Principal Investigator (PI): Nicholas Parazoo, NASA's Jet Propulsion Laboratory (JPL)
Measurements of Solar Induced chlorophyll Fluorescence (SIF) emitted from plants have provided a novel measure of photosynthetic activity (or Gross Primary Production, GPP) that can be measured globally from space and which yields significant insights for studying terrestrial carbon cycle dynamics. SIF has been retrieved from a number of satellites, including the NASA Orbiting Carbon Observatory-2 (OCO-2) mission since 2014. Apart from OCO-2, there are no official SIF retrievals from the other satellites but an abundance of independent retrievals, which can vary substantially from one another. The lack of a consistent SIF data record, including inter-calibration of different satellites currently hampers scientific interpretation, especially with respect to analysis of long-term trends or interannual variability.
The team is creating a set of observational SIF Earth Science Data Records (ESDRs) which calibrates and blends together independent retrievals from multiple satellites into a consistent, multi-decadal record spanning the period 1996-2020.
We are processing, calibrating, and standardizing observations of SIF from Global Ozone Monitoring Experiment-1/2 (GOME-1/2), SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY), Greenhouse Gases Observing Satellite (GOSAT), and OCO-2 satellite sensors as a critical first step to reconciling retrieval algorithm development and growing data inventories. The effort leverages newly available SIF observations from NASA’s OCO-2, which have substantially improved spatial resolution and data acquisition, providing sampling footprints traceable to CFIS airborne acquisitions and tower-based measurements. We are using multi-year OCO-2 SIF records overlapped with coarser resolution GOME-2 and GOSAT sensors and rapidly expanding tower and airborne networks to provide uncertainty quantification for spaceborne SIF datasets to optimize production of a 25-year harmonized SIF ESDR anchored by OCO-2 calibration to canopy measurements.
We are also using our SIF ESDR to derive value-added high-resolution (5-km, 16-day) products over the same period. First, we use data fusion methods to map SIF onto MODIS reflectance and MERRA-2 environmental datasets to develop a global, end-to-end, gap-filled SIF product. Second, we produce network-targeted SIF records at FLUXNET eddy covariance towers to derive biome-specific SIF-GPP linear relationships, enabling the delivery of global upscaled GPP products.
As a result of this research, we are delivering calibrated SIF and GPP products essential to carbon cycle modeling and observation communities.
Our primary objectives can be summarized as follows:
- Process and calibrate multiple overlapping satellite (GOME-1/2, SCIAMACHY, GOSAT, OCO-2) observations into a long term harmonized record (1996-2020) and validate against available ground-based SIF observations.
- Fuse harmonized SIF datasets with ancillary vegetation (MODIS) and environmental (MERRA-2) parameters into a global, high resolution, spatially continuous record.
- Establish global upscaled GPP record from linear regression of harmonized SIF records with ground GPP data from biome-diverse eddy covariance locations (FLUXNET).
- Provide uncertainty quantification for SIF and GPP products from various input error sources and validation against airborne and ground observations.