Category Archives: Air quality

Inversion Tidbits and Long-Range Prospects

Yesterday's satellite imagery summarized the ridge-dominated weather of western North America quite well with extensive fog found in the major basins, many of the valleys of British Columbia and the Northwest United States, and the Great Salt Lake Basin.  At the same time, smoke from the California Fires covered much of the offshore eastern Pacific Ocean.  If you look carefully, it appears that some of this smoke has been carried northward to the Queen Charlotte Islands.

Composite MODIS image from NASA.
Within the Salt Lake Valley, the pollution went into overdrive yesterday, with PM2.5 levels skyrocketing in the morning to unhealthy levels.  Unlike previous nights, when PM2.5 dropped considerably, levels declined only modestly overnight and remain unhealthy for sensitive groups. 

PM2.5 concentrations at Hawthorne Elementary.  Source: DAQ
Looking for a brightside?  The frosty trees make for a beautiful Christmassy scene.  


We are so desperate for weather that I feel the need to mention that there is actually a weak short-wave trough dropping down the back (eastern) side of the ridge and passing through our area Wednesday night.  


Yup, that's your weather for the week.  It will bring somewhat cooler temperatures to the mountains, perhaps helping with the snowmaking efforts and might stir the upper part of the inversion a bit.  Emphasis on might.  Low elevations will likely remained mired in pollution. 

I am a bit more optimistic that the trough on Saturday is strong enough to give us at least a partial mix out.  It's still soon to say if it will scour it all out.  Sometimes, the coldest, most polluted air at the lowest elevations can be quite stingy. 


Snowfall totals for the mountains presently look paltry.  About half the members in our downscaled NAEFS ensemble generate 2 inches or less.  A few members go for more.  A game changer is unlikely. 

The word "pattern change" is being thrown around a lot, but I bet you'll have a hard time finding anyone who can tell you what that means.  I have yet to see any indication from any ensembles that we are going to shift from the high-amplitude pattern that has dominated for weeks and in which there are very deep ridges and troughs at upper levels, to a more progressive pattern with stronger westerly flow.  Instead, there may be some shifts in the position of the ridges and troughs.  For example, some of the GEFS 10-day forecast members below have a ridge upstream of the west coast of North America, rather than near its present location along the west coast or just inland. 

Source: Penn State E-wall
Those shifts could be important if they lead to a slowly evolving but wet pattern for Utah.  However, looking at the GEFS solutions above, some might bring us some snow, others keep us dry.  Why waste time talking about this range of possibilities?  Like thermonuclear war, the best option is not to play.  


Thus, hope we get something from the trough on Saturday and at minimum hope it cracks the inversion.  It's the only slim hope we have for mountain snow over the next week.  After that, your guess is as good as mine. 

Diurnal Intricacies of the Inversion

PM2.5 concentrations during our current inversion event have shown remarkable variations from day to night.

Below is a time series of PM2.5 measured at our mountain meteorology lab at the University of Utah showing a clear long-term upward trend, but also a tendency for PM2.5 concentrations to spike just before noon, remain elevated until mid to late afternoon, and then decline.

Source: MesoWest
What are the causes of this diurnal behavior.  There are several possible contributors.

First, there is the possibility that photochemistry - chemical reactions occurring in the presence of sunlight, are contributing.  Comparison of the above plot with the incoming solar radiation below shows some relationship, with the PM2.5 exhibiting a bit of a lag relative to the solar radiation.

Source: MesoWest

Another possibility is that temperature is playing a role since it also affects the PM2.5 chemistry.  Again, there is some correlation.  

Source: MesoWest
Finally, there is the transport possibility as the winds are also changing diurnally, with a good correlation between wind direction and PM2.5 concentrations.  

Source: MesoWest
Another perspective is provided by the someone hacked-up graphs below, based on data collected at the University of Utah by our MesoWest team over the 24-hour period ending this morning at 10 AM (the hacking reflects my splicing of their multiple graphs together).  The top figure is derived using a laser that is shot vertically through the pollution.  The color fill is backscatter, a measure of how much of the laser light is reflected back to the ground, with higher values roughly correlated with greater PM2.5 concentrations (brown-white being the dirtiest air).

