Fires in Alaska, Canadian smoke over the Lower 48

June 29th, 2015
Suomi NPP VIIRS 3.74 µm infrared channel images, times as indicated (click to enlarge)

Suomi NPP VIIRS 3.74 µm infrared channel images, times as indicated (click to enlarge)

Suomi NPP 0.64 µm visible channel images, times as indicated (click to enlarge)

Suomi NPP 0.64 µm visible channel images, times as indicated (click to enlarge)

The 2015 Wildfire Season is off to a quick start in Alaska (continuing an observed trend). This map (from this site) shows more than 300 active fires over Alaska at 2000 UTC on 29 June 2015. This graph (from the Alaska Climate Info Facebook page) compares early burn acreage in 2015 to that in 2004 (the year with the most acreage burned — see this graph, courtesy of Uma Bhatt, University of Alaska-Fairbanks).

Soumi NPP VIIRS 3.74 µm infrared imagery from early morning on 29 June 2015 (top) shows numerous wildfire hot spots (dark black pixels) in the region surrounding the Yukon River (the middle portion of the imagery, south of Kotzebue Sound). VIIRS visible imagery from the same time, above, shows an extensive pall of smoke over much of central Alaska.

GOES-13 Visible (0.63 µm) imagery (click to play animation)

GOES-13 Visible (0.63 µm) imagery (click to play animation)

Meanwhile, thick smoke from fires burning over northern Canada (comparison of VIIRS visible and shortwave IR images from 28 June) was drifting southward over central portions of the Lower 48 states. The smoke plume on 28 June (above) was fairly narrow; however, a much broader and thicker plume was seen moving south on 29 June (GOES visible imagery below, then MODIS/VIIRS true-color RGB imagery as displayed using the SSEC RealEarth web map server). SSEC MODIS Today true-color imagery of this smoke plume is also available here. Pilot reports placed the lower and upper bounds of the thick smoke at 5000 and 17500 feet, with flight visibilities as low as 2 miles at 5000 feet. Some of the smoke subsided to the surface in southeastern South Dakota, restricting the surface visibility at Sioux Falls to 5 miles and raising the Air Quality Index there into the Unhealthy category. In fact, the smoke was so thick over far eastern South Dakota that it had the effect of reducing surface heating and slowing the rise of afternoon temperatures, such that convective temperatures were not being reached and probabilities of precipitation had to be scaled back:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
356 PM CDT MON JUN 29 2015

.SHORT TERM…(THIS EVENING THROUGH TUESDAY)
ISSUED AT 356 PM CDT MON JUN 29 2015

IN ADDITION…THICK PLUME OF SMOKE CONTINUES TO DRIFT SOUTHWARD IMPACTING NEARLY ALL OF THE FORECAST AREA…BUT MOST   NOTABLE ALONG AND EAST OF THE JAMES RIVER VALLEY. BECAUSE OF THIS…AFTERNOON TEMPERATURES ARE ABOUT 2 TO 4 DEGREES
COOLER THAN FORECAST AND WE ARE HAVING A HECK OF A TIME REACHING OUR CONVECTIVE TEMPERATURE. THEREFORE LOWERED THE LATE AFTERNOON AND EVENING POPS IN OUR EASTERN ZONES TO ONLY SLIGHT CHANCE POPS. BUT EVEN THOSE MAY BE TOO HIGH AND IF NOTHING DEVELOPS OVER THE NEXT COUPLE OF HOURS…THEY MAY NEED TO BE REMOVED ENTIRELY.

GOES-13 Visible (0.63 µm) imagery (click to play animation)

GOES-13 Visible (0.63 µm) imagery (click to play animation)

MODIS and VIIRS true-color imagery (click to enlarge)

MODIS and VIIRS true-color imagery (click to enlarge)

Daytime detection of smoke plumes is not difficult with visible (or true-color) imagery. At night, however, smoke detection is a challenge. The VIIRS Day/Night Band on Suomi NPP can detect smoke when Lunar Illumination is high (although detection is limited to one or sometimes two passes per night). Smoke is otherwise mostly transparent to infrared channels on the GOES Imager. Websites such as the NOAA/NESDIS IDEA and the GASP are helpful; however, the GASP product uses single-channel (visible) detection only.

Visible imagery from GOES-15, below, highlights the expansive region covered by smoke over northern Canada. Note that the smoke becomes less distinct with time as the sun rises higher in the sky, because forward scattering of visible light by smoke particles is more effective than backward scattering.

