Just like with any new technology, autonomous cars have faced their fair share of speed bumps from concept to product, especially when it comes to navigating in inclement weather. Recent developments in autonomous car technology, however, could be the solution to this problem.
Similar to human drivers, self-driving vehicles can have trouble „seeing” in inclement weather such as rain or fog. The car’s sensors can be blocked by snow, ice or torrential downpours, and their ability to „read” road signs and markings can be impaired.
The vehicle relies on a technology called LiDAR and radar for visibility and navigation, but each has its shortcomings. LiDAR works by bouncing laser beams off surrounding objects and can give a high-resolution 3D picture on a clear day, but it cannot see in fog, dust, rain or snow.
|A 3D illustration of a self-driving car in traffic. (Getty Images/
„A lot of automatic vehicles these days are using LiDAR, and these LiDAR are basically lasers, that shoot lasers that keep rotating to create points for a particular object,” Kshitiz Bansal, a computer science and engineering Ph.D. student at University of California San Diego, told AccuWeather in an interview.
However, Bansal said all of those lasers bounce off fog or rain or snow particles and are not able to give the required perception. It has been a challenge for these advanced cars to drive when their sensors cannot sense the road — and other objects — through snow or when visibility is limited by rain or fog.
Thanks to a team of electrical engineers at the University of California San Diego, self-driving cars are one step closer to navigating safely in inclement weather of all types.
The team has spent more than a year and a half developing a new way to improve the imaging capability of existing radar sensors so that they accurately predict the shape and size of objects in an autonomous car’s view. Radar, which transmits radio waves, can see in all weather, but it captures only a partial picture of the road scene. This is where the team came in to improve how radar sees.
„It’s a LiDAR-like radar,” said Dinesh Bharadia, a professor of electrical and computer engineering at the UC San Diego Jacobs School of Engineering. It’s an inexpensive approach to achieving bad weather perception in self-driving cars, he noted. „Fusing LiDAR and radar can also be done with our techniques, but radars are cheap. This way, we don’t need to use expensive LiDARs.”
The system consists of two radar sensors placed on the hood. Having two radar sensors arranged this way is key because they enable the system to see more space and detail than a single radar sensor.
„Say a car is coming toward you, what I would want is not just detecting that there is a car, but I would also want to know at what speed that car is coming toward me, what is the dimension of that car, particularly the length, width and height. And where the car is positioned. So, basically, the difference is that just a point detection is not enough,” Bansal said. „We need a lot of points on a particular car so that we can estimate all these dimensions and high-quality features of the object.”
To test if this concept worked or not, the engineers completed test drives on clear days and nights to show their system performed as well as a LiDAR sensor at determining the dimensions of cars moving in traffic. And, when the team added a foggy weather simulation, its performance did not change.
When the team „hid” another vehicle using a fog machine, their system accurately predicted its 3D geometry while the LiDAR sensor essentially failed the test.
„So, for example, a car that has LiDAR, if it’s going in an environment where there is a lot of fog, it won’t be able to see anything through that fog. But at the same time, with our radar, they can actually pass through all these bad weather conditions and can even see through fog or snow. And this is something that we also show in our book. And has been established with some past tests,” Bansal said.
The team uses millimeter radar, which is a small version of radar. The frequency of the lens is at a sweet spot that gives a lot more points for a particular object.
„For the radar that is used for automatic vehicles, we want a very high-resolution detection. So, for example, if you’re doing a test, as long as you see a dot followed by a particular object, you say okay, I have detected this object. Like when we’re talking about automatic vehicles, it’s not just about detecting the presence of a vehicle, it’s also about actually estimating the dimensions of the object,” Bansal said.
Traditional radar has typically suffered from poor imaging quality because when radio waves are transmitted and bounced off objects, only a small fraction of signals get reflected back to the sensor. As a result, vehicles, pedestrians and other objects appear as a sparse set of points.
„This is the problem with using a single radar for imaging. It receives just a few points to represent the scene, so the perception is poor. There can be other cars in the environment that you don’t see,” Bansal said. „So if a single radar is causing this blindness, a multi-radar setup will improve perception by increasing the number of points that are reflected back.”