The plot begins on the left at 10 AM on Sunday when the local flow just shifted to predominantly westerly (some variability from SW-NW).  Surface PM2.5 concentrations during this period are quite high and, in addition, the pollution is quite deep.  At just after 1700 MST (5 PM), the flow shifts abruptly to ENE, which reflects the onset of down valley flow from Red Butte Canyon.  This marks the beginning of a gradual decline of surface PM2.5 concentrations, as well as a decrease in PM2.5 concentrations aloft.

Source: MesoWest
There is a brief lull in the wind that occurs just before 2300 MST (11 PM MDT), with the flow becoming somewhat erratic.  Without the inflow of cleaner air from Red Butte Canyon during this period, the surface PM2.5 values climb, although things don't change too much aloft.  Finally, after midnight, the ENE flow returns and PM2.5 values drop again, although there are a few spikes during the night that may correlate with declines in wind speed (I haven't bothered to check yet...so take this comment for what it is worth).

At the end of the time period, the PM2.5 values climb again, abruptly, when the flow shifts to westerly.

All of this illustrates some of the intricacies of these inversion events.  Pollution concentrations vary in the vertical (yes, there is clean air up there), although if you look carefully at the plot above, you can see that it's not as simple as polluted air near the ground and non-polluted air aloft.  There are layers.  In addition, pollutant concentrations vary horizontally and at the University of Utah one can clearly see the migration of pollutant-laden air onto campus when the wind shifts to westerly in the morning.

What role photochemistry and temperature play in all of this is unclear to me.  I suspect it plays a secondary role compared to meteorological factors, but I am not an atmospheric chemist and over the years I've learned that when all you have is a hammer, everything looks like a nail.  In other words, as a meteorologist, I might be guilty of placing too much weight on meteorological factors.

One thing to keep in mind is that not all inversions look or behave like this and even this one might behave differently in the days to come.  As a scientist, I think what we see over the next few days will be "interesting."  As a citizen, I wish the damn thing would just blow away.

Scenes from the Inversion

Classic inversion conditions are now apparent over northern Utah.  Here are a few photos.

First, the view of the valley smoke that befuddled me, and is discussed in the previous post.  It sure looked like clouds this morning, but as soon as I descended down into it, I smelled campfire and knew I was in error.  Turns out it was smoke from a major arson fire near 500 South and 200 East. 


In contrast to the cesspool in Salt Lake, morning at Alta was splendid and whiter than expected.


A bit later.  A good example that no matter where you are in the Salt Lake Valley today, you're only a few hundred meters (vertically) from clean, pristine air. 


Valley cold pools can be found just about everywhere over northern Utah right now.  If there's emissions, there's pollution.  The smog below is in the Heber Valley. 


Just about anyone who has skied in Little Cottonwood knows this view.  Unfortunately, it is common in the wintertime.


And, this afternoon back in the Avenues.  Ick. 


On the positive side, air quality remains in the moderate category so far. 
Source: DAQ
On the negative side, we have at least 5 days left of this, and air quality is going to worsen.

Heartbreak Ridge Tightening the Inversion Noose

Noontime smog yesterday, looking southwest from the Natural History Museum of Utah, University of Utah
Given that our last storm was winding down on Monday, I'll call today Day 4 of Heartbreak Ridge.

So far, the pollution buildup has been modest.  Because the center of the ridge has been along the Pacific Coast, we've been on the downstream side, temperatures aloft have been cool, and the inversion relatively weak and elevated.  This has enabled some vertical mixing of pollutants through a decent portion of the valley atmosphere.  As a result, the increase in pollution has been gradual and we've been fluctuating between good and moderate air quality.  

Source: Utah Division of Air Quality
However, Heartbreak Ridge is sliding eastward and the inversion is strengthening, as can be seen in the soundings from yesterday afternoon (top panel below) and this morning (bottom panel below).  


