Eruption of the Pavlof Volcano in Alaska

November 15th, 2014
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

According to the Alaska Volcano Observatory, an eruption of the Pavlof Volcano began around 01:50 UTC on 13 November 2014. A comparison of nighttime images of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 3.74 µm shortwave IR data at 13:07 UTC or 4:07 am local time on 14 November (above) showed the bright glow of the eruption on the DNB image, with the hottest pixel being 52º C (red color enhancement) on the shortwave IR image.

With the subsequent arrival of daylight, a break in the clouds allowed the faint volcanic plume to be observed on GOES-15 0.63 µm visible channel images (below; click image to play animation), drifting northwestward over the Bering Sea.

GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

At 22:02 UTC on 14 November, the radiometrically-retrieved maximum volcanic ash mass loading value was 1.8 tons per km2, the maximum ash height was 16.8 km, and the maximum ash mass effective radius was 7.81 µm (below).

MODIS volcanic ash mass loading, ash height, and ash mass effective radius products

MODIS volcanic ash mass loading, ash height, and ash mass effective radius products

About an hour later, the volcanic ash plume could be seen on a 23:03 UTC Suomi NPP VIIRS Day/Night Band image, with a maximum 3.74 µm shortwave IR brightness temperature of 46º C at the summit of the volcano (below).

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

The brown hue of the volcanic ash plume was very evident on Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from the SSEC RealEarth web map server (below).

Suomi NPP VIIRS true-color RGB images

Suomi NPP VIIRS true-color RGB images

The intensity of the Pavlof eruption increased on 15 November, and a well-defined volcanic ash plume could be seen on GOES-15 0.63 µm visible channel images (below; click image to play animation). Pilot reports estimated that the top of the plume was as high as 38,000 feet.

GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

On a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 22:45 UTC (below), the coldest cloud-top IR brightness temperature value was -55º C.

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

At 22:29 UTC, the CLAVR-x POES AVHRR Cloud Top Temperature product indicated a minimum value of -54º C, with a maximum Cloud Top Height value of 9 km; the -54º C cloud top temperature corresponded to an altitude of around 29,000 feet or 8.7 km on the 16 November/00 UTC Cold Bay AK rawinsonde profile.

POES AVHRR Cloud Top Temperature and Cloud Top Height products

POES AVHRR Cloud Top Temperature and Cloud Top Height products

A Suomi NPP VIIRS true-color RGB image at 23:04 UTC (below) suggested that the volcanic plume consisted of a dense layer of tan-colored ash, with a layer of mostly ice cloud at the top of the plume.

Suomi NPP VIIRS true-color RGB image

Suomi NPP VIIRS true-color RGB image

Dusty Cold Front moves south through the Southern Plains

November 11th, 2014
GOES-13 0.63 µm Visible imagery (click to play animation)

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

A strong cold front moved southward over the High Plains of the US on Monday 10 November, and the strong winds produced a dust cloud that was apparent in GOES-13 visible imagery, above. The leading edge of the dust cloud in the satellite imagery indicated precisely the leading edge of the cold front. The animation below shows hourly observations plotted on top of the GOES-13 visible imagery. The correspondence between the leading edge of the dust and the wind shift is obvious. Note that multiple stations report Haze (H) after the wind shift occurs.

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

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

GOES-15 viewed this event as well (Visible animation; Visible animation with observations). The dust in the atmosphere was far more apparent in the GOES-13 imagery, however. This case is an excellent demonstration of how dust effectively forward scatters visible light from the setting sun towards GOES-13 at 75º W, but does not so effectively back scatter towards GOES-15 at 135º W. The toggle below shows visible imagery from GOES-13 and GOES-15, both at 2200 UTC.

