GOES-13 visible images

With an elongated ridge of high pressure in place along the British Columbia coast on 18 February 2010, nearly cloud-free conditions allowed for some nice satellite views of the Vancouver, British Columbia area (the site of the 2010 Winter Olympics). McIDAS images of GOES-13 visible channel data (above) showed the widespread snow-covered mountains that occupied much of the region, as well as the evolution of some of the cloud features during the day. Early in the animation, some small patches of fog and stratus clouds could be seen burning off as they slowly drifted southward over the waters of the Strait of Georgia. The locations of Vancouver (station identifier CYVR) and Whistler (station identifier CWAE) are indicated on the visible imagery

This animation also serves to highlight the improved Image Navigation and Registration (INR) of the GOES-13 satellite — there is much less image-to-image “wobble” compared to the previous generation of GOES satellites. NOTE: GOES-13 is scheduled to replace GOES-12 as the operational GOES-East satellite on 14 April 2010.

On the NOAA-19 false color Red/Green/Blue (RGB) image (below) using channels 01 (0.62 µm), 02 (0.86 µm), and 03 (3.7 µm), bare ground appears as shades of green to brown, snow cover is brighter white, and stratus clouds over the mountains farther to the east appear as shades of yellow.

NOAA-19 false color Red/Green/Blue (RGB) image

A comparison of 250-meter resolution MODIS true color and false color images from the SSEC MODIS Today site (below) shows even greater detail of the snow-covered terrain features of the region, as well as the few patches of fog/stratus cloud that remained over the northern portion of the Strait of Georgia at 19:07 UTC (where the AVHRR Sea Surface Temperature product showed that SST values were generally in the 40s F).

MODIS true color and false color images

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GOES-13 visible images

The National Weather Service forecast office at Kansas City / Pleasant Hill, Missouri posted a nice overview of the Valentine’s Day snow event that caused a number of multiple-vehicle accidents in the Kansas City area. McIDAS images of the 1-km resolution GOES-13 visible channel data (above) revealed the tight circulation of the system as it spiraled across the area, as well as the development of mesoscale convective elements that produced moderate to heavy snowfall rates on 14 February 2010.

An animation of the 4-km resolution GOES-13 6.5 µm water vapor channel images (below) showed the mid-tropospheric circulation associated with the disturbance as it propagated southeastward across the region.

GOES-13 6.5 µm water vapor images

An AWIPS image of the 1-km resolution MODIS 6.7 µm water vapor channel data (below) showed a better picture of the mid-tropospheric circulation at 19:32 UTC or 1:32 pm local time.

MODIS 6.7 µm water vapor image + METAR surface reports

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POES AVHRR visible channel and 10.8 µm IR images

AWIPS images of the 1-km resolution POES AVHRR visible channel and 10.8 µm IR channel data (above) and the 1-km resolution MODIS visible channel and 11.0 µm IR channel data (below) offered closer views of the convective elements that were producing mesoscale areas of moderate to heavy snowfall rates. Many of the cloud top IR brightness temperatures were in the -20º to -30º C range (cyan to dark blue color enhancement).

MODIS visible and 11.0 µm IR images

A comparison of 250-meter resolution MODIS Red/Green/Blue (RGB) true color images from the SSEC MODIS Today site (below, displayed using Google Earth) offered a very detailed view of the cloud structures at the time of the Terra satellite overpass (17:55 UTC or 11:55 am local time) and the Aqua satellite overpass (19:32 UTC or 1:32 pm local time).

Terra MODIS and Aqua MODIS true color images (displayed using Google Earth)

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GOES-12 visible images + METAR surface reports

A major eruption followed a partial dome collapse in the crater of the Soufriere Hills volcano on the West Indies island of Montserrat during the daytime hours on 11 February 2010. McIDAS images of the GOES-12 visible channel data (above) showed the rapid east-southeastward expansion of the volcanic cloud following the eruption around 17:00 UTC. Pilot reports placed the maximum height of the volcanic cloud around 50,000 feet above ground level (see the NOAA/NESDIS/SSD/OSDPD archive of Volcanic Ash Advisories and satellite images).

GOES-12 3.9 µm shortwave IR images (below) showed a thermal anomaly or “hot spot” during the hours leading up to the major eruption, with a maximum IR pixel value of 322 K or 49º C (yellow color enhancement) at 16:45 UTC. Also note the darker appearance of the western and southern portions of the volcanic cloud: these were areas of the cloud that were composed primarily of supercooled water droplet clouds, which strongly reflect solar radiation (which then leads to much warmer shortwave IR brightness temperature values).

GOES-12 3.9 µm shortwave IR images

GOES-12 10.7 µm longwave IR images (below) revealed an initial pulse of very cloud cloud top IR brightness temperatures within a couple of hours following the eruption — as cold as -75º C at 19:15 UTC — before the volcanic cloud appeared to thin out and exhibit warmer IR brightness temperatures as it spread eastward.

GOES-12 10.7 µm longwave IR images

AWIPS images of high-altitude GOES-12 derived atmospheric motion vectors in the vicinity of the volcanic plume (below) were generally in the 40-55 knot range — the 12 UTC rawinsonde data from station TFFR (Le Raiset, Guadaloupe) had maximum west-northwesterly winds of 68 knots at 280 hPa (around the 41,000 foot level).

GOES-12 IR images + GOES-12 atmospheric motion vectors

A comparison of 4-km resolution GOES-12 3.9 µm and 1-km resolution NOAA-15 AVHRR 3.7 µm shortwave IR images (below) showed the advantage of higher spatial resolution for detecting the magnitude of the volcano’s hot spot — the hottest pixel seen on the NOAA-15 image was 330 K or +57º C (red color enhancement), compared to only 293.5 K or +20º C (black color enhancement) on the GOES-12 image.

