Back Trajectories
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7-day Back trajectories to the ship have been calculated using the HYSPLIT
4 model. A description
of HYSPLIT can be found on the NOAA ARL web server. The
model runs were made using Global FNL grided data. Vertical motions
were calculated from the data vertical velocity (omega) field. Trajectories
were calculated at 6-hour intervals for trajectories arriving at the ship
location at altitudes of 500 (green), 2500 (red) and 5500 (black) meters
(nominally 950, 750 and 500 mbar). The numbers on each line are the
number of days (24 hour periods) back at that location from the arrvial
time at the ship location. The trajectories were plotted with FERRET
and the plots have been converted to gif files that are accessible from
the table below. The gif files are located on our ftp server (saga.pmel.noaa.gov/pub/indoex/data)
to facilitate downloading each entire set.
The trajectory data files are accessible as a tar-gzip (.tar.gz) data
file for each leg. The individual data files are named with the date
and hour in the file name followed by a 9,7 or 5 for the three heights.
After the first five header lines the data fields are: traj number, met
grid number, year, month, day, hour, minute, forecast hour, age of trajectory
(negative for back trajectory), lat,l ongt, height (meters), pressure (mbar).
A complete description of the data format can be found on page 21 of
the HYSPLIT_4
User's Guide, available in PDF format from the ARL server.
| Cruise Leg Plots |
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Plots for each cruise leg are available below. Each cruise leg
show the back trajectories (in blue) that arrived at the ship on 00Z each
day at 500m, 2500m (~750mb) and 5500m (~500m). The numbers in each
trajectory show where the air masses were on that number of days (24 hour
periods) back from arrival at the ship position. The cruise track
is shown in red. These plots do not show the vertical motion of the
back trajectories. The vertical motions are in the plots from the
table above
