Eruption of the Mount Pavlof volcano in Alaska

March 28th, 2016

Himawari-8 AHI Shortwave Infrared (3.9 µm) images [click to play animation]

Himawari-8 AHI Shortwave Infrared (3.9 µm) images [click to play animation]

A major eruption of the Mount Pavlof volcano on the Alaska Peninsula began shortly before 0000 UTC on 28 March, or 4:00 pm on 27 March Alaska time (AVO report), as detected by a thermal anomaly (or “hot spot”, yellow to red color enhancement) on Himawari-8 AHI Shortwave Infrared (3.9 µm) images (above). The hot spot decreased in size and intensity toward the later hours of the day, signaling a lull in the volcanic eruption.

It is interesting to note on a comparison of the 0000 UTC Himawari-8 and GOES-15 Shortwave Infrared (3.9 um) images the large difference in the magnitude of the thermal anomaly — even though the viewing angle was larger for Himawari-8, the superior spatial resolution (2 km at nadir, compared to 4 km with GOES-15) detected a hot spot with an Infrared Brightness Temperature (IR BT) that was 36.6 K warmer (below). The Infrared channels on the GOES-R ABI instrument will also have a 2 km spatial resolution.

Himawari-8 AHI (left) and GOES-15 Imager (right) 3.9 µm Shortwave Infrared images [click to enlarge]

Himawari-8 AHI (left) and GOES-15 Imager (right) 3.9 µm Shortwave Infrared images [click to enlarge]

With the aid of reflected light from the Moon (in the Waxing Gibbous phase, at 75% of Full), a nighttime view using the Suomi NPP VIIRS Day/Night Band (0.7 µm) from the SSEC RealEarth site (below) revealed the bright glow of the eruption, along with the darker (compared to adjacent meteorological clouds) volcanic ash cloud streaming northeastward. The corresponding VIIRS Shortwave Infrared (3.74 µm) image showed the dark black hot spot of the volcano summit.

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

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

The volcanic ash cloud continued moving in a northeastward direction, as seen in a sequence of GOES-15 Infrared Window (10.7 µm) and either Terra/Aqua MODIS or Suomi NPP VIIRS retrieved Volcanic Ash Height products from the NOAA/CIMSS Volcanic Could Monitoring site (below).

GOES-15 Infrared (10.7 µm) images, with Terra/Aqua MODIS and Suomi NPP VIIRS Ash Height products [click to play animation]

GOES-15 Infrared (10.7 µm) images, with Terra/Aqua MODIS and Suomi NPP VIIRS Ash Height products [click to play animation]

Due to the oblique satellite view angle, the shadow cast by the tall volcanic ash cloud was easily seen on the following early morning (Alaska time) Himawari-8 AHI Visible (0.64 µm) images (below). A closer view (courtesy of Dan Lindsey, RAMMB/CIRA) revealed overshooting tops and gravity waves propagating downwind of the eruption site.

Himawari-8 AHI Visible (0.64 um) images (click to play animation]

Himawari-8 AHI Visible (0.64 um) images (click to play animation]

A few select Pilot reports (PIREPs) are shown below, plotted on GOES-15 Infrared Window (10.7 µm) and Aqua MODIS Ash Height derived products. Numerous flights were canceled as the ash cloud eventually began to drift over Western and Interior Alaska (media report).

GOES-15 Infrared Window (10.7 um) image, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 µm) image, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 um) image, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 µm) image, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 um) image, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 µm) image, with METAR surface reports and Pilot reports [click to enlarge]

Aqua MODIS Ash Height product, with METAR surface reports and Pilot reports [click to enlarge]

Aqua MODIS Ash Height product, with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 um), with METAR surface reports and Pilot reports [click to enlarge]

GOES-15 Infrared Window (10.7 µm), with METAR surface reports and Pilot reports [click to enlarge]

A comparison of Suomi NPP VIIRS Shortwave Infrared (3.74 µm), Day/Night Band (0.7 µm), and true-color Red/Green/Blue (RGB) images (below) showed the volcanic hot spot and the brown to tan colored ash cloud at 2141 UTC on 28 March. Significant ash fall (as much as 2/3 of an inch) was experienced at the village of Nelson Lagoon, located 55 miles northeast of Pavlof (media report).

