NOAA Teacher at Sea Rebecca Kimport
NOAA Ship Oscar Dyson
June 30, 2010 – July 19, 2010
Mission: Summer Pollock survey
Geograpical Area:Bering Sea, Alaska
Date: July 10, 2010
Weather Weather Everywhere!
Weather Data from the Bridge
Latitude: 59.12 N
Longitude: 174.02 W
Cloud Cover: 5/8
Wind: 17 knots
Air Temperature: 8° C/ 46° F
Water Temperature: 7° C/ 45° F
Barometric Pressure: 1006.9 mb
Aside from weather helping you decide what to wear for the day, weather is critical on board a research vessel. Each hour the bridge collects the same data that is then input into the AMVER Sea system and sent to NOAA Weather. Some of the information included is: time, latitude, longitude, cloud cover, air and water temperatures, wind, barometric pressure, visibility, and swell height. This helps determine our exact location (check out NOAA Shiptracker for more information) as well as the weather at sea and also weather inland. It is not uncommon for marine weather systems to move inland. This information also helps us understand long term climate changes, precipitation, and ocean currents.
Exactly where are we?
The latitude and longitude help determine the position of the ship and the time is recorded to understand how the ship is moving and in what direction. This allows the scientists to follow the transects to conduct their research. If I told you at 1500 hours (3pm) our mark was 58.00N and 171.48W, you would be able to pinpoint our location on a map. Our latitude so far on this trip (July 7th) has been in the range of 56.12N-58.69N depending on the transect that we are following and the longitudes’ range is between 170.01W-171.48W.
It’s cloudy again?
It tends to be quite cloudy and foggy here in the Bering Sea and cloud cover is measured in eighths of the sky. For example, on July 6th the cloud cover at 1500 hours was 7/8 which means that 87.5% of the sky was filled with clouds. Cloud type and location can help predict the type of weather. The majority of our days have been 8/8 or 100% cloud cover with stratus clouds and lots of moisture in the air.
This is definitely not the heat wave they are getting back home!
This brings us to air temperature and wind. The temperature is always taken on the windward side of the ship because this is the side of the ship in the stream of air fresh from the sea that has not been in contact with or passed over the ship. There are two types of thermometers in each case on the deck in front of the bridge. The dry bulb measures the air temperature and the wet bulb has a muslin wick which absorbs heat from the thermometer. The temperature difference between the two, called the depression of the wet bulb, can help determine what the percent humidity is by referring to the humidity chart. Wind can affect these readings which is why there are thermometers on either side of the bridge. The wind direction is logged as the same direction from which the sea waves are coming. Average temperature through July 7th for Leg II has been 5.680C/420F with winds averaging 10.29 knots. The weather mentioned has been the trend for Leg II; however, this could be changing by the end of the week…stay tuned!
Hold on tight!
It’s July 10 and we are still waiting for the big seas to hit us. (not that I am complaining about calm weather!) The swells have gotten larger and the wind definitely picked up yesterday. The strongest wind recorded yesterday was 26 knots while on my shift. There is still a chance for NW sustained winds up to 25 knots and 10 foot seas before the weekend is up. Part of the reason for calmer seas yesterday was that we were so far north and the low pressure system was to the south of us. It was actually the farthest north I have ever been, and we will go even farther north before it is time to head back to Dutch Harbor.
Word of the day
barometric pressure: the downward force that the atmosphere exerts per unit of a certain area.
swell height: measure of wind waves generated locally; vertical distance between trough and crest
muslin wick: plain woven cotton fabric
humidity: the amount of moisture in the air
gale force winds: strong winds between 28-47 knots