GOES-13 0.63 µm Visible imagery and GOES-15 0.62 µm Visible Imagery, both at 2200 UTC 10 November (click to enlarge)

GOES-13 0.63 µm Visible imagery and GOES-15 0.62 µm Visible Imagery, both at 2200 UTC 10 November (click to enlarge)

Both Aqua (MODIS) and Suomi NPP (VIIRS) viewed this haboob in mid-afternoon on 10 November. What can the multispectral views of this feature tell us? Both the Visible and Snow/Ice channels give similar views of the leading edge of the cold front (the biggest difference between the visible and snow/ice channel in this image is that water features are so much darker in the snow/ice channel because water strongly absorbs 2.1 µm radiation; differences in the clouds between the visible and the snow/ice (2.1 µm) channel arise from viewing water-based vs. ice-based clouds). The cirrus channel — 1.37 µm — does not see the surface but it does clearly reveal high clouds. The 3.9-µm image — shortwave infrared — shows very warm temperatures right at the leading edge of the cold front in eastern Colorado. This is a region where the dust is effectively reflecting solar radiation. The longwave infrared imagery (10.7 µm) shows a more uniform cold edge to the cloud. Finally, even the water vapor imagery shows a signal from this cold front (known as a lee-side frontal gravity wave). It is unusual for surface features to have a signal in water vapor imagery; when it does occur, the atmosphere is usually very dry, and that’s the case in this event. Note in the toggle here between GOES water vapor channel weighting functions (computed here) at Amarillo between 0000 UTC — before the cold front — and 1200 UTC — after the cold front — shows how the layer from which 6.5 µm radiation will be detected has dropped in altitude.

Aqua MODIS Visible, Snow/Ice, Cirrus, Shortwave IR, Water Vapor and Longwave IR Imagery at 1917 UTC, 10 November (click to enlarge)

Aqua MODIS Visible, Snow/Ice, Cirrus, Shortwave IR, Water Vapor and Longwave IR Imagery at 1917 UTC, 10 November (click to enlarge)

Suomi NPP viewed the cold front 10 minutes before Aqua, below, and also about 90 minutes later (Favorable orbital geometry allowed sequential orbits to view eastern Colorado). The shortwave IR (3.74 µm) show warmer signatures in some of the dust plumes compared to the longwave IR (11.35 µm), similar to Aqua, a difference that is likely due to solar radiation being reflected by the dust.

Suomi NPP VIIRS data showing Visible, Day Night Band, Snow/Ice, Shortwave IR, and Longwave IR Imagery at 1907 UTC, 10 November (click to enlarge)

Suomi NPP VIIRS data showing Visible, Day Night Band, Snow/Ice, Shortwave IR, and Longwave IR Imagery at 1907 UTC, 10 November (click to enlarge)

Suomi NPP VIIRS data showing Visible, Day Night Band, Snow/Ice, Shortwave IR, and Longwave IR Imagery at 2049 UTC, 10 November (click to enlarge)

Suomi NPP VIIRS data showing Visible, Day Night Band, Snow/Ice, Shortwave IR, and Longwave IR Imagery at 2049 UTC, 10 November (click to enlarge)

Animations of 10.7 µm Brightness Temperature Data from GOES-13 showed the southward plunge of cold air overnight. The progress of this cold front could be monitored from space. Even the water vapor imagery continued to include a signature of the cold front.

GOES-13 Water Vapor (6.7 µm) Infrared Imagery (click to play animation)

GOES-13 Water Vapor (6.7 µm) Infrared Imagery (click to play animation)

The visible imagery at the top of this post ably captured the signature associated with blowing dust. Did the blowing dust continue through the night? Single-channel detection of dust at night is difficult. Historically, dust could be detected with brightness temperature differences between 10.7 µm and 12 µm channels on the GOES Imager, but that capability ended when the 13.3 µm channel replaced the 12 µm channel on the GOES Imager (the GOES-R ABI will contain a 12 µm channel). The VIIRS Day Night Band, below, from Suomi NPP at 0905 UTC on 11 November, does not show a distinct dust signature over south Texas. The leading edge of the front is obvious, however, as it is preceded by a Bore structure with parallel lines of clouds.