GOES-15 Visible (0.62 µm) imagery, times as indicated (click to animate)

GOES-15 Visible (0.62 µm) imagery, times as indicated (click to animate)

Calbuco volcanic eruption in Chile

April 23rd, 2015
GOES-13 (GOES-East) 0.63 µm visible and 10.7 µm IR channel images at 2138 UTC (with surface reports)

GOES-13 (GOES-East) 0.63 µm visible and 10.7 µm IR channel images at 2138 UTC (with surface reports)

The Calbuco volcano in southern Chile erupted around 2103 UTC or 6:03 pm local time on 22 April 2015. The first good satellite view of the volcanic cloud was provided by the 2138 UTC or 6:38 pm local time GOES-13 (GOES-East) 0.63 µm visible channel and 10.7 µm IR channel images (above). The coldest cloud-top IR brightness temperature at that time was -65º C, which was very close to the tropopause temperature as indicated on the nearby Puerto Montt rawinsonde reports from 1200 UTC on 22 April and 23 April — the height of the tropopause was between 12.3 and 15.6 km on each day (there were 2 tropopause levels TRO1 and TRO2 coded in both of the upper air reports).

However, before the volcanic cloud was seen, a well-defined thermal anomaly or “hot spot” was evident on the previous GOES-13 3.9 µm shortwave IR image at 2045 UTC or 5:45 pm local time (below). The hottest 3.9 µm IR brightness temperature at that time was 340.8 K (red pixel), which is very close to the saturation temperature of the GOES-13 3.9 µm detectors.

GOES-13 3.9 µm shortwave IR image at 2045 UTC

GOES-13 3.9 µm shortwave IR image at 2045 UTC

An oblique view of the early stage of the volcanic cloud was captured on a 2100 UTC GOES-15 (GOES-West) 0.63 µm visible image (below; closer view).

GOES-15 (GOES-West) 0.63 µm visible image at 2100 UTC

GOES-15 (GOES-West) 0.63 µm visible image at 2100 UTC

A sequence of GOES-13 (GOES-East) 10.7 µm IR channel images (below; click image to play animation; also available as an MP4 movie file) revealed that there was a second explosive eruption that began sometime before the 0508 UTC or 2:08 am local time image on 23 April. The coldest cloud-top IR brightness temperature with this second eruption was -68º C at 0808 UTC. Also, at 0508 UTC mesospheric airglow waves were seen with Suomi NPP VIIRS Day/Night Band imagery.

GOES-13 (GOES-East) 10.7 µm IR images (click to play animation)

GOES-13 (GOES-East) 10.7 µm IR images (click to play animation)

On the morning of 23 April, a 1200 UTC GOES-15 (GOES-West) 0.63 µm visible image (below) provided a good view of the large areal coverage of volcanic cloud material resulting from the 2 eruptions.

GOES-15 (GOES-West) 0.63 µm visible image

GOES-15 (GOES-West) 0.63 µm visible image

Finally, a before-eruption (21 April) and post-eruption (23 April) comparison of Aqua MODIS true-color Red/Green/Blue (RGB) images as visualized using the SSEC RealEarth web map server (below) showed the effect of ashfall on some of the higher terrain downwind of Calbuco, which was particularly evident on the snow-capped summits of the Osorno and Puyehue volcanoes (yellow arrows).

Before (21 April) and after (23 April) Aqua MODIS true-color RGB images

Before (21 April) and after (23 April) Aqua MODIS true-color RGB images

—– 24 April Update —–

A series of GOES-13 and Terra/Aqua MODIS volcanic ash height retrieval images from the SSEC Volcano Monitoring site (below; click image to play animation) showed that the ash from each of the two explosive eruptions reached heights of 18-20 km (black color enhancement), which was well into the stratosphere.

GOES-13 and Terra/Aqua MODIS volcanic ash height retrieval values (click to play animation)

GOES-13 and Terra/Aqua MODIS volcanic ash height retrieval values (click to play animation)

Ice over the Great Lakes

April 17th, 2015
Suomi-NPP Imagery:  Visible (0.64µm), Day Night Band (0.70µm) and near-IR (0.85µm) (click to enlarge)

Suomi-NPP Imagery: Visible (0.64µm), Day Night Band (0.70µm) and near-IR (0.86µm) images (click to enlarge)

Visible Imagery over the Great Lakes on Friday April 17th showed mostly open waters over the five lakes, with regions that could be ice confined to coastlines of Lakes Superior, Huron, Erie and Michigan. The animation above is of Suomi NPP VIIRS visible (0.64µm and 0.70µm) and near-infrared (0.86µm) data. Can you tell with certainty which of the white features over the lakes are clouds vs. ice?

