A previous post discussed the 5.1 micrometer channel that might be part of the imager (GXI) to fly on GeoXO, the next-generation satellite (beyond GOES-R) to be launched in the 2030s. That previous post, however, used Cross-track Infrared Sounder (CrIS) data, and CrIS observes close to, but not at, 5.1 micrometers. However, the Infrared Atmospheric Sounding Interferometer (IASI) that is part of the payload on Metop-B and Metop-C (it was on Metop-A as well!) does take observations at 5.1 micrometers. The animation shows a Metop-A IASI observations at 5.1, 6.19, 6.9 and 7.3 micrometers (or wavenumbers 1950, 1615, 1438 and 1369) from a granule over Europe. Of note is apparent moisture aloft — shown as cooler brightness temperatures especially at 6.9 micrometers — that has no apparent signal at 5.1 micrometers because of less sensitivity to mid-tropospheric water vapor at the shorter wavelength. Indeed, 5.1 micrometer brightness temperatures are much warmer than the other channels.

A greyscaled image of 5.1 micrometers, below, shows how the boundary layer influences the signal in clear air.

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What did geostationary imagery look like on this day? Meteosat-8 imagery at 6.19 and 7.3 micrometers is shown below.

How dry was this airmass over the Mediterranean? Soundings from 0000 and 1200 UTC on 15 January 2007 (link, from the Wyoming Sounding site) show total precipitable water values between 10 and 14 mm.

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The addition of the 5.1 micrometer channel is designed to aid in convective forecasting: gradients in water vapor very low in the atmosphere should be apparent.

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An extended period of hot temperatures across much of the western US — where drought conditions were widespread — helped set the stage for large wildfires which produced several pyrocumulonimbus (pyroCb) clouds in parts of Oregon, Idaho and California during the 07-10 September 2022 period.

===== 07 September =====

GOES-18 (GOES-West) Day Land Cloud Fire RGB images (above) displayed numerous wildfires (clusters of red pixels) from far eastern Oregon into Idaho on 07 September 2022. Three of the larger fires — one in Oregon and two in Idaho — produced one or more pulses of pyroCb clouds during the day.

1-minute GOES-18 True Color RGB images visualized using CSPP GeoSphere (below) showed the smoke-laden cloud tops (shades of tan) associated with some of the pyroCb pulses from the eastern Oregon and central Idaho wildfires.

4-panel displays of 1-minute Mesoscale Domain Sector GOES-18 Day Land Cloud Fire RGB, Shortwave Infrared (3.9µm), “Clean” Infrared Window (10.35 µm) and Cloud Top Temperature (below) provided a closer view of a vigorous pyroCb produced by the Moose Fire in far eastern Idaho (near the Montana border). During that time period, the maximum surface 3.9 µm infrared brightness temperature of the fire signature reached 137.88^oC (the saturation temperature of GOES-18 ABI Band 7 detectors). The coldest pyroCb cloud-top 10.35 µm infrared brightness temperatures were -52^oC, while the coldest Cloud Top Temperature derived product values were around -56^oC.

===== 08 September =====

1-minute GOES-17 (which resumed duty as GOES-West as of 1601 UTC on 08 September) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed a “marginal” pyroCb produced by the Mosquito Fire in California on 08 September 2022, whose coldest cloud-top 10.35 µm infrared brightness temperature reached -39^oC (just shy of the -40^oC threshold of pyroCb classification) — however, the Cloud Top Temperature derived product (not shown) did reach -42^oC.

1-minute GOES-17 True Color RGB images (below) displayed the smoke-laden (shades of tan) cloud top of this “marginal pyroCb”.

===== 10 September =====

As discussed in this blog post, the Cedar Creek Fire in Oregon had been producing a large smoke plume during the day on 09 September — and this trend continued into the overnight hours, as shown by a Suomi-NPP VIIRS Day/Night Band (0.7 µm) image valid at 1020 UTC on 10 September (below). Ample illumination by a Full Moon provided an excellent example of the “visible image at night” capability of the Day/Night Band (DNB).