Source: University of Wyoming
Note in particular the warming in the layer between about 800 and 700 mb (6500–10000 feet), which equates to a strengthening of the "lid" over the valley atmosphere.  This morning, temperatures near the base of that layer increase about 5ºC through a depth of around 50 mb (1500 feet). 

The NAM sounding loop below (note: this is a skew-t diagram, not directly comparable to the diagrams above) shows further warming aloft over next two days, with temperatures aloft warming an additional 5ºC.  
Thus, the inversion will be strengthening and lowering through the weekend.  It appears we will be in the grips of the inversion at least through the next work week, unless a system stronger than presently advertised slides down the back side of the ridge and gives it a stir. 

Model Products Information

We have been having some problems with the server that hosts weather.utah.edu and it has been down intermittently the past two days.  Behind the scenes (and unrelated to the outages), I've been updating some of our products.  Options for the GFS now include global and regional plots from the 0.25 degree latitude-longitude grid (we've been using the old 0.5 degree grids), higher frequency (every 3-h to 240 hours), more regional sectors (e.g.,  Intermountain, Northwest, Southwest), and time-height section options that match the time period of the NAM for comparison.  Some little used plots are gone, such as the Indian Ocean sector.  




Wildfires in southern California

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) images (above; also available as an animated GIF) showed the rapid development of wildfires driven by strong Santa Ana winds in Southern California on 05 December 2017. The fire thermal anomalies or “hot spots” are highlighted by the dark black to yellow to red pixels — the initial signature was evident on the 0230 UTC image (6:30 PM local time on 04 December), however the GOES-15 satellite was actually scanning that particular area at 0234 UTC or 6:34 PM local time. The Thomas Fire (the largest of the fires) advanced very quickly toward the southwest, nearly reaching the coast.

Nighttime image toggles between Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) data at 0904 UTC and 1044 UTC (below) revealed the large fire hot spots, along with the extensive smoke plume that was drifting over the adjacent nearshore waters of the Pacific Ocean. With ample illumination from the Moon (which was in the Waning Gibbous phase, at 95% of Full), the “visible image at night” capability of the VIIRS Day/Night Band — which will also be available from the recently-launched JPSS-1/NOAA-20 satellite — was clearly demonstrated.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images, with plots of surface reports [click to enlarge]

A toggle between the two VIIRS Day/Night Band images (below; courtesy of William Straka, CIMSS) showed initial darkness resulting from fire-related power outages in Santa Barbara County to the north, and Ventura County to the south (in the Oxnard/Camarillo area).

Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

This large wind-driven fire was also very hot — the maximum brightness temperature on the VIIRS 4.05 µm Shortwave Infrared image was 434.6 K or 322.6º F, which was above the saturation threshold of the VIIRS 3.75 µm Shortwave Infrared detectors (below).

Suomi NPP VIIRS 4.05 µm and 3.75 µm Shortwave Infrared images [click to enlarge]

Suomi NPP VIIRS 4.05 µm and 3.75 µm Shortwave Infrared images [click to enlarge]

In a comparison of daytime GOES-15 Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (below), the west-southwestward transport of smoke over the Pacific Ocean was clearly seen.

GOES-15 Visible (0.63 µm, top) and Shortwave Infrared (3.9 µm, bottom) images [click to play MP4 animation]

GOES-15 Visible (0.63 µm, top) and Shortwave Infrared (3.9 µm, bottom) images [click to play MP4 animation]

A more detailed view of the thick smoke originating from the 3 fires (from north to south: the Thomas, Rye and Creek fires) was provided by a 250-meter resolution Aqua MODIS true-color Red-Green-Blue (RGB) image from the MODIS Today site (below).

Aqua MODIS true-color RGB image [click to enlarge]

Aqua MODIS true-color RGB image [click to enlarge]

Immediately downwind of the Creek Fire, smoke was reducing the surface visibility to 1 mile at Van Nuys and adversely affecting air quality (below).

