NCDC Introduces the VIIRS Climate Raw Data Record

False Color VIIRS C-RDR Image from January 28, 2014

This false color image depicts the atmospheric conditions over Florida on January 28 using NCDC’s VIIRS C-RDR.

NCDC is now providing online access to an easy-to-read version of the Visible Infrared Imaging Radiometer Suite (VIIRS) raw data through the VIIRS Climate Raw Data Record (C-RDR). So, what is a C-RDR? It’s a dataset that’s an intermediate (NOAA Level 1B) between a Raw Data Record (RDR), which contains unprocessed data frames from a satellite instrument, and a Sensor Data Record (SDR), which contains scientific quantities in the form of geo-located images. A C-RDR contains all of the data from an RDR, separated into individual raw measurement variables, accompanied by the information needed to produce SDRs from those raw measurement variables. C-RDRs allow users to produce their own records from satellite raw data without having to navigate complex RDR formats.

The VIIRS C-RDR, in particular, provides this intermediate data for an instrument onboard the Suomi National Polar-orbiting Partnership or SNPP satellite that was launched in October 2011. The VIIRS instrument is a scanning radiometer that collects visible and infrared radiometric measurements of the land, atmosphere, cryosphere, and oceans. Using VIIRS data, scientists can measure cloud and atmospheric particle properties, ocean color, sea and land surface temperature, ice motion and temperature, fires, and the amount of sunlight reflected from the Earth’s surface. VIIRS collects data in 22 spectral channels, from visible to longwave infrared, at two different spatial resolutions: 375 meters and 750 meters at locations directly below the satellite.

To ensure that the VIIRS C-RDR can be widely used and easily understood years down the road, NCDC is building it using the Network Common Data Form 4 or netCDF-4 format. NetCDF-4 is a community-based standard format that is readable by a wide variety of software packages and programming languages. Each different raw measurement type found in the VIIRS RDR is stored as a separate time-series array variable that is annotated with information about its origin, valid range, and fill values. The coefficients and look-up tables that can be used to convert the raw measurements into calibrated, geo-located scientific quantities are likewise stored as separate, annotated variables.

In addition to the raw satellite data and conversion information, the VIIRS C-RDR also contains a robust set of metadata elements that conform to the netCDF Climate and Forecast Metadata Conventions and the Unidata Attribute Convention for Dataset Discovery. The VIIRS C-RDR metadata ensure that the contents of the dataset can be tracked back to its original sources.

Visit the Visible Infrared Imaging Radiometer Suite Climate Raw Data Record page to learn more about and access this dataset. The development of the VIIRS C-RDR is part of NOAA’s Climate Data Record Program.