Global 5G wireless networks threaten weather forecasts

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May 19, 2019

Next-generation mobile technology could interfere with crucial satellite-based Earth observations.

Image above: Water vapour over the continental United States is shown in this false-colour satellite image from the National Oceanic and Atmospheric Administration. Image Credits: NOAA/GOES.

The US government has begun auctioning off blocks of wireless radio frequencies to be used for the next-generation mobile communications network known as 5G. But some of these frequencies lie close to those that satellites use for crucial Earth observations — and meteorologists are worried that 5G transmissions from cellphones and other equipment could interfere with their data collection.

Unless regulators or telecommunications companies take steps to reduce the risk of interference, Earth-observing satellites flying over areas of the United States with 5G wireless coverage won’t be able to detect concentrations of water vapour in the atmosphere accurately. Meteorologists in the United States and other countries rely on those data to feed into their models; without that information, weather forecasts worldwide are likely to suffer.

“This is a global problem,” says Jordan Gerth, a meteorologist at the University of Wisconsin–Madison.

The US National Oceanic and Atmospheric Administration (NOAA) and NASA are currently locked in a high-stakes negotiation with the Federal Communications Commission (FCC), which oversees US wireless networks. NOAA and NASA have asked the FCC to work with them to protect frequencies used for Earth observations from interference as 5G rolls out. But the FCC auctioned off the first chunk of the 5G spectrum with minimal protection. The sale ended on 17 April and reaped nearly US$2 billion.

Sharing the sky

Because the United States is such a large communications market, the decisions the government makes about how to deploy 5G are likely to influence global discussions on how to regulate the technology. Regulators from around the world will gather starting on 28 October in Sharm el-Sheikh, Egypt, to hammer out international agreements for which frequencies companies will be able to use for 5G transmissions, and what level of interference with Earth-observation frequencies is acceptable.

Astronomers, meteorologists and other scientists have long worked to share the spectrum with other users, sometimes shifting to different frequencies to prevent conflicts. But “this is the first time we’ve seen a threat to what I’d call the crown jewels of our frequencies — the ones that we absolutely must defend come what may”, says Stephen English, a meteorologist at the European Centre for Medium-Range Weather Forecasts in Reading, UK.

Image above: Weather Satellites, an artist’s rendering of NASA’s new Global Precipitation Monitoring Core Observatory and partner satellites orbiting the Earth. Image Credit: NASA.

They include the 23.8-gigahertz frequency, at which water vapour in the atmosphere emits a faint signal. Satellites, such as the European MetOp probes, monitor energy radiating from Earth at this frequency to assess humidity in the atmosphere below — measurements that can be taken during the day or at night, even if clouds are present. Forecasters feed these data into models to predict how storms and other weather systems will develop in the coming hours and days.

But a 5G station transmitting at nearly the same frequency will produce a signal that looks much like that of water vapour. “We wouldn’t know that that signal is not completely natural,” says Gerth. Forecasts would become less accurate if meteorologists incorporated those bad data into their models.

Noisy neighbours

The recent FCC auction involved 2 groups of frequencies: one between 24.25 and 24.45 gigahertz and the other between 24.75 and 25.25 gigahertz. Wireless equipment transmitting near the lower end of that range could interfere with the 23.8-gigahertz water-vapour measurement. The FCC did not respond to Nature’s request for comment on the matter.

The situation is akin to having a noisy neighbour next door, Gerth says. If that person blasts music, a lot of the noise will probably bleed through the wall into your apartment. But if you can persuade the person to turn their music down, you’ll be able to sleep more peacefully.

Source: ITU

Radio-frequency engineers measure noise in units of decibel watts. Regulators set controls that limit the noise allowed; more-negative numbers indicate increasingly stringent controls. The FCC auction set a noise limit on the US 5G network of –20 decibel watts, which is much noisier than the thresholds under consideration by almost every other nation for their systems. The European Commission, for instance, has settled on –42 decibel watts for 5G base stations, and the World Meteorological Organization (WMO) is recommending –55 decibel watts.

Many hope that the WMO numbers will influence regulators to adopt strict global noise standards at the meeting in Egypt. Because of how the scale is devised, the US proposal would allow over 150 times more noise than the European proposal — and more than 3,000 times more than the WMO plan, says Eric Allaix, a meteorologist at Météo-France in Toulouse who heads a WMO steering group on radio-frequency coordination.

