Algorithm Descriptions
The Ocean Biology Processing Group (OBPG) produces and distributes a standard suite of ocean color products for all compatible sensors at Level-2 and Level-3, plus sea surface temperature (SST) products from MODIS and VIIRS. The OBPG also produces a suite of Level-3 evaluation products. The descriptions and references for these standard and evaluation products (provided below) are intended to satisfy the Algorithm Theoretical Basis Document (ATBD) requirement as defined by the NASA Earth Observing System Project Science Office.
Ocean Color Products
Flags: View quality indicators of Level-2 Ocean Color products.
Standard
- Remote Sensing Reflectance (Rrs; sr-1)
- The at-surface spectral remote-sensing reflectances observed by the satellite instrument after atmospheric correction. The aerosol optical thickness and aerosol Ångström exponent products are also described.
- Chlorophyll a (chlor_a; mg m-3)
- The concentration of the photosynthetic pigment chlorophyll a
- Diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd; m-1)
- The diffuse attenuation coefficient for downwelling irradiance over the first optical attenuation layer
- Particulate Organic Carbon (POC; mg m-3)
- The concentration of particulate organic carbon
- Particulate Inorganic Carbon (PIC; mol m-3)
- The concentration of particulate inorganic carbon
- Photosynthetically Available Radiation (PAR; Einstein m-2 d-1)
- Daily mean photosynthetically available radiation at the ocean surface
- Instantaneous Photosynthetically Available Radiation (iPAR; Einstein m-2 s-1)
- PAR at the ocean surface at the time of the satellite observation
- Normalized Fluorescence Line Height (nFLH; mW cm-2 µm-1 sr-1)
- Relative measure of water-leaving radiance associated with chlorophyll fluorescence
- Inherent Optical Properties from GIOP Algorithm (IOP, m-1)
- Spectral marine absorption and backscattering coefficients of water column constituents
Provisional/Developmental
- PIC - Color Index
- This algorithm derives the concentration of particulate inorganic carbon (PIC) in mol m-3, calculated using an empirical relationship derived from in situ measurements of PIC and remote sensing reflectance ($R_{rs}$) in the green-to-red region of the visible spectrum.
- Apparent Visible Wavelength (AVW)
- This algorithm returns the weighted harmonic mean of the visible-range (400 – 700 nm) remote sensing reflectance (Rrs) wavelengths, outputting the Apparent Visible Wavelength (AVW) in units of nanometers.
- Quality Water Index Polynomial (QWIP)
- This algorithm returns the Quality Water Index Polynomial (QWIP) score, representing a quantitative metric to evaluate the quality of ocean color remote sensing reflectance (Rrs) data (Dierssen et al. 2022).
- Phytoplankton Carbon Concentration (carbon_phyto)
- This algorithm returns the concentration of the phytoplankton carbon.
Special
- Inherent Optical Properties from GSM Algorithm (GSM; m-1)
- Spectral marine absorption and backscattering coefficients of water column constituents
- Inherent Optical Properties from QAA Algorithm (QAA; m-1)
- Spectral marine absorption and backscattering coefficients of water column constituents
- Euphotic Depth from Lee Algorithm (ZLEE; m-1)
- Depth of the euphotic zone
- Land Reflectance from NDVI algorithm (LAND)
- Land reflectance generated from the Normalized Difference Vegetation Index (NDVI) algorithm
Test
- Net Primary Production (NPP) Suite
- The Net Primary Production (NPP) Suite tracks the proportion of phytoplankton-sequestered carbon that is available to enter into the trophic cascades of the oceanic food web.
- Calcite (ci2)
- Calcite concentration derived from particulate inorganic carbon
Sea Surface Temperature Products
Flags: View quality indicators of SST products.
Standard
- 11 µm Sea Surface Temperature (SST; °C)
- Sea surface temperature derived from long-wave (11-12 µm) thermal radiation
- 4 µm Sea Surface Temperature (SST4; °C)
- Sea surface temperature derived from short-wave (3-4 µm) thermal radiation
- Triple-Window Sea Surface Temperature (SST3; °C)
- Sea surface temperature returned in three mid- and long-wave infrared bands
Developmental
This section lists algorithms that have been proposed and are under review. If accepted, the status will be updated to "Provisional" or "Standard". As developmental algorithms, those listed below ARE NOT used in OBPG data processing.
- Aerosol correction for VIIRS SST
- Aerosol correction for sea surface temperature
- Physical Deterministic (PD) SST
- Sea surface temperature using a physical deterministic method
