They scan the globe in pole-to-pole loops and feed important information into models for forecasting the most dangerous storms. But later this decade, a gap in these polar-orbiting satellites is foreseen. Could that prove costly for weather predictions?

The European Centre for Medium-Range Forecasting (ECMWF), widely praised for the superior predictions of its model during superstorm Sandy, conducted an interesting experiment: how would its 5-day model simulation for the devastating storm performed without any polar-orbiting satellite data?

The answer is astonishing: Rather than correctly simulating Sandy’s hard left turn into northern mid-Atlantic coast, an ECMWF model run without polar satellite data would have kept Sandy harmlessly out to sea.

(ECMWF/Tony McNally)

This experiment suggests the long lead time provided by the ECMWF - so critical for preparations - would have been compromised without any polar-orbiting satellites.

ECMWF researcher Tony McNally stressed this experiment represented just one case of the potential impact of satellite data on forecasts and was not conclusive.

The limitations of the experiment notwithstanding, it clearly raises questions about the impact of a possible future gap in polar-orbiting satellite coverage.

The prospect of a gap has arisen from delays in NOAA’s Joint Polar Satellite System (JPSS), due to mismanagement, billions of dollars in cost overruns, and technical development challenges according to Climate Central’s Andrew Freedman.

“This has pushed back the launch date of the next polar-orbiting satellite to 2017 at the earliest, which is past the design lifetime of the youngest polar-orbiting satellite currently in orbit,” Freedman writes.

But the potential “gap” in polar satellite coverage expected is just that - a gap, stressed Capital Weather Gang’s Steve Tracton, an expert in numerical weather prediction. Data would still stream in from other satellites. Since the ECMWF excluded all polar-orbiting satellite data in its experiment, it cannot be seen as a realistic representation of a possibile decline in forecast quality from the loss of a single satellite Tracton emphasized.

“[The experiment] leaves open to what extent any single satellite contributes to forecast improvements – and to what extent the total array of the global polar satellite network is required, ” Tracton said. “How much can European, Japanese polar orbiters, for example, make up for the deficiencies in the U.S. satellite programs?

In 2011, NOAA conducted a experiment examining the impact of the loss of satellite data on Snowmageddon forecasts which showed a significant decline in forecast quality. But, at the time, Tracton questioned the representativeness of those results. The experiment was “far too limited to draw general conclusions about the importance of the satellite data” Tracton said.

The exact impact of a gap in polar-orbiting satellite coverage remains an open question but NOAA is starting to plan for it. NOAA announced Monday it is “seeking comments, suggestions, and innovative ideas from the public on how to preserve the quality and timeliness of NOAA’s numerical weather forecasts” should the gap materialize.

NOAA says it will incorporate the public input into an “investigative study to broadly explore all available options” for mitigating the potential loss of data.

The study and request for public input come in the wake of three independent reviews of the management of NOAA’s satellite programs according to the New York Times.

“... each questioned the cost estimates for the program, criticized managers for not pinning down the designs and called for urgent remedies,” the Times wrote.

More broadly, the National Academy of Sciences released a report last spring that warned of a “rapid decline” in U.S. earth observation capabilities.

“The projected loss of observing capability will have profound consequences on science and society, from weather forecasting to responding to natural hazards,” said Dennis Hartmann, professor of atmospheric sciences at the University of Washington, Seattle, and chair of the committee that wrote the report. “Our ability to measure and understand changes in Earth’s climate and life support systems will also degrade.”