GOES-12 (top) and NOAA-15 (bottom) shortwave IR images

Similarly, the coldest longwave IR brightness temperature value seen on the 1-km resolution NOAA-15 AVHRR image was -72º C, compared to only -55º C on the 4-km resolution GOES-12 image (below).

GOES-12 (top) and NOAA-15 (bottom) longwave IR images

A natural color Red/Green/Blue (RGB) composite image using Aqua MODIS channels 01/04/03 (below) showed the volcanic cloud at 17:20 UTC, about 20 minutes after the explosive eruption. The tall volcanic cloud was casting a long shadow toward the north-northeast at that time. In addition, the hazy signal of previous volcanic emissions from earlier in the day could be seen covering a much larger portion of the region.

Aqua MODIS natural color Red/Green/Blue (RGB) image

A few hours later, a false-color Red/Green/Blue (RGB) composite image using NOAA-15 AVHRR channels 01/02/04 (below) shows a view of the volcanic cloud at 21:02 UTC. Again, the tall cloud feature was still seen to be casting a long shadow toward the north-northeast at that time. The thermal anomaly from the volcano hot spot appeared as the small yellow area on the RGB image.

NOAA-15 AVHRR false-color Red/Green/Blue (RGB) image at 21:02 UTC

A sequence of three sets of of images from the GOES-12 sounder (below) shows the sounder longwave IR window image (top panels) along with a sounder IR difference product (7.4 µm – 13.3 µm, bottom panels) before, during, and after the eruption. The darker gray to black image features intermingled with the brighter white water vapor and volcanic ash clouds are signals of a high concentration of SO2. The GOES Sounder is able to detect SO2 from a volcanic eruption, as long as it is not masked by both the water vapor and volcanic ash during and immediately following the eruption. This particular case was a situation where the extensive water vapor and volcanic ash clouds did in fact mask the SO2 signal resulting from the eruption of Soufriere Hills volcano. (GOES-12 sounder images provided by Tony Schreiner, CIMSS)

GOES-12 sounder IR images (top) and IR difference images (bottom)

===== 12 FEBRUARY UPDATE =====

The series of 4-panel displays below (provided by Mike Pavolonis, NOAA/NESDIS/ASPB) show AVHRR RGB images along with volcanic ash derived products (ash loading, ash height, and ash effective radius). Of particular interest was the fact that the maximum ash height decreased rather quickly, from 15.73 km (at 21:02 UTC on 11 February) to 5.58 km (at 06:24 UTC on 12 February) to 4.93 km (at 09:19 UTC on 12 February).

AVHRR RGB image and ash retrieval products

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AVHRR RGB image and volcanic ash retrieval products

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AVHRR RGB image and volcanic ash retrieval products

GOES-12 6.5 µm water vapor imagery with an overlay of Canadian Meteorological Center 400 hPa winds (below) revealed that an anticyclone was building aloft over the region following the eruption of the Soufriere Hills volcano — this would provide an environment of increasing mid-tropospheric subsidence that could explain the rapid decrease in retrieved volcanic ash heights. Subsequently, the water vapor image brightness temperature values were also increasing in the area of the building ridge, as seen by the warming trend of brightness temperatures averaging around -20º C (yellow color enhancement) to values averaging around -15º C (orange color enhancement).

GOES-12 water vapor images + CMC 400 hPa winds

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GOES waver vapor imagery + PV1.5 pressure + 500 hPa geopotential height

A strong potential vorticity (PV) anomaly was propagating southeastward just off the California coast on 09 February 2010 — and this feature had a striking presentation on AWIPS images of GOES-11 water vapor channel data (above), with a pronounced arc of very dry air (yellow color enhancement) seen around the periphery of the circulation. According to the CRAS model fields, the tropopause (taken to be the pressure of the PV1.5 surface) was being brought downward as low as the 600 hPa pressure level within the core of the PV anomaly.

Images of the GOES-11 sounder Total Column Ozone derived product (below) depicted ozone values as high as 430 Dobson Units (red color enhancement) in the vicinity of the PV anomaly, supporting the idea that the tropopause height was very depressed within the circulation feature.

GOES sounder Total Column Ozone + PV1.5 pressure + 500 hPa geoptential height

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GOES-11 Sounder and Imager water vapor channel images

A 4-panel comparison of the three water vapor channels on the GOES-11 Sounder (6.5 µm, 7.0 µm, and 7.4 µm) and the GOES-11 Imager 6.7 µm water vapor channel (above) showed that the dry air signature was even quite evident on the Sounder 6.5 µm channel (darker blue color enhancement, upper left panels) — this particular water vapor channel weighting function normally peaks quite high in the atmosphere (around 325 hPa), where these types of water vapor gradients and signatures are usually not as well-defined.

However, due to the dry air within the middle to upper troposphere associated with the PV anomaly, the weighting functions of all 4 of the GOES-11 water vapor channels (calculated using rawinsonde data from Vandenberg Air Force Base) peaked at altitudes that were quite a bit lower compared to the more “normal” conditions that would be seen in a US Standard Atmosphere or USSA environment (below). Convection moving onshore across southern California that day was responsible for at least one sighting of a waterspout in the San Diego area, and inland precipitation amounts of 1.0 to 1.5 inch were widespread.

GOES-11 sounder and imager water vapor weighting functions (Vandenberg vs USSA)

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