The team found that two eyes are better than one, which is why they spaced the two radar sensors 1.5 meters apart on the hood of the car.
„By having two radars at different vantage points with an overlapping field of view, we create a region of high-resolution, with a high probability of detecting the objects that are present,” Bansal said.
|Autonomous cars can drive on the roadway scanning both the roadway and other objects in the distance. (Getty Images/Andrey Suslov)|
„What happens is that by using these multiple radars, we can generate more points than the LiDAR would generate. With this, we finally create a system that can dig into these points generated by the radar and really give out the parameters that we’ve been talking about this object, the length, the width and all the other estimates that we want for a particular object,” Bansal said.
However, it wasn’t that simple. More radars also mean more noise, Bharadia noted.
When radars pick up noise, it is common to see random points in the radar images, which do not belong to any objects. According to the team, the sensor can also pick up what are called echo signals, which are reflections of radio waves that are not directly from the objects that are being detected.
To fix this problem, the team developed new algorithms that can fuse the information from two different radar sensors together and produce a new image free of noise. This led the team to one of their other innovations — the first dataset combining data from two radars.
„There are currently no publicly available datasets with this kind of data, from multiple radars with an overlapping field of view,” Bharadia said. „We collected our own data and built our own dataset for training our algorithms and for testing.”
The dataset consists of 54,000 radar frames of driving scenes during the day and night in live traffic, as well as in simulated fog conditions. Future work will include collecting more data in the rain. To do this, the team will first need to build better protective covers for their hardware.
The team’s success has given them the opportunity to work with Toyota to fuse the new radar technology with cameras. The researchers say this could potentially replace LiDAR in the future.
„Radar alone cannot tell us the color, make or model of a car. These features are also important for improving perception in self-driving cars,” Bharadia said.
Keep checking back on AccuWeather.com and stay tuned
Top winter activities that could send you to the emergency room
Kevin Kelly was walking to his home in Motherwell, Scotland, early on New Year’s morning when he slipped and fell on ice. The 45-year-old father of five was found unconscious and rushed to the emergency room where he was put on life support. Tragically, Kelly died from a massive head injury two days later.
According to the Centers for Disease Control (CDC), winter weather kills more than twice as many Americans as summer heat. If you keep yourself aware of the increased risk cold weather brings and understand the most common types of winter accidents, you can take steps to avoid them and stay safe.
Dr. Erick Eiting is the vice-chair of operations for Emergency Medicine at Mount Sinai-Downtown Hospital in New York City, and he told AccuWeather that winter is a busy time in the emergency room. Slips and falls on ice are a large part of the increase in visits.
„Sometimes when we get a lot of snow underneath that snow can actually be ice, so we don’t often actually appreciate how slippery the ground is,” Eiting said.
Eiting regularly sees sprains, strains and even broken bones related to slippery, wintry weather, particularly in elderly people.
„The older we get, the more likely we are to develop conditions like osteoporosis, which means that when we do fall, it makes it more likely that our bones would get injured or even break,” Eiting said. „The other piece too is that as we get older our balance and our ability to control ourselves when we’re on something like snow or ice is much more limited, so that too can make us much more susceptible to falling.”
Approximately 1 million Americans are injured annually as a result of falling on ice and snow. About 17,000 of these falls are fatal, the CDC says. A lot of these deaths are avoidable. Stay aware of freeze and thaw cycles, don’t text while walking, and walk on the grass when you can. Always treat slippery spots with ice melt, and if you have a family member with a cane or walker, make sure it has rubber feet.
In the span of a week, from late December to early January, temperatures high in the atmosphere above the Arctic jumped by 100 degrees Fahrenheit. While this may sound alarming, it’s a natural phenomenon that happens every couple of years, but experts say human-caused climate change may be making these events more likely.
The remarkable event is called a Sudden Stratospheric Warming (SSW), and it involves the temperatures 50,000 to 100,000 feet above the ground. It disrupts the typical winter climate pattern in the Arctic stratosphere famously known as the polar vortex, and typically leads to more extreme winter weather in parts of the United States.
