MODIS leaf area index products: From validation to algorithm improvement

Wenze Yang*, Bin Tan, Dong Huang, Miina Rautiainen, Nikolay V. Shabanov, Y. Wang, Jeffrey L. Privette, Karl Fred Huemmrich, Rasmus Fensholt, Inge Sandholt, M. Weiss, Douglas E. Ahl, Stith T. Gower, Ramakrishna R. Nemani, Yuri Knyazikhin, Ranga B. Myneni

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

233 Citations (Scopus)

Abstract

Global products of vegetation green Leaf Area Index (LAI) and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) are being operationally produced from Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) at 1-km resolution and eight-day frequency. This paper summarizes the experience of several collaborating investigators on validation of MODIS LAI products and demonstrates the close connection between product validation and algorithm refinement activities. The validation of moderate resolution LAI products includes three steps: 1) field sampling representative of LAI spatial distribution and dynamic range within each major land cover type at the validation site; 2) development of a transfer function between field LAI measurements and high resolution satellite data to generate a reference LAI map over an extended area; and 3) comparison of MODIS LAI with aggregated reference LAI map at patch (multipixel) scale in view of geo-location and pixel shift uncertainties. The MODIS LAI validation experiences, summarized here, suggest three key factors that influence the accuracy of LAI retrievals: 1) uncertainties in input land cover data, 2) uncertainties in input surface reflectances, and 3) uncertainties from the model used to build the look-up tables accompanying the algorithm. This strategy of validation efforts guiding algorithm refinements has led to progressively more accurate LAI products from the MODLS sensors aboard NASA's Terra and Aqua platforms.

Original languageEnglish
Article number1645288
Pages (from-to)1885-1896
Number of pages12
JournalIEEE Transactions on Geoscience and Remote Sensing
Volume44
Issue number7
DOIs
Publication statusPublished - Jul 2006
MoE publication typeA1 Journal article-refereed

Keywords

  • Fraction of Photosynthetically Active Radiation (FPAR) absorbed by vegetation
  • Leaf Area Index (LAI)
  • Moderate Resolution Imaging Spectroradiometer (MODIS)
  • Validation

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    Yang, W., Tan, B., Huang, D., Rautiainen, M., Shabanov, N. V., Wang, Y., Privette, J. L., Huemmrich, K. F., Fensholt, R., Sandholt, I., Weiss, M., Ahl, D. E., Gower, S. T., Nemani, R. R., Knyazikhin, Y., & Myneni, R. B. (2006). MODIS leaf area index products: From validation to algorithm improvement. IEEE Transactions on Geoscience and Remote Sensing, 44(7), 1885-1896. [1645288]. https://doi.org/10.1109/TGRS.2006.871215