Project Funding: 2011 - 2014

NRA: 2010 NASA: NPP Science Team for Climate Data Records   

Funded by NASA

Abstract:
Vegetation indices (VIs) are robust and seamless satellite data products computed the same across all pixels in time and space, regardless of climatic region, biome type, and soil type, and thus represent true surface measurements. VIs are optical measures of vegetation canopy "greenness", a direct measure of photosynthetic potential resulting from the composite property of total leaf chlorophyll, leaf area, canopy cover, and structure. They have become indispensable tools in climate, hydrologic, and biogeochemical studies, land cover and land cover change detection, agricultural and ecological applications, drought monitoring, and public health. Two VIs, the "top-of-atmosphere" normalized difference vegetation index (NDVI) and the atmospherically-corrected "top-of-canopy" enhanced vegetation index (EVI), have been selected as Environmental Data Records (EDRs) to the Visible/Infrared Imager Radiometer Suite (VIIRS) sensor on the upcoming National Polar-orbiting Environmental Satellite System Preparatory Project (NPP) and Joint Polar Satellite System (JPSS) missions. The development and provision of long-term data records, however, require the effective integration of new sensor technologies and improved algorithms to better characterize global and climate change impacts on ecosystems, while preserving the fundamental attributes of the existing data record. In this proposal, we continue the evaluation of VIIRS Vegetation Index EDRs and the development, testing, and evaluation of their algorithmic improvements to the EDRs, and quantitatively determine their quality and suitability for detecting surface-based "climate signals." We propose to use in situ observation networks for evaluating and validating long-term VI time series across multiple sensor systems [AVHRR (Advanced Very High Resolution Radiometer)-MODIS (Moderate Resolution Imaging Spectroradiometer)- VIIRS]. These networks are evolving into highly calibrated and traceable systems and include the (1) Aerosol Robotic Network (AERONET), (2) Phenological Eyes Network (PEN), (3) Spectral Network (SpecNet), (4) Baseline Surface Radiation Network (BSRN), and (5) FLUXNET. These provide independent, in situ measurements of surface VI values, vegetation canopy states [fraction of absorbed photosynthetically active radiation; vegetation canopy processes (gross primary production, or photosynthesis, and evapotranspiration); and vegetation phenology metrics (greening, browning, flowering)]. These in situ measurements are derived at higher quality (finer spatial and/or temporal resolution) than the satellite measurement, can be applied and cross-calibrated to multiple satellites, and facilitate various methods of quality, uncertainty, and cross-sensor continuity assessments. Through these detailed evaluation work with in situ data combined with image QA analysis, we expect to determine what constitutes a "climate-quality" pixel and develop an unified "climate-quality assurance" scheme across VIIRS, MODIS, and AVHRR. We will also conduct post-launch VI product inter-comparisons across VIIRS-MODIS-AVHRR, using Diagnostic Data Records (DDRs) produced by the Land Product Evaluation and Test Element (PEATE) for regional to global scale assessments of the VIIRS VI EDR and science VI product quality and their continuity/compatibility with the MODIS and AVHRR counterparts.

2013 NASA Terrestrial Ecology Science Team Meeting Poster(s)

• Vegetation Index EDR from Suomi NPP VIIRS: An Overview of the Current Status   --   (Tomoaki Miura)   [abstract]

2011 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Spectral Compatibility of VIIRS Vegetation Index EDR with MODIS and AVHRR   --   (Tomoaki Miura)   [abstract]

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile