Air Quality Map - populated areas are less polluted ?! (Fresno: agriculture, air pollution)

[millr]

I don't understand this map from NOAA's National Weather Service/Environmental Protection Agency - United States Air Quality Forecast Guidance :



It seems that the populated areas (SD, LA, Yuma, LV, Fresno) have less ozone. Is this right?

[GraniteStater]

Prevailing wind patterns are the answer. Winds often blow in off the ocean from the west and transport the poorer air quality to inland locations. This is why locales like Lake Arrowhead in the San Bernardino mountains have poor air quality and ozone affected trees, particularly in the past. The Central Valley sits in a geographic bowl and has some of the worst air quality in the US mainly due to geography, airborne transport of bad air, and agriculture.

[millr]

But what about LV, Fresno and Yuma? Why are they in the pockets of clean air?

On the other hand, why is the air over the ocean more polluted than over the coast?

[BVitamin]

Originally Posted by millr

I don't understand this map from NOAA's National Weather Service/Environmental Protection Agency - United States Air Quality Forecast Guidance :



It seems that the populated areas (SD, LA, Yuma, LV, Fresno) have less ozone. Is this right?

Read the words in the picture. Mornings are better, afternoons are worse.

Edit to add, I just went to the link ... it's fairly simple and not really hard to understand.

[Fontucky]

That link no workee here.

[millr]

Originally Posted by BVitamin

Read the words in the picture. Mornings are better, afternoons are worse.

Edit to add, I just went to the link ... it's fairly simple and not really hard to understand.

Which words are you referring to?

I just went back and played with the time period for the 8h average (this is not "8am average"), and L.A. looks like it has the best air quality of all of SoCal overall. Its air is typically better than the air over the ocean 50 miles off the coast. This can't be right, unless the surface wind blows from L.A. in all directions all the time (possible in principle, but I'm skeptical)

[millr]

Maybe cars and people consume ozone, thus cleaning up the air?

http://en.wikipedia.org/wiki/Ozone#Low_level_ozone

[millr]

Originally Posted by Fontucky

That link no workee here.

Sometimes, it doesn't work for me either. *gov website - pretty typical. Just try to reload.

[oldtrader]

You have to remember, it depends on which day you look for the air pollution level, time of day, wind direction or no wind conditions, temperature, if there is an inversion, and many other factors. What looks good at one moment, may an hour later look terrible..

[Fontucky]

That map reminds me of what used to happen in South OC when I was growing up. The mornings would be nice and clear with good air, but you could see the brown poison from L.A. hanging offshore, blocking the views of Catalina and S.C. Island. Somewhere around 1:30 the onshore flow would commence, and the poison would roll in, making it hard to breathe and reducing visibility.