Time series plot of surface reports at Van Nuys, California [click to enlarge]

Time series plot of surface reports at Van Nuys, California [click to enlarge]

===== 06 December Update =====

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images [click to enlarge]

The fires in Southern California continued to burn into the following night, as shown by Suomi NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (3.75 µm and 4.05 µm) images (above; courtesy of William Straka, CIMSS). A large-scale view with Day/Night Band imagery revealed the extent of smoke transport westward over the Pacific Ocean.

GOES-15 Shortwave Infrared (3.9 µm) images (below) displayed the thermal signatures exhibited by the fires. Note the appearance of a new fire — the Skirball Fire — first appearing on the 1300 UTC (5:00 AM local time) image, just north of Santa Monica (KSMO). Although the Santa Ana winds were not quite as strong as the previous day, some impressive wind gusts were still reported.

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly surface plots [click to play MP4 animation]

A toggle between 250-meter resolution Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color images from MODIS Today (below) showed significant pyrocumulus development from a flare-up along the northeast perimeter of the Thomas Fire. The cloud plume only exhibited a minimum infrared brightness temperature of +5.5º C on the corresponding Aqua MODIS Infrared Window image, far above the -40ºC threshold assigned to pyroCumulonimbus clouds.

Comparison of Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color RGB images [click to enlarge]

Comparison of Terra (1911 UTC) & Aqua (2047 UTC) MODIS true-color RGB images [click to enlarge]

===== 07 December Update =====

Suomi NPP Day Night Band Imagery, 3-7 December 2017, over southern California

RealEarth imagery of the Day Night Band over 5 days (one image each night from 3 through 7 December), above, shows the evolution of the fire complex (Imagery courtesy Russ Dengel, SSEC). Similarly, a closer view of daily composites of VIIRS Shortwave Infrared (3.74 µm) imagery (below) revealed the growth and spread of the Thomas Fire from 04-07 December.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge\

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image composites [click to enlarge]

In a toggle between Terra MODIS true-color and false-color RGB images (below), the large burn scar of the Thomas Fire (shades of red to brown) was very apparent on the false-color image.

Terra MODIS true-color and false-color images [click to enlarge]

Terra MODIS true-color and false-color images [click to enlarge]

Deadly Smog in India and Pakistan

Suomi NPP VIIRS Day Night Band Visible Imagery (0.70 µm) at Night, 05, 07 and 08 November 2017 (Click to enlarge).

Suomi NPP VIIRS Visible Imagery at Night (the Day Night Band Visible Image (0.7 µm) from 5 November, 7 November and 8 November), above, and Infrared Channel Brightness Temperature Difference  (11.45 µm – 3.9 µm) on 5 November, 7 November and 8 November), below, both show the presence of fog/smog over northern Pakistan and northwestern India from 05-08 November 2017 (Suomi NPP VIIRS Imagery courtesy of William Straka, CIMSS). The Smog led the Government of Punjab to ban burning of stubble; schools in Delhi were closed.  Vehicle crashes linked to reduced visibilities have killed at least 10 people (source).  Air Quality in the region is very poor as shown in this Screen Grab from this site.

Suomi NPP VIIRS Infrared channel Brightness Temperature Difference (11.45 µm – 3.9 µm) on 05, 07, and 08 November 2017 (Click to enlarge)

An animation of Meteosat-8 Visible Imagery, below, from 03-09 November, shows little improvement in conditions in the past week.

Meteosat-8 Visible Imagery (0.6 µm) at 0300 UTC from 03 to 09 November 2017 (Click to enlarge)

Daily composites of Suomi NPP VIIRS true-color Red-Green-Blue (RGB) images from RealEarth, below, showed the areal coverage of the smog during the 03-09 November period. Surface observations at New Delhi’s Indira Gandhi International Airport indicated that the visibility remained below one statute mile — with zero visibility at times — during the 72-hour period spanning 07 November, 08 November and 09 November (animation).

