Newsworthy Smog in Beijing

By: 24hourprof , 4:46 PM GMT on January 16, 2013

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I am an avid cyclist, but I would think twice about cycling through the heavy smog that shrouded Beijing, China, the past few days (check out the AP photograph below). Originally, smog referred to the reduction in visibility caused by the combination of smoke and fog, but, in more modern times, smog has come to describe a cauldron of pollution and fog that sometimes pose very serious health hazards in large urban and industrial areas.


Motorcycling through the smog in Beijing on January 12. Courtesy of the Associated Press.

Smog typically forms in weather patterns dominated by high pressure. The recent siege of smog over Beijing and other parts of eastern China was no different, as shown by the 12Z GFS model analysis of MSL isobars (note the gaggle of highs centered over eastern China). The lack of a surface pressure gradient over this region indicates that winds were generally light. In turn, weak surface winds curb the dispersion of any pollutants in the lower troposphere. Indeed, the meteogram at Beijing (ZBAA) from 08Z on the 12th to 09Z on the 13th (see image below) confirms the presence of light winds.


The meteogram for Beijing, China, from 08Z on January 12 to 09Z on January 13, 2013. To the right of present weather and restrictions to visibility, I circled (in red) freezing fog and haze. Courtesy of the University of Wyoming.

To understand the connection I'm making between the dispersion of pollutants and wind speeds, I'll tell you a story about my commute to Emory University in Atlanta when I was in graduate school there in the mid 1970s. Each day, I rode my bike from my house to my office in the math department, usually leaving my house around 7 A.M. and leaving my office around 4 P.M. My commute included a stretch of dirt road, and, on clear mornings with light winds (high pressure), I dreaded when cars passed me because choking dust would just hang in the air the rest of ride. In the late afternoon, however, when there was a breeze (usually a result of momentum mixed downward from faster winds aloft), dust dispersed rather quickly after a car passed me on the dirt road. I hope my story helps.

By the way, the present weather symbol at 12Z on January 12 on Beijing's meteogram (circled in red) corresponds to freezing fog that deposits rime ice (supercooled water drops in the fog freeze on contact with cold surfaces). Note that 12Z temperature was 19 degrees Fahrenheit, so, yes, fog droplets were supercooled (revisit my blog about the issue of freezing). In this case, the sky is discernible (pdf file of WMO icons).

A typical vertical profile of temperature associated with smog episodes includes a subsidence inversion on the eastern flank of a high-pressure system, where the air is sinking from the upper troposphere to roughly 850 mb. To understand how subsidence inversions form, I recommend you carefully go through this instructive flash animation, courtesy of Penn State's certificate program. At any rate, subsidence inversions act like a lid, preventing air below the inversion from mixing upward.

In this case, there really wasn't a classic subsidence inversion (see 12Z skew-T below). In my view, the upper-air pattern at 12Z on January 12 was not conducive to subsidence through a deep layer of the troposphere (note the short-wave trough over eastern China on this 500-mb GFS model analysis at 12Z on January 12). Rather, there was a deep stable layer from the ground up to 850 mb (an inversion to roughly 900 mb and a roughly isothermal layer above the inversion), which was similar to the early morning conditions through which I rode my bicycle to Emory University in the mid 1970s. Clearly (no pun intended), pollutants, dust, fog, haze...you name it...that was "added" to the lower troposphere over Beijing just hung in the air. And, without stronger winds to disperse the smog, pollutants just built up over time, posing a serious health threat.


The 12Z GFS model skew-T showing the temperature (red) and dew-point (green) soundings over Beijing, China, on January 12, 2013. There was a temperature inversion in the lowest layer of the atmosphere and a roughly isothermal layer above it, making the lower troposphere highly stable and thereby trapping low-level pollution. Courtesy of NOAA.

Jeff Masters pointed out this MODIS visible satellite of China at 03Z on January 14, 2013. The relatively thin haze layer (compared to thicker low clouds over eastern China that appear bright white) appears as a grayish layer (Beijing is located near the northern tip of the mass of low clouds over eastern China).

Lee

Postscript:

I received an e-mail from a former (and great) student who graduated from the certificate program at Penn State, Winn Soldani. Winn is a businessman who travels a great deal. Here's his e-mail (it's really incredible):

Lee:

Haven't read your full blog, but saw the topic. I was in Beijing last week...Arrived late on the 10th and departed on the 12th. The pollution was like nothing I've ever imagined. It was so bad that visibility INDOORS (e.g. in the airport arrivals hall) was affected. Horrible.

