2023年北美重大天气事件追踪（存档）

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NYC's air quality ranked worst of any major city on Wednesday. With climate change, will it happen again?
Story by Rebecca Sohn • 3h ago


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© David Dee Delgado / Stringer via Getty Images

On Wednesday (June 7), the air quality in New York City was the worst of any major city in the world, due to smoke billowing over the northern U.S. border from wildfires in eastern Canada. With wildfires predicted to become more commonplace with climate change, the alarming pollution could be a sign of what's to come.

The National Weather Service first issued an air quality alert for New York City on Tuesday (June 6); this alert will remain in effect until the end of Thursday (June 8), but could be extended if necessary. By Wednesday afternoon, an intense yellow-orange haze hung over the city. Pollution from wildfire smoke consists of tiny particles, called particulate matter (PM), that can cause damage to the respiratory system when inhaled.

"We recommend all New Yorkers limit outdoor activity to the greatest extent possible," New York City Mayor Eric Adams said in a statement Tuesday. "Those with pre-existing respiratory problems, like heart or breathing problems, as well as children and older adults, may be especially sensitive and should stay indoors at this time."

The current air pollution cloaking the city comes from more than 200 forest fires burning in eastern Canada.

Winds from a weather system off the coast of New England set off a flow of smoke southeast from Canada, directly toward New York, Cheila Avalon Cullen and Neal Phillip, environmental scientists at the City University of New York (CUNY), told Live Science in an email.

Heat from wildfires can push smoke high into the atmosphere, where it is less impacted by weather, Daniel Westervelt, an associate research professor at Columbia University's Lamont-Doherty Earth Observatory, told Curbed. Other types of particles in the atmosphere would fall to Earth with rain fairly quickly, he said. But this process has allowed smoke to persist across the more than 300 miles (480 kilometers) from southern Quebec to New York City.

"Looking at the … upper air flow map that guides weather systems at the ground, it can clearly be seen that the flow lines are coming straight down from Canada and then curves towards the east coast and NYC," Cullen and Phillip said.

Wildfire smoke contains a type of particulate matter called PM2.5, so called for its minuscule size, which is less than 2.5 microns wide. (A micron is one-thousandth of a millimeter.) In the short term, exposure to high amounts of PM2.5, also called "fine" particulate matter, can cause coughing, nose and throat irritation, and shortness of breath, and it can worsen asthma and heart disease, according to the New York Department of Health. Long-term exposure, defined as months to years, is associated with increased chronic bronchitis, hospital admissions and deaths from conditions such as lung cancer and heart disease.

Besides wildfires, other sources of PM2.5 include traffic pollution and cigarette smoke. Phillip and Cullen said that daylong exposure to an air quality index (AQI) of 300, which New York City far exceeded on Wednesday, would be similar to smoking 15 cigarettes, according to a model developed by researchers at Stanford University. AQI is an air quality measurement that incorporates several types of air pollution, including levels of PM2.5, ozone, carbon monoxide and sulfur dioxide. The scale runs from 0 to 500, with 0 to 50 being "good" air quality and 301 and higher being "hazardous."

The air quality in the city on Wednesday was unprecedented, breaking the record for the worst air quality since the city started keeping records in 1999. The AQI in New York City is typically between 15 and 40, which is considered "good," Cullen and Phillip said.

While many people in the Northeast may not have experienced smoke pollution from wildfires, it's common in much of the western U.S. during warmer months. For instance, wildfires in Alberta in late May impacted air quality in several northwestern states, such as Montana, Colorado, Idaho and Utah, and wildfires are becoming increasingly common in western states, especially California.

But although wildfire smoke has been historically uncommon on the East Coast, climate change is predicted to increase the severity and frequency of wildfires all over the country and the world, according to the U.S. Environmental Protection Agency.

While New York's air has cleared somewhat since the smoky haze descended on the city, the AQI on Thursday was still at unhealthy levels, between 130 and 200, and it's predicted to get worse Thursday night, according to the National Weather Service.