Future fears

There’s relatively little research on exactly how bad weather forecasts could get as interference increases at 23.8 gigahertz and other frequencies crucial for Earth observations, says Gerth. “But the more we lose, the greater the impact will be,” he says.

NOAA and NASA have reportedly finished a study on the effects of differing levels of noise interference, but it has not been made public, despite at least one formal request from Congress. A 2010 report from the National Academies of Sciences, Engineering and Medicine concluded that losing scientific access to the 23.8-gigahertz signal would eliminate 30% of all useful data in microwave frequencies, which contribute significantly to global weather forecasts.

Weather Satellites around the world. Image Credit: CEOS

And not having atmospheric data from the United States can dramatically hurt forecasts for Europe, whose weather patterns are often steered by conditions over the United States 3–4 days earlier, says English.

The Department of Commerce, which oversees NOAA, said that it «strongly supports the administration’s policy to promote US leadership in secure 5G networks, while at the same time sustaining and improving critical government and scientific missions.» NASA administrator Jim Bridenstine declined to comment, but spoke at length about his concerns over 5G at an agency meeting earlier this month. «This is a big deal,» Bridenstine said.

The FCC plans to begin its next 5G auction, which will be the country’s largest ever, in December. It will involve three more frequency bands — some of which are used for satellite observations of precipitation, sea ice and clouds.

Related article on Nature:


Related link:

European Centre for Medium-Range Weather Forecasts:

Images (mentioned), Text, Credit: Nature.

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Seasonal Monsoon Rains Block Key Ocean Current

NASA — Soil Moisture Active Passive (SMAP) patch.

May 19, 2019

Our oceans and the complex «conveyer belt» system of currents that connects them play an important role in regulating global climate. The oceans store heat from the Sun, and ocean currents transport that heat from the tropics to the poles. They release the heat and moisture into the air, which moderates climate nearby. But what happens if part of that conveyer belt jams?

Animation above: This animation shows a time lapse of sea surface salinity and soil moisture from NASA’s Soil Moisture Active Passive (SMAP) satellite from April 2015 through February 2019. Image Credits: NASA/JPL-Caltech/GSFC.

It’s not a theoretical question. Scientists have observed that a major ocean current called the Indonesia Throughflow, which provides the only tropical connection between the Pacific and Indian oceans, slows dramatically near the surface during the Northwest Asia monsoon season — usually December through March. And a team of scientists, led by Tong Lee of NASA’s Jet Propulsion Laboratory in Pasadena, California, has figured out why.

«We have found that this current, which is a very important element of the global ocean current system, is significantly affected by local precipitation,» Lee said. «It is fairly common knowledge that winds drive ocean currents. In this case, however, the precipitation is actually a dominant factor during the monsoon season.»

It’s a discovery that will improve our understanding of complex Earth processes. During this season, about 10 feet (3 meters) of rain fall over the maritime continent, a region of Southeast Asia between the Indian and Pacific oceans through which the Indonesia Throughflow current travels. This influx of local rain reduces the pressure force that drives the current through the region.

How does that work?

Gravity causes water to travel «downhill» from areas of relatively higher sea level toward areas of lower sea level unless opposed by another force. In the tropical Pacific, trade winds also influence the flow of water. They blow from east to west, causing ocean currents to transport large amounts of water from the U.S. westward toward Asia. This raises the sea level on the Asian side of the Pacific Ocean and provides enough force to keep the Indonesia Throughflow moving, connecting the two oceans.

However, the influx of rain during monsoon season temporarily but significantly raises the local sea level in the Indonesian seas that sit between the Pacific and Indian oceans enough to essentially eliminate the downhill flow. Think of it like a ball rolling freely downhill versus a ball on a flat surface, which has little momentum to move forward.

Although the slowing of this current is primarily seasonal, it still affects the amount of heat transported from the Pacific Ocean to the Indian Ocean, which can change regional climate in Southeast Asia.

Soil Moisture Active Passive (SMAP) satellite. Image Credit: NASA

«The increase in local sea level due to the seasonal freshening of seawater pushes against the normally higher sea level from the Pacific Ocean,» said Lee. «It restricts the surface flow of this current during the monsoon season, which prevents a lot of the heat normally carried by the current from making its way to the Indian Ocean.»

