Calculate Vegetation Fraction
For some of the biomes it is recognised that the temporal variation of the vegetation fraction is important.
The exact source of fractional vegetation is the subject of on-going research, but two methods of estimating fractional vegetation from visible satellite observations are being evaluated:
Both methods make use of the differing visible properties of soil and vegetation at red and near infra-red (NIR) wavelengths. However, existing research and application is best suited to implementation of an NDVI-based climatology but at high temporal frequency.
In SLSTR Level-2 processing, the vegetation climatology is specified as a fractional vegetation (FV) index with maximum value of '1' (corresponding to 100% vegetation) and '0' (corresponding to 0% vegetation) in a specific auxiliary data file.
The FV fields will be similar to, but not necessarily identical to, the spatial resolution of the biome map. A nearest neighbour approach is employed to find the relevant FV fields for the LST. FV fields are interpolated to the current time of the measurement.