Swath Data Representation in netCDF-CF Files

NetCDF is a self-describing binary file format widely adopted in the international geosciences community for data exchange. The Climate and Forecast (CF) metadata convention has been steadily gaining adoption in the netCDF data user community in the last 10 years. It had been developed primarily for gridded data as produced by the numerical weather and climate prediction computer simulations but observational data is increasingly being provided with the varying level of CF compliance. A large part of the observational data in geosciences is being generated by remote sensing instruments aboard satellites and, lately, also on aircraft or unmanned aerial vehicles. These type of data is commonly referred to as swath because of the geospatial extent they cover. Although such data has been collected for decades, and several attempts by the CF satellite community to agree on the conventional representation, there is no adopted standard in the CF convention yet. Given the volume, variety, and, since recently, the velocity of swath data, as well as the multitude of different types of collecting instruments, having a standardized representation will be a boon for data providers and CF-compliant software tool developers. Already very rich ecosystem of software for netCDF-CF data access and visualization could be further extended to include swath data. The on-going work towards specifying the representation of swath data will be presented in the context of the U.S. NSF EarthCube's project titled "Advancing netCDF-CF for the Geosciences Community". Examples of swath data file organization for both the radiometric (a.k.a. Level 1) and geophysical (a.k.a. Level 2) domains will be shown, as well as what types of swath data may be better represented by other CF convention constructs, e.g. discrete sampling geometries.