Period: 1981 – 2014

Sensor: MODIS & AVHRR

Frequency: Yearly

Resolutions: 5.6km

Extent: Global

Data can be accessed here.

Algorithm description: Following information is available in this product: Start, End and Length of the growing season, Day of peak, Magnitude of peak, Rate of greening, Rate of senescence, Cumulative green.

The algorithm produces NDVI and EVI global datasets. Phenology metrics are estimated using a Modified Half-Max VI method, where VI is NDVI or EVI.

The products are derived from AVHRR (1981-1999) and MODIS (2000 to 2014). Cross calibration between two sensors has been done to ensure consistency.

Accuracy:  Overall errors due to reflectance input uncertainty are small (~0.05) except sparsely vegetated areas due to very small signal. Errors are largest in winter.

It has also been noted in the ATBD of the product that errors associated with the indices and phenology parameters can be large and complex; however, it is difficult to characterise them due nature of the index itself.

Marshal et al (2016) compared VIP collection (both EVI and NDVI) with GIMMS collection version 3 on global scale. GIMM NDVI data are purely based on AVHRR sensor reflectance unlike VIP. They found VIP NDVI and EVI2 (version 3) performed worse that GIMMS NDVI. They were higher in magnitude, noisier and less inconsistent in terms of long term trend compared to GIMMS. Majority of these discrepancies were attributed to the fact that VIP relies on blending of AVHRR and MODIS  that have different sensitivities.

Limitations:

  • Marshal et al (2016) report worse performance of EVI compared to NDVI.
  • Product is generally suitable for studying long term phenological changes.
  • Inconsistencies in MODIS and AVHRR derived products.

Reference:

Didan, K. et al. Multi-Sensor Vegetation Index and Phenology Earth Science Data Records Algorithm Theoretical Basis Document and User Guide Version 4.0. 1–84 (Vegetation Index and Phenology Lab.,  University of Arizona, 2015).

Marshall, M., Okuto, E., Kang, Y., Opiyo, E. & Ahmed, M. Global assessment of Vegetation Index and Phenology Lab (VIP) and Global Inventory Modeling and Mapping Studies (GIMMS) version 3 products. Biogeosciences 13, 625–639 (2016).