Winn

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12. WunderAlertBot (Admin)
4:53 PM GMT on January 18, 2013
24hourprof has created a new entry.
11. georgevandenberghe
4:19 PM GMT on January 18, 2013
We do sometimes get the summer combination of a marine CCN distribution and high relative humidity in the DC area. It's usually associated with a southeast wind in summer and a tropical airmass and is associated with strikingly blue skies, very good visibility and absence of haze and sharp contrasts with the white convective clouds that form in the afternoons. I've often again cynically muttered that on a clear day here in summer the sky is white. This makes physical sense when the solar beam is scattered by large particles rather than molecules.

What causes dry haze to be present or absent in an atmosphere with a lot of CCN?. I'm posing this as a question, not leading into
a discussion.


I did get the point that you're seeing pollution (or high CCN) in haze
rather than humidity. I tried to make the two points, that not all CCN are pollutants, and the unrelated point that not all pollution is visible (again ozone which is the one I, perhaps exaggeratedly, fear).

In Tallahassee summers we got a lot of both types. Marine distributions were correlated with east to south deep layer winds and continental were correlated with west to northwest winds (by the way northwest is not a cool or pleasant wind direction in summer in Tallahassee).

Thanks for stimulating posts. I'm starting to fear I have some preconceptions and misconceptions that need to be cleared so absolutely don't hesitate to call me out on them!


(Oh. that haze in Bejing. not a close call. It's obviously filthy and polluted and I'd certainly not want to be in it!!)


I added "very good visibility and absence of haze" 11:36AM.. not in my original post which made it read less well
Member Since: February 1, 2012 Posts: 17 Comments: 1630
10. 24hourprof
3:42 PM GMT on January 18, 2013
Quoting georgevandenberghe:


But to take a contrarian attitude, not all haze is pollution. My belief (don't confuse my beliefs with facts I might be wrong) is the primary determinant of haze density in a moderately humid airmass is whether you have a continental or marine CCN distribution. Continental provides 1-3 orders of magnitude more particles to condense around. CCN will start collecting moisture at between 50 and 70% relative humidity depending on how hygroscopic they are.

And what you see isn't always what's poisoning you especially in the summer ozone case I harped about previously.

A previous post mentioned wood smoke. In valleys where people heat with woodstoves it is indeed very bad and many localities sensibly require catalytic converters on new installations.

I'm fortunate in this aspect to live in the DC area where winter air quality is not a big issue. We're usually pretty well ventilated. Summers are rougher because of ozone.




I think you're misunderstanding me. Yes, haze particles are hygroscopic. I'm not denying that. All I'm saying is that all these people see is moisture, not the underlying cause...pollution.

And you are incorrect to suggest that haze requires moisture. There is also dry haze, which forms at low relative humidity. The underlying cause, however, is usually pollution.

The fact that I was talking about the warm season in the East meant that I assumed relative humidity was relatively high.

So I think you missed my point.
Member Since: October 24, 2012 Posts: 90 Comments: 798
9. georgevandenberghe
3:09 PM GMT on January 18, 2013
Quoting 24hourprof:


Thanks so much for your contribution. The photograph is stunning.

In the East, there are some meteorologists who look at haze during the warm season and "see moisture." They wrongfully assume that high dew points automatically translate to haze. I have heard at least one on-air forecaster recite this "manta."

I always tried to instill into my students that when they take a vacation to a tropical island, where dew points are frequently high, they won't see any haze because of the lack of pollution from heavy industry.

No, when I see haze here in the East, the first thing that comes to my mind is not "moisture"...instead, I just see a health hazard.

Thanks again.


But to take a contrarian attitude, not all haze is pollution. My belief (don't confuse my beliefs with facts I might be wrong) is the primary determinant of haze density in a moderately humid airmass is whether you have a continental or marine CCN distribution. Continental provides 1-3 orders of magnitude more particles to condense around. CCN will start collecting moisture at between 50 and 70% relative humidity depending on how hygroscopic they are.

And what you see isn't always what's poisoning you especially in the summer ozone case I harped about previously.

A previous post mentioned wood smoke. In valleys where people heat with woodstoves it is indeed very bad and many localities sensibly require catalytic converters on new installations.

