"sea water sigma theta" . . "Climate and Forecast (CF)" . . "Sigma-theta of sea water is the potential density (i.e. the density when moved adiabatically to a reference pressure) of water having the same temperature and salinity, minus 1000 kg m-3. Note that sea water sigma is not the same quantity as the dimensionless ocean sigma coordinate (see Appendix D of the CF convention), for which there is another standard name." . . .