NASA LAI and Fpar ESDR

Product User GuidePI - Ranga Myneni (Boston University)
Product ATBD Co-I: Yuri Knyazikhin (Boston University)


Global LAI/FPAR Earth System Data Records from NPP-VIIRS to Extend the EOS-MODIS Time Series

The justification for continuing the EOS MODIS LAI/FPAR data series with NPP-VIIRS and NPOESS measurements may be succinctly summarized as follows: (1) these products have a large user base, (2) the algorithm is mature and proven to generate accurate products, (3) the products can be generated with minimal investment from VIIRS data, and (4) the resulting continuous, well-characterized, long time series will help us to address the many critical Earth system science, global change, and/or applied sciences questions, thus meeting the primary goal of the NPP/NPOESS missions. Thus the goal is to produce a continuous, well-characterized, long time series of global LAI and FPAR products, spanning the EOS and NPP era, that are suitable for research in Earth system science, global change and applied sciences.

The VIIRS Look-Up-Tables (LUTs) are developed by adjusting certain parameters of the stochastic radiative transfer model such that the modeled reflectances match the measured reflectances and at the same time the retrieved LAI distributions are similar to a pre-set standard (e.g. Aqua MODIS or a large set of measurements; bottom panels).

That is why it is important to have simultaneous measurements from two sensors (e.g. MODIS and VIIRS) in order to ensure continuity of the data record.

Comparison of MODIS and VIIRS LAI/FPAR

lai/fpar VIIRS/MODIS

Both products show distinct annual seasonality of each biome, VIIRS LAI product tend to be higher than MODIS LAI

 

LAI viirs/modis comparison

Comparison of LAI & FPAR for Aqua MODIS and Suomi VIIRS (August & September 2012)

MODIS-like LAI/FPAR products are being produced from Suomi VIIRS data at the Land SIPS using MODIS (C6) code with adjustments for VIIRS sensor. Comprehensive and exhaustive testing of C6 MODIS LAI/FPAR (Terra/Aqua) and Suomi VIIRS LAI/FPAR is required, using at least 2 overlapping years of data.


Product Details and DAAC links

Product Name Product ID
NPP/VIIRS LAI/Fpar 8-day L4 Global 500 m SIN Grid V001 VNP15A2H

 

Validation Plan

The validation approach for VIIRS LAI/Fpar is similar to that of MODIS Collection 6. We will utilize the VIIRS subsets and the EOS Core Validation Sites as well as the BELMANIP2 sites to achieve our goal of CEOS level 2 validation stage. We also plan to perform intercomparisons with LAI/Fpar produced from other sensors.