales de la BIOsphère, UMR 5126 CNRS–UPS–CNES–IRD, Toulouse, France
  • | 3 Centre de Recherches de Climatologie, UMR5210 CNRS, University of Burgundy, Dijon, France
  • | 4 Centre d’Etudes Spatiales de la BIOsphère, UMR 5126 CNRS–UPS–CNES–IRD, Toulouse, France
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Abstract

The interannual and intraseasonal variability of West African vegetation over the period 1982–2002 is studied using the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR).

The novel independent component analysis (ICA) technique is applied to extract the main modes of the interannual variability of the vegetation, among which two modes are worth describing. The first component (IC1) describes NDVI variability over the Sahel from August to October. A strong photosynthetic activity over the Sahel is related to above-normal convection and rainfall within the intertropical convergence zone (ITCZ) in summertime and is partly associated with colder (warmer) SST in the eastern tropical Pacific (the Mediterranean). The second component (IC2) depicts a dipole pattern between the Sahelian and Guinean regions during the northern summer followed by a southward-propagating signal from October to December. It is associated with a north–south dipole in convection and rainfall induced by variations in the latitudinal location of the ITCZ as a response to the occurrence of the tropical Atlantic dipole.

The analysis of the intraseasonal variability of the Sahelian vegetation relies on the analysis of the seasonal marches and their main phenological stages. Green-up usually starts in early July and shows a very low year-to-year variability, while senescence ends by mid-November and is prone to larger interannual variability. Six types of vegetative seasonal marches are discriminated according to variations in the timing of phenological stages as well as in the greening intensity. These types appear to be strongly dependent on rainfall distribution and amount, particularly those recorded in late August. Finally, year-to-year memory effects are highlighted: NDVI recorded during the green-up phase in year j appears to be strongly related to the maximum NDVI value recorded at year j − 1.

* Current affiliation: European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom

Corresponding author address: Nathalie Philippon, Centre de Recherches de Climatologie, UMR5210 CNRS, University of Burgundy, bât. Sciences Gabriel, BP 27877, 21078 Dijon CEDEX, France. Email: nathalie.philippon@u-bourgogne.fr

Abstract

The interannual and intraseasonal variability of West African vegetation over the period 1982–2002 is studied using the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR).

The novel independent component analysis (ICA) technique is applied to extract the main modes of the interannual variability of the vegetation, among which two modes are worth describing. The first component (IC1) describes NDVI variability over the Sahel from August to October. A strong photosynthetic activity over the Sahel is related to above-normal convection and rainfall within the intertropical convergence zone (ITCZ) in summertime and is partly associated with colder (warmer) SST in the eastern tropical Pacific (the Mediterranean). The second component (IC2) depicts a dipole pattern between the Sahelian and Guinean regions during the northern summer followed by a southward-propagating signal from October to December. It is associated with a north–south dipole in convection and rainfall induced by variations in the latitudinal location of the ITCZ as a response to the occurrence of the tropical Atlantic dipole.

The analysis of the intraseasonal variability of the Sahelian vegetation relies on the analysis of the seasonal marches and their main phenological stages. Green-up usually starts in early July and shows a very low year-to-year variability, while senescence ends by mid-November and is prone to larger interannual variability. Six types of vegetative seasonal marches are discriminated according to variations in the timing of phenological stages as well as in the greening intensity. These types appear to be strongly dependent on rainfall distribution and amount, particularly those recorded in late August. Finally, year-to-year memory effects are highlighted: NDVI recorded during the green-up phase in year j appears to be strongly related to the maximum NDVI value recorded at year j − 1.

* Current affiliation: European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom

Corresponding author address: Nathalie Philippon, Centre de Recherches de Climatologie, UMR5210 CNRS, University of Burgundy, bât. Sciences Gabriel, BP 27877, 21078 Dijon CEDEX, France. Email: nathalie.philippon@u-bourgogne.fr

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