Hi Jules,
I am sorry for the long silence. Meanwhile, I got some information from the CARRA team regarding the issue what you have indicated.
We think that the problem is properly understood now and the main conclusion is that the change of the grid is a metadata issue and not a problem related to the model.
This means that after 1st of July 2022 the CARRA data files contain wrong grid information and the grid before 1st of July 2022 is the right one. Therefore, if you wish to use the data through this date then you need to take into account the grid information prior to 1st if July.
We are going to describe this problem in the known issues part of the documentation in the following way:
Small changes in the dataset after 1st July 2022 - after the move of the CARRA production from the HPC in Reading to that in Bologna (1 July 2022 in the produced data set), there are two unintended changes to the dataset:
- The projection information in the output files changed. This impacts only the projection metadata in the output files; the physiographic and meteorological data are unaffected. Thus, the users experience a slight shift (typically corresponding to less than a km) in latitude/longitude (latlon) values provided for a grid point. The correct values are the ones used before 1st July 2022, so if you are comparing old and new data on a latlon point and require highest possible accuracy, you need to look at grid point values rather than latlon values to get a correct comparison and you should take the old latlon values as the correct ones. More precisely the change concerns the value of a parameter called “shapeOfTheEarth” which was set to 6 before, and has changed to 0 after. This corresponds to assuming a spherical Earth with Earth radius of 6 371 229.0 m before, and 6 367 470.0 m after. The shift of location for the grid points varies, and is typically less than a km.
- The “typeOfLevel” entry for the parameter 228141 (Snow depth water equivalent) changed from “surface” to “heightAboveGround”.
I hope, it helps, sorry for the problem and thanks for pointing to it.
Best regards
Andras