I'm fortunate in this aspect to live in the DC area where winter air quality is not a big issue. We're usually pretty well ventilated. Summers are rougher because of ozone.


Member Since: February 1, 2012 Posts: 17 Comments: 1630
8. 24hourprof
12:52 PM GMT on January 18, 2013
Quoting JNCali:
I grew up in the 60's just south of Los Angeles and can remember stage 3 alerts when we would not get to go outside for recess at school.. We had an ocean view from our backyard and could see the island of Catalina sitting about 20 miles of the coast.. when the offshore winds would blow I always felt sorry for people on the island because all the smog would blow out to them, but we could finally see the mountains that where only 50 miles away..


Thanks so much for your contribution. The photograph is stunning.

In the East, there are some meteorologists who look at haze during the warm season and "see moisture." They wrongfully assume that high dew points automatically translate to haze. I have heard at least one on-air forecaster recite this "manta."

I always tried to instill into my students that when they take a vacation to a tropical island, where dew points are frequently high, they won't see any haze because of the lack of pollution from heavy industry.

No, when I see haze here in the East, the first thing that comes to my mind is not "moisture"...instead, I just see a health hazard.

Thanks again.
Member Since: October 24, 2012 Posts: 90 Comments: 798
7. JNCali
4:02 AM GMT on January 18, 2013
I grew up in the 60's just south of Los Angeles and can remember stage 3 alerts when we would not get to go outside for recess at school.. We had an ocean view from our backyard and could see the island of Catalina sitting about 20 miles of the coast.. when the offshore winds would blow I always felt sorry for people on the island because all the smog would blow out to them, but we could finally see the mountains that where only 50 miles away..
Member Since: September 9, 2010 Posts: 5 Comments: 1034
6. 1911maker
9:44 PM GMT on January 17, 2013
4. Cee2SLC 8

I hear you. I lived in Loveland CO in the late 80's. I worked just south and east of Longmont. I drove down a dirt road (now a 4 lane black top road) to get to work. When the inversions got going in the winter I could see Longs Peak from a high point in the road that looked down over Longmont. I could not see longmont however. IT was covered in a smog layer. From above it looked like a flat gray plain. IT was dense enough to look solid.

I left CO because I could not take the air. During the search to move, we checked out Salt Lake City, after checking out Boise. I figured out in a hurry neither of them would be better then the Front Range.

Wood smoke was a big part of it in Boise (I knew people there) and the Front Range.
Member Since: February 25, 2011 Posts: 0 Comments: 474
5. 24hourprof
9:43 PM GMT on January 17, 2013
Great point Cee2SLC.

I was in Salt Lake City back in the late 1990s and I remember a pollution episode. Driving down from Snowbird, I remember seeing a hazy layer over the city.
Member Since: October 24, 2012 Posts: 90 Comments: 798
4. Cee2SLC
8:28 PM GMT on January 17, 2013
Yep, things are bad in China, but keep an eye on what is going on in Salt Lake City. The Salt Lake Valley is ringed by mountains that rise abruptly from the valley floor, and when high pressure ridges settle in, cold air draining down from the mountains at night becomes trapped in the valley, and emissions of pretty much any kind get trapped in the cold stagnant air layer. If it's snowed recently, the "inversion" will get foggy, as water vapor submlimed from the snow will form fine ice crystals that get suspended in the stagnant air layer and can't settle out (not even enough of a breeze to get them to stick to things as rime). Even in a good winter, it's pretty normal to get a 2-4 week period of high pressure, often beginning right after the solstice (when days are shortest and solar warming is at its minimum). The longer the inversion goes, the foggier it gets (often you can't see across a parking lot in the morning or evening). The other characteristic is that while it's 28 +/- 5 degrees day and night in the valley, in the mountains it will be sunny and in the 40's during the day, with temps plunging into the single digits at night, which of course adds to the pool of cold stagnant air getting stuck in the valleys in the morning. This makes being stuck in the fog even more frustrating, because it's warm and sunny 2000 feet above your head but you just can't see it.

