04.13.11: Vertical structure of BVF during SMLI¶
I study here the vertical structure of the Brunt-Vaisala frequency (BVF), mostly within features associated with a sea surface temperature (SST) filament and surface mixed layer instability (SMLI). Fig. 18 is typical of the results found. It shows several vertical profiles of BVF within such feature together with the spatially-averaged BVF plus and minus one standard deviation (red) and one single profile that is not associated with a SST gradient and a SMLI (black). Within a SMLI feature, the mixed layer is indeed overall restratified with the BVF profile being more uniform with depth than in the rest of the domain. Furthermore, although in the lower part of the mixed layer (50-100 m), the BVF within a SMLI feature is not always dissimilar from the background BVF, in the upper part (0-30 m), the BVF is always much larger than in the surrouding. The average profile within and outside a SST filament for a particular day and for January-March is shown in Fig. 42 as a synthesis of these results.
I do not see any qualitative difference between SMLIs in mid-January, the beginning and end of February suggesting that the shape of the vertical profile taken during SMLI is not too time-dependent.
I also study the evolution of a SMLI over several days as in between Feb. 21 and 26. At first, the large BVF values near the surface are constrained to the SST filaments but, on Feb. 24, this restratification seems to spread over a larger area around the filaments (compare Figs. 26 and 27, and Figs. 32 and 33). I do not know what causes this spreading of the restratification.
Jan. 15, 2010¶
SST gradient and BVF at 10-m¶
Figure 1: SST gradient (colors) and BVF at 10 m (white ci=0.1:0.1:1 1e-2 1/s) on Jan. 15, 2010. The red dash lines show the latitudes of the zonal sections of BVF shown in Fig. 2.
Zonal sections of BVF across SMLI features¶
Figure 2: Zonal sections of BVF at the locations shown by the red dash lines in Fig. 1. The black contour is the SST gradient at the same latitude.
Single profiles of BVF within SMLI features¶
Figure 3: Individual profiles of BVF within SMLI features along 24.75°N on Jan. 15, 2010. The red profiles in this figure and all similar ones corresponds to the spatially averaged BVF.
Figure 4: Individual profiles of BVF within SMLI features along 24.25°N on Jan. 15, 2010.
Figure 5: Individual profiles of BVF within SMLI features along 23.35°N on Jan. 15, 2010.
Figure 6: Individual profile of BVF within SMLI features along 23.00°N on Jan. 15, 2010.
Figure 7: Individual profiles of BVF within SMLI features along 22.50°N on Jan. 15, 2010.
Figure 8: Individual profiles of BVF within SMLI features along 22.15°N on Jan. 15, 2010.
Evolution of fields between Jan. 18 and 21, 2010¶
SST gradient and BVF at 10-m¶
Figure 9: Same as Fig. 1 but for Jan. 18, 2010.
Figure 10: Same as Fig. 1 but for Jan. 19, 2010.
Figure 11: Same as Fig. 1 but for Jan. 20, 2010.
Figure 12: Same as Fig. 1 but for Jan. 21, 2010.
Zonal section along 25.4°N of BVF across SMLI features¶
Figure 13: Zonal section of BVF along 24.5°N (red dash line in Fig. 9) for Jan. 18, 2010. The black contour is the SST gradient at the same latitude.
Figure 14: Same as Fig. 12 but for Jan. 19, 2010.
Figure 15: Same as Fig. 12 but for Jan. 20, 2010.
Figure 16: Same as Fig. 12 but for Jan. 21, 2010.
Single profiles of BVF within SMLI features¶
Figure 17: Individual profiles of BVF within SMLI features along 24.5°N on Jan. 18, 2010. On top of the spatially averaged BVF in dash red, I also plotted plus or minus one standard deviation to show that the profiles within a SMLI features are outliners.
Figure 18: Same as Fig. 18 but for Jan. 19, 2010. In the left panel, on top of the spatially- averaged BVF and plus and minus one standard deviation, is also plotted the individual profile at 202°E and 24.5°N to illustrate that profiles outside SMLI features are indeed quite different (consistent with the spatially averaged profile plotted in red).
Figure 19: Same as Fig. 18 but for Jan. 20, 2010.
Figure 20: Same as Fig. 18 but for Jan. 21, 2010.
Feb. 8, 2010¶
We explore here if the vertical structure changes toward Spring. The answer is no.
Figure 21: Same as Fig. 1 but for Feb. 8, 2010.
Figure 22: Same as Fig. 2 but for Feb. 8, 2010 and along 23.5°N
Figure 23: Same as Fig. 17 but for Feb. 8, 2010.
Evolution of fields between Feb. 21 and 26¶
Here I explore the full evolution of a SST filament and its re-stratification. In particular, this is an example where after a couple of days, the re-stratification becomes widespread (Feb. 25-26).
SST gradient and BVF at 10-m¶
Figure 24: Same as Fig. 1 but for Feb. 21, 2010.
Figure 25: Same as Fig. 1 but for Feb. 22, 2010.
Figure 26: Same as Fig. 1 but for Feb. 23, 2010.
Figure 27: Same as Fig. 1 but for Feb. 24, 2010.
Figure 28: Same as Fig. 1 but for Feb. 25, 2010.
Figure 29: Same as Fig. 1 but for Feb. 26, 2010.
Zonal section along 23.5°N of BVF across SMLI features¶
Figure 30: Same as Fig. 2 but for Feb. 21, 2010 and along 23.5°N.
Figure 31: Same as Fig. 2 but for Feb. 22 2010 and along 23.5°N.
Figure 32: Same as Fig. 2 but for Feb. 23, 2010 and along 23.5°N.
Figure 33: Same as Fig. 2 but for Feb. 24, 2010 and along 23.5°N.
Figure 34: Same as Fig. 2 but for Feb. 25, 2010 and along 23.5°N.
Figure 35: Same as Fig. 2 but for Feb. 26, 2010 and along 23.5°N.
Single profiles of BVF within a SMLI feature¶
Figure 36: Same as Fig. 17 but for Feb. 21, 2010.
Figure 37: Same as Fig. 17 but for Feb. 22, 2010.
Figure 38: Same as Fig. 17 but for Feb. 23, 2010.
Figure 39: Same as Fig. 17 but for Feb. 24, 2010.
Figure 40: Same as Fig. 17 but for Feb. 25, 2010.
Figure 41: Same as Fig. 17 but for Feb. 26, 2010.
Averaged vertical BVF profiles¶
Figure 42: Averaged vertical profile (plus and minus one standard deviation) of BVF inside and outside SST filaments: (a) for Jan. 15, 2010 and (b) for January-March 2010. The black line in (b) is the averaged profile for January-March from the ARGO floats. Calculated with vert_prof_BVF_inside_outside_SST_filament.m in RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/FSLE/analysis/HYCOM on the main disk.
computed with link_gradSST_N_ano.m in RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/FSLE/analysis/HYCOM/ on the central disk.