Early Spatial and Temporal Validation of MODIS LAI Product in Africa

We evaluate the operational MODIS Leaf Area Index (LAI) product using field-sampled data collected at five sites in southern Africa in March 2000. One site (Mongu, Zambia) was sampled monthly throughout the year. All sites were along the IGBP Kalahari Transect, which features progressively lower annual precipitation, and hence lower vegetation productivity, from north to south. The soils are consistently sandy. At each site, we sampled the vegetation overstory along three 750 m transects using the Tracing Radiation and Architecture in Canopies (TRAC) instrument. The resulting plant area index values were adjusted with ancillary stem area data to estimate LAI. Despite some instrument characterization and production issues in the first year of MODIS operations, our results suggest the MODIS LAI algorithm correctly accommodates structural and phenological variability in semi-arid woodlands and savannas, and is numerically accurate to within the field measurement uncertainty. Limitations of this study and its conclusions are also discussed.