Fires over Alaska, smoke over the Lower 48

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

Suomi NPP 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 url) 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).

The 3.74 µm infrared imagery from early morning on 29 June 2015 (top) shows numerous hot spots in the region surrounding the Yukon River (visible in the imagery south of the Kotzebue Sound). Visible Imagery from the same time, above, shows an extensive pall of smoke over central Alaska.

GOES-13 Visible (0.63 µm) imagery, times as indicated (click to enlarge)

GOES-13 Visible (0.63 µm) imagery, times as indicated (click to enlarge)

Smoke from fires over Alaska and over northern Canada (image from 28 June 2015) have led to considerable smoke over the northern Plains of the Continental United States. The plume on Sunday 28 June (above) was fairly narrow; however, a larger plume is now moving south (GOES Imagery below, then MODIS True-Color displayed in SSEC‘s RealEarth). (MODIS Today imagery of this event is also available here.)

GOES-13 Visible (0.63 µm) imagery, times as indicated (click to enlarge)

GOES-13 Visible (0.63 µm) imagery, times as indicated (click to enlarge)

MODIS True-Color imagery for 29 June 2015 (click to enlarge)

MODIS True-Color imagery for 29 June 2015 (click to enlarge)

Day-time detection of smoke plumes is not difficult with visible imagery. At night, however, smoke detection is a challenge. The Day Night Visible Band on Suomi NPP can detect smoke when Lunar Illumination is high (although detection is limited to one pass per night). Smoke is otherwise mostly transparent to infrared channels on the GOES Imager, however. Websites such as NOAA/NESDIS’s IDEA and the GASP site are helpful. The GASP data uses single-channel detection only — visible data.

Visible Imagery from GOES-15, below, underlines the extensive 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 by smoke particles of visible light 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)

Natural gas pipeline explosion in Texas

June 15th, 2015

GOES-15 (left) and GOES-13 (right) 3.9 µm shortwave IR channel images [click to play animation]

GOES-15 (left) and GOES-13 (right) 3.9 µm shortwave IR channel images [click to play animation]

An explosion occurred along a natural gas pipeline near Lindenau, Texas just after 01 UTC on 15 June 2015 (8:00 pm local time on 14 June). The thermal signature or “hot spot” of the resulting fire was detected on both GOES-15 (GOES-West) and GOES-13 (GOES-East)  3.9 µm shortwave IR imagery (above; click image play animation). The images have overlays of surface reporting stations (yellow), Interstate highways (cyan), and primary highways (gray). The relatively small but very hot fire exhibited IR brightness temperatures as high as 341.1 K on GOES-13 and 340.0 K on GOES-15, which is close to the saturation temperature for the 3.9 µm detectors on those satellites. Since GOES-13 was in Rapid Scan Operations (RSO) mode at the time, the fire hot spot was first detected by that satellite (at 0107 UTC) — and the IR brightness temperature remained at 341.0 K for another 40 minutes after initial detection (0115 to 0155 UTC).

A subtle signature of the fire’s smoke plume (lighter gray enhancement) could be seen moving northwestward and then northward away from the fire hot spot. On the 0125 UTC GOES-13 shortwave IR image (below), and overlay of the CRAS model winds showed them turning from southeastward at the surface (in agreement with regional METAR surface reports) to southerly at an altitude of 3 km, suggesting that the smoke plume may have reached that height.

GOES-13 3.9 µm shortwave IR image (with METAR surface reports and CRAS surface. 1km, 2km, and 3km winds)

GOES-13 3.9 µm shortwave IR image (with METAR surface reports and CRAS surface. 1km, 2km, and 3km winds)

Strong arctic cold front: grass fires, blowing dust, and a lee-side frontal gravity wave

March 17th, 2015
GOES-13 3.9 µm shortwave IR channel images (click to play animation)

GOES-13 3.9 µm shortwave IR channel images (click to play animation)

After a day of record high temperatures in parts of Nebraska — the 91º F at North Platte set a new record high for the month of March, and was also the earliest temperature of 90º F or above on record at that site — a strong arctic cold front plunged southward across the state late in the day on 16 March 2015. With strong winds (gusting to 40-50 knots at some locations) in the wake of the frontal passage and dry vegetation fuels in place, GOES-13 3.9 µm shortwave IR images (above; click image to play animation) showed the “hot spot” signatures (black to yellow to red pixels) associated with a number of large grass fires that began to burn across the state.

