The Weather

[ScottyMet]

Hello everyone. I figured I'd start off my time here right and provide some (hopefully) helpful information to the forum.

I have been a meteorologist for roughly 10 years now. I started off working for the Ontario Government, doing air quality (smog) forecasting, then worked for The Weather Network as a meteorologist (behind-the-scenes, with very minimal on-air time, just fyi), and now I'm back to air quality forecasting in Atlanta, GA. My main specialties are air quality and operational weather forecasting. Also fyi, I haven't been keeping up on the whole climate change topic, except for just the very basics. My main interest is severe weather, especially lightning. I'm not too interested in tornadoes or storm chasing, mostly because I'm not insane.

I will post info here from time to time about the science of meteorology and weather forecasting, but I thought I would also offer up this thread for people to ask questions about the weather. I will endeavor to answer your questions to the best of my ability, and if I don't know the answer, I'll look it up, thus increasing my own knowledge!. Also, feel free to post your own knowledge, if you want. I promise to be gentle if I need to correct anything, and don't be afraid to correct me on something either. I don't know it all. heh

I'll start off with some basic air quality information.

[ScottyMet]

The biggest air quality "offenders" are fine particulate matter and ground level ozone. Both together are primarily what make up smog (although other pollutants can be, and usually are, included as well, just in smaller, or less "effective" concentrations), and these are the two main pollutants that air quality forecasters look for.

Fine particulate matter mainly comes from burning diesel fuel, wood smoke, and power plants. The exact components of fine particulate matter can vary greatly, but they typically act directly on the lungs to physically gum up the membranes and prevent uptake of oxygen. These particles are small enough that they can be breathed deep down into the lungs, bypassing all our built-in defense mechanisms, and do their damage there.

Ground level ozone, although chemically the same as the ozone in the stratospheric ozone layer... O3... has different effects. The stratospheric ozone layer is incredibly beneficial to life on his planet, because it absorbs the more energetic types of UV radiation that the sun emits. Ground level ozone acts as a lung irritant in animals. Because O3 is chemically very close to O2, which our lungs are specifically designed to preferentially absorb, the lungs attempt to absorb O3, and the molecules bond to the membranes in your lungs, rather than passing through into the bloodstream, thus inhibiting the membranes from absorbing as much O2.

There is always a small amount of ground level ozone, a "background" amount, which typically does not have any noticeable adverse affect on people unless their respiratory system is extremely compromised. It is increased concentrations of it that are the major concern. We get these increased concentrations as a byproduct of incomplete fossil fuel burning, with the major culprit being automobile engines, but coal burning power plants also contribute quite a bit. When fossil fuels are burned, one of the chemicals emitted is Nitric Oxide (NO). At the temperatures NO is typically emitted, post-burning, it reacts with the background O3 molecules, cleaving off one oxygen atom from the O3 and bonding with it, so that you are left with NO2 and O2. Now, oxygen is good for us, right, so this is good... right? Well, yes. O2 is good. However, NO2 is not, environmentally speaking. If we could immediately remove that nasty NO2 from the atmosphere, we'd be set, but unfortunately, as photons from the sun strike NO2, it breaks off one of those oxygen atoms, and gives us back NO and O3.

The problem then becomes one of accumulation and concentration. Each morning, millions of cars get out on the road and chug out their NO exhaust, which reacts with whatever O3 that happens to be around at the time, to make NO2 and O2, and the sun gets high enough in the sky so that its photons can retain enough energy by the time they reach the surface and they break up the NO2 again and we get back NO and O3. The more NO and O3 that are left at the end of one day can have a large effect on how much we get the next day.

[ScottyMet]

A big factor in these two sources of pollution becoming a problem is the weather conditions, and something we call The Atmospheric Boundary Layer. This is the lowest layer of the atmosphere, the one in direct contact with the surface.



The thickness of this layer usually depends on the temperature profile of the atmosphere, that is, the rate at which the temperature drops as you go upwards. If you have relatively dry conditions, temperatures go down by 1 degree Celsius for every 100 meters you go up from ground level. This is called "The Dry Adiabatic Lapse Rate", and the line of this rate on a temperature vs height graph is called "The Dry Adiabat". If you have humid conditions (where relative humidity is near or at 100%), the temperature goes up by about 1/2 a degree per 100 meters, and this is called The Moist Adiabatic Lapse Rate, and the line of this on the graph is called "The Moist Adiabat". You can use these two lapse rates to figure out at what height above the ground clouds will begin to form, given a specific set of atmospheric conditions, and even how tall those clouds will be.

If the temperature goes up with height, instead of down, you have what is called "a temperature inversion". Where the temperatures start to rise with height is the bottom of the inversion layer, and where temperatures begin to go down with height again is the top of the inversion layer.



