Comparing Optical and Microwave Remote Sensing-based Vegetation Density over Mongolia for 1988-2006.

Liu, Y.Y., R.A.M. De Jeu, M.F. McCabe, J.P. Evans, A.I.J.J.M. Van Dijk
3rd International Symposium on Remote Sensing of Environment, Sydney, Australia, 10-15 April 2011.


Vegetation density plays an important role in water and energy balance. Satellite-based optical and microwave sensors are expected to provide complementary vegetation information. Here we compared NDVI from AVHRR and vegetation optical depth (VOD) from SSM/I over Mongolia from 1988 through 2006. Both products show similar spatial distribution in annual average and are able to capture similar inter-annual variations. However, the long term changes reflected by them are divergent. Microwave based VOD shows considerable decreasing trends over grassland, whereas NDVI shows slight declines and even increasing trends. Further investigations are required to identify the causes for their divergence.

Key Figure

albedo & vegetation fraction

Figure 4: Trend in peak monthly NDVI and VOD of each year during 1988 – 2006 using Mann-Kendall analysis.

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