Daily composites of Suomi NPP VIIRS true-color RGB images (click to enlarge)

Daily composites of Suomi NPP VIIRS true-color RGB images (click to enlarge)

Worth noting on a nighttime comparison of Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Day/Night Band (0.7 µm) images, below, was the appearance of a cloud shadow being cast by moonlight onto the top of the boundary layer smog/fog.

Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Dat/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Lessons in Boundary Layer Meteorology

The boundary layer is the lower portion of the atmosphere that is affected by friction and the transfer of heat from the earth's surface into the atmosphere.  It's depth varies depending on the time of day, the environmental conditions, and the local land surface and topographic characteristics.

Typically the evolution of the boundary layer is conceptualized as shown below.  During the morning, sunlight heats the Earth's surface, resulting in a transfer of heat into the atmosphere.  This erodes the shallow stable layer that typically forms overnight from radiational cooling.  The boundary layer then continues to grow, eventually reaching maximum depth later in the day (the time varies depending on conditions).  Within the boundary layer, turbulence driven by wind shear and surface heating results in considerable mixing.  Concentrations of gasses like water vapor and carbon dioxide are often nearly constant with height in the boundary layer.  Hence, the "mixed layer" label in the schematic.  Often there is a stable layer or inversion at the top of the mixed layer. 
Source: COMET/METED
Near and after sunset, the Earth's surface cools rapidly.  Heat is transferred from the atmosphere, which cools rapidly near the Earth's surface.  This forms a shallow nocturnal stable boundary layer, that may be tens or perhaps one or two hundred meters deep.  Above this layer, the old remnants of the boundary layer remain.  This layer is called the residual layer.

In quiescent weather conditions, this pattern repeats itself daily: 1. The sun rises;  2. The nocturnal stable boundary layer is "burned off";  3. The boundary layer grows rapidly into the residual layer and constituents (including pollutants) are mixed through its depth;  4. The sun sets and the nocturnal boundary layer forms and strengthens, leaving a residual layer aloft.

Evidence of these processes was very apparent on my ride above Ensign Peak this morning.  At the time, the top of the pollution layer was perhaps 1 km above the valley floor.  There was a very clear discontinuity in the pollution at that level.  It was early enough that I suspect that discontinuity did not mark the top of today's boundary layer, but instead the top of the residual layer, which was loaded with pollutants from emissions from yesterday.


I've added by eye yesterday's sounding (red=temperature, green=dewpoint) from the airport.  In this case, the temperature or dewpoint decrease if the line slopes to the left and increase if it slopes to the right.  The top of the residual layer was very near the elevation of an inversion in yesterday's sounding, as one might expect.  Below that inversion, the atmosphere yesterday afternoon was relatively well mixed.  For example, temperature decreased rapidly with height at a rate of about 10ºC per kilometer, which is consistent the density being constant with height.  Dewpoint decreased with height at a rate close to that expected if the concentration of water vapor is constant with height.  However, the decrease with height near the surface was more rapid than one might expect if the atmosphere is well mixed.  This isn't unusual as the turbulence typically can't mix the atmosphere fast enough right near the ground to make the water vapor concentration constant with height if there is evaporation or transpiration occurring.

Expect views like this most days this week due to the presence of high pressure.  Note that the sharp top of the residual layer is most apparent in the morning and evening if you are at an elevation somewhat above the valley floor and you face somewhat toward the sun (but perhaps not right at it).  This is an optical effect related to how pollution scatters sunlight.

Announcement

I'm pleased to announce that we will be exhibiting the Doppler on Wheels mobile radar (pictured below) at the Natural History Museum of Utah this coming Saturday, November 4, from 10–5 PM.  Bring yourself, the family, and friends.  The exhibit is also one of their Behind the Scenes days when they open the place up for a public viewing of their collections.  Come and geek out!


