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Don Paul: Polar orbiters are unsung heroes of spot-on weather forecasts

Don Paul

What you see is less than what most meteorologists get.

On television, we generally can only show you satellite imagery from geostationary satellites which stay in place and look down on the planet from the same location. They are in an orbit about 22,000 miles high, synchronized with the rotation of the planet. They supply increasingly sophisticated and multi-layered imagery and data, which also brings the gift of spectacular beauty as a side benefit.

The unsung satellite heroes, however, are not geostationary. Geostationary satellites have their limitations in data detail due to their very altitude and locations.

The as-not-seen-on-TV satellites are the polar orbiting satellites which travel at a much lower altitude, traversing the globe from pole to pole at different longitudes with each pass. They are unsung to the public because we can’t really show them on our weathercasts.

Television stations purchase NOAA satellite data through vendor companies. Those companies have no way currently of supplying polar orbiter data with any continuity because of the constantly shifting paths. We can access NOAA and NASA polar imagery stills on the internet. But because of their constantly progressing orbits, the imagery cannot be put together into a loop. So, they are not as useful as geostationary satellites for identifying intensification trends in large and small storms. They are snapshots. This is a typical 24 hour cycle of a polar orbiter.

So, what’s so great about these polar orbiters? Dr. Marshall Shepherd, University of Georgia Atmospheric Science Chair, has detailed some of their major advantages in a recent Forbes magazine article. Some of the pluses start with greater clarity, more data and higher resolution. Here is an image  from NASA’s MODIS imager of Nov. 5 wildfires on the South African coast:

The European Space Agency/ESA is sending a new, more sophisticated polar orbiter up this week. MetOp-C will orbit at 497 miles altitude, passing over the poles at 50-minute intervals. It will afford the meteorological community snapshots of many types of data, including volcanoes, fire and climate assessment, and will be sending an extremely valuable stream of data into numerical weather prediction models, which are the models we always talk about.

ESA has already seen forecasting results from MetOp-C’s aging predecessors, MetOp-A and B. The agency states: “The economic and social benefits of accurate weather forecasts are huge so there is a continued effort to improve forecasts even further. Recent studies show that MetOp-A and MetOp-B have already reduced errors in one-day forecasts by 27 percent. MetOp-C will add to the family and guarantee the provision of these essential data well into the 2020s. In addition, it ensures the smooth transition to the next generation of MetOp satellites, which are currently being built. The MetOp satellites are developed by ESA under a cooperation agreement to form the space segment of the Eumetsat Polar System. This system is Europe’s contribution to a multi-orbit polar system shared with the US NOAA agency.”

In other words, even though this is a European community weather satellite, its data will be fully shared with NOAA and enhance our weather models, as well as European models. Polar orbiters, especially these newer-generation satellites, have a superior capability to gather profile cross-sections of the atmosphere, measuring temperatures and humidity at many levels of the atmosphere. Profiling is critical to running more accurate weather models.

Weather balloons are launched only twice a day. This huge addition of more timely temperature and moisture data will continue to increase the reach of the models further out in time. The most important example of the polar orbiter contribution came with disastrous Superstorm Sandy of 2012. Some of you may remember how the European model was days out ahead of the American GFS model on that storm's rare hard left turn into the Eastern Seaboard. In 2014, a study on model performance for Sandy was published in the journal Monthly Weather Review. In the study the European model was run as it did with polar orbiter data included, and then with the polar data excised. This NOAA image in the study shows the dramatic, and life-saving difference between model runs with polar data and without polar data for the European model/ECMWF.

As the study revealed, “On the other hand, without polar-orbiting satellites (which represent 90 percent of the volume of currently ingested observations) the ECMWF system would have given no useful guidance 4–5 days ahead that the storm would make landfall on the New Jersey coast.”

Dr. Shepherd, among many researchers, was very worried a few years ago when U.S. polar orbiters and the previous ESA orbiters were outliving their projected useful lives. The example above illustrates what we would all be missing if such a gap developed. The new MetOp-C will be filling that gap, offering superior data and coverage, and offer some redundancy for forecasting, research and public safety.

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