TOULOUSE, France — Weather forecast accuracy in the last 30 years has increased dramatically, especially in the Southern Hemisphere, with much of the improvement due to meteorological satellites in both geostationary and polar low Earth orbit, according to European weather specialists.
A three-day forecast in the early 1980s was likely to be accurate only 85 percent of the time in the Northern Hemisphere, where population density and economic development mean terrestrial meteorological tools including balloons are launched on a daily basis in many regions. That accuracy figure has climbed steadily to 98 percent today, said Florence Rabier, a member of the research team for Meteo France, the French meteorological agency.
The improvement of forecasts in the Southern Hemisphere, where the huge expanses of ocean and less-developed regions including Africa mean balloon coverage is less dense, has been even more dramatic, Rabier said here Nov. 7 during a briefing on Europe’s Metop polar-orbiting weather satellites.
A three-day forecast for the Southern Hemisphere in the early 1980s was only 70-75 percent accurate, Rabier said. Since then — largely because of increased satellite coverage, especially with polar-orbiting spacecraft — the accuracy of predictions for the Southern Hemisphere has climbed to where it is nearly equal to that of forecasts in the Northern Hemisphere.
“There is really not much difference now between the Northern and Southern hemispheres,” Rabier said, adding that given the difficulty and expense of assuring regular balloon launches in ocean regions and in Africa, the Southern Hemisphere’s improvement is a direct consequence of satellite coverage.
With public budgets in Europe and the United States under pressure, users of meteorological satellite data are emerging into the public domain to defend the investments satellite systems that they say save billions of dollars or euros a year — not to speak of lives — because of advance warnings of floods or storms.
The 26-nation Eumetsat organization of Darmstadt, Germany, which operates Europe’s Metop system as well as the Meteosat series of geostationary orbiting satellites, has assembled figures showing 4 billion euros ($5.4 billion) in damage caused annually by floods in Europe.
Some 800 million euros a year in damages are averted because of accurate short-term weather forecasts allowing communities to prepare for the flooding. Eumetsat has calculated that the arrival of the Metop satellites — the first was launched in 2006 — is responsible for a quarter of those savings, or 200 million euros a year. The organization has assembled similar figures for storms in Europe.
The Metop program consists of three identical satellites launched at six-year intervals between 2006 and 2018, with operations running until 2023. The 19-nation European Space Agency (ESA) invested about 1.5 billion euros in Metop when the investment is converted into 2011 economic conditions. Eumetsat’s share was 2.4 billion euros.
Metop includes U.S.-provided instruments as part of an arrangement between Eumetsat and the U.S. National Oceanic and Atmospheric Administration (NOAA), which has just launched the first of its next-generation polar-orbiting satellites, called NPP. Crossing the equator at different times of the day to provide maximum meteorological forecast benefit, the combined U.S. and European systems are called the Joint Polar System.
Eumetsat Director-General Alain Ratier, addressing the briefing here, said the value of the U.S. and European systems together is far greater than either system alone in terms of weather forecast accuracy. “One plus one is greater than two,” Ratier said.
Because of NOAA’s current budget problems and the European government budget crisis, Ratier said weather experts need to demonstrate the value of satellites to political leaders and lay citizens who otherwise might not draw the connection between weather forecasting and satellite investment.
NOAA officials have already begun warning that by the middle of this decade gaps in satellite coverage will develop that will have a direct impact on weather forecasting unless investments are made now in assuring the continuity of satellite coverage.
The Metop satellites are built by Astrium Satellites, whose biggest satellite production facility is located here. Astrium officials said one of the biggest challenges in the program was assuring that the two Metop satellites built near the same time as the first one launched in 2006 will not degrade during the many years of storage.
Bruno Le Stradic, director of Earth observation at Astrium Satellites, said Metop B, to be launched in May aboard a Soyuz rocket operated from Russia’s Baikonur Cosmodrome in Kazakhstan, was stored in three separate locations since 2005 before being assembled for testing to prepare for the launch. Metop C, to be launched in 2018, will spend an even longer period in storage.