When I first moved here in the early 1980's, the inversions were annoying and depressing if you couldn't get out of the valley, but not particularly noxious unless you had a really sensitive respiratory system. However, 30 years later, there are now so many people and so many cars in the valley that we are literally choking in our own waste. Salt Lake has a minimal mass-transit system, with big service holes all over the valley. For me for example, my 60 minute mass transit adventure, featuring 1/2 mile walks on either end, and 3 transfers required in the middle. This year for the first time, I noticed that I would get a catch in my throat and an involuntary cough every time I walked out the door.

Salt Lake had an uncharacteristic flu epidemic the first 10 days of January-- while the flu hit hard on the east coast (probably due to the flu and norovirus outbreak in Europe), it was only filtering back to the west. If you compare SLC's flu rates with surrounding population centers (Denver, Las Vegas), we are definitely an anomaly. I think that it's because either smog-related respiratory symptoms presenting in the ER were diagnosed as flu (similar symptoms), or (or "and") the respiratory stress lowered peoples' resistance to the actual flu. On a cellular basis, it's easy to see how PM2.5 - 10 sized chunks of carbon and other gook could scratch or irritate the cells of your lung enough to give a nice little incubation pad for a flu germ to land on.

Watch this space. We're having a cold winter and we have lots of snow on the ground, and we are currently in a high-pressure pattern that is supposed to prevail until Jan 30th or beyond. We've busted the Air Quality Criteria once already this winter-- with a longer inversion it's going to happen again. While we're pointing at China let's pay attention to those other three fingers that are pointing back at us.
Member Since: January 17, 2013 Posts: 0 Comments: 0
3. 24hourprof
8:16 PM GMT on January 16, 2013
I just received an e-mail from a former (and great) student who graduated from the certificate program at Penn State, Winn Soldani. Winn is a businessman who travels a great deal. Here's his e-mail...it's really incredible:

Lee:

Haven't read your full blog, but saw the topic. I was in Beijing last week...Arrived late on the 10th and departed on the 12th. The pollution was like nothing I've ever imagined. It was so bad that visibility INDOORS (e.g. in the airport arrivals hall) was affected. Horrible.

Winn
Member Since: October 24, 2012 Posts: 90 Comments: 798
2. 24hourprof
8:09 PM GMT on January 16, 2013
Quoting georgevandenberghe:
There is also a summertime situation which produces hazardous conditions The air looks cleaner but it's dangerous to breathe. I'm not up on the chemistry but basically hydrocarbons from internal combustion engines and also some from vegetation, are photochemically decomposed in a process that produces Ozone (O3). Ozone is sometimes present in high enough concentrations to produce significant crop damage in the midwest and east. It is also a hazard to anyone who exercises during midday and evening hours when concentrations are highest and it can be present when the air doesn't look very hazy.
When I was young and fit I was very heat tolerant (more so than most people) but would not jog during midday or evening hours in summer during stagnant anticyclonic periods (half of summer days here) because of the ozone threat in DC in summer. This is more of a summer and daytime/evening problem because you need strong sunshine for the reactions.



Good observation, George.

Of course, probably the worst pollution episode in the Unites States, Denora, PA, occurred in the year I was born not far from where I was living at the time (the Denora tragedy occurred in October, 1948). I was born in Butler, PA (a little more than 50 miles to the north of Denora). During the years I grew up, Butler was also a steel-mill town. I still remember the grit that would accumulate on cars.

So the anticyclones of autumn are no slouch either when it comes to high pollution levels.
Member Since: October 24, 2012 Posts: 90 Comments: 798
1. georgevandenberghe
7:41 PM GMT on January 16, 2013
There is also a summertime situation which produces hazardous conditions The air looks cleaner but it's dangerous to breathe. I'm not up on the chemistry but basically hydrocarbons from internal combustion engines and also some from vegetation, are photochemically decomposed in a process that produces Ozone (O3). Ozone is sometimes present in high enough concentrations to produce significant crop damage in the midwest and east. It is also a hazard to anyone who exercises during midday and evening hours when concentrations are highest and it can be present when the air doesn't look very hazy.
When I was young and fit I was very heat tolerant (more so than most people) but would not jog during midday or evening hours in summer during stagnant anticyclonic periods (half of summer days here) because of the ozone threat in DC in summer. This is more of a summer and daytime/evening problem because you need strong sunshine for the reactions.

Member Since: February 1, 2012 Posts: 17 Comments: 1630

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Retired senior lecturer in the Department of Meteorology at Penn State, where he was lead faculty for PSU's online certificate in forecasting.

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