 by Ned Rozell December 11, 2004
I am south of Osaka, Japan, riding seven miles above the ocean in a Boeing 747-400 jet, returning home from a family vacation in Vietnam. An aircraft-tracking program on the seatback in front of me is displaying the wonder of a device that can carry more than 500 people over the breadth of the Pacific Ocean. Powered by four huge engines, this plane weighs 399,000 pounds empty and is one-third heavier than that now, with more than 50,000 gallons of fuel in its tanks. During this trip, we will burn more than 300 pounds of fuel for each of the 524 passengers on board. The video display shows a map of Earth with a little plane making a red arc from Hong Kong to Los Angeles. The flat map suggests that a straight line across the Pacific is the short way, but the Earth is a sphere, and the pilots have chosen the most efficient route, one that will take us close to the Aleutian Islands, just south of Adak. Flying from the U.S. to Southeast Asia a few weeks ago, we passed over the volcanoes that make up the mid-Aleutians. Looking out the window into the darkness below, I thought of the Alaska Volcano Observatory in Fairbanks and Anchorage, which would alert the FAA of any ash clouds that might be floating about. The pilots decided to shorten the earlier flight; instead of going from Los Angeles to Hong Kong, they instead went to Seoul to refuel because the plane bucked headwinds the whole way. On this return trip from Hong Kong to L.A., the pilots are taking advantage of the jet stream. During winter months, the jet stream-a high-altitude river of flowing air-blows from west to east across the Pacific in the area we're flying, according to Dan Hancock, a meteorologist and forecaster with the National Weather Service in Fairbanks. A tailwind high over Tokyo registered onscreen at 192 miles per hour. "Not only does (the jet stream) save fuel, but the airlines don't have to carry as much (when flying with it instead of against it)," Hancock said. Somewhere above the ocean south of Adak and north of Hawaii, we cross the International Date Line. The date line zigzags through the unoccupied Pacific; geographers invented the line so the Eastern hemisphere would always be one day ahead of the Western hemisphere. With the date line, people traveling around the world do not lose or gain a day, as Magellan and his crew lost a day when they first sailed across the world. Before 1867, people considered Alaska part of the Eastern hemisphere because most reached it by ship from Russia. After the U.S. purchased Alaska, we pulled the date line west of the state; here, the dateline makes its most dramatic bend to keep Attu Island in the same hemisphere as New York. This ride on the jet stream allows us to cover most of the 7,000-mile trip from Hong Kong to Los Angeles in about 11 hours. As we cross over California's San Fernando Valley at 37,000 feet, the temperature is minus 80 degrees F, the same as Alaska's all time low recorded off the Dalton Highway in 1971. We're flying near the tropopause, the boundary between the troposphere and the atmosphere. The tropopause is the coldest place in the atmosphere, Hancock said. The air quickly warms to 62 above as the plane descends over Beverly Hills. Coming in for a landing, the plane slows to 130 miles per hour. As 16 tires bite the LAX tarmac with puffs of smoke, the amazing journey from Hong Kong to Los Angeles is over. But the travel day will soon continue, with two more incredible rides left-from Los Angeles to Seattle, and from Seattle back home to Fairbanks.
This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell ( nrozell@gi.alaska.edu ) is a science writer at the institute.
|