Ozone pollution improving in the U.S.

By: Dr. Jeff Masters , 7:03 PM GMT on May 01, 2007

Air pollution season is here, and the good news is that ozone pollution in 2006 was considerably better than in previous years. Along with pollution due to small particles (particulate matter), ground-level ozone is the most serious pollutant in the U.S. Ozone levels in 2006 showed improvement in 23 out of 35 of the major cities in the U.S. (Figure 1) compared to 2005, and was at or below the 10-year average in all but five cities. Atlanta, Georgia, showed the greatest jump in the number of unhealthy days, from 17 in 2005 to 30 days in 2006; however, this number was still below the 10-year average. Many western cities reached levels at or above the 10-year average, including San Diego, Sacramento, Denver, and Las Vegas. This was in part due to much above average summertime temperatures in the western U.S. (Figure 2). Los Angeles had the worst ozone pollution in the U.S., with 46 unhealthy days. Los Angeles also was the most polluted city overall in 2006, according to the American Lung Association. However, Los Angeles' bad ozone days declined by 16% in 2006 compared to 2005.

Figure 1. The number of days in May through September of 2005 and 2006 in which ground-level ozone reached Unhealthy for Sensitive Groups--an Air Quality Index (AQI) above 100. Corresponding 10-year averages are also shown. Image credit: EPA.

Ozone pollution has improved
Is the improvement seen in ozone levels in 2006 merely due to a lack of meteorological conditions that favor air pollution? To check, I've plotted the difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005 (Figure 2). The chemical reactions that form ozone are most efficient at high temperatures, so if the summer of 2006 was cooler than usual, we'd expect a drop in ozone levels. However, the summer of 2006 was the second warmest in U.S. history--but ozone levels still dropped. All of the cities where ozone increased significantly in 2006 over 2005 levels were areas where temperatures were above average. Los Angeles had summer temperatures more than 1 degree C above normal, yet still recorded a drop in ozone, suggesting that strategies to control ozone pollution there are paying dividends. In fact, new rules to limit nitrogen oxide emissions from power plants have been enacted nation-wide in the past few years, and the ozone pollution statistics from 2006 are evidence that these emissions rules are working. Ozone pollution since 1980 has dropped 21% (Figure 3), despite the fact that the average summer temperatures have generally been increasing.

Figure 2. The difference in surface temperature (degrees C) from May-September 2006, compared to the 10-year average from 1995-2005. Temperatures were above the 10-year average across most of the country, except for New Mexico, and portions of the Ohio Valley surrounding Kentucky. Image credit: NCAR/NCEP.

Figure 3. Trends in ozone air pollution in the U.S. (white line) and uncertainty (blue areas, marking the standard deviation). The federal standard of 0.08 ppm is indicated by the dashed line. Since 1980, maximum ozone levels have declined 21%. Since 1990, the decline has been 9%. Note that the lowest ozone levels were recorded in 2004, which was an exceptionally cool summer across most of the U.S. Image credit: U.S. EPA.

Next blog (Thursday): Pollution costs and deaths exceed the impact of a new Hurricane Katrina hitting the U.S. each year.

Jeff Masters

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388. franck
12:14 AM GMT on May 03, 2007
Did you guys see the President on 'American Idol'?
Dang I missed that.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
387. StormJunkie
12:15 AM GMT on May 03, 2007
Already been mentioned a few times mel...lol

We are all awaiting the arival of the stone tablets!
Member Since: August 17, 2005 Posts: 26 Comments: 17143
386. StormJunkie
12:14 AM GMT on May 03, 2007
Long day TCW...
Member Since: August 17, 2005 Posts: 26 Comments: 17143
385. melwerle
12:14 AM GMT on May 03, 2007
StormJunkie!!! Oh my - we're all back a bit early. Do I mention the ST name or is lightning going to strike me?
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384. melwerle
12:11 AM GMT on May 03, 2007
bay - i help out with our high school team - 420s and crew on lightnings on my own (yes, my legs are black and blue - real attractive in a dress). The volunteer thing sounds awesome - I do the gig for senior's meals on wheels but this sound great. Just have to get involved with hospice beforehand apparently (which I thought about doing already). Thanks for the link!
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383. TheCaneWhisperer
7:59 PM EDT on May 02, 2007
Evening SJ! How's it going?
382. StormJunkie
11:56 PM GMT on May 02, 2007
Evening TCW!

