Vog plume streaming off the island of Hawaii

January 10th, 2013 |
Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm IR channel images

Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm IR channel images

A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel, 3.74 µm shortwave IR channel, and 11.45 µm IR channel data (above) showed a broad “vog” plume streaming westward off the Big Island of Hawaii on 10 January 2013. The primary source of this vog plume was likely the active Kilauea volcano — and the 3.64 µm shortwave IR image revealed a small “hot spot” at the summit of the volcano, which exhibited a brightness temperature value of 49.5º C (orange color enhancement).

The VIIRS 0.64 µm visible channel image with an overlay of 1-hour interval MADIS atmospheric motion vectors (or “satellite cloud-tracked winds”) showed the typical easterly trade wind flow regime that usually transports the vog plume westward away from the Hawaiian Islands (below). However, synoptic-scale disturbances that disrupt this trade wind flow can cause the vog plume to move over inhabitied portions of the islands, causing air quality problems.

Suomi NPP VIIRS 0.64 µm visible channel image + MADIS 1-hour interval atmospheric motion vectors

Suomi NPP VIIRS 0.64 µm visible channel image + MADIS 1-hour interval atmospheric motion vectors

Other examples of Hawaiian vog plumes can be found here on the CIMSS Satellite Blog.

Hawaiian “vog” plume

January 1st, 2010 |
GOES-11 and GOES-14 visible channel images

GOES-11 and GOES-14 visible channel images

McIDAS images of GOES-11 and GOES-14 visible channel data (above) revealed a large hazy plume streaming northeastward from the Hawaiian Islands on 31 December 2009 – 01 January 2010. The primary source of this plume was ongoing emissions from the Kilauea volcano on “The Big Island” of Hawaii — the resulting “vog” (volcanic smog) is air pollution that forms when sulfur dioxide and other gases/particles emitted by an erupting volcano react with oxygen and moisture in the presence of sunlight. On 31 December the haze was reducing visibility to 5 miles at Lahaina on Maui island.

This GOES-11 vs GOES-14 visible image comparison helps to highlight two important points: (1) due to a more favorable “forward scattering” geometry with GOES-14 positioned at 105º West longitude, the extent of the “vog” plume shows up with greater clarity on GOES-14 images later in the day compared to GOES-11 (positioned at 135º West longitude), and (2) the performance of the GOES visible channel detectors degrades over time, so the much older GOES-11 (launched in 2000) visible imagery appears significantly darker (the enhancement of the images is the same). GOES-14 (launched in 2009) was emulating GOES-West during the final days of its NOAA Science Test.

Under typical conditions, the dominant northeasterly trade winds act to advect the plume of “vog” toward the southwest — but in this case, an AWIPS image of the GOES-11 IR channel with an overlay of ASCAT scatterometer winds (below) showed that there was a southwesterly flow in advance of an approaching cold front.

GOES-11 IR image + ASCAT scatterometer winds

GOES-11 IR image + ASCAT scatterometer winds

An image of the Aura satellite Ozone Measuring Instrument (OMI) Total Column Sulphur Dioxide (SO2) product (below; courtesy of NOAA/NESDIS) confirms that elevated levels of SO2 were present within the “vog” plume seen on GOES visible imagery.

OMI SO2 product (courtesy of NOAA/NESDIS)

OMI SO2 product (courtesy of NOAA/NESDIS)

White Christmas in Hawai’i

December 25th, 2014 |
GOES-15 0.63 µm visible channel images (click to play animation)

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

According to the National Operational Hydrologic Remote Sensing Center, only 35.5% of the Lower 48 states had snow cover on 25 December 2014. However, a deep cutoff low over the Hawaiian Islands had brought unusually cold air aloft (the 500 hPa temperature on the Lihue rawinsonde report was as cold as -18º C, which is extremely cold by Hawaiian standards) and strong winds, which prompted Blizzard Warnings to be issued for the high elevation summits of the Big Island of Hawai’i on 23-24 December. As the cutoff low departed and skies began to clear, GOES-15 (GOES-West) 0.63 µm visible channel images (above; click image to play animation) revealed the bright white snow-covered summits of Mauna Kea and Mauna Loa on Christmas Day.

A toggle between a Suomi NPP VIIRS 0.64 µm visible channel and a false-color Red/Green/Blue (RGB) “snow vs cloud discrimination” image at 23:22 UTC (below) confirmed that the bright white features seen in the GOES-15 visible images was indeed snow cover — snow (and fully-glaciated ice clouds) appear as darker shades of red on the RGB image. Cloud tops that are partially glaciated appear as lighter shades of pink.

