Forecasting Arctic Weather

Jonathan Pazol, high school AP science teacher in the Chicago area, onboard through the ARMADA Teachers Program

We’re still heading north at about 4.5 knots (nautical miles per hour), which, if you don’t know ships, is very slowly. It is still foggy and when the wind picks up, it is very cold.  Whose idea was it to go to the Arctic in August when it’s 90^◦ F in Chicago?

One of the other science activities that occurs on board is the collection of weather data.  Twice daily, at 6 a.m. and 6 p.m., members of the Navy launch a weather balloon off the flight deck.  AG1 (Aerographers Mate 1^st Class) Richard Lehmkuhl is in charge of the operations.  He is based in Norfolk, Virginia at the Naval Meteorology and Oceanographic Center, and in his 14 years of service has traveled the world.  Supervising AG1 is Navy Commander William Sommer from the Naval Oceanographic Office in Stennis, MS.  The Navy has formed a task force on climate change and is onboard Healy to work with and learn from the Coast Guard about Arctic surface operations and engineering, including navigation through the ice, polar communications, weather forecasting, and developing ice prediction systems.

AG1 Lehmkuhl is responsible for preparing the balloons. It’s more than a balloon, really — a battery-powered radiosonde, which is a small white box containing a transmitter, hangs suspended from the balloon.  The radiosonde contains sensors that collect information about wind direction, temperature, humidity, and air pressure, and a GPS transmitter that sends the data back to Healy.

In the helicopter hangar, the balloon is filled with helium, and then the radiosonde is attached. Then it is carried carefully to the edge of the flight deck and released. This can be a tricky operation because handling an almost five-foot diameter balloon in strong winds is difficult.  AG1 Lehmkuhl and Commander Sommer have to be careful that the equipment does not bang into the flight deck, and that the balloon flies off the ship without becoming entangled in any of the equipment on board.

The balloon will gather data as it travels up almost 6 kilometers (3.6 miles). At that point, the air pressure drops to about 50 millibars, causing the balloon to expand so much it pops.  If it doesn’t reach this altitude, the batteries will stop transmitting data after about 2 hours.

Once AG1 Lehmkuhl receives the data, he forwards it along so it can be used to provide weather forecasts for the Navy, Coast Guard, other Department of Defense groups, and NATO units.

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  The 2009 U.S.-Canada Arctic Continental Shelf Survey is underway from August 7 - September 16. Blog posts from sea are authored by the various agencies collaborating during the expedition. More information on the U.S. Extended Continental Shelf Project can be found at continentalshelf.gov.

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