Furthermore, since all of these currents are connected globally, less warm water is transported into the Indian Ocean, and in turn, less warm water is transported from the Indian Ocean to the Atlantic Ocean over the long term. So the Indonesia Throughflow — one element of a much larger system — can have a significant effect thousands of miles away from where it flows.

The results of this study will help to improve climate models by enabling scientists to factor in these effects and changes. Titled «Maritime Continent water cycle regulates low-latitude chokepoint of global ocean circulation,» the study was recently published in Nature.

NASA satellite data, particularly ocean salinity measurements from the Soil Moisture Active Passive (SMAP) satellite, were instrumental in these findings. Although SMAP was designed primarily to measure soil moisture, its radiometer is also able to measure sea surface salinity. The results of this paper demonstrate the utility of SMAP salinity data in exploring changes in the water cycle, sea level, ocean circulation and climate.

More information on SMAP is available here:

Animation (mentioned), Image (mentioned), Text, Credits: NASA/JPL/Esprit Smith.

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Asteroid Apophis 2029 It’s Coming Very Close to the Earth

Asteroid Watch.

May 18, 2019

Asteroids are out there, even if you can’t always see them.

Image above: Artist illustration of the asteroid Apophis making a close flyby of Earth. Image Credit: European Space Agency (ESA).

Want some naked-eye proof? It’s coming, in the form of a mountain of space rock named Apophis, for the Egyptian god of chaos; his task is to prevent the sun from rising.

Stretching three-and-a-half football fields long, Apophis will cruise within 19,000 miles of Earth—the closest this large an asteroid has come in recorded history. Apophis will swing inside our ring of geosynchronous satellites on April 13, 2029.

And yes, that is a Friday.

Animation above: This animation shows the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach in 2029. The blue dots are manmade satellites orbiting our planet, and the pink represents the International Space Station. Animation Credits: NASA/JPL-Caltech.

But don’t worry, NASA has it all figured. Any bad luck that may befall you on that day won’t come from Apophis—probably. An earlier worst-case prediction that gave a 2.7 percent chance of Apophis striking the Earth has since been downgraded to practically nil. Actually, that’s an upgrade.

Apophis is a Sparkle in NASA’s Eye

In fact, NASA scientists look forward to Apophis’ near miss. Given a decade to prepare, NASA might even send a robotic probe to rendezvous with the rock. At minimum, it’s an incredible opportunity to make close-up observations of a large asteroid. Apophis is large enough, and will be close enough, to see with our bare eyes, so Earth-based optical and radio telescopes will have an unprecedented view of the spectacle.

Image above: Astronomers discovered asteroid Apophis on June 19, 2004. At first, when its orbit was not well understood, there was brief concern it had the potential to strike Earth in this century. Image Credits: UH/IA/NASA.

At the 2019 Planetary Defense Conference held in Maryland this April, scientists brainstormed all the possible ways to take advantage of a flyby that others might see only as a narrowly averted disaster.

NASA has used radio telescopes before to produce rudimentary images of some passing asteroids, though these were either smaller ones or much farther away. The last time any rock this size passed close to Earth was in 2001, the asteroid 2017 VW13. That one is estimated to have passed within 76,000 miles, a third of the distance to the moon. And, since it wasn’t discovered until 2017, no one even noticed it fly by!

God of Chaos

Apophis is classified today as a «Potentially Hazardous Asteroid» (PHA). This means that it periodically crosses Earth’s orbital path, and is large enough to do some major damage if it were to hit us.

Far from being an infrequent visitor from deep space as many comets are, coming around only every few decades or centuries, Apophis is a denizen of the inner solar system. Its 324-day orbit carries it from just outside Earth’s orbit at its farthest point from the sun, almost to the orbit of Venus at its closest.

Image above: Diagram showing the orbits of the planets of the inner solar system, and the asteroid Apophis. Image Credits: NASA/JPL.

You might think that because Apophis crosses Earth’s orbit more than once each year, the chance of collision is an ever-present threat.

