I'm going to have an interesting day today as I leave suffering for misery. This morning, I'm in upstate New York. It was -11F when I woke up this morning and was brutally cold. Upstate New Yorkers like to say that there's no such thing as bad weather, only inappropriate dress. However, they are a hardy lot. My niece left for the bus this morning wearing a thin pair of slip on shoes. Ah, teenagers...
Later tonight I arrive in Salt Lake City where misery awaits. I've been watching the air quality there the past few days and it looks nasty as the PM2.5 concentrations have been flirting with the National Ambient Air Quality Standard for several days. One thing that is interesting and that I don't understand are the huge fluctuations from day to night in PM2.5 concentration. These are as large as I've seen. Perhaps someone out there who knows more about air chemistry can comment.
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| PM2.5 concentrations in the Salt Lake Valley. Source: Utah Division of Air Quality |
The models hint that Salt Lake may get some relief tomorrow. I'm keeping my fingers crossed that happens as I've learned to enjoy breathing clean air the past couple of weeks.
Check out the wind direction - it appears to cycle similarly.
ReplyDeleteMy thought is that this is cleaner drainage air from canyons and mountain slopes arriving right at the surface during the night, which mixes with the dirty air above it by mid-morning. Maybe the exceptionally calm wind conditions would allow this to be more pronounced? It would be interesting to have a PM detector up on a tall building and one on the ground to compare.
ReplyDeleteI agree with the cleaner drainage air hypothesis. In the upper part of Olympus Cove above 5500 feet, I've experienced the air completely clearing every evening as soon as downsloping flow on Mt. Olympus and down Neff's Canyon begins. You can watch the smog move northwestward with time as it is illuminated with city lights. Very early in the morning, the east bench is usually completely out of the smog. A little farther west into the city, the clean air may be undercutting the dirty air as David suggests. At locations lower than the east bench, fog and frost have been forming as well and I usually have a bit of deposition on my car in the morning...not sure if that matter at all.
ReplyDeleteIt seemed like there was a lot more mixing last night (Jan 22-23) within the inversion layer due to overlying winds, and there was no distinct dip observed in the PM 2.5 level. Visually it looks to be mixing out quite a bit this afternoon so hopefully we can get rid of some of this. I think that with a lot of bare ground the sun may be strong enough now to warm the valleys a bit more if we can get rid of the fog and haze.
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