The polar vortex is a huge low-pressure gyre of cold winds spinning counter-clockwise, which rotate quickly around the Arctic Circle from west to east. But when an SSW occurs, if it is a strong enough event, winds will often reverse and become easterly, and the polar vortex will split into two or three separate vortices, which then drift southward towards the mid-latitudes carrying cold air along with them.
This is a nice way image to illustrate what is happening in the Stratosphere right now. The Polar Vortex which typically would be near the North Pole and very cold (purple) is displaced south and split as the Sudden Stratospheric warming occurs. More here. https://t.co/IKJa3evTxp pic.twitter.com/nJqtehrESU
— Jeff Berardelli (@WeatherProf) January 6, 2021
In most cases the SSW propagates down through the clouds to the Earth’s surface over the course of a few weeks. When this happens it throws the Arctic upper-level wind patterns off-kilter and the domino effect leads to convoluted jet stream patterns around the world in the mid-latitudes like Canada, the U.S., Europe and Asia. That means it will almost certainly result in some extreme winter weather, and given the expected pattern in the U.S., that will most likely happen along the East Coast.
The SSW that is happening right now is in fact characterized as a „major” event. Since late December temperatures have increased from around minus-110 degrees Fahrenheit to minus-10 degrees — a jump of 100 degrees — at a height of 100,000 feet above the North Pole.
In the image below the purple line shows the abrupt heating this past week, compared to the much flatter black line which is the average temperature.
Causes of sudden stratospheric warming
Dr. Judah Cohen is an expert on sudden stratospheric warming events and the connection between changes in the Arctic and mid-latitude weather patterns at Atmospheric and Environmental Research (AER), a Verisk company.
He says the beginnings of the sudden warming in the stratosphere starts much closer to the ground, in a layer of the atmosphere called the troposphere. But in order for this abrupt disruption to reach upward from the troposphere into the stratosphere, you need the excess energy of an extreme weather pattern — something that has been in no short supply lately in the Arctic.
When all the numbers are crunched, 2020 will beif not the warmest year on record in the Arctic. This is especially true in northern Asia near the Barents, Kara, Laptev and Siberian Seas, where parts of the region averaged a remarkable 10 degrees Fahrenheit above normal.
Earth has a fever in more ways than one. Some places averaged + 5-7 °C warmer than normal for the ENTIRE YEAR of 2020.An enormous area of anomalous warmth plagued Arctic Siberia effectively all year but it was not just the Arctic where we saw record shattering warmth.THREAD pic.twitter.com/L4BOR71S8T
— Scott Duncan (@ScottDuncanWX) January 4, 2021
Even for anat three times the pace of the rest of the globe due to climate change — a phenomenon known as Arctic amplification — this is an extreme departure from normal. The result was record-breaking low sea-ice extent near the Siberian coast.
The persistent „warmth” over Siberia was one of the most remarkable weather/climate events of 2020. It’s no surprise that sea ice averaged the lowest on record along its coast. Plenty more graphics in the coming weeks to summarize this event… pic.twitter.com/NwNHQqT6Fr
— Zack Labe (@ZLabe) December 29, 2020
According to Cohen’s theory, theand the fact that it took a few weeks longer than typical to recover this autumn set into motion a chain of events where the typical prevailing winter jet stream pattern across Asia was enhanced. That enhancement in turn helps initiate the Sudden Stratospheric Warming.
The animation below is an idealized illustration of the effect, in which there is an enhanced heat dome (known as a ridge) over northwest Russia and an enhanced dip in the jet stream (known as a trough) in eastern Asia and the North Pacific.
The jet stream is a river of fast-flowing air in the upper atmosphere which guides storms from one place to another. Just like waves in the ocean, it undulates up and down, from north to south, as it flows around the Earth. These undulations are known as atmospheric waves. And while most of the energy flows around the globe horizontally, some of the wave energy can move vertically, transferring energy upward or downward, especially when those waves are amplified.
Cohen explains that any given time the wave pattern is naturally elongated over Eurasia as compared to the rest of the globe. In a typical pattern this would have no impact on the stratosphere. But when this already large wave becomes even more enhanced by Arctic amplification, the energy in the wave can propagate upward into the stratosphere and cause chaos.
