NOMAD: NASA bio-Optical Marine Algorithm Dataset

NOMAD is a publicly available, global, high quality in situ bio-optical data set for use in ocean color algorithm development and satellite data product validation activities. Data products include coincident observations of water-leaving radiances and chlorophyll a concentrations, along with relevant metadata, such as the date, time, and coordinates of data collection and binary processing flags. Inherent optical properties (IOPs; e.g., spectral absorption and backscattering coefficients) and aerosol optical thicknesses have been or will be included in the near future. The entire dataset is available via a digital text file provided below under Downloads. Additional background details, such as the motivation for creating such a data set, and a historical perspective of such data sets, are provided in the Werdell and Bailey reference listed below.

 

NOMAD is available for research uses only. It was compiled by the NASA Ocean Biology Processing Group at Goddard Space Flight Center, Maryland, USA, using generous data contributions from the ocean color research community. Source bio-optical data are available online via a suite of SeaBASS Search Engines. Optimum interpolation (OI) sea surface temperature (SST) data were acquired from the NOAA Climate Diagnostics Center. ETOPO2 water depths were acquired from the NOAA National Geophysical Data Center. NOMAD Data access and use are governed by the SeaBASS Data Access Policy. Please direct comments, questions, and identified outliers to the SeaBASS Administrator.

How to Use SeaBASS

The SeaBASS website contains several tools and options to help you find data files and products. The main options for aquiring data can be found under the "Get Data" drop-down in the main menu. The "File Search" is a good starting place as it allows you to perform custom searches for data files based on parameters such as particular measurement types (e.g. CTD, Chl, etc), investigator names, date, location and other options. Alternately, you can manually browse through files and folders using the "Archive" option, but it is generally recommended to use the File Search which simplifies downloading multiple files. The "Validation Search" allows you to search for and download post-processed datasets of successful match-ups between satellite sensors and field measurements. "NOMAD" will direct you to a specific subset of co-located measurements that were organized for algorithm development.
 
The "Lists" main menu option provides links to pages that contain alphabetically sorted lists of different types of information archived in SeaBASS. Visit those pages to view all contributing Investigators, Affiliations, Cruises and Experiment. These options can be useful for cross-referencing, for example, you can click on a particular cruise page to see a summary of all the associated data, or you can click on a particular investigator to see a sortable list of all the experiments and cruises they have contributed to.
 
The "Wiki" includes a number of articles and documents related to a variety of SeaBASS topics. You can browse through the articles or else use the search bar to look for articles that match particular keywords. For example, use the search to find an article containing a MATLAB SeaBASS file reader or a small dataset containing examples of hyperspectral Rrs measurements.
 
If you are interested in contributing data to SeaBASS, please visit the links under "Contribute Data" in the main menu for more information. You are also welcome to reach out with questions to the people listed under "Contact Us."

Standardized Fields and Units

Below is a table of the standard field names and associated units for use in submitting data to the SeaBASS bio-optical archive. The field names are NOT case sensitive. Use the search bar or the find function in your browser to search the table for words or patterns found in the field names, units or descriptions.

 

Special notes regarding wavelength-specific measurements: There are two different ways to indicate wavelengths in a SeaBASS file. If metadata such as date, location or depth vary within a file, then wavelength should be appended to the field name for every measurement combination. For example, downwelling irradiance measured at 412.3 nm would become 'Ed412.3' (listed along with any other Ed measurements, like Ed416.2, Ed419, etc), or aerosol optical thickness measured at 1020 nm would become 'AOT1020'. Alternately, if date, location and depth are assumed to be approximately constant for all measurements in the file, then use the field 'wavelength' to provide a column of the measured wavelengths and don't include them as part of the field names (this layout is commonly used for reporting spectrophotometric measurements).

 

To provide additional information about a field, for example, the standard deviation of the reported average of replicate measurements, refer to the tables of field name suffixes and modifiers below. These tables offer consistent patterns used to name certain types of measurements without having to hardcode a new name in SeaBASS. For example, standard deviations are explained in the table of suffixes, for example "chl_sd" or "ag510_sd". The table of modifiers includes ways to dynamically report special measurements, such as size fractionated data (see _###filt and _###prefilt). Please contact SeaBASS staff if you want to discuss adding new fields.

 

Notes on HPLC pigment field names

Data Format and Submission

To account for the continuous growth of the bio-optical data set and the wide variety of supported data types, the NASA Ocean Biology Processing Group felt it essential to develop efficient data ingestion and storage techniques. While this requires a specific data file format, the data protocols were designed to be as straightforward and effortless as possible on the part of the contributor, while still offering a useful format for internal efforts. The system was intended to meet the following conditions: simple data format, easily expandable and flexible enough to accommodate large data sets; global portability across multiple computer platforms; and web accessible data holdings with sufficient security to limit access to authorized users.

Metadata Headers

Standard metadata headers are required in every SeaBASS file. Select a header to view its definition, or if you are just getting started, scroll down just below the table of content to see an example header.

Data Access Policy and Citation

Access to the data archived within SeaBASS follows the NASA Earth Science Data and Information Policy. 

NASA's Earth Science program was established to use the advanced technology of NASA to understand and protect our home planet by using our view from space to study the Earth system and improve prediction of Earth system change. To meet this challenge, NASA promotes the full and open sharing of all data with the research and applications communities, private industry, academia, and the general public. The greater the availability of the data, the more quickly and effectively the user communities can utilize the information to address basic Earth science questions and provide the basis for developing innovative practical applications to benefit the general public. In this regard, all users incorporating SeaBASS data into their research are expected to acknowledge both their data sources (the original data contributors and SeaBASS) and NASA, and to abide by the Access Policy.

FCHECK

To assist with the standardization of SeaBASS data files, the SIMBIOS Project developed feedback software, named FCHECK, to evaluate the format of submitted data files. Since then, it has been rebuilt from the ground up by the SeaBASS development team to make it available to the end-users. Using FCHECK, contributors may evaluate the format of their SeaBASS-compatible files prior to submission.

Who We Are

High quality in situ measurements are prerequisite for satellite data product validation, algorithm development, and many climate-related inquiries. As such, the NASA Ocean Biology Processing Group (OBPG) maintains a local repository of in situ oceanographic and atmospheric data to support their regular scientific analyses. The SeaWiFS Project originally developed this system, SeaBASS, to catalog radiometric and phytoplankton pigment data used their calibration and validation activities. To facilitate the assembly of a global data set, SeaBASS was expanded with oceanographic and atmospheric data collected by participants in the SIMBIOS Program, under NASA Research Announcements NRA-96 and NRA-99, which has aided considerably in minimizing spatial bias and maximizing data acquisition rates. Archived data include measurements of apparent and inherent optical propertiesphytoplankton pigment concentrations, and other related oceanographic and atmospheric data, such as water temperature, salinity, stimulated fluorescence, and aerosol optical thickness. Data are collected using a number of different instrument packages, such as profilers, buoys, and hand-held instruments, and manufacturers on a variety of platforms, including ships and moorings.

Frequently Asked Questions

Questions we often get asked.

User Resources

The following section contains various examples for SeaBASS submitters and users.