Sigma coordinate system

The sigma coordinate system is a common coordinate system used in computational models for oceanography, meteorology and other fields where fluid dynamics are relevant. This coordinate system receives its name from the independent variable σ {displaystyle sigma } used to represent a scaled pressure level. The sigma coordinate system is a common coordinate system used in computational models for oceanography, meteorology and other fields where fluid dynamics are relevant. This coordinate system receives its name from the independent variable σ {displaystyle sigma } used to represent a scaled pressure level. Models that use a sigma coordinate system include the Princeton Ocean Model (POM), the COupled Hydrodynamical Ecological model for REgioNal Shelf seas (COHERENS), the ECMWF Integrated Forecast System, and various other numerical weather prediction models. Pressure at a height p {displaystyle p} may be scaled with the surface pressure p 0 {displaystyle p_{0}} , or less often with the pressure at the top of the defined domain p T {displaystyle p_{T}} . The sigma value at the scale reference is by definition 1: i.e., if surface-scaled, σ 0 = 1 {displaystyle sigma _{0}=1} .