Watch how the stratospheric polar vortex evolves from a strong symmetrical system in December to a disturbed version now as significant warming invades the Arctic in a Sudden Stratospheric Warming event. This disruption will likely have implications in the mid lats for weeks. https://t.co/8yOL4GH4IJ
— Jeff Berardelli (@WeatherProf) January 5, 2021
This connection between the warm Arctic, low sea-ice cover and an amplified jet stream is the reason why Cohen believes climate change is leading to more frequent SSWs. But he acknowledges that the topic is controversial.
And while the theory behind the connection makes meteorological sense and some studies do support the connection, Dr. Zack Labe, an Arctic climate scientist at Colorado State University, says you can find an equal number of scientific papers finding a connection versus no connection. „Due to all of the chaos and noise in our atmosphere, it still remains challenging to understand connections between Arctic climate change and the polar vortex, explains Labe. „This topic remains an active area of scientific research and debate.”
But in a recent paper, Labe was indeed able to find a robust connection between Arctic amplification and a stronger, colder area of high pressure over eastern Siberia, something that is a key to Cohen’s theory. Labe’s analysis finds that this effect will intensify if global warming gets worse.
Cohen theorizes that the warming process underway in the stratospheric Arctic right now was initiated in October. In northwest Russia and Scandinavia, the warmer Arctic Ocean results in an enhanced heat dome which pushes the jet stream north.
With less sea-ice cover due to a warmer Arctic, the overlying atmosphere absorbs more moisture from the Arctic Ocean and, when it is cold enough, dumps more snowfall east of the heat dome. That snow cover, Cohen says, creates an extra-cold air mass over interior Siberia, Kazakhstan and Mongolia. This colder air has the opposite effect on the jet stream in eastern Siberia and the northern Pacific, pushing it south.
In what is not likely a coincidence, this pattern yielded two astonishing records last week. On December 28, the unofficial highest pressure ever recorded on Earth happened in Mongolia.
Looking at 2100 UTC obs in Mongolia, Tosontsengel is reporting 1089.5 hPa. This station is the record-holder from 2001 (1084.8 hPa). Further, Tsetsen Uul (labelled w/ H) is reporting 1093.5 hPa (32.29″). These, along with other reports, if verified, would break the world record. pic.twitter.com/jXx24W4JP5
— Mike Adcock (@MikeAdcockWx) December 28, 2020
Then just three days later the opposite occurred: the North Pacific and Alaska recorded their lowest pressures on record as a huge Aleutian low reached a pressure as low as a Category 5 hurricane.
A new Alaska land-based low pressure record has been set! Shemya, AK dropped to 924.8mb at 2159Z (1259 AKST) today. The previous accepted record was from a ship in Dutch Harbor at 925mb in 1977. Pressure is now slowly rising at Shemya. #akwx #hurricaneforce pic.twitter.com/1yiYOPvsTr
— NWS Anchorage (@NWSAnchorage) December 31, 2020
„I would argue that all these events are linked,” says Cohen, „A strengthened Siberian high coupled with a deep Aleutian low are critical for triggering a Sudden Stratospheric Warming. Most important in my opinion is the Siberian high but coupled with a deep low in the North Pacific is a one-two knockout punch.”
In other words, processes in the atmosphere do not happen in a vacuum — everything is connected — so one extreme can sometimes help yield another. And this „one-two punch” was an amplified enough pattern to send energy into the stratosphere, causing the sudden warming and polar vortex disruption.
Extreme winter weather pattern coming up
Cohen says that after a stratospheric warming event, the biggest impacts typically follow in about two weeks as the atmosphere shuffles systems around and new patterns become established. The timing and degree varies from event to event.
In the Arctic the sudden warming in the stratosphere typically leads to blocking areas of high pressure — like a mountain of warm air — known as the negative Arctic oscillation, or -AO. As it turns out, the -AO is already underway and this SSW episode should act to prolong it. This blocking pattern forces and redirects the jet stream and cold Arctic air southward.
For this particular SSW event it appears the main Arctic outbreak will occur first over Europe and eastern Asia through mid-January. But then computer models show a shift occurring, with the potential for Arctic invasions in the U.S. later this month.
Along with a gradual building of cold air over the coming weeks in the East, the jet stream setup will provide many opportunities for snow storms. While many will not materialize, with a prolonged pattern favorable for extreme winter weather, odds are that pieces of the puzzle will come together for a couple of memorable winter storms.