While it's difficult to predict exactly when the air quality will improve, the smoke should start to clear in the next few days. An AQI monitoring website run by the World Air Quality project forecasts that the air will start to clear by Friday, while the Weather Channel forecast predicts it will begin to clear over the weekend.

"Although the Canadian forest fires will most likely continue burning, we [in New York] will get some relief once the air pattern aloft goes to a more west to east flow pattern," Cullen and Phillip said. "Currently it has a north to south pattern which is funneling all the smoke down from Canada."

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How long will the smoky siege last?
Story by Laura L. Davis, USA TODAY • 1h ago


The Manhattan skyline is seen during sunrise amid hazy conditions due to smoke from Canadian wildfires on Thursday.
© Michael M. Santiago, Getty Images

Wildfire smoke continues to hover over much of the U.S., but for how long? And a nonsurgical alternative to spaying cats is showing promise.

Wildfire smoke still swarming the US

There's something in the air. And for some, it isn't going away anytime soon. As dystopian orange skies lingered, New Yorkers were gripped by the worst urban air quality in the world Thursday, and Americans could face days or even weeks of drifting haze from Canadian wildfires. Outdoor spaces from Canada to North Carolina sat empty as air quality readings in many areas ranging from unhealthy to hazardous.

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North American smoke alerts in maps and images
7h ago


North American smoke alerts in maps and images
© Reuters

Intense wildfires in Canada have sparked pollution alerts across swathes of North America as smoke is blown south along the continent's east coast.

Toronto, Ottawa, New York and Washington DC are among the cities that have already been badly affected and, although conditions have improved in some of those places, unhealthy air quality is forecast to hit several southern metropolitan cities, including St Louis, Missouri and Louisville, Kentucky.

Where are the fires?

Much of the smoke is coming from Quebec, where more than 150 fires are burning, and there are more than 420 active fires across Canada.

The biggest wildfire complex in eastern Canada is the Donnie Creek fire in British Columbia which is now blazing over more than 3,000 square km.


North American smoke alerts in maps and images
© BBC

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Where has the smoke travelled?

The Canadian government said nearly 100m people in the US and Canada would experience very poor air quality.

Toronto and Ottawa in the province of Ontario were badly hit earlier in the week - with views from Toronto's landmark CN Tower showing the density of the smoke there.


North American smoke alerts in maps and images
© BBC

Environment Canada classified the air quality in Ontario as "very high risk" on Wednesday morning and, despite a brief respite later in the day, authorities warned they were likely to worsen again and remain at a high risk level until the weekend.

Across the border, cities including New York, Washington DC and Philadelphia have also been experiencing some of their worst air quality in years.

An orange haze blanketed the New York skyline and shrouded landmarks including the Empire State Building.

A view of Manhattan Bridge that has become popular with photographers and tourists over the years was given a distinctly sepia tint by the smoke.


North American smoke alerts in maps and images
© BBC

And from the top of the Rockefeller Center, the Hudson River could no longer be seen through the skyscrapers that dominate Manhattan.


North American smoke alerts in maps and images
© BBC

As the haze descended on the US Capitol building, US President Joe Biden described the fires as a "stark reminder of the impacts of climate change".


North American smoke alerts in maps and images
© BBC

The smoke has caused the cancellation of school outings and sporting events, and public health officials have cautioned people not to exercise outside and to minimise their exposure to the smoke as much as possible, as the air poses immediate and long-term health risks.

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Why is the smoke causing such problems?

Nasa said winds usually carry smoke from wildfires in the Quebec area east and out to sea but a low pressure area over Prince Edward Island has driven the smoke southwards to the United States.


North American smoke alerts in maps and images
© BBC

Atmospheric scientist Ryan Stauffer said the surface smoke pollution from New York to the DC region is the most significant since at least July 2002 when Quebec fires caused a similar problem - and could end up being worse.