Sometimes the bottom of the inversion layer starts at the surface and sometimes it starts higher up. If you are ever driving in to work and you see a thin layer of brown haze hanging over the city, but it is clear underneath and above, you can be sure that it is due to a thin inversion layer, where the bottom of the layer is well above the ground. If the entire city, from the ground up, seems choked with pollution, then the ground is the bottom of the inversion layer. The latter case is the more common, so that is what this discussion will mostly deal with. Wind speeds are almost always lower than the wind speed above the inversion layer, and at times, the difference is quite pronounced. Inversions happen quite often. Nearly every day, in fact. Overnight, surface temperatures drop, which also cools the air above it. When the sun rises in the morning, it will begin heating the air above the ground first, since its photons encounter those molecules of air first. Thus, we end up with warmer temperatures above, and cooler temperatures below. As the sun heats the ground, the air above the ground heats up, and when the temperature of that air exceeds the temperature of the air higher up, that was heated first by the morning sun, the inversion "breaks", and the depth of the boundary layer increases from there. These inversions can persist for a long time, depending on atmospheric conditions. If there is a slightly different wind direction higher up, and winds come from a slightly warmer area, you can end up with warmer air aloft that will stay warmer than the air at the surface, no matter how hot the air near the surface gets. This "persistent" inversion can last all day, or it can break very briefly, in the middle of the day, when surface temperatures are at their highest.

[ScottyMet]

Now to combine all these factors, and give you the full picture.

Case 1: In conditions with a deep boundary layer and good winds (typically when you have a Low Pressure Trough, that big "L" you see on weather maps), the amount of pollution put out into the atmosphere by daily human activity does not have much effect on air quality concentrations, because not only is there a large volume of air for these pollutants to mix into, but much of the pollution blows downstream in the wind flow after it is produced, and it is dispersed at the same time, becoming less concentrated with distance. The morning rush hour will produce amounts of NO from gasoline combustion, this will react with any O3 left over from the previous day, produce NO2 and O2, then when the sun gets high enough in the sky, and its photons can reach the surface with high enough energy, they break the NO2 back into NO and O, and that O combines with O2 to produce O3. This O3 then mixes into the large volume of the deep boundary layer and is blown downstream in the wind flow as well. There is very little pollution that actually stays in the urban area, and air quality levels remain low, and since the wind also disperses the pollution with distance, even those areas downstream from the urban centers experience low concentrations.

Case 2: In conditions similar to above, but with light winds, there is still a very large volume of air for the pollutants to mix into, so although air quality levels may rise some, they will still remain relatively safe (although very sensitive people may still feel it).

Case 3: In conditions with a shallow boundary layer and light winds (such as when an area is under a High Pressure Ridge.. the "H" symbol you see on weather maps), this same amount of pollution can have a much greater impact on us. The cars put out the same amount of exhaust as the above example, but in this case, the NO does not travel very far before it is converted to NO2 and O2, and is still quite close to its source when the sun then converts it back to NO and O3. The first day of this will probably not be very bad, however, because this pollution has stuck around all night, trapped in the nocturnal boundary layer and residual layer, due to the light winds, when the cars start producing more pollution in the morning, it will add to what is already there. There will be even more O3 left around from the previous day for the NO from the cars to react with, creating even more NO2 than the previous day, which will then convert back to NO and O3 when the sunlight interacts with it, and concentrations will build. If these conditions persist, even more O3 will be around over the next night, and the following morning, it escalates again... and this can go on and on, getting worse and worse each day.

Case 4: In conditions with shallow boundary layer and stronger winds, the same situation can happen, although concentrations will be slightly lower, but will have a much farther reach. Cities downwind of larger urban centers can experience a direct impact on their air quality due to this.

[ScottyMet]

This sort of situation rarely abates on its own.

A smog event such as in Case 3 will likely persist until the conditions causing it move on. Usually this happens when a Front moves through the area (the red line with the bumps and/or blue line with the spikes). The cold front (the blue line with the spikes) is usually accompanied by instability and strong winds, as well as a wind shift from southerly to northwesterly after the cold front passes by. When watched on a map of weather and pollution conditions, it will appear as though the cold front is literally sweeping the polluted air away, as ozone and fine particulate matter levels drop when the cold front moves past. What is really happening is that the increase in wind speed and the deeper boundary layer associated with the air behind the cold front is mixing the pollution up into the greater volume of cleaner air behind the front and the concentrations drop in response. Particulate matter can also act as cloud condensation nuclei, thus getting physically taken up into the clouds and then being washed out in the raindrops.


The warm air represents the smoggy area. The cold air is the approaching cleaner air.

When a warm front passes through, and brings less instability, but more persistent rain, the air quality values can drop as the particulate matter is sucked up into the clouds. Ozone levels will also drop by the same mechanism of mixing into the larger volume, but the mechanism for ozone production will also be stopped by the clouds, which will substantially reduce the number of photons that reach the surface with sufficient energy to split NO2.

[FBM]

Wow. Cool.

[Xamonas Chegwé]

Just skimmed a little for now but I will be back to read more, Scotty. Fascinating stuff. but then, I'm English, talking about the weather is our national obsession!