However, most of the time when Apophis crosses our path, Earth is at a different point in its orbit. It’s only those times when our orbital positions sync up that there’s any chance of bumping into each other. Think of a carnival carousel and that brass ring you try to grab each time your horse passes by it. You only have a shot at getting that ring if it swings close when you pass—and even then there’s no guarantee.

April 13, 2029 is one of those match-ups, and scientists are keenly eyeing the brass ring of new discovery that will be briefly within their reach.

What Are the Chances?

While small objects pass close to Earth on a routine basis, and even collide with us more often than you might think, most go unnoticed. Three quarters of them fall over open ocean, most of the rest over sparsely populated land. And those that don’t break up in the atmosphere have limited effects when they hit the water or the ground anyway.

Larger, more dangerous rocks make appearances with far less frequency—and the bigger they are, the rarer the encounter.

Image above: A model of the shape of asteroid Apophis, generated from its light curve and assuming that all areas of the asteroid have a similar albedo and reflectivity, via the Database of Asteroid Models from Inversion Techniques (DAMIT) and and Wikimedia Commons.

Notable impacts in recent history include the Tunguska comet or meteorite impact in Siberia in 1908, and the Chelyabinsk event in Russia in 2013. Both were smaller than Apophis, but were relatively large objects: between 200 and 600 feet across in the case of Tunguska, and about 66 feet for Chelyabinsk. They exploded in Earth’s atmosphere, producing significant effects on the ground below, though no known fatalities.

Larger collisions with greater regional and even global effects can be found in prehistoric times, such as the impact that formed Barringer Crater (aka «Meteor Crater») in Arizona 50,000 years ago.

To find a «dinosaur killer» impact event you’d have to look all the way back to, well, the dinosaur killer impact, 66 million years ago. The asteroid that contributed to ending the dinosaurs’s long reign on Earth, which struck the northern end of the Yucatan Peninsula near Chicxulub, Mexico, was probably six miles across.

Image above: Diagram detailing the remnants of the Chicxulub impact crater on the Yucatan Peninsula. Though now buried under jungle and ocean sediment, evidence of the crater can be found through radar imaging and mineral analysis of rock samples. Image Credits: NASA/JPL-Caltech/David Fuchs.

Defending Against Near Earth Objects

Fortunately, we aren’t completely in the dark about the dangers posed by Near-Earth Objects. We’re also not completely helpless when it comes to defending our planet from them.

For years now, an international coalition of observers and researchers have collaborated to find, measure, and track Near-Earth Objects. The data they collect are used to calculate the probability of a collision, and to predict the level of damage in the event of a hit. (Related articles links).

Ultimately, a major asteroid impact with Earth is a matter of when, not if. But the good news is that none are predicted in the foreseeable future.

Asteroid impact on Earth

The current approach to planetary defense hinges on the idea that the further in advance we can predict an impact, the more time we have to do something about it. If we know it’s coming years before the fact, a tiny «nudge» to the asteroid’s trajectory can make the difference between a catastrophic impact and a harmless near miss.

What About Apophis’ Next Flyby?

The probability of Apophis hitting the Earth in 2029 has been practically ruled out. Its close passage through Earth’s gravitational field, though, will result in a change in its orbital path, so careful observations of the flyby will yield more than scientific discovery, it will let us make more precise collision predictions for future encounters.

As things stand now, Apophis will make another close encounter with Earth in 2036, but will come no closer than 14 million miles. Beyond that, the chance of it hitting us anytime between 2060 and 2105 is 1 in 110,000.

Astronomers will be watching!

For more information about asteroids and near-Earth objects, visit: Updates about near-Earth objects are also available by following AsteroidWatch on Twitter at

Bottom line: Astronomers met on April 30, 2019, at the Planetary Defense Conference to discuss plans to observe asteroid 99942 Apophis, a relatively large asteroid that’ll sweep past Earth safely – but rather closely – a decade from now.

Related articles:

NASA’s First Planetary Defense Technology Demonstration to Collide with Asteroid in 2022

Earth vs. asteroids: humans strike back

Work begins on ESA’s part of planetary defence test

Related links:

2019 Planetary Defense Conference:

Potentially Hazardous Asteroid» (PHA):

Near-Earth Objects:

Images (mentioned), Animation, Text, Credits: NASA/KQED Science/Ben Burress/ Aerospace/Roland Berga.

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