First decompostion into surface and interior mode in OFES

I show here the first decomposition into a surface and interior mode in OFES using Lapeyre (2009)’s code. The domain is from 210°E to 220°E and 35°N to 45°N and the snaphot is from Jan. 3, 2004. Several comments/questions:

1. I am surprised by how deep the cancellation of the surface and interior modes occurs in the relative vorticity (Figs. 1c and d; Fig. 3).
2. I do not know if it is normal that the surface component of the relative vorticity does not go to zero at depth (Fig. 3a).
3. I do not know if the surface and interior components of the potential density anomaly in Fig. 3b look normal. In particular, why don’t they behave like in the relative vorticity case? Why the surface component does not look more “exponentially” decaying?

Figure 1: Relative vorticity field at 240 m on Jan. 3, 2004 in OFES: (a) initial field, (b) modified after Rudnick (1996) to fulfill the thermal wind balance, (c) surface mode and (d) interior mode (sum of the barotropic and baroclinic modes).

Figure 2: Potential density anomaly at 240 m on Jan. 3, 2004 in OFES: (a) initial field (for this case only, anomaly is defined as the total potential density minus 1025.5), (b) modified after Rudnick (1996) to fulfill the thermal wind balance, (c) surface mode and (d) interior mode (sum of the barotropic and baroclinic modes).

Figure 3: Profiles of (a) relative vorticity and (b) potential density at one location in the domain.

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The matlab file is OFES_surf_normal_mode_decomp_210E_220E_35N_45N_20040103.mat computed with main_script_1.m in RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/Decomp_Surface_Normal_Modes/analysis/OFES_qscat_0_1_global_3day.