Gravity Waves Associated with Calbuco Volcanic Eruption

April 23rd, 2015
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Suomi NPP VIIRS 11.45 µm imagery, 0509 UTC 23 April 2015 (Click to enlarge)

Suomi NPP overflew the erupting Calbuco Volcano in southern Chile around 0509 UTC or 2:09 am local time on 23 April 2015. The image above is the VIIRS 11.45 µm infrared imagery (click here for a similar view).

The shock of the volcanic eruption generated mesospheric gravity waves (or “mesospheric airglow waves”) that were evident in the Day/Night Band, shown in the toggle below between the 11.45 µm and the night-time visible imagery. No lunar illumination was present, so the waves were apparent via the Earth’s airglow as the primary light source; this “night glow” is emitted from a variety of high-altitude (80-105 km) gases located near the mesopause (reference).

IO5_DNB_04315_0509_Calbuco_VolGW

Toggle between VIIRS 11.45 µm infrared image and 0.70 µm Day/Night Band image, 0509 UTC 23 April 2015 (Click to enlarge)

(VIIRS images courtesy of William Straka, SSEC)

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 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 around 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)

Himawari-8 visible images

April 19th, 2015
Himiwari-8 AHI 0.63 µm visible channel images (click to play animation)

Himiwari-8 AHI 0.63 µm visible channel images (click to play animation)

0.5-km resolution Himawari-8 AHI 0.63 µm visible channel images from the SSEC RealEarth web map server (above; click image to play animation) revealed a number of interesting features from the Sea of Okhotsk to the Bering Sea during the 18 April – 19 April 2015 period, which included (1) a series of lee waves immediately west of the Kuril Islands (the chain of islands south of the Kamchatka Peninsula), (2) the cyclonic circulation that formed over the western Bering Sea off the Russian coast, along the far northern edge of a remnant frontal boundary, and (3) cloud streets in the central Bering Sea, streaming southward and southwestward from the sea ice across the open waters.

A comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images with an overlay of the19 April / 00 UTC surface analysis (below) showed the location of the remnant frontal boundary, which was an axis of convergence between strong northerly winds over the central Bering Sea (causing the cloud streets and heavy freezing spray which would be a concern for shipping activities in that area) and a ridge of high pressure southeast of the Kamchatka Peninsula.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel  images.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images.

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)