Relative Greenness (RG) ranges from 0-100% and indicates how green each 1-km square pixel of land is in relation to a 16-year historical (1989-2004) database of greenness values for that particular pixel. An RG value of 100% signifies that this is the highest greenness level ever reached during the multi-year period, while an RG value of 0% indicates that this is the lowest greenness level reached over that same period. RG is calculated from weekly composite satellite imagery (AVHRR) using NDVI (Normalized Difference Vegetation Index) and is updated on OK-FIRE every Tuesday. If a given pixel is cloudy during the entire weekly period, the RG value used is taken from the last available valid value for that pixel. RG is a very important variable in the fire danger model used in OK-FIRE. It is used to model live fuel moisture (herbaceous and woody) and to apportion the fuel load distribution between 1-hour dead fuels and live herbaceous and live deciduous woody fuels.
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