July 05, 2024

July 4th Smoke, Wildfires, and the White Sky

When you looked at this morning did you notice the hazy whiteness in the sky?   July 4th fireworks are too blame.    And such fireworks have started wildfires, including a major burn near Wenatchee.

Let's start by look at the Seattle Panocam at 6:30 AM this and yesterday mornings (below).  I bet you can see the difference.  At my home, the sky looked white near the horizon.  Why white?  More later.

Today

Yesterday, July 4.

Fireworks smoke has caused significant air quality degradation over much of the region.

The western map at 830 AM (courtesy of the Puget Sound Clean Air Agency), show poor air quality (red and purple colors) over extensive areas downwind of population ceners.


And the US EPA's AirNow graphic also show poor air quality near Wenatchee (see below)


Why Wenatchee?  Because someone ignited a major grass fire west of the town with fireworks (see map below).  That individual has been arrested.


 There is another grass fire, supposedly started by powerlines, southeast of Chelan.    The visible satellite image at 6:30 AM shows the smoke from these fires, plus the Pioneer Fire up Lake Chelan.



Plots of air quality (actually small particle concentrations) at Seattle and Marysville (both shown below) illustrate the rapid increase in smoke last night.  The Marysville numbers were crazy high (about 130).


Seattle

Marysville

Finally, why do these particles turn the sky white?

It turns out this is due to something call Mie Scattering.    When light from the sun interacts with smoke particles is it scattered by the particles in many different directions (see below)

Image courtesy of Virtual Labs

Light from the sun includes all wavelengths of visible light (from red to blue/violet).   Light appears white when all wavelengths are represented and if you were above the atmosphere the sun looks pretty white.


Large smoke particles from fireworks scatter all wavelengths of visible light similarly, thus producing a white-looking sky.  This is what is meant by Mie Scattering.  In contrast, small particles in a clean atmosphere (such as the typical gases) scatter shorter wavelengths (like blue) more (called Rayleigh Scattering), which gives the sky a blue cast.    

Heavily polluted cities in China have a lot of big particles, so their skies almost always look white.  Perhaps it is ironic that our fireworks come from China.  They export their white skies to us during our day of celebration of independence.  






21 comments:

  1. "Perhaps it is ironic that our fireworks come from China. They export their white skies to us during our day of celebration of independence."

    I'm trying to think of one thing that China creates that makes the world a better place. Let's see.. thinking.. hmmm.. I'm drawing a blank.

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    1. This is amazing, as if China somehow is forcing anyone to pollute the air and start fires by selling their fireworks. I'm sure they would gladly sell show drones instead. It is a conscious choice made by Americans, take responsibility for once.

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    2. Avalon - you make a good point and you are 100% correct about the fireworks. But you responded to me and you missed the point. I still can't think of one good thing that comes out of China. Help me out here. Can you think of one? What has China created, on their own volition, that leaves the world a better place?

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    3. While I agree that people should be held responsible and fined/arrested for illegal/careless use of fireworks, I disagree with the premise that the pollution I so off-putting one night for a couple hours a year, they should be banned. Or that people are dumb for enjoying them. Can't people just have a little bit of fun? Especially with a centuries old tradition? I have to enjoy mine at new years as we are to dry here during summer, and the designated legal spot is to chaotic for me.

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    4. China has given us many. many things, not even counting art and literature: https://china.usc.edu/sites/default/files/forums/Chinese%20Inventions.pdf
      paper, movable type, compass, mechanical clock, tea, silk, iron smelting, earthquake detector, etc., etc.

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  2. The absolute maximum AQI value I measured at my location in Bellingham was 210 about about 10 minutes to 1AM. I noticed that, while there were plenty of celebrations occurring around the area where I live, it seemed somewhat more subdued than in recent previous years. The maximum AQI value I measured at my location associated with Independence Day celebrations was a whopping 644 at about 20 minutes before 1AM. My Davis AirLink air quality monitor reported values as high as 800 during 7/4-5/2022 which is probably the highest that I've seen.

    Since NWS Seattle has issued a fire weather watch for the west slopes of the Cascades, I hope patriotic revelers exercised due care in those areas as the forecast heatwave which is inexorably approaching our area appears to be expected to be quite intense. I'm seeing predicted temperatures by all the major forecast providers (NWS, Weather Channel/Weather Underground/Accuweather/etc. approaching triple digits for areas south of Seattle. This one's gonna be a scorcher and sure to set some records - we certainly don't need wildfires to add to the mix!

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    1. The fire weather watch for the western slopes of the Cascades makes no sense... that only happens with strong easterly winds, which ARE NOT being predicted.

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    2. Dropped to a Red Flag warning...which to me still doesnt make sense. To you?

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    3. I mean DNR hasn't even banned campfires in our zone (methow fdra on their map) yet in designated burn pits, your fuels cannot be that dry on westside. Which I must say this is latest I have seen without an outright ban to outdoor fires for a very long time in our area.

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    4. It may be a bit early for a serious fire on the west side considering the recent moist period there, however I disagree with you that only strong east wind episodes warrant red flag warnings for the west side. I have pointed out to you past west side fires (the start of the 1933 Tillamook fire and the 1967 Evergreen Mt. fire near Skykomish) as examples of fires that got quite large for west side fires without an east wind pattern. Both of these were under conditions we are seeing now; strong warm high pressure with mainly northerly or terrain driven winds. This coming hot, dry period will quickly put east side areas, which went through a dry spring, into high fire danger and will also speed up drying of the west side forests greatly raising the fire danger there, although the west side will not likely see a strong east wind period in July.

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    5. wxman...you are not correct about the Tillamook fire and other major westside fires..they ALL were associated with strong easterly winds. I repeat all of them. I am writing a paper right now on this topic. I have run high resolution weather simulation for all the major westside fires of the past 120 years. ALL of them associated with easterly flow. ..cliff

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    6. I agree with you that the very large mega fires of the west side had strong east winds associated with them. However, the 1933 Tillamook fire started on August 14 and burned mainly south and southwestward during the next two days indicating a northerly and upslope (on east side of coast range) wind, reaching about 40,000 acres during this period, which is a large fire for the west side. After about a week of cooler weather with little increase in size, strong east winds then blew this fire to over 200,000 acres.
      I was fire weather meteorologist on the Evergreen Mt. fire near Skykomish in 1967 and I can assure you that the fire spread was mainly toward the east from westerly up valley, upslope winds in the Rapid River valley during very warm, dry unstable conditions with significant afternoon blow ups which spread the fire eastward mainly by spotting. There was only one day of rather weak easterly winds near the end of the fire but this did not result in a significant increase in acres burned. I know that really large fires on the west wide need strong easterly winds but there have been other fires such as the early part of the Tillamook fire and the Evergreen Mt. fire that are large relative to the usual west side fires and burned during non east wind periods. I think these cases can require a red flag warning even if strong east winds are not expected.

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    7. wxman.... so we are agreed...large fires on the western side require easterly winds. No one is arguing that hot/dry conditions are good for fire...there is a reason they generally occur in mid to late summer. Can you give me the exact dates of the Evergreen Mt fire and how that fire grew over time? This was not a large fire (6000 acres) and occurred on a south facing rocky slope and was started by forestry operations. South facing rocky slopes have lots of grass/small vegetation and have upslope flow during the day....good for fire. Supplies its own wind. Tillamook --again started by forestry operations... started modest but only exploded with the easterly winds. By the way, with a wet/cool June isn't a blow up on the western Cascade slopes unlikely?

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    8. The Evergreen Mt. fire began about August 25 and burned pretty hot until the end of August, with rain and cool temperatures arriving by September 2. At that time there was a pretty good forest cover on the south side of Evergreen Mt. so plenty of fuel. The fire would calm down at night, at least in the lower part of the valley where it cooled off but with a strong inversion at mid slope and higher. When this inversion broke about mid day, the lower part would suddenly blow up and the fire would race to the top of the ridge, with a westerly wind that would spot fires to the east, so for several days the fire spread was up the Rapid River valley. About the 30th of August there was one day of east winds and the fire boss was very worried that this would cause major problems. It did wake up the west end of the fire and it began to move down valley toward our fire camp, which was near where the Rapid River entered the Beckler River. We were about to abandon the camp when a timely retardant drop checked the westward fire spread. While there was some fire spread to the west during this time, the major part of the fire spread was to the east, up the Rapid River valley in the days before. The weather conditions were much like what we have today, a very warm upper ridge, temperatures in the 90s, humidity 15 to 25%, but just usual daytime up valley, up slope winds except for that one day of east winds. Two years before this, in late July 1965, I was on the Union Creek fire up near the Cascade crest west of Yakima. Although this is east of the crest it is in a climate zone much like the west side. This fire was very similar to the Evergreen Mt. fire, plenty of fuel, and started during very warm temperatures under a strong upper ridge with generally light diurnal winds. It also blew up every afternoon for about 3 days and spread due to spotting. The fire camp for this fire was on the top of Raven Roost, about 3 air miles from the fire and all fire fighting people and equipment had to be airlifted by helicopter to the fire. I operated out of a special fire weather camper parked there on the top of the mountain where there was not much room for air operations. One day, a helicopter came down too hard and the rotor dipped and chopped off the tail assembly sending pieces of it flying all over the camp. One piece lodged in a pickup sitting next to my camper. Close call.
      Yes I think the recent wet period on the west side should delay the fire season over there but this extended warm, dry period is going to quickly dry things out. However, strong east wind patterns are not common in July so probably no problem with a big fire there for now. A different situation here in Eastern Washington as our late spring rains were light, most areas getting only 50-60% of normal rain in May and June and when we get into these hot, dry patterns, that is when the fire situation usually gets critical over here. If we get dry lightning and wind, which looks possible later, this could bring serious problems.
      Also, I know I have been critical of some of your comments and opinions but I do like much of what you write in the blog and as a old time fire weather and frost forecaster, have very much appreciated the work you and your helpers have done creating the fine scale forecast models. They are a real help, especially when dealing with the forecast problems with fire weather and frost forecasting.

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    9. Wxman... I appreciate your comments...we are both trying to find the truth here. I went back to the observations/analysis for August 25/26, 1967 and there was easterly flow coming over the Cascades. Reanalysis grids show it and the surface chart is consistent with it (thermal trough over western Washington). There is a real threat in eastern WA midweek as cooler air moves into the west and MUCH stronger westerly flow develops on the eastern Cascade slopes. First area is now below normal...cliff

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    10. Would love to hear about this in next blog! I haven't see many "dry lightning" events in recent years for Okanogan Valley. We generally do see some rain. Most our lightning fires in forest would be considered sleepers, or in case of Carlton Complex not a sleeper but mismanaged in beginning. Our grasses, however, if lightning touches them, even if get good rain, can take back off as winds usually dry the grasses out quickly.

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  3. Cliff, this notation is incorrect: "Why Wenatchee? Because someone ignited a major grass fire east of the town with fireworks (see map below)." It should say, "...west of the town...". The top of the map is north, making the fire area west of the town of Wenatchee.

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    1. thanks... just a typo.... east should have been west...fixed

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  4. I don't think we're gonna have a cool summer like some have hoped, 80's and 90's for the foreseeable future.

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  5. The Wenatchee fire is more north than anything else, not east. from this site:
    https://www.kasiaandjason.com/Wildfire-activity
    I can get info using Google Earth. Current map shows 4 squares,

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  6. Coming from Chicago where for decades my neighborhood was set alight by everything under the sun (including MD - 80's that literally shook my building as they went off), I hoped that after I moved to Portland that it wouldn't be quite as nasty, to no avail. BTW, it doesn't end after the 4th around here, it continues throughout the week, and I'm sick of it. I can understand setting off a few fireworks after the official fireworks show is over, but continuing into the wee hours and for days afterwards is way beyond the scope of just celebration. It's lawlessness and disrespect for everyone else who has to go to work and needs to get some actual sleep. I won't even mention the effects on veterans of combat and dogs, which should be obvious.

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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