Are there more wildfires than usual?

The short answer is yes. It is on course to be a record year with more than 3.5 million hectares - 12 times the 10-year average for this time of year - already burned this year, according to the Canadian Wildland Fire Information Service.


North American smoke alerts in maps and images
© BBC

Experts have pointed to a warmer and drier spring than normal as the reason behind the trend and these conditions are projected to continue throughout the summer.

Most of the 2,000 fires recorded this year are thought to have been started by humans but some, particularly in Quebec, were sparked by lightning strikes.

How bad is the air quality?

Data from the US Environmental Protection Agency's Air Quality Index (AQI) shows that cities in North America had the worst air quality in the world on Thursday morning.

Some parts of Janvier in Alberta, for example, had a peak AQI of 338, while areas of Washington DC reached 293 - a level above 200 is rated as very unhealthy and once it reaches 300 it is considered hazardous by the agency.

And looking at the daily averages you can see how air quality in some cities has been affected this year compared with last year.


North American smoke alerts in maps and images
© BBC

A similar table for a selection of other cities around the world shows that the daily averages have changed much less.


North American smoke alerts in maps and images
© BBC

How long will it last?

A new area of low pressure is expected to move up from the south this weekend and will bring fresher conditions to the north-east and mid-Atlantic states.

However, at the same time a ridge of high pressure across eastern Canada could trap the smoke there and even make conditions worse until rain hits next week.

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Air quality over the US and Canada is slowly getting better. But the threat of more wildfires sending smoke across the border looms
Story by Aya Elamroussi • Yesterday 10:50 AM

Major US cities trapped under a thick, orange blanket of smog this week will soon get a reprieve, as the Canadian wildfires spewing noxious fumes across the border are easing up.

Fire activity in the province of Quebec has improved, and the area covered by smoke is now just 7% of what it was last week. Slightly cooler temperatures and higher humidity in Canada mean less smoke billowing across the border.

But there are two big caveats: It’s still early in the Canadian fire season, meaning more wildfires could flare up this summer. And several US states are still suffering poor air quality, which could cause health problems.

“Smoke from Canadian wildfires continues to be transported south by winds into the U.S. resulting in moderate to unhealthy air quality across parts of the Northeast, mid-Atlantic, Ohio Valley, and Midwest on Friday,” the National Weather Service said. “Some improvement is expected this weekend.”

While the worst has passed for most of the Northeast and mid-Atlantic regions, potentially harmful air pollutants in New York City, Philadelphia and Washington, DC, are expected to linger Friday before slowly clearing over the next several days.

Philadelphia’s air quality index exceeded 150 early Friday, making it “unhealthy,” according to the monitoring website AirNow. New York City’s air quality index was below 150 early Friday and deemed “unhealthy for sensitive groups.”

The oppressive smoke this week has postponed professional sports games, grounded flights due to poor visibility, shuttered zoos and beaches and forced many to mask up outdoors. Climate experts have warned such events are becoming more frequent due to human-induced climate change.

About 50 million people across several Midwest and East Coast states were under air quality alerts early Friday, but the number could change as conditions improve in some areas.

Here’s what to expect:

• Entire states’ air quality is compromised: All of Pennsylvania, Delaware, Connecticut, Rhode Island, New Jersey and Indiana are under air quality alerts, as well as parts of Ohio, Michigan, Maryland, Virginia and North Carolina.


Air quality over the US and Canada is slowly getting better. But the threat of more wildfires sending smoke across the border looms
© Provided by CNN
The US Capitol in Washington, DC, was shrouded in smoke Thursday. - Al Drago/Bloomberg/Getty Images

• Schools go remote: Public schools in New York City, Philadelphia and Washington, DC, have remote learning Friday to help reduce exposure to air toxins.

• New York City will improve: After having the world’s worst air quality multiple times this week, according to IQAir, the Big Apple could see some “significant improvement,” Mayor Eric Adams said Thursday. “As of right now, the smoke models are not indicating another large plume over the city,” Adams said, though he urged people to mask well when outside.

