Leaf Area Index (LAI) indicates the amount of live green leaf material per unit of ground surface. Many agro-meteorology, atmospheric general circulation, and biogeochemical models rely on LAI to parameterize the vegetation interactions with the atmosphere. Several space agencies have generated global LAI products at various spatial and temporal resolutions, using optical satellite sensors. However, to effectively use these LAI products in various disciplines, it is critical to get the knowledge of the quality of these products.

Prof. FANG Hongliang, Institute of Geographic Sciences and Natural Resources Research (IGSNRR) and his colleagues evaluated quantitatively the uncertainties of two major global LAI products derived from MODIS aboard the Terra and Aqua satellites, and the CYCLOPES project from the SPOT/VEGETATION.

Researchers built a global field LAI measurement database based on a wide literature survey. Consequently, the MODIS LAI product suite, containing the Terra Collection 4 (C4), Terra Collection 5 (C5) and Terra+Aqua combined C5, and the CYCLOPES V3.1 LAI products were compared with the global field measured LAI. They found that the MODIS LAI has improved consistently over all releases. Uncertainties for the best MODIS C5 and CYCLOPES estimates were around 0.9-1.1. The overall mean differences between the best MODIS C5 and CYCLOPES were within ±0.10. Results indicate that the uncertainties in current LAI products (around ±1.0) are still unable to meet the accuracy requirement of Global Climate Observation System (±0.5). Further studies about the global LAI uncertainties are currently underway.

The studies have been published in the Remote Sensing of Environment（Fang, H., S. Wei, and S. Liang, 2012. Validation of MODIS and VEGETATION LAI products using global field measurement data. Remote Sensing of Environment, 119, 43-54. Doi:10.1016/j.rse.2011.12.006）.

For more information, contact

Hongliang FANG, Ph.D, Professor

LREIS, Institute of Geographic Sciences and Natural Resources Research

Chinese Academy of Sciences

11A Datun Road, Beijing, 100101, China

Tel: +86 10 6488 8005

Fax: +86 10 6488 9630

Email: fanghl@lreis.ac.cn

References:

Global validation sites from major field campaigns and the literature. http://www.lreis.ac.cn/upload/dataset/Global_Field_LAI.pdf