Tracer initialization in hybrid vertical coordinates ( Z_INIT_REMAP_GENERAL)

[gustavo-marques]

MOM6 has the following option that is used during initialization:

Z_INIT_REMAP_GENERAL =     !   [Boolean] default = False
                           ! If false, only initializes to z* coordinates. If true, allows initialization
                           ! directly to general coordinates.

In all HYCOM1 runs done so far, we have used Z_INIT_REMAP_GENERAL = False, which only works for z* coordinates.
When Z_INIT_REMAP_GENERAL = True, regridding is done before T & S are remapped on the destination grid.

The table below compares the initial potential temperature profiles at a grid point in the Lab Sea for the cases with Z_INIT_REMAP_GENERAL = False (case A) and Z_INIT_REMAP_GENERAL = True (case B).

Level #	Case A, depth (m)	Case A, temp (C)	Case B, depth (m)	Case B, temp (C)	A - B, depth (m)	A - B, temp (C)
1	-1.25	3.67	-1.25	3.67	-0.00	0.00
2	-3.75	3.67	-3.75	3.67	-0.00	0.00
3	-6.25	3.65	-6.25	3.65	-0.00	0.00
4	-8.75	3.62	-8.75	3.62	-0.00	0.00
5	-11.25	3.62	-11.25	3.62	-0.00	0.00
6	-13.75	3.62	-13.75	3.62	-0.00	-0.00
7	-16.25	3.62	-16.25	3.62	-0.00	0.00
8	-18.75	3.62	-18.75	3.62	-0.00	0.00
9	-21.25	3.63	-21.25	3.63	-0.00	0.00
10	-23.75	3.63	-23.75	3.63	-0.00	0.00
11	-26.25	3.64	-26.25	3.64	-0.00	0.00
12	-28.75	3.64	-28.75	3.64	-0.00	0.00
13	-31.25	3.64	-31.25	3.64	-0.00	0.00
14	-33.75	3.64	-33.75	3.64	-0.00	0.00
15	-36.25	3.64	-36.25	3.64	-0.00	0.00
16	-38.75	3.64	-38.75	3.64	-0.00	0.00
17	-41.25	3.64	-41.25	3.64	-0.00	0.00
18	-43.75	3.63	-43.75	3.63	-0.00	0.00
19	-46.25	3.63	-46.25	3.63	-0.00	0.00
20	-48.75	3.64	-48.75	3.64	-0.00	0.00
21	-51.25	3.64	-51.25	3.64	-0.00	0.00
22	-53.75	3.64	-53.75	3.64	-0.00	0.00
23	-56.25	3.64	-56.25	3.64	-0.00	0.00
24	-58.75	3.65	-58.75	3.65	-0.00	0.00
25	-61.25	3.65	-61.25	3.65	-0.00	0.00
26	-63.75	3.65	-63.75	3.65	-0.00	-0.00
27	-66.25	3.64	-66.25	3.64	-0.00	0.00
28	-68.75	3.64	-68.75	3.64	-0.00	0.00
29	-71.25	3.64	-71.25	3.64	-0.00	0.00
30	-73.75	3.63	-73.75	3.63	-0.00	0.00
31	-76.25	3.62	-76.25	3.62	-0.00	0.00
32	-78.75	3.61	-78.75	3.61	-0.00	0.00
33	-81.25	3.61	-81.25	3.61	-0.00	0.00
34	-83.75	3.61	-83.75	3.61	-0.00	0.00
35	-86.25	3.61	-86.25	3.61	-0.00	0.00
36	-88.76	3.60	-88.76	3.60	-0.00	0.00
37	-91.30	3.60	-91.30	3.60	-0.00	-0.00
38	-93.87	3.60	-93.87	3.60	-0.00	0.00
39	-96.47	3.60	-96.47	3.60	-0.00	0.00
40	-99.09	3.60	-99.09	3.60	-0.00	0.00
41	-101.74	3.60	-101.74	3.60	-0.00	0.00
42	-104.43	3.60	-104.43	3.60	-0.00	0.00
43	-107.19	3.60	-107.19	3.60	-0.00	0.00
44	-110.15	3.60	-110.15	3.60	-0.00	0.00
45	-113.40	3.59	-113.40	3.59	-0.00	0.00
46	-117.03	3.59	-117.03	3.59	-0.00	0.00
47	-121.13	3.59	-121.13	3.59	-0.00	0.00
48	-125.83	3.59	-125.83	3.59	-0.00	0.00
49	-131.31	3.59	-131.31	3.59	-0.00	0.00
50	-137.78	3.59	-137.78	3.59	-0.00	-0.00
51	-348.41	3.83	-348.41	3.83	-0.00	0.00
52	-762.66	3.51	-762.66	3.51	-0.00	-0.00
53	-1176.95	3.33	-1176.95	3.32	-0.00	0.01
54	-1591.26	3.31	-1591.26	3.32	-0.00	-0.01
55	-1901.28	3.22	-1899.85	3.20	-1.43	0.02
56	-2082.41	3.09	-2082.47	3.10	0.07	-0.01
57	-2231.36	2.98	-2232.37	2.97	1.00	0.00
58	-2364.17	2.86	-2362.64	2.86	-1.53	0.00
59	-2482.95	2.74	-2483.52	2.75	0.56	-0.00
60	-2594.84	2.63	-2596.70	2.63	1.86	-0.00
61	-2705.88	2.50	-2705.89	2.50	0.00	0.01
62	-2817.12	2.38	-2805.59	2.39	-11.52	-0.01
63	-2923.27	2.24	-3057.27	2.03	134.00	0.21
64	-3021.34	2.10	-3313.03	1.57	291.70	0.53
65	-3113.22	1.95	-3361.52	1.05	248.29	0.90
66	-3201.07	1.79	-3361.52	1.05	160.45	0.74
67	-3288.33	1.62	-3361.52	1.05	73.19	0.57
68	-3346.92	1.50	-3361.52	1.05	14.60	0.45
69	-3361.52	1.47	-3361.52	1.05	-0.00	0.42
70	-3361.52	1.47	-3361.52	1.05	0.00	0.42
71	-3361.52	1.47	-3361.52	1.05	0.00	0.42
72	-3361.52	1.47	-3361.52	1.05	0.00	0.42
73	-3361.52	1.47	-3361.52	1.05	0.00	0.42
74	-3361.53	1.47	-3361.53	1.05	0.00	0.42
75	-3361.53	1.47	-3361.53	1.05	0.00	0.42

Large differences occur at depth. For example, the depth difference of layer index # 65 is 248.29 m, and the corresponding potential temperature difference is 0.9 C.

@mnlevy1981, @fobryan3, @klindsay28