ertel_potential_vorticity
complete
Created: 5 Feb 2024
Proposer: Beate Geyer/Ronny Petrik
Proposed Date: 2020-03-11
Change Date: 5 Feb 2024, 4:17 p.m.
Term: ertel_potential_vorticity
Unit: K m2 kg-1 s-1
Unit ref: KMSS
AMIP: vorpot
GRIB:
The Ertel potential vorticity is the scalar product of the atmospheric absolute vorticity vector and the gradient of potential temperature. It is a conserved quantity in the absence of friction and heat sources [AMS Glossary, http://glossary.ametsoc.org/wiki/Ertel_potential_vorticity]. A frequently used simplification of the general Ertel potential vorticity considers the Earth rotation vector to have only a vertical component. Then, only the vertical contribution of the scalar product is calculated.
Change Date: 5 Feb 2024, 4:24 p.m.
Term: ertel_potential_vorticity
Unit: K m2 kg-1 s-1
Unit ref: KMSS
AMIP: vorpot
GRIB:
The Ertel potential vorticity is the scalar product of the atmospheric absolute vorticity vector and the gradient of potential temperature. It is a conserved quantity in the absence of friction and heat sources [AMS Glossary, http://glossary.ametsoc.org/wiki/Ertel_potential_vorticity]. A frequently used simplification of the general Ertel potential vorticity considers the Earth rotation vector to have only a vertical component. Then, only the vertical contribution of the scalar product is calculated. It is strongly recommended to include a units_metadata attribute.
Change Date: 9 Feb 2024, 3:45 p.m.
Term: ertel_potential_vorticity
Unit: K m2 kg-1 s-1
Unit ref: KMSS
AMIP: vorpot
GRIB:
The Ertel potential vorticity is the scalar product of the atmospheric absolute vorticity vector and the gradient of potential temperature. It is a conserved quantity in the absence of friction and heat sources [AMS Glossary, http://glossary.ametsoc.org/wiki/Ertel_potential_vorticity]. A frequently used simplification of the general Ertel potential vorticity considers the Earth rotation vector to have only a vertical component. Then, only the vertical contribution of the scalar product is calculated. In order to convert the units correctly, it is essential to know whether a temperature is on-scale or a difference. Therefore this standard strongly recommends that any variable whose units involve a temperature unit should also have a units_metadata attribute to make the distinction. units_metadata="temperature: difference" means that the temperature quantity is the difference between two temperatures, so the origin of the scale is irrelevant, and only the unit of measure matters. It is strongly recommended to include the attribute units_metadata="temperature: difference".
Change Date: 23 Feb 2024, 4:22 p.m.
Term: ertel_potential_vorticity
Unit: K m2 kg-1 s-1
Unit ref: KMSS
AMIP: vorpot
GRIB:
The Ertel potential vorticity is the scalar product of the atmospheric absolute vorticity vector and the gradient of potential temperature. It is a conserved quantity in the absence of friction and heat sources [AMS Glossary, http://glossary.ametsoc.org/wiki/Ertel_potential_vorticity]. A frequently used simplification of the general Ertel potential vorticity considers the Earth rotation vector to have only a vertical component. Then, only the vertical contribution of the scalar product is calculated. It is strongly recommended that a variable with this standard name should have the attribute units_metadata="temperature: difference", meaning that it refers to temperature differences and implying that the origin of the temperature scale is irrelevant, because it is essential to know whether a temperature is on-scale or a difference in order to convert the units correctly (cf. https://cfconventions.org/cf-conventions/cf-conventions.html#temperature-units).