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

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

A comparison of the 3 Himawari-8 AHI Water Vapor bands (7.3 µm, 6.9 µm and 6.2 µm) covering the first 14 hours of the eruption from 0000 to 1400 UTC is shown below. Note that volcanic plume was best seen on the 7.3 µm images, which indicated that it began to move over the coast of Western Alaska after around 0600 UTC; this is due to the fact that the 7.3 µm band is not only a “water vapor absorption” band, but is also sensitive to high levels of SO2 loading in the atmosphere (as was pointed out in this blog post).

Himawari-8 AHI Water Vapor 7.3 µm (left), 6.9 µm (center) and 6.2 µm (right) images [click to play animation]

Himawari-8 AHI Water Vapor 7.3 µm (left), 6.9 µm (center) and 6.2 µm (right) images [click to play animation]

Undular bore over Texas

March 18th, 2016

GOES-15 Visible (0.63 µm) images with surface plots [click to play animation]

GOES-15 Visible (0.63 µm) images with surface plots [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed the wave clouds associated with an undular bore moving southeastward across Texas during the day on 18 March 2016. The leading undular bore (and packet of solitary waves behind it) were propagating ahead of the advancing cold front (reference).

A nighttime Suomi NPP VIIRS Day/Night Band image at 0814 UTC or 3:14 am local time (below) showed the early stage of bore wave cloud formation over the Texas Panhandle. Due to ample illumination from the Moon (in the Waxing Gibbous phase, at 78%  of Full), this example illustrated the “visible image at night” capability of the Day/Night Band.

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

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

CLAVR-x POES AVHRR Cloud Top Temperature and Cloud Top Height products (below) indicated values of around +6º C and 2 km, respectively, for the undular bore wave cloud features ahead of the cold front at 1714 UTC.

POES AVHRR Cloud Top Temperature and Cloud Height products [click to enlarge]

POES AVHRR Cloud Top Temperature and Cloud Height products [click to enlarge]

The 2 km cloud top height was consistent with the depth of the stable layers seen above the surface seen in rawinsonde data profiles at Midland (KMAF) and Forth Worth (KFWD), 2 locations which were ahead of the cold frontal boundary at 1200 UTC.

Midland (KMAF) and Fort Worth (KFWD) rawinsonde data profiles at 1200 UTC [click to enlarge]

Midland (KMAF) and Fort Worth (KFWD) rawinsonde data profiles at 1200 UTC [click to enlarge]

Solar eclipse shadow as seen from geostationary satellites

March 9th, 2016

Himawari-8 true-color images [click to play MP4 animation]

Himawari-8 true-color images [click to play MP4 animation]

The shadow of the total solar eclipse of 09 March 2016 was captured by a number of geostationary satellites, including JMA Himawari-8 (above; also available as either a large 140 Mbyte animated GIF, or a YouTube video: large) | small) and KMA COMS-1 (below). The Himawari-8 true-color Red/Green/Blue (RGB) images were created using the Simple Hybrid Contrast Stretch (SHCS) method by Yasuhiko Sumida, SSEC visiting scientist from JMA.

COMS-1 Visible (0.67 um) images [click to play animation]

COMS-1 Visible (0.67 um) images [click to play animation]

Toward the end of the eclipse, the shadow was also seen with NOAA GOES-15 (below) as it moved northwest and north of Hawai’i.

GOES-15 Visible (0.63 um) images [click to play animation]

GOES-15 Visible (0.63 um) images [click to play animation]

In addition, the eclipse shadow was captured with the Chinese satellites FY-2E and FY-2G (below).

