masscello rho_0 rhozero; thkcello rounding

[chrisdane]

Hi

As far as I understand, thkcello and hence masscello are currently (feat/cmip7-awiesm3-veg-hr, 465afa4) derived from

awi-esm3-veg-hr-variables/core_ocean/cmip7_awiesm3-veg-hr_ocean.yaml
  - name: thkcello_fx
    inputs:
        pattern: mesh.nc

  - name: masscello_fx
    reference_density: 1025.0


examples/custom_steps.py
def compute_thkcello_fx(data, rule):
        thickness = _layer_thickness_from_bnds(data["depth_bnds"].values)

def _layer_thickness_from_bnds(bnds):
    thickness = np.diff(bnds)

First, appendix G3 of Griffies et al. 2016 reports 1035 kg m-3 as a boussinesq reference density, not 1025 kg m-3.

Second, appendix H4 defines

dz measures the distance (in metres) between surfaces of constant vertical coordinates.

, i.e. the question is now the bounds of the vertical levels are defined.

The dars2 example above uses

ncdump -v depth,depth_bnds /work/ab0246/a270092/input/fesom2/dars2/mesh.nc

 depth = 2.5, 7.5, 15, 25, 35, 45, 55, 65, 75, 85, 95, 107.5, 122.5, 137.5, 
    152.5, 170, 190, 212.5, 237.5, 262.5, 287.5, 312.5, 337.5, 362.5, 387.5, 
    425, 475, 525, 575, 625, 675, 750, 850, 970, 1110, 1255, 1415, 1600, 
    1810, 2035, 2275, 2525, 2775, 3025, 3275, 3525, 3775, 4025, 4275, 4525, 
    4775, 5025, 5275, 5525, 5825, 6125, 3160 ;

 depth_bnds = -0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 115, 130, 145, 
    160, 180, 200, 225, 250, 275, 300, 325, 350, 375, 400, 450, 500, 550, 
    600, 650, 700, 800, 900, 1040, 1180, 1330, 1500, 1700, 1920, 2150, 2400, 
    2650, 2900, 3150, 3400, 3650, 3900, 4150, 4400, 4650, 4900, 5150, 5400, 
    5650, 6000, 6250, 70 ; 

(The last values of depth and depth_bnds are obviously wrong which seems to be a bug in the python version of spherlab.)

depth_bnds are the 1st nlev values from aux3d.out:
https://github.com/FESOM/spheRlab/blob/0424b811a911de58215bdbfda7b5398b71cde9e7/R/sl.grid.readFESOM.R#L104

Somehow, thickness = np.diff(bnds) seems to introduce some rounding issue:

ncks -F -d time,1,1 -d nod2,78802,78802 /scratch/a/a270092/pycmor_hr/cli37_extraatm_512g_filecache_vec/cmorized/core_ocean/cmorized/thkcello_tavg-ol-hxy-sea_mon_glb_gn_AWI-ESM-3_picontrol_r1i1p1f1_158701-158712.nc

The above output is the last column:

no | depth | depth_bnds | thkcello        
-- | ----- | ---------- | ----------------
1  | 2.5   | 0          | 5               
2  | 7.5   | 5          | 5.0000147819519 
3  | 15    | 10         | 10              
4  | 25    | 20         | 10.0000295639038
5  | 35    | 30         | 10              
6  | 45    | 40         | 10.0000295639038
7  | 55    | 50         | 10              
8  | 65    | 60         | 10.0000295639038
9  | 75    | 70         | 10              
10 | 85    | 80         | 10.0000295639038
11 | 95    | 90         | 10              
12 | 107.5 | 100        | 15.0000295639038
13 | 122.5 | 115        | 15              
14 | 137.5 | 130        | 15.0000295639038
15 | 152.5 | 145        | 15              
16 | 170   | 160        | 20.0000591278076
17 | 190   | 180        | 20              
18 | 212.5 | 200        | 25.0000591278076
19 | 237.5 | 225        | 25              
20 | 262.5 | 250        | 25.0000591278076
21 | 287.5 | 275        | 25              
22 | 312.5 | 300        | 25.0000591278076
23 | 337.5 | 325        | 25              
24 | 362.5 | 350        | 25.0000591278076
25 | 387.5 | 375        | 25              
26 | 425   | 400        | 50.0001182556152
27 | 475   | 450        | 50              
28 | 525   | 500        | 50.0001182556152
29 | 575   | 550        | 50              
30 | 625   | 600        | 50.0001182556152
31 | 675   | 650        | 50              
32 | 750   | 700        | 100.00023651123 
33 | 850   | 800        | 100             
34 | 970   | 900        | 140.000473022461
35 | 1110  | 1040       | 140             
36 | 1255  | 1180       | 150.000473022461
37 | 1415  | 1330       | 170             
38 | 1600  | 1500       | 200.000473022461
39 | 1810  | 1700       | 220             
40 | 2035  | 1920       | 230.000473022461
41 | 2275  | 2150       | 250             
42 | 2525  | 2400       | 250.000473022461
43 | 2775  | 2650       | 250             
44 | 3025  | 2900       | 250.000473022461
45 | 3275  | 3150       | 250             
46 | 3525  | 3400       | 250.000473022461
47 | 3775  | 3650       | 250             
48 | 4025  | 3900       | 250.000473022461
49 | 4275  | 4150       | 250             
50 | 4525  | 4400       | 250.000473022461
51 | 4775  | 4650       | 250             
52 | 5025  | 4900       | 250.000473022461
53 | 5275  | 5150       | 250             
54 | 5525  | 5400       | 250.000473022461
55 | 5825  | 5650       | 350             
56 | 6125  | 6000       | 250.000473022461
   |       | 6250       |                 

Cheers,
Chris