GOES-14 « CIMSS Satellite Blog

Drifting ice fields on Lake Erie

January 14th, 2010

GOES-12 and GOES-14 visible images

McIDAS images of GOES-12 and GOES-14 visible channel data (above) showed that large chunks of ice (known as “ice fields”) were drifting north-northeastward across the western portion of Lake Erie on 14 January 2010. Southerly to southwesterly winds were beginning to increase on that day, helping to move the ice features across the surface of the lake.

AWIPS images of MODIS false-color Red/Green/Blue (RGB) composites (below) confirmed that these were indeed ice features — snow and ice appear darker red on this false color imagery, in contrast to supercooled water droplet clouds which appear as brighter shades of cyan to white. Surface METAR reports plotted on the imagery indicated that wind speeds were generally in the 10-20 knot range. This example offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS II software.

MODIS false color RGB images

A closer look using 250-meter resolution MODIS true color images from the SSEC MODIS Today site (below) revealed how far the ice fields drifted between the 16:58 UTC overpass of the Terra satellite and the 18:42 UTC overpass of the Aqua satellite.

MODIS true color images

Posted in GOES-12, GOES-14, MODIS, Red/Green/Blue (RGB) images | Comments Off

Galeras volcano erupts in Colombia

January 3rd, 2010

GOES-11, GOES-14, and GOES-12 10.7 µm IR and 6.7/6.5 µm water vapor images

The Galeras volcano in Colombia (located in the Andes Mountains near Colombia’s border with Ecuador) experienced an explosive eruption around 00:43 UTC on 03 January 2010 (Washington VAAC advisory messages). McIDAS images of the GOES-11, GOES-14, and GOES-12 10.7 µm IR (top 3 panels) and 6.7/6.5 µm water vapor channel data (bottom 3 panels) showed the volcanic cloud as it spread outward and drifted to the west for several hours following the eruption.

GOES-11 (GOES-West, positioned at 135º West longitude) only imaged the region once every 3 hours during a full disk scan (in this example, at 00:00, 03:00, and 06:00 UTC). GOES-14 (positioned at 105º West longitude) was emulating GOES-West operations during the final days of its NOAA Science Test, and except for the 3-hourly full disk scans, its imaging area was terminated just to the east of the volcano. GOES-12 (GOES-East, positioned at 75º West longitude) had the best, most consistent view of the South American region.

Note how the signature of the volcanic cloud becomes more difficult to follow on the IR imagery, but is still faintly recognizable for an additional 1-2 hours on the water vapor imagery. The different appearance of the GOES-11 water vapor imagery is due to the fact that the 6.7 µm water vapor channel on GOES-11 is a much “narrower” channel (spectrally) compared to the 6.5 µm water vapor channel on GOES-12 and GOES-14; in addition, the large viewing angle from GOES-11 has shifted the water vapor weighting function to higher (colder) altitudes, making the features appear darker blue to white with this particular water vapor color enhancement.

GOES-11 IR difference product (10.7 µm - 12.0 µm)

A simple method for identifying and tracking volcanic ash clouds is the use of a “reverse absorption” or “split window” IR difference product, subtracting the brightness temperature values of the 12.0 µm IR channel from the 10.7 µm IR channel. The GOES-11 IR difference product at 03:00 and 06:00 UTC (above) showed that the volcanic ash cloud had drifted westward over Ipiales (station identifier SKIP) and Pasto (station identifier SKPS) in Colombia, and was moving just to the north of Quito, Ecuador (station identifier SEQU). Note that on the more recent GOES satellites — GOES-12 and beyond — the 12.0 µm IR channel on the Imager instrument has been replaced with a 13.3 µm IR channel, preventing the application of this type of IR difference volcanic ash identification on the more recently-launched GOES satellites.

A corresponding IR difference product using the MODIS 11.0 µm and 12.0 µm channels at 03:25 and 06:25 UTC is shown below. With finer spatial resolution than GOES (1 km, vs 4 km), the edges of the ash cloud feature appear with greater clarity on the MODIS images.

MODIS IR difference product (11.0 µm - 12.0 µm)

Posted in GOES-11, GOES-12, GOES-14, MODIS, Volcanic activity | Comments Off

Hawaiian “vog” plume

January 1st, 2010

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

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.