Suomi NPP VIIRS 0.64 µm visible channel and false-color

Suomi NPP VIIRS 0.64 µm visible channel and false-color “snow vs cloud discrimination” RGB images

===== 26 December Update =====

Using the SSEC RealEarth web map server, the comparison below shows 375-meter resolution Suomi NPP VIIRS true-color RGB images of the Big Island of Hawai’i on 20 December (before the snowfall on the Mauna Kea and Mauna Loa summits) and also on 25-26 December (after the snowfall). On the 26 December image, you can see that the patches of snow had melted somewhat at the 2 summits; in addition, an increase in hazy volcanic fog (vog) can be seen drifting southeastward off the island; this vog was being generated by the ongoing eruption of the Kilauwea volcano in the Hawai’i Volcanoes National Park.

Suomi NPP VIIRS true-color RGB images

Suomi NPP VIIRS true-color RGB images

Strong cold front moves through the Hawaiian Islands

January 23rd, 2014 |
GOES-15 6.5 µm water vapor channel images (click to play animation)

GOES-15 6.5 µm water vapor channel images (click to play animation)

McIDAS images of 4-km resolution GOES-15 6.5 µm water vapor channel data (above; click images to play animation) showed the dramatic signature of rapid intensification of a very large mid-latitude cyclone over the eastern Pacific Ocean during the 20 January – 23 January 2014 time period.

A comparison of AWIPS images of 1-km resolution Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel data (below) revealed the tightly-wrapped center of circulation at 13:01 UTC on 20 January. Intricate mesoscale banding structures could also be seen within portions of the warm conveyor belt southeast and east of the storm center (which was analyzed to have a central pressure of 956 hPa).

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

A Suomi NPP VIIRS 0.64 µm visible channel image (below) showed a small but well-defined comma-shaped cloud feature marking the center of the storm at 00:13 UTC on 21 January (which was analyzed to have a central pressure of 952 hPa).

Suomi NPP VIIRS 0.64 µm visible channel image

Suomi NPP VIIRS 0.64 µm visible channel image

A Suomi NPP VIIRS 0.64 µm visible channel image at 23:54 UTC on 21 January (below) depicted the band of clouds associated with the 950 hPa cyclone’s cold front as it approached the northwestern portion of the Hawaiian Island chain. A narrow “rope cloud” marked the leading edge of the cold frontal boundary.

Suomi NPP VIIRS 0.64 µm visible channel image

Suomi NPP VIIRS 0.64 µm visible channel image

In a closer view centered over the Hawaiian Islands at 23:54 UTC on 21 January (below), a hazy “vog” plume (from the active Kilauea volcano on the Big Island) could be seen blowing northeastward ahead of the approaching cold front. Note how the areal coverage of the vog plume shows up better in the broadband 0.7 µm Day/Night Band image compared to the 0.64 µm visible channel image with its more narrow spectral width.

Suomi NPP VIIRS 0.64 µm visible channel and 0.7 µm Day/Night Band images

Suomi NPP VIIRS 0.64 µm visible channel and 0.7 µm Day/Night Band images

Finally, a Suomi NPP VIIRS 0.64 µm visible channel image at 23:35 UTC on 22 January (below) showed the cold frontal band as the leading edge was about to move southeast of the Big Island of Hawaii. Note that Honolulu (PHNL) had a temperature/dewpoint of 78ºF/45ºF, with northwesterly winds gusting to 34 knots at 00 UTC. Wind speeds on the summits of the Big Island of Hawaii were sustained hurricane force, with gusts to near 100 mph. The strong winds also caused a giant northwesterly ocean swell, with significant wave heights as high as 31 feet at Buoy 51101 (located 91 miles northwest of Kauai). There was also a notable air temperature drop at Buoy 51101 as the cold front passed, with a peak wind gust of 39 knots.

Suomi NPP VIIRS 0.64 µm visible channel image

Suomi NPP VIIRS 0.64 µm visible channel image

GOES-15 0.63 µm visible channel images (below; click image to play animation) showed the cold front as it was passing through the Hawaiian Island chain on 22 January. A few areas of orographic wave clouds could be seen as the strong northwesterly winds in the wake of the cold front interacted with the topography of the islands.

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

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