Interannual Variability and Decadal Trend of Global Fractional Vegetation Cover Since 1982

Fractional vegetation cover (FVC) is one of the most important variables in land surface modeling and also provides a continuous field to complement discrete land cover classification. A global 8-km FVC dataset from 1982-2000 is derived using the NOAA/NASA land pathfinder normalized difference vegetation index data. The confidence in the dataset is provided by the insensitivity of our algorithm to the data resolution (between 1 km and 8 km), the good agreement of our results with the field survey data over Germany, the consistency of our results with previous observational studies over the savannas in North Africa and the forests in Bolivia, and the robustness of our algorithm as demonstrated by the small interannual variability of FVC over areas where anthropogenic land cover change is expected to be small based on the 30-m Landsat data analysis. Significant interannual variability is found over shrubland, savanna, and grassland, while both positive and negative trends exist over different areas of the same region in many parts of the world. In particular, our trend analysis pinpoints areas with statistically significant trends (i.e., `hotspots') for further study using higher resolution satellite data and field survey data. Additional results using both AVHRR and MODIS data will also be presented.