Wildfires in Northern California

GOES-16 Shortwave Infrared (3.9 µm) images, with county outlines plotted in gray (dashed) and surface station identifiers plotted in white [click to play MP4 animation]

GOES-16 Shortwave Infrared (3.9 µm) images, with county outlines plotted in gray (dashed) and surface station identifiers plotted in white [click to play MP4 animation]

* GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing *

GOES-16 Shortwave Infrared (3.9 µm) images (above) showed the “hot spot” signatures (black to yellow to red pixels) associated with numerous wildfires that began to burn in Northern California’s Napa County around 0442 UTC on 09 October 2017 (9:42 PM local time on 08 October). A strong easterly to northeasterly Diablo wind (gusts) along with dry fuels led to extreme fire behavior, with many of the fires quickly exhibiting very hot infrared brightness temperature values and growing in size at an explosive rate (reportedly burning 80,000 acres in 18 hours).

A comparison of nighttime GOES-16 Shortwave Infrared (3.9 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (below) offered another example of nocturnal fire signature identification — the bright glow of the fires showed up well on the 1-km resolution 1.61 µm imagery. Especially noteworthy was the very rapid southwestward run of the Tubbs Fire, which eventually moved just south of station identifier KSTS (Santa Rosa Sonoma County Airport; the city of Santa Rosa is located about 5 miles southeast of the airport. These Northern California fires have resulted in numerous fatalities, destroyed at least 3500 homes and businesses, and forced large-scale evacuations (media story).

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared “Snow/Ice” (1.61 µm, right) images [click to play MP4 animation]

A toggle between 1007 UTC (3:07 AM local time) Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images (below) provided a view of the fires at an even higher spatial resolution. Since the Moon was in the Waning Gibbous phase (at 82% of Full), it provided ample illumination to highlight the dense smoke plumes drifting west-southwestward over the adjacent offshore waters of the Pacific Ocean.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A closer VIIRS image comparison (with county outlines) is shown below.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

A comparison of Suomi NPP VIIRS true-color and false-color Red/Green/Blue (RGB) images from RealEarth (below) helped to discriminate between smoke and cloud features offshore over the Pacific Ocean.

Suomi NPP VIIRS True-color and False-color RGB images [click to enlarge]

Suomi NPP VIIRS True-color and False-color RGB images [click to enlarge]

===== 10 October Update =====
Suomi NPP VIIRS true-color and false-color images [click to enlarge]

Suomi NPP VIIRS true-color and false-color images [click to enlarge]

With the switch to southwesterly surface winds on 10 October, smoke plumes could be seen moving northeastward on RealEarth VIIRS true-color imagery, while the burn scars of a number of the larger fires became apparent on VIIRS false-color RGB imagery (above).

===== 11 October Update =====

Landsat-8 false-color RGB images, from 04 October (before the Tubbs Fire) and 11 October (after the Tubbs Fire) [click to enlarge]

Landsat-8 false-color RGB images, from 04 October (before the Tubbs Fire) and 11 October (after the Tubbs Fire) [click to enlarge]

A toggle (above)  between 30-meter resolution Landsat-8 false-color RGB images from 04 October (before the Tubbs Fire) and 11 October (after the Tubbs Fire) showed the size of the fire burn scar (shades of brown) which extended southwestward from the fire source region into Santa Rosa.

===== 12 October Update =====
Suomi NPP VIIRS true-color RGB images, with VIIRS-detected fire locations [click to enlarge]

Suomi NPP VIIRS true-color RGB images, with VIIRS-detected fire locations [click to enlarge]

A transition back to northerly winds on 12 October helped to transport the wildfire smoke far southward over the Pacific Ocean (above). Smoke was reducing surface visibility and adversely affecting air quality at locations such as San Francisco (below).

Time series plot of surface observations at San Francisco International Airport [click to enlarge]

Time series plot of surface observations at San Francisco International Airport [click to enlarge]

Suomi NPP VIIRS Aerosol Optical Depth values were very high — at or near 1.0 — within portions of the dense smoke plume (below).