• Evacuated Canadians can go home: Most of the Halifax residents evacuated because of the wildfires will be allowed to return home Friday, Mayor Mike Savage said. About 16,000 people fled their homes during the height of the wildfire evacuations, and about 4,100 remain evacuated.

• Firefighters will get help: New York state plans to send forest rangers to help fight the wildfires in Quebec Friday, Gov. Kathy Hochul said. Federal resources have also been deployed, the White House has said.

Scientists warn such routine-altering weather events are more likely to continue disrupting daily life as the planet warms, creating the ideal environment for more severe and frequent wildfires.

When flames burn, the smoke can travel thousands of miles, which puts millions more people in harm’s way.

Wildfire smoke is particularly dangerous because it contains tiny particulate matter, or PM2.5, the tiniest of pollutants. When inhaled, it can move deep into lung tissue and enter the bloodstream.

It comes from sources including the combustion of fossil fuels, dust storms and wildfires. Such smoke has been linked to several health complications including asthma, heart disease and other respiratory illnesses.

CNN’s Jennifer Gray, Brandon Miller, Robert Shackelford, Andrea Cambron, Laura Ly, Caroll Alvarado, Kristina Sgueglia, Sara Smart and Jen Christensen contributed to this report.

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What is a Central American Gyre?
Story by Andrew Wulfeck • 1h ago

Nearly every hurricane season, the FOX Forecast Center monitors a broad area of low pressure in the western Caribbean Sea and eastern Pacific Ocean, known as a gyre.

Due to its location, the circulation is known as the Central American Gyre and usually occurs during the rainy season from May through November.

Impacts expand outwards several hundred miles and lead to threats of torrential rainfall, flooding and mudslides for more than a dozen countries centered in and around Central America.

It is not uncommon to see numerous inches of rain as the pattern can exist for several days.

According to a 2017 study published in the Bulletin of the American Meteorological Society, the higher terrain in combination with nearby waterways, likely to play a significant role in the event’s formation.


A general overview of the Central American Gyre and its typical impacts. FOX Weather
© Provided by Fox Weather

In some occasions, energy associated with the gyre can produce a tropical disturbance, if water temperatures and upper-level winds are conducive for development.

Due to the weather pattern’s complex nature, forecast models generally have a difficult time accurately predicting the formation of tropical cyclones from the Central American Gyre.

According to researchers at the National Weather Service’s Environmental Modeling Center, the Global Forecast System computer forecast model – commonly known as the GFS – is notorious for predicting the formation of tropical cyclones in the western Caribbean that never actually develop.

The FOX Forecast Center said sometimes slugs of moisture have a difficult time breaking apart from the main circulation and therefore are never able to form into a cyclone.

Both the early and late months of the hurricane season are more notorious for actually seeing a tropical disturbance break away from Central America and form into a tropical entity in either the eastern Pacific, Bay of Campeche or western Caribbean Sea.

On average, about once every other year, the Central American Gyre produces a tropical cyclone, with some that develop into full-fledged hurricanes if conditions allow.

Due to their formation hotspots in the Caribbean or regions in the southern Gulf of Mexico, many go on to threaten the Southeast coast.

Tropical Storm Amanda (2020), Tropical Storm Cristobal (2020), Hurricane Michael (2018), Tropical Storm Andrea (2013) and Hurricane Ida (2009) are all examples of areas of disturbed weather that formed off the Central American Gyre.

Hurricane Michael struck the Florida Panhandle as a Category 5 hurricane in 2018 after spending a week embedded in the overall gyre off the coast of Central America.

Usually, due to their formations in the early or late seasons, cyclones directly influenced by the Central American Gyre tend to be weaker when impacting the U.S. due to the prevalence of inhibiting factors such as cooler water temperatures and hostile upper-level winds.