Good to see you too Mel and MissB ☺
Member Since: August 17, 2005 Posts: 26 Comments: 17143
381. MissBennet
6:53 PM CDT on May 02, 2007
Posted By: weatherguy03

MissB. You definitely have the concept! Last summer over the Eastern Half of the U.S we had more of a trough setup. This moved the Bermuda High more west, thus you saw alot of storms head for Bermuda. Thats the perfect setup for all of us!! The way the High has been for the past month or so would be bad for the Gulf Coast states. So, you can see what is good and bad.

Thanks Weatherguy and Levi for your answers. It helps me alot. =)
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380. StormJunkie
11:52 PM GMT on May 02, 2007
Evening all! Good to see you Bay!

DDR, I think you can find that imagery site from here as well as some very good forecast model pages.

Also, for those who have not seen, I have some pretty good year to year SST comparison maps for the Gulf Stream and the GOM in my blog. The maps are now updated and the John Hopkins site is back on line.

Alright y'all, I will check back in later. Working on a 15hr day and still have a couple of more to go.

See y'all later
Member Since: August 17, 2005 Posts: 26 Comments: 17143
379. TheCaneWhisperer
7:54 PM EDT on May 02, 2007
Severe wheather flaring up in SEFL! Lightning ahead of the storms, hopefully it doesn't spark some fires!
378. Baybuddy
11:43 PM GMT on May 02, 2007
She is an eighteen foot Edgewater center console with a 115 Yamaha four-stroke. Her name is Loup Garou. Lets see if any of the South Louisiana folks recognize the name!
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377. Baybuddy
11:40 PM GMT on May 02, 2007
Thanks mel, My wife is the new executive director. The founder lost his wife to cancer several years ago and met a sick baby girl who was at the same hospice as his wife. The girl passed away and gave him the idea of providing some comfort to sick children. He is a saint. Sort of a cross between Burl Ives and Earnest Hemmingway.
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376. melwerle
11:35 PM GMT on May 02, 2007
hey baybuddy - what kind of boat? I'm a sailor (crew actually) but love boating of any kind.
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375. melwerle
11:26 PM GMT on May 02, 2007
Hey Baybuddy - nice link - saved it to my favorites. What a wonderful way to volunteer.
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374. Baybuddy
11:33 PM GMT on May 02, 2007
I am going to begin an addition on my house in early September, so I for one hope for many, Many fish storms this year.
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373. Baybuddy
11:29 PM GMT on May 02, 2007
Me too.
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372. Bamatracker
11:28 PM GMT on May 02, 2007
your correct mel...it still early for anything to form off Africa. i think this storm will dissipate soon after getting over water.
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371. Bamatracker
11:26 PM GMT on May 02, 2007
I've been doing good. Im just trying to get back in bloggin' mode after the winter.
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370. Baybuddy
11:24 PM GMT on May 02, 2007
Great Bama, just lurking a bit. I was waxing my boat but the skeeters got too bad. How are you?
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369. melwerle
11:22 PM GMT on May 02, 2007
Wow! Checking out that wave but it's a bit early - what does this mean though - it's just a wave rolling out and hitting brazil or something? T-storms etc or does it form - i think it's a bit early for this though if I'm not mistaken.
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367. Baybuddy
11:24 PM GMT on May 02, 2007
If anyone feels like it, This is a worthy cause. If yall know any santas who wish to volunteer, drop them a line.Link
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365. Bamatracker
11:22 PM GMT on May 02, 2007
sup baybuddy!!!!! how ya been?
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364. Baybuddy
11:20 PM GMT on May 02, 2007
Greetings All!!
Roll Tide!!!
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363. DDR
11:10 PM GMT on May 02, 2007
Taz. where did you get that infrared imagery?
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362. Tazmanian
4:02 PM PDT on May 02, 2007
Posted By: 882MB at 3:32 PM PDT on May 02, 2007.


882MB her you go!