Suomi NPP VIIRS true-color RGB image and Aerosol Optical Depth product [click to enlarge]

Suomi NPP VIIRS true-color RGB image and Aerosol Optical Depth product [click to enlarge]

Widespread Smoke in the Pacific Northwest

GOES-16 data posted on this page are preliminary, non-operational and are undergoing testing

Dry weather over the Pacific Northwest (and over Idaho and Montana) has created an ideal environment lately for wildfires, and much of the region is shrouded in smoke from those fires as shown in the Suomi NPP True Color Imagery, above, from this site.  Note the red points that are Suomi-NPP-detected fires; they persist from day to day, and some grow in size during the course of the animation. GOES-16 Animations of True Color (in this case, the CIMSS Natural True Color product that is created using Bands 1, 2 and 3 (0.47 µm, 0.64 µm and 0.86 µm, respectively)), below, (also available here; a similar product from CIRA is available here), show the pall of smoke as well. Air Quality Alerts from the National Weather Service were widespread on 6 September.

CIMSS Natural True Color, every 15 minutes, from 1400-2130 UTC on 6 September 2017 (Click to animate)

GOES-16 has multiple channels and products that can view both the Smoke and the Fires that produce the smoke. In addition to the visible imagery, Fire Products, below, can characterize the Temperature, Power (in megawatts) and area (in square meters) of the fire detected by GOES-16.  On this day, clouds over the fires in Oregon mean that satellite detection is challenged, even though the by-product, smoke, is apparent.  Fires over Idaho are readily apparent however.  These fires were also detected by the 3.9 µm Shortwave Infrared channel on GOES-16, the traditional fire-detection channel (used in concert with 10.3 µm, the clean window channel).  Imagery at 1.6 µm and 2.2 µm imagery can also be used to highlight hot fires;  that will be the subject of a future blog post.

GOES-16 Fire Products: Fire Temperature, Fire Power and Fire Area, 2037 UTC on 6 September 2017 (Click to enlarge)

 

The mp4 animation, below, shows CIMSS Natural True Color over the Full Disk on 5 September 2017.  The Full Disk View allows a better visualization of how the smoke is moving (and underscores how widespread it is) — and it shows Hurricane Irma as well.

CIMSS Natural True Color, every 15 minutes, on 5 September 2017 (Click to animate)

 

NOAA creates many Smoke-related products, some of which are easily accessible at this link.

A Smoky Day Ahead

Over the past few days Utah has fortuitously been located just to the south of some thick, smoky air, but that changed overnight as the winds shifted.  The Wasatch Mountains this morning look more like the Great Smokies.


That photo was taken about 7 am.  As things stand now (8:20 AM) I can barely see the base of the Oquirrh Mountains from my office at the University of Utah.

It's a bit too early to get a good look at the smoke in visible satellite imagery, but we can see it very clearly in ceilometer observations.  A ceilometer is an instrument that sends out a laser pulse and measures the amount and delay of the signal returned to ascertain cloud base height.  Smoke and other particles in the atmosphere, known as aerosols, also scatter some energy back, which is known as backscatter.

The plot below shows a profile of backscatter recorded from a ceilometer at the University of Utah Mountain Meteorology laboratory at Red Butte Canyon.  Time increases to the right and is in MDT.  Note the arrival of dense smoke denoted by the change in color from green to yellow at around 3 AM MDT.  You can also see that the smoke moved over this site first aloft and then near the surface.

Source: MesoWest
Today we will have an air quality double whammy of elevated PM2.5 and ozone.  PM2.5 at the Mountain Meteorology Lab has been running near or above 25 ug/m3 since about 4 MDT (consistent with the plot above).

Source: MesoWest
That rates as "moderate".  Keep in mind, however, that ozone levels the past few afternoons have been at or above the unhealthy threshold (red shading below).
Source: Utah Division of Air Quailty
I'm not sure where we'll end up today.  Sometimes the chemicals accompanying smoke enable a boost in daytime ozone production.   Keep an eye on things if you have concerns.  I'm planning on taking a day off from exercising.