MTSAT 0.73 µm visible channel images (click image to play animation)

An annular eclipse of the sun took place on May 21, 2012, and its shadow was visible from satellite imagery (A previous example from this blog is here). The loop above shows MTSAT imagery; the shadow of the eclipse emerges shortly after sunrise and tracks northeastward into the Pacific Ocean. The loop below shows GOES-West imagery, tracking the shadow from the north Pacific Ocean to the coast of North America around sunset.

GOES-15 0.62 µm visible channel images (click image to play animation)

A portion of the eclipse shadow could also be seen on an AWIPS image of POES AVHRR 0.86 µm visible channel data (below), extending from the far northern Pacific Ocean across the Aleutian Islands and into the southern Bering Sea.

POES AVHRR 0.86 µm visible channel image

GOES-13 0.63 µm visible and 3.9 µm shortwave IR images (click image to play animation)

A few large wildfires flared up during the afternoon hours on 20 May 2012 across parts of far eastern Ontario and far western Quebec. In a comparison of GOES-13 0.63 µm visible channel and 3.9 µm shortwave IR channel images (above; click image to play animation; also available as a QuickTime movie), large smoke plumes could be seen emanating from the larger fires, as the fire “hot spots” (black pixels on the shortwave IR imagery) grew in size. The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-10 minutes (compared to the routine operational 15-minute image interval).

AVHRR 10.8 µm, MODIS 11.0 µm, and VIIRS 11.45 µm IR images

The 2012 Atlantic Basin tropical cyclone season began with the formation of Tropical Storm Alberto off the coast of South Carolina on 19 May 2012. A sequence of AWIPS images of 1-km resolution POES AVHRR 10.8 µm, Terra/Aqua MODIS 11.0 µm, and Suomi NPP VIIRS 11.45 µm IR images (above) showed the growth of deep convecion associated with Alberto as the system moved southwestward — cloud top IR brightness temperatures were as cold as -72º C on the MODIS image at 16:03 UTC.

A comparison of the 18:27 UTC 1-km resolution Suomi NPP VIIRS 11.45 µm IR image with the 18:15 UTC 4-km resolution GOES-13 10.7 µm IR image (below) demonstrated the improvement in cloud top feature identification with higher spatial resolution, as well as showed the effect of parallax due to the large satellite viewing angle from GOES-13.

GOES-13 10.7 µm IR + Suomi NPP VIIRS 11.45 µm IR image

An animation of GOES-13 0.63 µm visible channel images from the CIMSS Tropical Cyclones site (below) showed the development of a more organized cloud structure during the day. In addition, a 21 UTC ship report near the center of Alberto noted wind gusts to 65 knots, which promted NHC to issue an update to note an increase in intensity.

GOES-13 0.63 µm visible channel images + Ship reports

An AWIPS night-time image of the Suomi NPP VIIRS 0.7 µm “Day/Night Band” (below) revealed some of the cloud structure associated with Tropical Storm Alberto at 06:45 UTC (2:45 am local time). Given that there was a “New Moon” phase at this time, not a great deal of reflected light was avaiable to allow the Day/Night Band imagery to show more cloud detail.

Lights from cities and towns across the far southeastern US could also be seen in the Day/Night Band image (although some of the urban area light signatures were attenuated somewhat by overhead cloud cover).

Suomi NPP VIIRS 0.7 µm Day/Night Band image

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

The GOES-15 satellite was placed into Super Rapid Scan Operations (SRSO) mode on 17 May 2012, in support of the Deep Convective Clouds and Chemistry (DC3) field experiment. SRSO provides bursts of imagery at 1-minute intervals (compared to the standard operational 15-minute interval). McIDAS images of 1-km resolution GOES-15 0.63 µm visible channel data (above; click image to play animation) showed the development of widespread deep convection over Colorado and the adjacent states during the afternoon hours.