In a closer view of of the Cedar Creek Fire, a toggle between the corresponding Suomi-NPP VIIRS DNB and Shortwave Infrared images (below) displayed the bright nighttime glow of the more active individual fires (as well as the dense smoke plume drifting northwestward) in the DNB image — and the thermal signature of fires along the northwestern perimeter was evident in the Shortwave Infrared image, even though the dense smoke plume was overhead.

During the subsequent daytime hours, a sequence of 1-minute GOES-17 Day Land Cloud Fire RGB, Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Cloud Top Temperature product (below) showed that the Cedar Creek Fire produced a pyroCb cloud late in the day on 10 September 2022. During that particular time period, the maximum surface 3.9 µm infrared brightness temperature of the fire signature reached 138.71^oC (the saturation temperature of GOES-17 ABI Band 7 detectors). The coldest cloud-top 10.35 µm infrared brightness temperature was -45^oC, while the coldest Cloud Top Temperature derived product value was -49^oC.

1-minute GOES-17 True Color RGB images (below) showed the Cedar Creek Fire pyroCb rising through and towering above the large pall of lower-altitude smoke.

During the following overnight hours, a toggle between Suomi-NPP VIIRS Day/Night Band (0.7 µm) and Shortwave Infrared (11.45 µm) images valid at 1002 UTC (below) revealed that the nighttime glow and thermal signature of larger active fires along the perimeter of the Cedar Creek Fire were still apparent, in spite of dense smoke that lingered over the area and high clouds that were beginning to move overhead from the west.

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CSPP Geosphere animations from GOES-West (above, link) and GOES-East (below, link) both show an active fire — the Cedar Creek fire — over Oregon (previously discussed here). Low-level winds (as shown in the 1200 UTC sounding from Medford OR) are moving the smoke plume out over the Pacific Ocean. The oblique side-view from GOES-East (below) gives a better view of the structure of the smoke plume.

Later in the day, a brief pyrocumulus jump ejected smoke to higher altitudes, where westerly winds prevailed:

A pyrocumulus jump associated with the #CedarCreekFire ejected smoke to higher altitudes (at least 7.5 km), where westerly winds transported some of the smoke eastward – @NOAASatellites #GOES17/#GOESwest True Color RGB images: https://t.co/UPGA0MMeHB; @NWSPortland #ORwx pic.twitter.com/wk9Y69UKSQ

— Scott Bachmeier (@CIMSS_Satellite) September 10, 2022

Fires over Idaho are also producing smoke that has been trapped in valleys, as shown below. Much of Idaho is under an Air Quality Alert (link). A current map of Air Quality can be viewed here. The image from 2000 UTC on 9 September is here.

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Advanced Clear-Sky Processor for Ocean (ACSPO) temperatures over Lake Superior on 6 September, shown above, show a large area of surface temperature below 55^oF (magenta and white in the enhancement) over central Lake Superior. Clear early-Autumn skies allowed for this mostly complete view of the Lake Surface. Although Lake Superior was quite cold with respect to normal in late June (see this graph), its surface waters are now very close to normal. Note how much warmer the northern end of Lake Michigan is! The yellow enhancement shows temperatures close to 70^oF.

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The animation below shows VIIRS ACSPO temperatures off the coast of Oregon from 3 separate overpasses. The strong north winds observed at the buoys strengthen oceanic upwelling, leading to the very cold ocean surface temperatures (51^o – 52^oF) along the Oregon coast.

GOES-R Satellites have level-2 Sea Surface Temperature products as well (link) that something like the ACSPO algorithm — albeit at lower spatial resolution. The toggle below compares the two products. VIIRS better captures the cold ribbon of water right along the coast. The GOES-R algorithm cloud mask at the time below is perhaps too stringent.

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On 4 September, strong nighttime radiation cooling led to the Lake Superior water temperatures being several degrees F warmer than the surface air temperatures at nearby inland locations (overnight minimum temperatures included 33ºF in far northern Wisconsin and 34ºF in Upper Michigan; note that the color scale used in the tweet below differs from the one above):

A sure sign of Autumn: when the #NOAA20 and #SuomiNPP #VIIRS sea surface temperatures of Lake Superior are warmer than the surface air temperatures at nearby inland sites… https://t.co/KyRC5PmfzP #MNwx #WIwx #Mwx pic.twitter.com/5lNMHRzIIf

— Scott Bachmeier (@CIMSS_Satellite) September 4, 2022

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