Bug in HEMCO vertical regridding when using CAM

[lizziel]

What happened?

This is a bug report for HEMCO when using CAM, either CAM-chem or GEOS-Chem. The bug report is on the HEMCO GitHub but I am also posting here as an FYI for CAM users who use HEMCO for emissions.

From geoschem/HEMCO#315:

While investigating differences in CESM output when using HEMCO with different core counts I discovered a bug in vertical regridding using MESSy. The MESSy regridding scheme is used by models that input 3D atmospheric data on a different vertical grid than model grid, e.g. CESM and WRF-GC but not GEOS-Chem Classic or GCHP.

The collapse of the HEMCO grid 3D pressure sigma array into a 1D vector passed to the MESSy regridding scheme is at odds with how it is used within MESSy. Swapping two dimensions of the collapse (lat and lon) fixes the bug. This bug is not part of MESSy (written in 2002) but the interface to MESSy within HEMCO (written in 2014). It has been present since MESSy was originally implemented into HEMCO.

The bug causes the wrong horizontal layout of sigma pressure profiles during vertical regridding. In MPI models, the profiles within a given core are correct but are distributed across the regional grid of that core incorrectly.

What are the steps to reproduce the bug?

Read 3D emissions using HEMCO within CAM. This is done for both CAM-chem and GEOS-Chem configurations that use HEMCO, which are cases with suffix _HCO and _GC respectively.

What CAM tag were you using?

cam6_4_038

What machine were you running CAM on?

CISL machine (e.g. cheyenne)

What compiler were you using?

Intel

Path to a case directory, if applicable

No response

Will you be addressing this bug yourself?

Yes

Extra info

I have a bug fix at geoschem/HEMCO#314. It is going into HEMCO version 3.10.3 which I will include in the CAM PR for GEOS-Chem 14.5 and dependencies (#1247).