FY-2E Visible (0.73 µm) images [click to enlarge]

FY-2E Visible (0.73 µm) images [click to enlarge]

FY-2G Visible (0.73 µm) images [click to enlarge]

FY-2G Visible (0.73 µm) images [click to enlarge]

Why 1-minute satellite data matters: Monitoring Fires

February 18th, 2016

GOES-14 0.63 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play MP4 animation]

GOES-14 0.63 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play MP4 animation]

Extensive wildfires (well-forecast by the Storm Prediction Center) occurred over the southern Plains on Thursday 18 February 2016, while GOES-14 was operating in SRSO-R mode. A comparison of 1-minute GOES-14 Visible (0.63 µm) and Shortwave Infrared (3.9 µm) images (above; also available as a large 112 Mbyte animated GIF) showed the broad areal coverage of smoke plumes and fire hot spots (dark black to yellow to red pixels) during the day over eastern Oklahoma.

GOES-14 0.63 µm Visible (left) and 3.9 µm Shortwave Infrared (right) images [click to play MP4 animation]

GOES-14 0.63 µm Visible (left) and 3.9 µm Shortwave Infrared (right) images [click to play MP4 animation]

Of particular interest was a rapidly-intensifying and fast-moving grass fire over northwestern Oklahoma, in Harper County just west-northwest of the town of Buffalo, which burned 17,280 acres (media report). Note the warm air temperatures as seen in the surface plots — the high of 90º F at Gage OK (KGAG, south of the fire) tied for the warmest February temperature on record at that site. A closer view of the Buffalo fire is shown above — county outlines are shown as dashed white lines, while US and State highways are plotted in violet (also available as a large 63 Mbyte animated GIF). The shortwave infrared images revealed the initial appearance of a color-enhanced fire hot spot (exhibiting an IR brightness temperature of 327.5 K) at 2045 UTC; three minutes later (at 2048 UTC), the IR brightness temperature had already increased to 341.2 K (red enhancement) which is the saturation temperature of the GOES-14 shortwave IR detectors. The hot spots could also be seen racing northeastward toward the Oklahoma/Kansas border, with the fire eventually crossing US Highway 183 (which runs south-to-north through Buffalo and across the Kansas border). The early detection and subsequent accurate tracking of such rapid fire intensification and propagation could only have been possible using 1-minute imagery.

The two plots below show GOES-14 pixel values of 3.9 µm IR brightness temperature at the initial Buffalo fire site (top plot, at 36:51º N, 99:48º W) and at a site just to the northeast (bottom plot, at 36:54º N, 99:43º W) through which the moving fire propagated. The blue line shows every value, nominally at 1-minute intervals. The red dots show points sampled every five minutes. Very small temporal scale changes in the fire cannot be captured with a 5-minute sampling interval.

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at 36:51:36º N, 99:48:27º W, 2040-2230 UTC on 18 February 2016 [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at 36:51:36º N, 99:48:27º W, 2040-2230 UTC on 18 February 2016 [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at 36:54:44º N, 99:43:22º W, 2115-2200 UTC on 18 February 2016 [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at 36:54:44º N, 99:43:22º W, 2115-2200 UTC on 18 February 2016 [click to enlarge]

 

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm Shortwave Infrared images covering the initial period 2030-2100 UTC [click to play animation]

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm Shortwave Infrared images covering the initial period 2030-2100 UTC [click to play animation]

For the Buffalo fire, a three-satellite comparison of Shortwave Infrared (3.9 µm) images from GOES-15 (operational GOES-West), GOES-14, and GOES-13 (operational GOES-East) is shown for the initial 30-minute time period 2030-2100 UTC (above). The images are displayed in the native projection of each satellite. In terms of the first unambiguous fire hot spot detection (via a hot color-enhanced image pixel) during that initial period, it would appear from the image time stamps that both GOES-14 and GOES-13 detected the fire at 2045 UTC — however, because GOES-14 was scanning a much smaller sector, it did indeed scan the fire at 20:45 UTC (while GOES-13 scanned the fire at 2049 UTC, 4 minutes after its larger scan sector began in southern Canada). Also note that there were no GOES-15 images during that 30-minue period between 2030 and 2100 UTC, due to the satellite having to perform various “housekeeping” activities — so if a NWS forecast office AWIPS were localized to use GOES-15, initial fire detection would not have been posible until reception of the 2100 UTC image (which actually scanned the fire at 2104 UTC).

