Direction of the vertical velocity: Difference between revisions

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A data file may start before an instrument is even in the water. Vertical profilers are often held near the surface before they are released. During such a time, the vertical velocity may fluctuate significantly around a mean of zero, but the data cannot be used for dissipation rate estimation. A data file may also contain many profiles that are interrupted by useless data, such as the retrieval of a tethered profiler back to the surface. The direction of profiling can be used to eliminate such segments.
The direction of the vertical velocity of the profiler is important.
Most vertical profilers collect data while they are '''descending''', and the data collected while '''ascending''' is useless because the probes are in the wake of the instrument and there is no oncoming flow over the shear probes.  
However, some profilers are designed to collect data while they are ascending and the data collected during it descent is not useable.
'''Gliders can produce meaningful data while descending and ascending'''.
So, it is important to know what type of instrument was used to collect your shear-probe data, so that you select data from when it was travelling in the appropriate direction.  
 
 
 
 
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[[Category:Shear probes]]

Latest revision as of 16:07, 6 June 2024

The direction of the vertical velocity of the profiler is important. Most vertical profilers collect data while they are descending, and the data collected while ascending is useless because the probes are in the wake of the instrument and there is no oncoming flow over the shear probes. However, some profilers are designed to collect data while they are ascending and the data collected during it descent is not useable. Gliders can produce meaningful data while descending and ascending. So, it is important to know what type of instrument was used to collect your shear-probe data, so that you select data from when it was travelling in the appropriate direction.




return to Flow chart for shear probes