Best And Worst Time Of Day For Air Pollution
34 replies to this topic
Posted 2010-03-07 19:39:04
I find the mornings bad because the air tends to be still but conversly there are more fires in the afternoon. I think it comes down to if the wind is blowing and from where.
It could be blowing worse air or better depending on the situation.
Posted 2010-03-07 19:50:38
I find it better when all the TV members are on line and at its worst when they are off line.
Posted 2010-03-07 20:41:00
I find that it is essential fires season thread #9 so far. And that's a little more than anecdotal.
I wonder if we'll make it to 20 ?!
Posted 2010-03-07 21:30:11
Yes I believe this is true about the wind. I was in mae Sai the other day and pollution level was much higher than here but did not seem as bad because it was windy. Also, this proves that my teacher did not know about this forum. He said if you ask a stupid question you get a stupid answer. But on this forum it is guaranteed if you ask any question at all, you will get at least one stupid answer.
Posted 2010-03-07 22:20:39
You got the stupid part right. T.V. is like a super dense black hole universe sucking nuclear magnet for attracting the retards.
When I mentioned wind I was more referring to the issue that the CM valley tends to have inversion air circulation pattern which holds and intensifies the air issues. Often times when the wind is blowing it can blow in cleaner air in and bad air out. This time of year wind might just be blowing in more smokey air from as far as Myanmar. So I would not count on wind to always make conditions safer.
Maybe Priceless has a theory on that.
While its true the air feels fresher when the wind is blowing it does not mean the levels of particulate matter are lower.
If I am deciding to exercise I use a smell and visibility test to decide if its a good idea.
Posted 2010-03-07 22:24:40
I'm not sure there are daily fluctuations in pollution. (For sure there are fluctuations from day to day, but less sure there are regular patterns within a single day). For sure there are fluctuations in visibility though, with mornings being not as a good as evenings. However that may be due to higher mosture levels in the air in the morning.
Posted 2010-03-08 01:09:28
If the problem was smog like they have in Los Angeles, the best air would be early morning and late afternoon/early evening which is confirmed by the available results of hourly data for LA. But the LA problem is gases and the problem here seems to usually be particulates. My guess is that wind helps only if it is strong and long enough to clear the valley significantly and as CSN stated, the wind is bringing clean air.
Posted 2010-03-08 02:50:47
Looking at the data for all provinces surrounding Chiang Mai, why would the wind bring clean air? Where would the clean air come from?
Posted 2010-03-08 11:54:53
LA is located by the sea, isn't it? At least to my limited understanding that would seem to mean a completely different type of weather cycle. Chiang Mai is in a mountain valley far from the sea and no direction I can think of has less burning or cleaner air...
Posted 2010-03-08 12:14:46
Sawasdee Khrup, Khun Tomahawk,
Yes, that it is a wonderful feature of this forum, and so many other on-line forums: you have the opportunity to develop skills in recognizing ignorance, grandiosity, sociopathy, and brain-damage at the same time as you practice recognizing pro-social behavior, empathy, sincere concern for other's welfare, and open-hearted generous sharing of helpful information
Posted 2010-03-08 12:18:21
That is my thought also that wind right now does not really help but wind is more complicated than that with elevation layers like jet stream effects which can be affected by mountain ranges etc.
There is a weather prediction for a high pressure system from China to arrive soon(mar 10) and cause some thunderstorms and strong gusts in N. Thailand. Keeping my fingers crossed it will put some of these particulates onto the ground.
Posted 2010-03-08 13:23:17
Sawasdee Khrup, Khun CobraSnakeNecktie,
We were just wondering why WeatherUnderground.com was predicting a high of only 28C (82F) with twenty percent chance of rain this Wednesday, while ThaiVisa's weather service (a few hours ago was predicting a high of 19 C !) is now predicting 29C. As of now, TV is predicting a low of 24C, and WeatherUnderground a low of 19C.
We're going to cross our legs behind our back and join you in praying for Chinese mercy of the meteorological flavour !
Down with particulate matter !
p.s. in Mae Sai yesterday (Sunday); severe haze; estimated visibility about a kilometer at most.
Posted 2010-03-08 13:25:25
If this is true, maybe you have a theory as to why the Chiang Mai valley regularly has less air pollution than the provinces outside the valley, i.e. on the other side of the mountain ranges?
Posted 2010-03-08 13:29:51
Yes, LA is different. A significant off shore wind can push the bad air out to sea. The more common onshore wind just keeps it in the LA basin.
And yes, I too think it is a very unlikely possibility that at this time of year Chiang Mai would get a wind bringing significant clean air. Perhaps we will be pleasantly surprised by CSN's high pressure system due to arrive in 2 days, rain seems to bring relief.
Posted 2010-03-08 13:59:53
Possibly because the polluted air from Burma etc. has more trouble to cross the mountain ranges and into our valley? This may explain why other areas experience higher pollution levels before we do. On the same token, this may mean it sticks around longer once here, unless of course rain enters the equation and rains all the crap into the ground.
