Vegetation variables are important for evaluating the status and temporal processes of vegetated land surfaces. Using the AVHRR reflectance data it is possible to derive such vegetation variables consistently over large regions (regional and continental) and for long time periods.
The Leaf Area Index (LAI) is a dimensionless variable, quantifying the total one-sided area of green leaves (in m²) per surface area (in m²). The LAI corresponds to the total of the canopy also including the understory layers (Sellers 1985) and is an Essential Climate Variable (ECV) defined by the Global Climate Observing System (WMO 2011). A satellite-based estimation of LAI always implies indirect approaches exploiting the relationship between LAI and the characteristics of the solar radiation reflected by the canopy (GTOS 2009). Within TIMELINE statistical relationships between the NDVI and the LAI will be used to retrieve the LAI. Here, specific; unique relationships will be used for the land cover classes of Europe.
Example of the LAI Product from August 1990.
GLOBAL TERRESTRIAL OBSERVING SYSTEM (GTOS) (2009), LAI. Assessment of the status of the development of the standards for the terrestrial essential climate variables. GTOS 66. Available online at: http://www.fao.org/gtos/doc/ECVs/T11/T11.pdf
Sellers PJ (1985) Canopy reflectance, photosynthesis and transpiration. Int J Remote Sens, 6, 1335–1372
WMO (2011) GCOS Systematic Observation Requirements For Satellite-Based Data Products for Climate - 2011 Update