The strong northwesterly winds behind the cold front also lofted dry soil into the boundary layer, creating blowing dust whose hazy signature was evident on GOES-13 0.63 visible channel images (below; click image to play animation). Visibility was reduced to 7 miles at some locations.

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

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

After sunset and into the pre-dawn hours on 17 March, a lee-side frontal gravity wave signature could be seen on GOES-13 6.5 µm water vapor channel images (below; click image to play animation). This warmer/drier (darker blue color enhancement) arc on the water vapor imagery followed the position of the surface cold front, which meant that the upward-propagating frontal gravity wave reached altitudes where the water vapor channel was sensing radiation.

GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)

As the frontal gravity wave was approaching the Kansas/Oklahoma border region around 05 UTC, a pilot reported light to moderate turbulence at altitude of 6000 feet (below).

GOES-13 6.5 µm water vapor channel image with pilot report of turbulence

GOES-13 6.5 µm water vapor channel image with pilot report of turbulence

A 4-panel comparison of the three Sounder water vapor channels (6.5 µm, 7.0 µm, and 7.4 µm) and the standard Imager 6.5 µm water vapor channel (below; click image to play animation) showed that the southward propagation of the frontal gravity wave signature was most evident on the Sounder 7.0 µm and Imager 6.5 µm images, although there was also a more subtle indication on the Sounder 7.4 µm images. The new generation of geostationary satellite Imager instruments (for example, the AHI on Himawari-8 and the ABI on GOES-R) feature 3 water vapor channels which are similar to those on the current GOES Sounder, but at much higher spatial and temporal resolutions

GOES-13 Sounder 6.5 µm (upper left), 7.0 µm (upper right), 7.4 µm (lower left), and Imager 6.5 µm (lower right) - click to play animation

GOES-13 Sounder 6.5 µm (upper left), 7.0 µm (upper right), 7.4 µm (lower left), and Imager 6.5 µm (lower right) – click to play animation

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GOES-13 Sounder and Imager water vapor channel weighting functions for North Platte, Nebraska

GOES-13 Sounder and Imager water vapor channel weighting functions for North Platte, Nebraska

The depth and altitude of the layer from which a particular water vapor channel is detecting radiation is shown by plotting its weighting function — for example, at North Platte, Nebraska (above), the Imager 6.5 µm plot (black) and the 7.0 µm plot (green) exhibited lower-altitude secondary peaks around the 500 hPa level — while farther to the south at Dodge City, Kansas (below) these 2 water vapor channel plots had their peaks located slightly higher in the atmosphere. Even though the bulk of the radiation was being detected from higher altitudes (due to the presence of moisture and cirrus clouds aloft over much of the southern Plains region), the sharp signal of the lower-altitude cold frontal gravity wave was strong enough to be seen in the deep layer average moisture brightness temperature depicted in the water vapor images.

GOES-13 Sounder and Imager water vapor channel weighting functions

GOES-13 Sounder and Imager water vapor channel weighting functions

The King Fire in California

September 19th, 2014
Suomi NPP VIIRS true-color images

Suomi NPP VIIRS true-color images

The King Fire began burning in central California (between Sacramento and Lake Tahoe) during the evening hours on 13 September 2014. A sequence of daily (12-19 September) Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server site (above) showed that as the prevailing southwesterly wind pattern switched to easterly on 19 September, there was a major change in the transport of smoke from the King Fire. The final image in the series zooms out to show how much of central California had become over-run with thick smoke.

A comparison of AWIPS-II images of Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR image at 09:18 UTC or 2:18 AM local time (below) revealed the bright glow of the large fire complex, along with the large fire “hot spot” signature (black to yellow to red color enhancement).

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 3.74 µm shortwave IR images

Suomi NPP VIIRS 3.74 µm shortwave IR images during the overnight hours (just after 2 AM local time) on 17 and 18 September (below) showed the dramatic northeastward advance of the fire hot spot signature during that 24-hour period. Smoke from the fire was reducing the surface visibility to 3-4 miles as far to the northeast as Lovelock (KLOL) and Fallon (KNFL) in Nevada.

Suomi NPP VIIRS 3.74 µm shortwave IR images

Suomi NPP VIIRS 3.74 µm shortwave IR images