Suomi NPP VIIRS Day Night Band (.7 µm) Visible Imagery at 0905 UTC 11 November 2014 (click to enlarge)

Suomi NPP VIIRS Day Night Band (.7 µm) Visible Imagery at 0905 UTC 11 November 2014 (click to enlarge)

Nuri transforms into a strong extratropical storm

November 9th, 2014
MTSAT-2 6.75 µm IR water vapor channel images (click to play animation)

MTSAT-2 6.75 µm IR water vapor channel images (click to play animation)

Super Typhoon Nuri has completed its transition to one of the strongest extratropical cyclones ever on record in the Bering Sea (Link; Shemya Island had a gust to 96 miles per hour!). The animation above (click here for an mp4, or view it on YouTube) covers the entire lifecycle, from birth out of the ITCZ over the western Pacific to occlusion 7500 km north in the Bering Sea. (A faster animation is available as a animated gif or mp4).

Total Precipitable Water, 0000 6 November 2014 through 0600 9 November 2014 (click to enlarge)

Total Precipitable Water, 0000 6 November 2014 through 0600 9 November 2014 (click to enlarge)

Animations of Total Precipitable Water (from MIMIC) from 6-9 November, above, show that deep tropical moisture associated with Nuri did not make it up into the Bering Sea, but instead was shunted off to the east. Earlier, moisture from Nuri was entrained into the development of a storm in the Bering Sea on 4-5 November. A streamer of high-level moisture in the outflow from Nuri moves northeastward and eastward. That storm subsequently slipped southeastward and made landfall over the Pacific Northwest on 8 November.

Suomi NPP Day Night Band Visible Imagery (0.70 µm) over the Bering Sea, 7-10 November 2014 (click to enlarge)

Suomi NPP Day Night Band Visibe Imagery (0.70 µm) over the Bering Sea, 7-10 November 2014 (click to enlarge)

Suomi NPP overflew the developing storm in the Bering Sea about every twelve hours, and the imagery above, from the GINA Direct Broadcast Antenna at the University of Alaska-Fairbanks, shows the rapid development of a tight swirl of clouds by early on 8 November. Subsequently, the weakening storm drifted northward through the Bering Sea.

GOES-15 also viewed the strong development, both in the window channel (YouTube video) and in the water vapor channel (YouTube video (Color Enhanced)). The visible animation, below, shows a strong cyclone by 0300 UTC on 8 November; at the subsequent sunrise, 2000 UTC, the system had occluded.

GOES-15 0.62 µm IR Visible Imagery on 7, 8 and 9 November 2014 (click to play animation)

GOES-15 0.62 µm IR Visible Imagery on 7, 8 and 9 November 2014 (click to play animation)

GOES-15 Rapid Scan Operations for Hawai’i

November 5th, 2014
GOES-15 6.5 µm water vapor images and atmospheric motion vector (AMV) winds

GOES-15 6.5 µm water vapor images and atmospheric motion vector (AMV) winds

As seen on a sequence of 3-hourly GOES-15 (GOES-West) 6.5 µm water vapor images with satellite-derived atmospheric motion vector (AMV) winds from the CIMSS Tropical Cyclones site (above), a weak but persistent trough aloft over the Hawai’i region was acting to destabilize the atmosphere and create an environment conducive to the development of widespread showers and thunderstorms — some of which were producing heavy downpours over parts of the island chain — during the 04-05 November 2014 period.

Due to radar outages, the NWS forecast office in Honolulu HI requested that the GOES-15 satellite be placed into Rapid Scan Operations (RSO) mode (NOAA/NESDIS bulletin), providing 10 images per hour (compared to only 4 per hour during routine operations). An animation of GOES-15 0.63 µm visible channel images (below; click image to play animation) begins at 17:30 UTC with routine 15-minute interval images, and then after 21:30 UTC transitions into the RSO images to demonstrate how the development and motion of features can be more carefully monitored with improved temporal resolution.

GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

Additional details on GOES-15 RSO sectors which were implemented during October 2014 can be found here.