quarta-feira, 20 de janeiro de 2016

Fleet of Sensors Heads into the Heart of El Niño

Climate scientists this week began a research blitz to study El Niño, the climate trouble-maker that disrupts weather around much of the globe. For the next two months, US researchers will use specially outfitted planes, a research ship and hundreds of weather balloons to monitor the region in the tropical Pacific Ocean where El Niño forms. Ultimately, the scientists say, their measurements could help to improve weather forecasts and unlock secrets about how powerful El Niño events evolve.
“We’re seeing an extreme climate state—one that we know tends to produce extreme climate conditions worldwide,” says Randall Dole, lead scientist on the project and a meteorologist with the US National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado. “We’re going right into the heart of that.”
The El Niño warming that has bloomed in the equatorial Pacific is one of the strongest on record, with ocean temperatures reaching as much as 3 °C above normal across the central and eastern parts of the ocean basin. That heat triggers convection in the atmosphere that re-routes major air currents, often sending strong storms towards California while drying out parts of southeast Asia, Australia and eastern South America. But researchers have few data on the atmospheric changes in the core of the El Niño region because the remote equatorial Pacific is essentially a meteorological black hole.
To begin the campaign, NOAA sent its Gulfstream-IV research jet to Hawaii, its base for about 20 flights south towards the Equator. Using onboard remote-sensing equipment and dropsondes—packages of instruments released from the plane—the team will measure winds, temperature, air pressure and moisture from a height of 12–14 kilometres down to the ocean surface (see ‘Hunting Godzilla’).
NATURE NEWS JANUARY 20 DOI:10.1038/529267A
In February, NASA’s unmanned Global Hawk aircraft will join the effort, prowling the eastern part of the Pacific in 4 flights lasting up to 24 hours each. At the same time, NOAA will launch instrument packages on weather balloons from Kiritimati, or Christmas Island, an atoll near the Equator in the heart of the region in which El Niño forms. And researchers will also release balloon-borne instruments from the NOAA research ship Ronald H. Brown as it conducts a previously planned cruise in the central Pacific.
Seizing the moment
The idea for the roughly US$3-million campaign developed as the warming gathered strength last year; Dole and his colleagues realized that they had a rare opportunity to collect the first detailed atmospheric measurements of a monster El Niño. NOAA scrambled to pull the campaign together in a few months—rather than the usual two to three years that it usually takes to mount a major meteorological field project.
The agency had some resources to spare: thanks to the way El Niño alters conditions over the Atlantic, there were relatively few tropical storms there last year. That meant that NOAA did not use all of the flying time budgeted for the Gulfstream-IV hurricane hunter, which flies over storms to collect data useful for forecasters. The quiet hurricane season also meant that the Global Hawk did not make as many research flights in the Atlantic as planned last year.
“We’ve done this largely by reallocating,” says Dole. “We’re working within the existing budget and shifting everything around.”
Alexey Fedorov, a climate modeller at Yale University in New Haven, Connecticut, says that because extreme El Niño events are so rare, “it is important to use any opportunity to gather as much data as possible”. Fedorov, who is not part of the campaign, says that researchers lack a full understanding of the way that strong El Niños evolve and alter global weather patterns.
The information gathered over the next few months could yield long-term dividends for El Niño researchers, says Dole. “If we do this well, it will impact our community for the next 10 or 20 years.”
But the project’s immediate goal is to help forecasters to understand how the unruly atmosphere will affect weather now. By gathering direct measurements from this data-poor zone, leaders of the NOAA campaign hope to improve weather forecasts and allow researchers to test weather models to better understand the source of errors in those models.
Data from the Global Hawk will also aid meteorologists tracking El Niño-spawned storms as they barrel down on the western United States, says Dole. Over the past few weeks, coastal California has been pummelled by such storms, and more are expected. As part of the El Niño campaign, NOAA has installed a scanning X-band radar south of San Francisco Bay that will measure precipitation in approaching storms.
The agency will upload data from the field campaign to the World Meteorological Organization’s Global Telecommunications System, so that forecasters around the globe can access the observations. Peter Bauer, an atmospheric modeller at the European Centre for Medium-Range Weather Forecasts in Reading, UK, says that he plans to feed the data into model experiments with the aim of improving forecasts for Europe. The campaign, he says, “has potentially a very big impact”

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