Member Since: May 21, 2006 Posts: 5096 Comments: 117196
361. Bamatracker
11:04 PM GMT on May 02, 2007

African wave is still looking impressive!!
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360. Bamatracker
10:53 PM GMT on May 02, 2007
evening everyone!!
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359. 882MB
10:31 PM GMT on May 02, 2007
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358. NRAamy
3:31 PM PDT on May 02, 2007

Thank you!!!!!!


Member Since: January 24, 2007 Posts: 319 Comments: 31956
357. weathermanwannabe
6:28 PM EDT on May 02, 2007
We should be okay so long as all these "early" waves do not "go west"..............
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356. Inyo
10:15 PM GMT on May 02, 2007
whoever asked about why LA has severe smog...

the biggest reason for the smog is that a coastal inversion often forms, preventing air from rising above 3000 feet or so. Los Angeles is surrounded by mountains averaging 4000 to 7000 feet tall on one side, and the ocean on the other side. The ocean breezes blow smog under the inversion and it can't get over the mountains.

This is the reason the smog is so bad... the reason the smog is created in the first place is that there are too many cars in the city. However, even before there were cars, the area was known for its 'natural' smog caused by wildfires, small campfires, etc.
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354. DDR
10:14 PM GMT on May 02, 2007
yes seem things in africa are firing up a bit, soon we'll see some wave action
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353. weatherboykris
10:09 PM GMT on May 02, 2007
Posted By: HurricaneMyles at 11:51 AM GMT on May 02, 2007.

I wonder what the difference is between what we are seeing coming off the coast of Africa now and what we will see in a few months. What we have now appears to be inverted surface troughs, the same as tropical waves - the only difference I can see is that waves now are 5-10 degrees farther south then they will be in August.

Sigh.this is the last comment I'm making on this issue.A tropical wave...as defined by the NHC:

Tropical Wave:
A trough or cyclonic curvature maximum in the trade-wind easterlies. The wave may reach maximum amplitude in the lower middle troposphere.

You see...there is no latitude requirement for it to be called a TW.It is a kinking of the normal northeasterly trade winds to the SE.It is a tropical wave by definition.It won't develop,so it really doesn't matter anyway.BBL
Member Since: December 9, 2006 Posts: 125 Comments: 11346
352. 882MB
10:06 PM GMT on May 02, 2007
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351. weatherboykris
10:08 PM GMT on May 02, 2007
We already had our first tropical wave.Look at last night's comments.
Member Since: December 9, 2006 Posts: 125 Comments: 11346
350. DDR
10:01 PM GMT on May 02, 2007
Good night everyone.Has anyone noticed the large cluster of t-storms along the west african coastline.I think this might be our first tropical wave. what do you guys think?
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348. melwerle
9:45 PM GMT on May 02, 2007
we moved here two years ago from san diego and it rained for almost two weeks straight. I haven't seen rain like that since then. When Alberto came through, it was like getting a spritz - the outside sprinklers were stronger.
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346. melwerle
9:33 PM GMT on May 02, 2007
I'm in Georgia and we haven't seen any rain forever. I would love for even just one day of showers...
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344. franck
9:28 PM GMT on May 02, 2007
Storyofthecane..Yes, the residential areas around Orlando/Winter Park are so lush green. I'll never forget how huge the grassblades were around those numerous little lakes.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
343. i12BNEi
9:16 PM GMT on May 02, 2007
Maaan,I started back on here too early this year.I'm already looking and looking.I can't sleep.But,It does not look like anything is going to start anytime soon with the latest GFS Shear runs.West central fl. is HOT today.
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340. melwerle
9:00 PM GMT on May 02, 2007
Evening all - anything interesting going on?
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339. Caymanite
8:51 PM GMT on May 02, 2007
Yes Kmanislander but still no rain.The Island looks like it is ready to catch afire. I still lurk every day and thanks to you for keeping the island represented in the blog.
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338. StoryOfTheCane
8:54 PM GMT on May 02, 2007
if youve ever been golfing in Central Florida there is absolutely nothing like it, 365 days a year, wet season you lose a little more balls than youd like though, puddles kind of show up in random places and dont go away until the dry season
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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