Suomi-NPP Infrared Imagery (3.74 µm),  (click to enlarge)

Suomi-NPP Infrared Imagery (3.74 µm) (click to enlarge)

Infrared data can give clues. The 3.74 µm imagery, above, shows the brightness temperature. Note how the white regions over Lakes Superior, Michigan and Ontario are about the same temperature as the surrounding water. In contrast, white regions over Lakes Erie and Ontario are much darker (warmer) in the 3.74 µm than the surrounding water. This is testimony to the superior scattering abilities around 3.74 µm of water-based clouds compared to lake ice. More solar radiation scattered towards the satellite by the clouds means a warmer temperature is detected.

Suomi-NPP Imagery:  Toggle between Visible (0.64µm) and near-IR (1.61 µm) (click to enlarge)

Suomi-NPP Imagery: Visible (0.64µm) and near-IR (1.61 µm) (click to enlarge)

The 1.61 µm near-infrared channel is useful because ice strongly absorbs solar radiation at that wavelength, appearing dark. The toggle above, of visible (0.64) and near-infrared (1.61) neatly distinguishes between clouds and ice. Ice (dark in the 1.61 µm because it does not reflect; at that wavelength, it absorbs) is apparent over eastern Lake Superior, eastern and northern Lake Huron and some small bays in northern Lake Michigan. There is no ice apparent on Lakes Erie or Ontario: features there exhibit signatures which are white in both visible and at 1.61 µm.

Another method to aid in the discrimination of snow/ice vs supercooled water droplet clouds is the creation of Red/Green/Blue (RGB) products. The example below toggles between the 0.64 µm visible image and an RGB image (which uses the VIIRS 0.64 µm/1.61 µm/1.61 µm data as the R/G/B components) — snow cover and ice appear as darker shades of red on the RGB image (in contrast to supercooled water droplet clouds, which are brighter shades of white). The snow depth on the morning of 17 April was still 13 inches at Munising in the Upper Peninsula of Michigan.

Suomi NPP VIIRS 0.64 µm visible and false-color RGB images (click to enlarge)

Suomi NPP VIIRS 0.64 µm visible and false-color RGB images (click to enlarge)

On this day there was only 1 pass of the Landsat-8 satellite over any of the ice-covered portions of the Great Lakes; the 15-meter resolution panchromatic visible (0.59 µm) image below shows a very detailed view of the far western portion of the ice that was north of the Keweenaw Peninsula in Lake Superior (zoomed image).

Landsat-8 panchromatic visible (0.59 µm) image (click to enlarge)

Landsat-8 panchromatic visible (0.59 µm) image (click to enlarge)

Terra and Aqua both carry the MODIS sensor, and MODIS can detect radiation at 1.38 µm, a wavelength at which cirrus is highly reflective. A 1.38 µm image from the 17th, below, shows the horizontal extent of cirrus.

MODIS Imagery:  near-IR (1.38 µm) (click to enlarge)

MODIS Imagery: near-IR (1.38 µm) (click to enlarge)

Dust storm in southern Nevada and California

April 14th, 2015
GOES-13 0.63 µm visible channel images (click o play animation)

GOES-13 0.63 µm visible channel images (click o play animation)

GOES-13 (GOES-East) 0.63 µm visible channel images (click image to play animation; also available as an MP4 movie file) showed the hazy signature of a cloud of thick blowing dust moving southward across southern Nevada and parts of southern California, along and behind a strong cold frontal boundary on 14 April 2015.

Areas where the dust cloud was more dense could be identified using the Terra and Aqua MODIS 11-12 µm IR brightness temperature difference (BTD) product (below). The 12 µm IR channel is no longer available on the imager instrument of the current series of GOES satellites — however, the ABI instrument on the upcoming GOES-R satellite will have a 12 µm IR channel, allowing the creation of such BTD products to aid in the identification and tracking of similar dust features.

Terra and Aqua MODIS 11-12 µm IR brightness temperature difference

Terra and Aqua MODIS 11-12 µm IR brightness temperature difference

At 1833 UTC, a pilot reported that the top of the dust cloud was at 11,500 feet near its leading edge (below). Farther to the south, strong winds interacting with the terrain were causing pockets of moderate to severe turbulence.

Terra MODIS 11-12 µm IR brightness temperature difference, with pilot reports

Terra MODIS 11-12 µm IR brightness temperature difference, with pilot reports

The blowing dust cloud was also evident on true-color Red/Green/Blue (RGB) images from MODIS and VIIRS, as visualized using the SSEC RealEarth web map server (below).

MODIS and VIIRS true-color RGB images

MODIS and VIIRS true-color RGB images