Important Update for VIIRS ET/PET Data Users: Transition to Collection 2.1

Data users are advised that the Collection 2 (C2) VIIRS Evapotranspiration (ET) and Potential Evapotranspiration (PET) 8-day and annual data products-derived from Suomi-NPP (VNP16A2GF/A3GF), JPSS-I (VJ116A2GF/A3GF), and JPSS-2 (VJ216A2GF/A3GF)- contain known issues. To ensure the highest data quality for ET/PET estimates, users should transition to the reprocessed Collection 2.1 (C2.1) data products.
The anomalies in the C2 data stem from two issues within the ET/PET Product Generation Executables (PGEs):

1. Wet Canopy Fraction Calculation: During a biophysiological parameter update, the equation used to estimate the fraction of wet canopy was inadvertently modified. Consequently, the fraction of wet canopy is underestimated when the relative humidity exceeds 70%. This perceived reduction in available water leads to an underestimation of ET, particularly in humid ecosystems.
2. PGE Memory Leak:Updates to the 8-day composite processing introduced a memory leak, resulting in inconsistent processing behavior. As a result, certain 10-degree Sinusoidal map projection tiles generated 8-day composites utilizing fewer than the full 8 days of data.

The C2.1 VIIRS ET/PET reprocessing corrects both of these issues by restoring the proper wet canopy equation and resolving the memory leak. The C2.1 products are confirmed to be free of these anomalies. To ensure the correct files are being used, product versions can be verified via their HDF5 filenames: legacy C2 utilizes the string ".002.", while the updated C2.1 uses ".021.".
Further technical details regarding the C2 data are documented on the LDOPE website at: C2 VIIRS ET PET Issues Technical Document