There is some good out there if you happen to be above the air pollution, but for the most part, the weather right now in the Salt Lake Valley is simply bad and ugly.
Let's begin with a quick look at the morning sounding. The surface temperature was -0.3˚C (31.4˚F) and increased with height to 3.4˚C at 818 mb (about 6000 feet). The humidity near the surface was also very high.
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| Source: SPC |
Below are observations from the Salt Lake City International Airport. They are in "METAR" format, a sort of short hand for summarizing weather observations. The first column in the station ID (in this case, KSLC), then the time (in UTC or "Z" time, then the wind direction and speed (ending in KT), and then the visibility and present weather. Time increase from bottom to towp. Note the transition from HZ (Haze) late yesterday to BCFG (patchy fog), and finally FZFG (freezing fog).
Thanks to the formation of fog, the temperature at the airport has gone practically nowhere today and sits presently at 32˚F.
Surface observations from Mesowest during the hour ending at 1952 UTC (1252 MST) show the incredible structure of the inversion in the Salt Lake Valley. During that period, it was 32 at the Salt Lake City Airport, 37 at the University of Utah, and 42 at Mountain Dell in Parley's Canyon.
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| Source: MesoWest |
Air quality is awful. Here's a view looking west from the University of Utah toward downtown. I believe the official scientific terms is "gross."
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| Source: University of Utah |
PM2.5 concentrations show some short-term fluctuations, but also a long term trend toward higher and increasingly unhealthy values. The DAQ sensor at Hawthorne Elementary at 700 East and 1700 South reached 58 ug/m3 yesterday for a 1-hour average (maroon line), which is in the "unhealthy" category and appears to be on its way there today. the 24-hour average (blue line), which smooths out some of the variability, is currently 42.4 ug/m3.
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| Source: DAQ |
Lower cost sensors sometimes give spuriously high readings when the humidity is high, but the sensor on the University of Utah's Browning Building is a high quality one that has eclipsed 100 ug/m3 twice today. These are disturbing numbers well into the unhealthy range.
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| Source: University of Utah |
Where does all this pollution come from? Us. Large industrial emissions (i.e., point sources) are 13% of our PM2.5 emission sources. The rest are mobile sources (cars, trucks, trains, aircraft), and area sources (smaller stationary sources such as home heating, smoke from wood burning, restaurant emissions, dry cleaners, etc.).
It's something akin to tragedy of the commons or death by 1000 cuts. The beatings will continue until we change our ways and get serious, really serious, about clean energy, mass transit, and the like.
FWIW, at 1pm I drove from South valley to downtown, and back on an errand. Downtown area is atrocious, but South Valley is actually clearing out a good bit.
ReplyDeleteVisibility can be a poor indicator of PM2.5 concentrations. The Trax mounted sensor just recorded PM2.5 concentrations > 80 ug/m3 in Draper, which is quite high. Downtown looks especially bad due to the presence of high humidity and fog, but the reality is the air even in the south valley is also unhealthy.
DeleteHave any of the local newscasts contacted you to do in-depth interviews when the inversions come? Your pie chart,insight,and opinions might influence people's behavior. :)
ReplyDeleteThat's quite doubtful. Ultimately such shifts will or will not occur based on technological innovation, economics, and values.
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ReplyDeleteI tried looking up aggregate pm2.5 #s by year. I ended up on this page: http://www.airmonitoring.utah.gov/dataarchive/archpm25.htm. Looking at that, it looked like pm 2.5 is flat or going down? Any good charts for annual representations of pm2.5?
ReplyDeleteSee https://www.sciencedirect.com/science/article/abs/pii/S1352231014004580. Sadly the paper is paywalled.
DeleteA key thing that the paper does is that it attempts to control for "meteorology". Large fluctuations in annual PM2.5 occur not due to changes in emissions, but instead meteorology.
Looks like the inversion is strong enough that some freezing rain is falling at the Salt Lake airport as I type this. Reading through the METAR reports, it looks like they've seen .05" of ice accretion so far even though the temperature has remained at or slightly above freezing.
ReplyDeleteHow rare is accumulating ice from freezing rain at KSLC? I know we had the big ice storm in 2013 and maybe a couple smaller events since then, but is there a searchable database somewhere of freezing rain events?
I just found your blog and it's really interesting. I'm trying to understand how you're reading the soundings---when you say that temperature "increased with height to 3.4˚C at 818 mb" that seems too precise to just be from eyeballing the chart. I'd guess there's got to be some way to get to the data that the SPC is plotting, but I found the SPC Sounding Analysis Page and I can't find a way to get to the data that the chart is built from. Is there something I'm missing? Thanks -KeithAlleman
ReplyDeleteOn the SPC sounding page, there is a link below the sounding graphics that provides access to the tabular sounding data. Alternatively, http://weather.uwyo.edu/upperair/sounding.html allows you to access the tabular data.
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