The cloud motions revealed the presence of a strong cyclonic circulation aloft over the region, which was verified by satellite-derived atmospheric motion vectors and NAM model 500 hPa heights plotted on an AWIPS image of MODIS 6.7 µm water vapor channel data at 19:35 UTC (below).

MODIS 6.7 µm water vapor image + Satellite atmospheric motion vectors + NAM 500 hPa height

AWIPS images of 1-km resolution Suomi NPP VIIRS 11.45 µm, POES AVHRR 12.0 µm, and MODIS 11.0 µm IR channel data at 19:04, 19:14, and 19:35 UTC (below) revealed that cloud top IR brightness temperatures were as cold as -60 to -62 C (darker red color enhancement) with many of the stronger areas of convection.

VIIRS 11.45 µm, AVHRR 12.0 µm, and MODIS 11.0 µm IR channel images

GOES-15 (left) and GOES-13 (right) 0.63 µm visible channel images (click image to play animation)

McIDAS images of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel data (above; click image to play animation) revealed the large smoke plume associated with the “Sunflower Fire” that was burning near Payson, Arizona on 15 May 2012. Note toward the end of the animation the appearance of pyrocumulous clouds with overshooting tops over the fire source region. Due to the different satellite viewing angles, the overshooting tops were brightly illuminated on the GOES-15 images, while casting a distinct shadow onto the top of the cloud/smoke plume on the GOES-13 images. Photos of the Sunflower fire from the ground can be seen on the Weather Underground site. Other fires were also burning at that time in Arizona, including the “Gladiator Fire“  located to the northwest of the Sunflower fire.

The GOES-13 satellite was placed into Rapid Scan Operations (RSO) mode later in the day, providing images as frequently as every 5-10 minutes (compared to the routine 15-minute image interval with GOES-15).

GOES-13 enhanced Fog Product (10.7 µm - 3.9 µm)

On the morning of May 14th, a clear morning, the GOES-13 Legacy “Fog Product” that exploits the brightness temperature differences observed by the GOES Imager at 3.9 µm and 10.7 µm, which differences arise because of wavelength-dependent emissivity differences in water clouds, showed fog first on the eastern shores of Lakes Huron and Michigan (at 1015 UTC), and then on the western shores of Lakes Huron and Michigan (at 1401 UTC, and afterwards). These returns occurred despite clear skies.

A similar effect occurred on the morning of May 15th. The image at 1015 UTC showed fog along the eastern side of the Lakes, and the image at 1255 UTC showed fog along the western side of the Lakes. (Note that more widespread mid-level clouds reduced the signal on this day). A POES Fog Product image from 1020 UTC on May 15th (link) did not show the fog signal along the shoreline.

GOES-13 10.7 µm and 3.9 µm channel images (click image to toggle between images)

The image toggle above shows highly magnified imagery over Lake Michigan at 1255 UTC on May 15 2012. There is an apparent 1-pixel shift between the 3.9 µm and the 10.7µm imagery. If the start element of the image is shifted by 1 infrared pixel, then the toggle between the two images contains no shift. The legacy ‘Fog Product’ is therefore diagnosing fog because the 3.9 µm pixel is over water (cold) and the 10.7 µm pixel is over land (warm). When the 1-pixel shift is rectified, both pixels are either over water, or both over land.

Scientists at SSEC are working to find the source of this difference.

GOES-13 0.63 µm visible channel images (click image to play animation)

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) revealed widespread areas of blowing dust moving southward across northern Mexico on 14 May 2012. This airborne dust was generated along a southward-moving cold front, which was reinforced by low-level convective outflow boundaries. At Chihuahua, Mexico (station identifier MMCU), the temperature/visibility dropped from 88 F/10 miles to 77 F/0.5 mile within one hour as the leading edge of the blowing dust moved through that location.

A comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) visible channel images (below; click image to play animation) showed the advantage of a more frequent image scanning schedule: the GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode (providing images as often as every 5-10 minutes), in contrast to the routine 15-minute image interval available from GOES-15.

