Sunday, November 6, 2011

Meteorological and sea surface data

Peter here to talk a bit about the meteorological and sea surface data that we get on a daily or more frequent basis that helps us make decisions and plan our scientific activities. The L.M. Gould has several real-time displays of the air and sea surface water properties along with navigation information. The Data Acquisition System (DAS) provides this information. The information is displayed on monitors in the labs and other public spaces on the ship (see Fig. 1) and also on the ship’s intranet website. A recent display shows, for example, that the wind speed from both the port and starboard anemometers was about 16 kts out of the northeast, the air temperature was about 1 degree C (33 degrees F), and the sea surface temperature was -0.9 C.

Fig 1.
When this image was taken on the morning of Nov. 6th, the Gould was sitting close to the Cape Shirreff camp site on Livingston Island, waiting for the fog to lift so that the setup of the camp for the summer season could begin.  Much higher winds and seas on Nov. 5th prevented the movement of gear, food, and other supplies to be ferried by zodiac boat from the Gould to the shore at the foot of the camp. With the winds in a safe working range and the seas diminishing, what was needed was for the camp to be visible from the ship, but fog hampered the start of the operation. The navigation information on the DAS display provided the ship’s position (latitude and longitude), speed, course, yearday, and time.

Fig. 2.
Also available on the website are isobar images of sea level pressure (millibars), sea ice images, wind charts, wave height charts, and weather forecasts. The wind charts are especially useful because they provide not only the current status, but also forecasts for 24 or 48 hrs ahead of the current day. See the chart (Fig. 2) showing the region from the southern part of South America on the right to the Western Antarctic Peninsula on the left. The red dot just north of Livingston Island marks the location of the Gould. This chart is a 24 hr forecast for the wind strength and direction for Nov. 7th.  The bars on the stick flags provide a measure of wind speed. One full flag bar is 10 kts and a half-bar is 5 kts. Thus 2 ½ is 25 kts.  Wind direction is indicated by the stick with flow towards the stick base away from the flag.  While working conditions were good on Nov. 6th, with winds around 15 kts, on Nov. 7th the winds will be much stronger (around 30 kts) and blowing from west to east at Cape Shirreff. 

Once the camp at Cape Sherriff is setup, the Gould will begin the trek to Palmer Station to offload more gear, supplies, and people. On the way, we will do a first station where we will take an IKMT trawl sample, do a CTD cast, and take a MOCNESS tow. We will use the wind chart above to help us determine which of the station locations we have chosen to sample at to do first. It will have to be protected from the high winds and seas.

-- Peter Wiebe (Woods Hole Oceanographic Institution)

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