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01.03.11: First analysis of glider data

I have here a first look at the data of some of the gliders that have been deployed around Hawaii these recent years. The data and information on data can be found on the HOT website. The data are those from mission 4 of glider 147. The trajectory of the glider during that mission is a bow-tie pattern around station ALOHA during about 100 days in 2009 (Fig. 1).


Figure 1: Trajectory of glider 147 during its mission 4.

Fig. 2 shows the latitude of the glider versus the distance along track and the decimal days in 2009. Fig. 3 shows the potential density σ referenced at the surface. First, notice that the mesoscale event near day ... is associated with the glider having difficulty in keeping track of the bow-tie shape (Fig. 1). Second, the one mesoscale event during these 100 days is consistent with the WHOTS data as well as the analysis of Sakamoto et al. (2004) that report about 3-5 mesoscale events per year. Third, it seems also that some of the high-frequency signal in density may be due to the tides, consistent with Figs. 7a and 8a from this note. Unfortunately, we have concluded with Kelvin that it would take some time to remove these tides as there is enough resolution in time (about 5 points a day) to remove them properly; one idea would be to use the output of a tide model. Furthermore, the horizontal resolution is 6 km near the surface so that the data do not resolve well features less than 10-20 km. Thus, it might not be worthy enough for now to purse the analysis in order to gain information on submesoscale features near station ALOHA.


Figure 2: Latitude of the glider at the surface versus along-track distance and decimal days (of 2009).


Figure 3: Potential density σ versus along-track distance and decimal days (of 2009).

The data and the MATLAB routine that grids them can be found in RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/Gliders/data/sg147/mission4 on gyoji2.