A faster animation covering a longer 2.5-hour period from 2030-2300 UTC is shown below. Again, a true sense of the fast northeastward speed of fire propagation could only be gained using 1-minute imagery.

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm Shortwave Infrared images covering the 2.5-hour period 2030-2300 UTC [click to play animation]

GOES-15 (left), GOES-14 (center), and GOES-13 (right) 3.9 µm Shortwave Infrared images covering the 2.5 hour period 2030-2300 UTC [click to play animation]

GOES-14 Shortwave Infrared (3.9 µm) images [click to play animation]

GOES-14 Shortwave Infrared (3.9 µm) 9mages [click to play animation]

The animation above shows another view of 1-minute GOES-14 Shortwave Infrared (3.9 µm) imagery, centered over northeastern Oklahoma — in these images, the hottest fire pixels are darkest black. Time series of infrared brightness temperature values at two individual fire pixels (shown here) are plotted below. The Blue lines show the 1-minute data; Red dots show how 5-minute monitoring would have adequately captured the events. Pixel Brightness Temperature changes that occur on the order of 1 or 2 minutes are common, and peak values can be missed with 5-minute granularity.

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at, 2138-2301 UTC on 18 February 2016 at 35:31:17 N, 96:05:55 W [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures from 2138-2301 UTC on 18 February 2016, at 35:31:17º N, 96:05:55º W [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures at, 2138-2301 UTC on 18 February 2016 at 35:23:51 N, 95:20:52 W [click to enlarge]

GOES-14 Shortwave Infrared (3.9 µm) Brightness Temperatures from 2138-2301 UTC on 18 February 2016, at 35:23:51º N, 95:20:52º W [click to enlarge]

In the GOES-R era, Fire Products will be produced every 5 minutes. Individual NWS Forecast Offices will be able to request Rapid-Scan Imagery (1-minute intervals) over a 1000 km x 1000 km mesoscale sector.

===== 19 February Update =====

Seen below are RealEarth comparisons of Aqua MODIS and Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the early afternoon of 18 February (before the Buffalo OK fire) and 19 February (after the Buffalo OK fire), which revealed the long southwest-to-northeast oriented burn scar. As seen on the GOES-14 animation above, the fire crossed US Highway 183 just to the north of Buffalo (that portion of the highway was closed for several hours).

Aqua MODIS true-color images on 18 February and 19 February [click to enlarge]

Aqua MODIS true-color images on 18 February and 19 February [click to enlarge]

Suomi NPP VIIRS true-color images on 18 February and 19 February [click to enlarge]

Suomi NPP VIIRS true-color images on 18 February and 19 February [click to enlarge]

In addition, a comparison of Suomi NPP VIIRS true-color and false-color images (below) helps to discriminate between the darker burn scar and the cloud shadows seen on the true-color image — the Buffalo fire burn scar appears as varying shades of brown in both the true-color and the false-color images.

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

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

===== 27 February Update =====

Landsat-8 false-color RGB images on 18 February (a few hours prior to the start of the fire) and 27 February (several says after the fire) [click to enlarge]

Landsat-8 false-color RGB images on 18 February (a few hours prior to the start of the fire) and 27 February (several says after the fire) [click to enlarge]

A comparison of 30-meter resolution Landsat-8 false-color (created using OLI bands 6/5/4) RGB images from 18 February (about 3.5 hours prior to the start of the Buffalo OK fire) and 27 February (several days after the fire) provided a very detailed view of the burn scar. Note that a few green fields remained within the burn scar, and also appeared to prevent the spread of the fire along portions of its perimeter — this is a result of the vast difference between the very low moisture content of the dry grassland (which burned quickly and easily) and the high moisture content of the well-irrigated fields of winter wheat, alfalfa, and canola crops.