[ScottyMet]

I was away this week at the National Air Quality Conferences, in Raleigh, NC, and now that I'm back, I thought I'd share some things I learned, specifically to correct some of the information I'd related above.

My ideas about the effects of Ozone on the lungs was a tiny bit outdated, it seems. I attended a talk by Dr. David B. Peden, Professor of Pediatrics, Medicine, Microbiology & Immunology, at the University of North Carolina School of Medicine, and he gave a very interesting presentation about the Health Effects of Air Pollution.

One aspect of ozone exposure that had a lot of people scratching their heads was the fact that most hospital admissions due to respiratory distress occurred the day AFTER elevated levels of ozone were experienced. Initial thoughts, which I mentioned in previous posts, was that exposure to elevated concentrations of ozone increased sensitivity to other pollutants in the environment by irritating the tissues of the lungs. This is partially correct, however the mechanisms involved have more to do with allergic responses.

Eosinophils are white blood cells that are a component of the immune system, which are responsible for fighting off multi-cellular parasites. They are largely a left-over in our biology, as we do not tend to suffer from parasites as much as we used to, as a species. However, if you have certain allergic reactions, such as hay fever, pet dander, or dust mite allergy, it is these cells that are responsible. They interpret the pollen, dander, or dust mite "dirt" as a multi-cellular parasite and attach to it, coating it in chemical substances which would kill a multi-cellular parasite. These chemical substances are what cause irritation in the lungs and upper respiratory system, causing you to produce mucus, sneeze, your eyes to water, etc, all in an effort for your body to flush these irritants from your system.

Ozone has been found to increase the number of eosinophils in the respiratory tract, causing an over-reactive response to any possible allergens that may be present in your respiratory tract at the time (pollen, particulate matter, etc).

[Animavore]

Coinkadink. I just happen to be reading this right now.



It's totally related

[Rum]

Well this is very informative! Thanks for taking the trouble!

[Azathoth]

Great stuff Reminds me of an argument I had with one of the tinfoil hat brigade on facebook the other week. The mad bastard has an ozone generating machine in his house. Of course all the problems I pointed out with this are just new world order propaganda because ozone destroys the mind control chemicals dropped in chemtrails. Loonies are funny.

[ScottyMet]

Coinkadink. I just happen to be reading this right now.

It's totally related

It totally is! It's part of what makes weather forecasting so interesting.

I'll have to pick that one up.

Great stuff Reminds me of an argument I had with one of the tinfoil hat brigade on facebook the other week. The mad bastard has an ozone generating machine in his house. Of course all the problems I pointed out with this are just new world order propaganda because ozone destroys the mind control chemicals dropped in chemtrails. Loonies are funny.

I remember giving a talk to a group of highschool students visiting my university about ozone, and one girl mentioned that her parents have an ozone generating machine and run it often, since it's supposed to improve indoor air quality. She was concerned that the concentrations that were being generated might be harmful. At the time, I reassured her that it was likely harmless at the concentrations that those things generate, but with the studies I've seen since, I'm not so sure... repeated or constant exposure to low-level concentrations can have the same effect of increasing sensitivity to allergens.

Chemtrails are hilarious. I hear this one a LOT. We try to fight against it by explaining what contrails are, and why they show up, but the people in this country are just too infatuated with the idea that their gubberment is out to get them.

[Woodbutcher]

The painters at work have an ozone generator whenever they have to paint somewhere where a person objects to the smell ( I work in schools). The generator makes a clicking sound when it's operating. It does not produce any ozone, as it hasn't worked properly for years, but as long as it is running the people with sensitivities notice a great improvement in air quality.

[FBM]

My friend's mother-in-law had a ozone generator. She'd also been abducted by aliens.

As for weather, I was thinking about this the other day. Here in Korea, there's hardly ever any thunder and lightning during storms. It does happen, but with far less frequency than in the US Southeast, where I used to live. The number of storms and amount of rainfall aren't drastically different. I like thunder and lightning. Wouldn't mind more of them. Why doesn't Korea have as much as the Southeast US?

[ScottyMet]

That's very interesting, FBM. I had no idea that thunder and lightning were so rare in Korea.

I don't know of any specific meteorological reason for it, so it might simply be due to your local geography.

If you live in Seoul, storms you get there would likely be due to orographic lift. Moist winds blow onshore and up the side of the mountains, and they dump out that moisture as rain as they rise. Conditions weren't necessarily good for storms to begin with (the orographic lift forces the issue), so the necessary processes to produce the charge differentiation for lightning to occur couldn't get going until the storms are further up the mountain. This would likely be the case for any locations on the west side of the country (west of the mountains).

If you're further south or east, let's say in Pusan, that lies in a river valley. Winds blowing from the west would cross the mountains to the west of the city and dump most of their rain (and lose a lot of energy). The storms would be suppressed as the air flowed down the eastern side of the mountains (sinking air is very stable and resists convection), but could start to build again as they approached Pusan, but would likely not build to the right intensity to produce lightning.

That's off the top of my head, anyway. I'll look into it more, and see if I can come up with anything else.