GOES-15 (top) and GOES-13 (bottom) 0.63 µm visible images (click image to play animation)

MODIS Sea Surface Temperature product

An AWIPS image of the 1-km resolution MODIS Sea Surface Temperature (SST) product on 10 May 2012 (above) revealed that much of Lake Superior exhibited SST values in the 40s F (darker blue color enhancement), with the coldest SST value being 39.1 F off the coast of far northeastern Minnesota.

After several hours of daytime heating and generally light winds across the region, 1-km resolution GOES-13 0.63 µm visible channel images (below; click image to play animation) showed that a well-defined lake breeze boundary began to appear on the cumulus cloud field. Note that there was a similar lake breeze boundary seen surrounding Lake Nipigon in southern Ontario, Canada (where SST values were as low as 33.5 F).

GOES-13 0.63 µm visible channel images (click image to play animation)

A comparison of 1-km resolution MODIS visible channel, Land Surface Temperature (LST), and Normalized Difference Vegetation Index (NDVI) is shown below. LST values were generally in the 60s to 70s F surrounding Lake Superior, creating a large thermal contrast to the cold waters of the lake. To the northwest and southwest of Lake Superior, there were a number of areas exhibiting much warmer LST values (in the 80s  to around 90 F, darker red color enhancement) — and these areas of warmer LST values generally corresponded to features with a lower NDVI value. In particular, the large Pagami Creek wildfire burn scar (located east of Ely, Minnesota — station identifier KELO) had a maximum LST value of 96 F, with NDVI values less than 0.3 within the large burn scar.

MODIS 0.65 µm visible channel + Land Surface Temperature + Normalized Difference Vegetation Index

GOES-12 Imager from 1045 UTC 9 May 2012 (click image to play animation of all bands)

GOES-M was launched in 2001 and as GOES-12 served as the operational GOES-East satellite from April 1, 2003 until April 14th, 2010, and has been serving recently as GOES-South America, providing Weather Services on that Continent with routine Imager and Sounder data.

Recently, the GOES-12 Imager has been experiencing ‘cycle slips‘, which manifest themselves in imagery as lines that are shifted, as shown in the loop above of the 5 Imager channels (Individual channels are here: 0.65 µm, 3.9 µm, 6.5 µm, 10.7 µm, 13.3 µm). Cycle slips occur as the satellite on-board software loses track of where the image mirror used to view the Earth is in its scan cycle. After the scan system initializes at the start of a scan cycle, the system expects consistent behavior, and no resources are allocated to track which cycle the mirror is in. Only increments are tracked. If the mirror is moving and a hiccup occurs, that anomaly (which is manifest as a shift in the center of the line) continues until the next system initialization.

The reason for the uptick in the number of Cycle Slips is unknown.

The images in this blog entry were generated using McIDAS-V.

Suomi NPP VIIRS 0.7 µm Day/Night Band + 11.45 µm IR + "Fog/stratus product" images

An AWIPS comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB), 11.45 µm IR, and IR brightness temperature difference “Fog/stratus product” images at 06:51 UTC on 09 May 2012 (above) revealed several ribbons of the aurora borealis (which showed up as bright west-to-east oriented features on the DNB image over Ontario and Quebec, Canada). Note that there was no correlation between these bright DNB aurora features and any high cloud features on the 11.45 µm IR image, or  any low cloud or fog features on the legacy “fog/stratus product” image.

These aurora features would have been along the southern periphery of the auroral oval, which was expanding southward at that time  according to images from the Space Weather Prediction Center (below).

Space Weather Prediction Center auroral oval product images

Photos of the aurora borealis were taken from Upsala, Ontario — located approximately halfway between Thunder Bay (station identifier CYQT) and Dryden (station identifier CYHD) — and posted on Spaceweather.com. These photos were taken about an hour prior to the VIIRS images shown above.