The algorithms for retrieval of ocean color radiometry and sea surface temperature from satellite radiometry make use of a number of ancillary data sources, in addition to the sensor observed radiometry. Examples include meteorological data (windspeed, surface pressure, relative humidity) and concentrations of atmospheric gases (water vapor, ozone, nitrogen dioxide). In general, the optimal ancillary data is not available when the satellite radiometry is first acquired, so the NASA OBPG processing uses best available ancillary data sources for processing satellite data in near realtime, and then reprocesses the data about one week later to refine the products using the optimal ancillary data.
The primary sources of ancillary data used in NASA ocean color and SST processing are described here. When a primary source is not available, a back-up source is used. If the primary nor it's backup source is available, the secondary source is used.
Dynamic Sources
Toggle Accordion Title
Meterological
Primary GMAO MERRA2 Meteorological data:
Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) meterological data from NASA/Goddard's Global Modeling and Assimilation Office (GMAO)
post-processing notes: Various GEOS 2-D datasets are aggregated in order to generate the aforementioned OBPG product.
GMAO Forward Processing for Instrument Teams Meteorological data:
The FP-IT stream generates only assimilation products. FP-IT processing uses a "semi-frozen" Goddard Earth Observing System (GEOS) system to ensure long-term continuity and reproducibility. FP-IT products serve primarily the NASA EOS Instrument Teams who require stable products over a long period of time. Reprocessing of historical periods using the FP-IT system is conducted as needed in coordination with Instrument Teams.
The real time ozone data is derived from TOMS-like instrument data. Until Feb 2023, we used data from the AURA OMI instrument (AURAOMI), and prior to 2005, we used data from the Nimbus-7 (N7TOMS) and Earth Probe (EPTOMS) TOMS instruments. We apply a normalization to all the ozone data based on a de-trended merged SBUV record.
filename composition: NYYYYDDD00_O3_III_24h.hdf where YYYY=year, DDD=day-of-year, III= instrument, N7TOMS, EPTOMS or AURAOMI. (e.g. N201918800_O3_AURAOMI_24h.hdf)
Toggle Accordion Title
Surface Properties
Primary GHRSST Level 4 CMC Global Foundation Sea Surface Temperature:
This dataset merges infrared satellite SST at varying points in the time series from the (A)TSR series of radiometers from ERS-1, ERS-2 and Envisat, AVHRR from NOAA-16,17,18,19 and METOP-A, and microwave data from TMI, AMSR-E and Windsat in conjunction with in situ observations of SST from drifting buoys and ships from the ICOADS program. It uses the previous days analysis as the background field for the statistical interpolation used to assimilate the satellite and in situ observations. This dataset adheres to the GHRSST Data Processing Specification (GDS) version 2 format specifications.
We currently use a monthly climatology of NO2 based on the Aura OMI data. Currently, only the climatology is used in ocean color processing. The climatology is created from the daily OMI NO2 files. The daily files of NO2, as it comes from the DAAC has many gaps and only has good coverage when averaged into monthly files.
source: GES DISC
spatial resolution: 0.25° x 0.25° (1440 x 720 grid)
Water mask in geographic projection for the Contiguous United States, covering latitudes 23 to 55 degrees and longitudes -127 to -65 degrees. Most values were aggregated to 2-arcsec resolution from Shuttle Radar Topography Mission 1-arcsecond data; missing or erroneous values were corrected with data from other sources.
Global Land/Water flags in geographic projection, with water classified into one of 7 types. Original 15-arcsecond files aggregated into a single global file, using 30-arcsec values where higher resolution is unavailable. Used only for VIIRS geolocation processing.
MODIS/TERRA+Aqua BRDF/ land Albedo Gap-Filled Snow-Free 8-Day climatology, L3 Global 30ArcSec CMG, 2001-2017 for bands at 0.659, 0.858, 1.24, 1.64, and 2.13 microns.
Mixed layer depth is a type of atmospheric boundary layer characterized by vigorous turbulence tending to stir and uniformly mix, primarily in the vertical, quantities such as conservative tracer concentrations, potential temperature, and momentum or wind speed.
Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., et al. (2011), The ERA-Interim reanalysis configuration and performance of the data assimilation system. Q.J.R. Meteorol. Soc., 137: 553-597. doi: 10.1002/qj.828
Derber, J.C., D.F. Parrish, and S.J. Lord, 1991:L The new global operational analysis system at the National Meteorological Center. Wea. Froecasting, 6, 538-547.
Kanamitsu, M., W. Ebisuzaki, J Woollen, S.-K. Yang, J. J. Hnilo, M. Fiorino, and G. L. Potter, 2002: NCEP-DOE AMIP-II Reanalysis (R-2), Bull. Amer. Meteor. Soc., 83, 1631-1643.
Kou, L., D. Labrie, P. Chylek, 1993, Refractive indices of water and ice in the 0.65-2.5 m spectral range, Appl. Opt.,32, 3531-3540.
Pope, R. M. and E. S. Fry, 1997, Absorption spectrum (380-700 nm) of pure water. II. Integrating cavity measurements, Appl. Opt.,36, 8710-8723.
