The CAMS Global Reanalysis contains a parameter (variable) called 'GEMS Total column ozone' and a parameter called 'Total column ozone'. What is the difference between the two?
Moreover, some CAMS Global datasets have two parameters (variables) called 'GEMS Ozone' and 'GEMS Total column ozone'. What is 'GEMS' in this context?
Is 'GEMS Ozone' different from the 'Ozone' in other ECMWF-produced data?
1 Comment
Antje Inness
CAMS data users please use the 'GEMS Ozone' and 'Total Column GEMS Ozone'.
The CAMS Global data is one of multiple datasets produced by ECMWF's IFS model. The IFS computes two types of ozone fields:
The name 'GEMS' refers to a predecessor project of CAMS.
What does 'Total Column' mean?
'Total column X' describes the total amount of X contained in the whole height of the atmosphere.
Background:
CAMS Global data differentiates horizontally by latitude and longitude, and vertically by levels. Think of the levels as multiple layers of atmosphere:
Some data however is not differentiated vertically, for example the 'Total column' parameters, or 2m temperature. These parameters by definition have a single value in the vertical. In the data archive such 2-dimensional data is classified as 'levtype=sfc'.
So 'GEMS Ozone' refers to GEMS Ozone at a particular model level or pressure level. The unit is kg/kg. 'Total Column GEMS Ozone' refers to GEMS Ozone integrated over the whole height of the atmosphere. The unit is kg/m**2.