Cohen warns that the chance for extreme winter weather may last for quite a while. „Following an SSW the period of increased risk of cold air outbreaks and snowstorms usually lasts from four to eight weeks. It is not cold and snowing continuously but rather it is episodic,” he explained.
After years of studying these phenomena, Cohen says a clear pattern has emerged. Warm Arctic conditions and a weaker stratospheric polar vortex, is linked to more cold extreme episodes in some parts of the mid-latitudes.
This is not to say that winters are getting colder in the mid-latitudes. To the contrary, overall winters are warming due to climate change, although some pockets are indeed warming more slowly because of this effect. That’s because these types of mid-latitude cold air episodes are made more likely by Arctic amplification, and research has found an increasing frequency in weak polar vortex states over the past four decades, linked to human-caused climate change.
For the U.S. the trends are clear: Cohen’s research shows a direct connection between intense warming events in the Arctic and more episodes of extreme winter weather in the eastern U.S.
In the below graph for the city of Boston, the blue lines indicate a cold Arctic, the red lines indicate a warm Arctic, and the green lines represent the Accumulated Winter Season Severity Index (AWSSI), a measure of snow and cold. Cohen points out just how straightforward the trend is: As the Arctic warms (red), cold and snow (green) increase in Boston. This is especially true following episodes of major Arctic warming, as is happening now. This is also the case for much of the eastern U.S.
In what may seem paradoxical, as global warming has intensified in recent years, the number of big Northeast snowstorms has increased. In fact, many of the biggest snowstorms in New York City history, like the January blizzard of 2016, have happened in the past two decades. While some of this may be related to natural variability, Cohen feels changes in the Arctic clearly play a role.
In the bar graph below, the Northeast Impact Snowfall Scale (NESIS) is plotted for each decade from 1958 through 2018. You can clearly see the spike in activity in the last decade shown, 2008 to 2018.
It should be noted that this trend in bigger snowstorms is likely also due to other factors related to a warmer climate like warmer ocean temperatures, more available moisture and more intense storms due to extra energy in the system.
This means, for now, climate change can lead to bigger snowfalls for areas where there’s more moisture and it is still cold enough to snow, like the Midwest and Northeast. But in areas where temperatures are warming above thresholds for snow more often, like the nation’s midsection, the trend in snowfall is downward. The below image makes this trend clear.
Change in annual snowfall (percent) for the 1991-2020 period compared to the 1981-2010 period. Stations with ≤ 2 missing days for all months (including summer) for 22+ years in each climate period are shown (min 6″ annual average). n=1572. pic.twitter.com/5hioGrajY6
— Brian Brettschneider (@Climatologist49) January 5, 2021
So, for at least the next few weeks, if you live in the eastern half of the nation, prepare for real winter weather and the possibility of snow.
According to AFP, thermometers showed minus 3.3 degrees Fahrenheit (-19.6 degrees Celsius) in Beijing on Thursday morning, local time, breaking a previous daily cold-weather record set in 1969.
|People wearing face masks to help curb the spread of the coronavirus head to work as the capital city is hit by cold wind in Beijing, Wednesday, Jan. 6, 2021. (AP Photo/Andy Wong)|
The cold reading was the lowest since 1966 when temperatures in the city reached minus 17.3 F (27.4 below zero C), AFP added.
On Wednesday, the temperature dropped from about 23 F (5 below zero C) to about minus 1 F (minus 18 C). The arrival of the frigid air along with wind gusts around 30-40 mph (48-64 km/h) made it feel even colder.
People on the streets of Beijing could be seen bundled up with heavy winter jackets as they walked along city streets while also wearing face masks to guard against the spread of the novel coronavirus.
According to AFP, residents took to the internet to complain about the unusual cold using one hashtag that read „How cold is this winter?” on the social media platform Weibo.
Despite the subfreezing conditions, a group of daring swimmers still managed to find time for an outdoor swim on Wednesday.
The normal low temperature for the city during January is 15.3 F (minus 9.3 C).