Posted 2010-03-08 14:06:32
Well define regularly? Recently it has been better but that has changed in the last few days as CM PCD readings have climbed into dangerous levels.
An inversion effect would tend trap in local emissions. One benefit is that as time goes on CM valley is decreasing its percentage of agriculture use as land values increase and subdivisions etc are built.
Is anyone postulating that the CM valley does not have periodic inversion air flows which trap emissions?
Some of the other provinces you allude to are almost 100% agriculture based so I would expect their seasonal burning to produce more emissions and hence higher PM levels.
CM certainly has more emissions from car, tuk tuks, restaurants etc due to the denser population and traffic. Modern car emissions increase the PM <2.5 which aren't even measured in Thailand.
During periods of non agriculture burning I anectdotally observe the air tends to be cleaner outside the valley. Perhaps that is due to less traffic and restaurants etc.
I don't think its a simple analysis by any stretch. Many variable factors to consider.
Posted 2010-03-09 22:03:43
I based my statement about "regularly" on three (albeit inter-related) criteria: Average yearly pollution level, average monthly pollution level during the "peak season" and number of "bad days" (i.e. with PM<10 greater than the PCD standard of 120 µg/m3).
PCD only started posting full-year data for Northern provinces other than Chiang Mai and Lampang from the beginning of 2009, so there is not that much data available as of yet. These are the yearly pollution levels (in µg/m3) for 2009 with the number of "bad days" in parentheses:
Chiang Mai: 41.6 (16)
Chiang Rai: 49.4 (28)
Lampang: 57.6 (33)
Lamphun: 45.4 (18)
Mae Hong Son: 45.6 (33)
The average monthly pollution levels can be seen in this graph:
Northern_Thailand_2009.jpg 124.87KB 11 downloads
Your "anecdotal" observation that "the air tends to be cleaner outside the valley" does not seem to be supported by this graph (or the underlying table). I would actually have expected more of a difference in non-burning season, due to greater traffic, population density and so on, but the greatest difference (i.e. with Chiang Mai having a higher value) in 2009 was 5.3 µg/m3, i.e. very marginal.
The number of "bad days" so far this year can be seen in the following graph:
Bad_days_2010.jpg 69.98KB 8 downloads
It is very interesting that you (implicitly) claim that Chiang Mai has an unusually high incidence of inversions. Have you got a source for this?
It is rather self-evident that pollution has many different sources. It would require a lot more serious research to prove anything in this case, in particular with only just over a year of data, but I still tend to agree with WinnieTheKwai that neighbouring countries, in particular Burma, may play a much greater role than what is generally thought. It appears to me that the mountains, rather than trapping pollution in and around CM, may actually be protecting us from the worst of the onslaught.
A further case in point: On 27 February PCD started posting pollution figures for Mae Sai, i.e. even closer to the Burmese border than Chiang Rai. The (scary) results for the eleven days of records so far are:
Mae_Sai_pollution.jpg 54.97KB 7 downloads
Posted 2010-03-09 23:24:01
Priceless I think you read into I was saying CM has an 'unusually' high number of inversion days. I'm not in the "its really bad camp" or the "its fine camp" when it comes to air pollution. I'm not sure what constitutes average or above average inversion days. Local small aircraft pilots might have an idea. Anyway inversions tend to occur at the base of mountains as the air is not powerful enough to flow over and just recirculates similar to an eddy in the water. Temperature gradients have something do with inversions also.
When I said the air tends to be cleaner out of the valley then how could you know the air quality up in the mountains is not better? Isn't the mobile station up by the palace almost always better air quality? I would still stick to that anectdotal analysis if based on nothing more than just more trees to clean and refresh the air. When I used to live in Boulder Colorado at the base of the rockies it was common to have inversion flows and when descending back into the valley it was apparent because it like a brown cloud. Feels the same to me here. Perhaps that is just localized pollution and not an inversion. Not sure really.
I would tend to agree Myanmar really looks like a major likely source of a lot of this now and perhaps a lot of the year. The high levels at Mae Sai seem to really implicate Myanmar.
Posted 2010-03-10 06:38:57
A buddy just came back from visiting Luang Prabang and reports that the whole town and the whole area is immersed in one big cloud of smoke. That is what it looked like 10 years ago at this time of year, so this is nothing new.
Posted 2010-03-10 08:34:38
it's raining !!!!! how cool is that
Edited by CobraSnakeNecktie, 2010-03-10 08:47:21.
Posted 2010-03-10 12:03:10
Well, what's wrong is that yesterday (todays' report) was the first 'bad' day this season. The numbers for Mae Hong Son, Chiang Rai and especially Mae Sai remain horrific though. I seriously hope that crap doesn't come our way, and/or the area gets some decent rain today.
Posted 2010-03-10 12:26:06
YAAAAY!!!! Raining as I was writing my last post!!! Great! Let's have some more! AND it's a bit windy...
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