HOT Shipboard ADCP Plots

As part of the hydrographic (WOCE) component of the Hawaii Ocean Timeseries ( HOT ) Program, a hull-mounted Acoustic Doppler Current Profiler (ADCP) is used to measure the velocity of upper-ocean currents below the ship, both when on station and underway. Velocity data for these cruises are available from the NODC Joint Archive for Shipboard ADCP (JASADCP.)

Links to vector and contour plots of the velocity data in png format are provided here for recent cruises. Selecting "View Overview Plots" or "View Contour Plots" will access an image map of the cruise track. Within this image map, selecting any of the labeled sections of the cruise will show a vector plot of upper ocean velocities from that section over topography, with temperatures color-coded on the vectors. Contour plots of both zonal and meridional velocity versus depth and the appropriate horizontal dimension are accessible from these vector plots.

Links to vector fields of the velocity data in jpg format are provided under the same menu.  Two figures are available: one showing current data collected on Station Aloha, one showing current data collected while underway.

Contour Plots

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Contour plots of upper-ocean currents will be shown in one of these two formats, depending on the date of the cruise. Both formats show the contours of both zonal, in the east-west direction, and meridional, in the north-south direction, velocities. These plots display shaded velocity values between +/- 100 cm s-1 typically, with divisions at +/- 10 cm s-1. Several cruises offer more than one set of data labeled by instrument, such as OS38BB. Most often, one of the data sets is from a broadband sensor and the other from a narrowband.

 

 

 

 

 

Vector Plots

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Vector plots will be shown in one of the two formats shown above, depending on the date of the cruise. Current vector data can be viewed by the whole cruise in a vector plot overview, or by labeled sections of the cruise track in separate plots. Water temperatures are color-coded on vectors in all plots. Positive and negative values are demarcated with a black line.

Vector Fields

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Vector fields will be shown in both of these two formats for available cruises.

Selecting “On Station” will provide the format on the left with two figures. One figure will show hourly averages at 20-m depth intervals while the ship was on station. The orientation of each stick gives the direction of the current: up is northward, to the right is eastward; the length gives the magnitude. The other figure under “On Station” will show the results of a least-squares fit of hourly averages to a mean, trend, semidiurnal and diurnal tides; the on-station time series were not long enough to fit an inertial cycle. In the first column, the arrow shows the mean current, the headless stick shows the sum of the mean plus the trend at the end of the station. For each harmonic, the current ellipse is shown in the first column. The orientation of the stick in the second column shows the direction of that harmonic component of the current at the beginning of the station, and the arrowhead at the end of the stick shows the direction of rotation of the current vector around the ellipse.


Selecting “In Transit” will provide the format on the right, with two vector fields: one for the transit to Station Aloha, one for the returning trip.  Velocity is shown as a function of depth and latitude, averaged in 10-minute time intervals.

 

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