It is not unusual for rounds of cold air to sink south across China during the winter months. When the polar vortex, typically situated around the North Pole, weakens, it can send pockets of colder air southward over Russia. Areas of high pressure can help to bring this air even farther south into eastern Asia.
This phenomenon can also bring Arctic air into Canada and the United States.
Nearly a month ago, another round of frosty air plunged into eastern Asia. Beijing recorded low temperatures of 13 F (minus 11 C) on Dec. 14-15. The normal low temperature in December is 20 F (7 below zero C).
As this cold air spread south into China, it also pushed east across Japan, creating sea-effect snow across the Sea of Japan.
|A woman wearing a face mask to protect against the coronavirus walks on an unseasonably cold day at an office and shopping complex in Beijing, Wednesday, Jan. 6, 2021. China’s Hebei province is enforcing stricter control measures following a further rise in coronavirus cases in the province, which is adjacent to the capital Beijing and is due to host events for next year’s Winter Olympics. (AP Photo/Mark Schiefelbein)|
Sea-effect snow is similar to lake-effect snow. These snow showers develop as cold air rushes over a warm body of water, creating bands of persistent, heavy snowfall.
From Dec. 16-18, heavy snowfall blanketed the northern coast of Japan. The bulk of the heaviest snow was focused on Niigata and Gunma prefectures, where about 6.6 feet (2 m) of snow accumulated over three days.
About 1,000 people were stranded in their cars on an expressway that connects Niigata to Tokyo after the snow made the road impassable, said the Guardian. Members of the self-defense forces were called in to provide food, blankets and fuel to motorists forced to spend the night in their cars.
Around 10,000 households along the northern coast reported power outages with this event.
Frigid air and rounds of snow are forecast to continue across eastern Asia in the coming days as temperatures remain below normal for the time of year and another round of sea-effect snow showers arrives in Japan.
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ROME (Reuters) – World food prices rose for a seventh consecutive month in December, with all the major categories, barring sugar, posting gains last month, the United Nations food agency said on Thursday.
The Food and Agriculture Organization’s food price index, which measures monthly changes for a basket of cereals, oilseeds, dairy products, meat and sugar, averaged 107.5 points last month versus 105.2 in November.
The November figure was previously given as 105.0.
For the whole of 2020, the benchmark index averaged 97.9 points, a three-year high and a 3.1% increase from 2019. It was still down more than 25% from its historical peak in 2011.
Vegetable oil prices continued recent strong gains, jumping 4.7% month-on-month in December after surging more than 14.0% in November. For the whole of 2020, the index was up 19.1% on 2019.
FAO said supply tightness in major palm oil producing countries had pushed prices up, while trade was also impacted by a sharp hike in export duties in Indonesia. Prices for soy oil rose partly because of prolonged strikes in Argentina. [POI/]
The cereal price index posted a more modest 1.1% rise in December from the month before. For all of 2020 the index averaged 6.6% above 2019 levels.
Export prices for wheat, maize, sorghum and rice all rose in December, moving higher in part due to concerns over growing conditions and crop prospects in North and South America as well as Russia, the Rome-based FAO said.
The dairy index climbed 3.2% on the month, however, over the whole of 2020, it averaged some 1.0% less than in 2019.
In December, all components of the index rose due to strong global import demand triggered by concerns over drier and warmer conditions on Oceania’s milk production as well as high internal demand in Western Europe.
The meat index pushed up 1.7% last month, while its full-year average was 4.5% below that of 2019. FAO said poultry quotations rebounded in December, partly due to the impact of avian influenza outbreaks in Europe. However, pig meat prices fell slightly, hit by the suspension of German exports to Asian markets following African Swine Fever outbreaks.
Bucking the rises in other indices, average sugar prices dipped by 0.6% in December. For 2020 as a whole, the sub-index posted a most 1.1% gain on 2019 levels. FAO said the relative firmness of latest data reflected a surge in imports by China and increased demand for refined sugar from Indonesia.
FAO did not issue an updated forecast for worldwide cereal harvests in January. Its next estimate is due in February.
Last month, FAO revised down its forecast for the 2020 cereal season for a third month running, cutting it to 2.742 billion tonnes from a previous 2.75 billion tonnes.
(Reporting by Crispian Balmer)