POES AVHRR 10.8 µm IR + MODIS 11.0 µm IR images

A major surge of arctic air from Canada helped to produce the first surface air temperatures of -40º F (-40º C) or colder over the Lower 48 states during the Winter of 2010/2011 — the coldest official minimum temperature was -46º F (-43º C) at International Falls, Minnesota on the morning of 21 January 2011, with a number of locations across northern Minnesota and northern Wisconsin in the -30º F (-34º C) to -40º F (-40º C) range.

A series of AWIPS images of 1-km resolution POES AVHRR 10.8 µm IR and MODIS 11.0 µm IR data (above) shows the increase in areal coverage of surface IR brightness temperatures of -40º C and colder (purple to white color enhancement). The coldest surface IR brightness temperature on the images was -49º C (-56º F) at 08:41 UTC — but surface IR brightness temperatures do not always correlate well with surface air temperatures (which are generally measured in a shelter at a height of about 5 feet above the surface). Note the significantly warmer waters along the north shore of Lake Superior (yellow to red color enhancement) — MODIS Sea Surface Temperature values there were still in the low to middle 30s F.

On the 04:29 UTC MODIS image, some features of curiosity are the 3 northwest-to-southeast oriented “streaks” that resemble plumes near Hibbing (station identifier KHIB). These could be plumes from industrial sites (mining, or power plants) — in fact, we have seen similar plumes coming from that same area in the past on 1-km resolution MODIS fog/stratus product imagery. A comparison of MODIS 11.0 µm IR and MODIS Land Surface Temperature (LST) product images (below) shows that the “plumes” exhibited LST values near -20º F (darker blue color enhancement), compared to adjacent LST values in the -30s F (violet color enhancement).

MODIS 11.0 µm IR image + MODIS Land Surface temperature product

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MODIS true color and false color Red/Green/Blue (RGB) images (Green Bay WI region)

As a result of the influx of cold arctic air, a dramatic increase in ice formation was seen in the nearshore waters of Lake Michigan. Comparisons of 250-meter resolution MODIS Red/Green/Blue (RGB) true color (created using bands 04/03/01) and false color (created using bands 07/02/01) images from the SSEC MODIS Today site show filaments of ice extending offshore into Lake Michigan in the Green Bay, Wisconsin area (above), with more extensive ice formation farther to the south in the southwestern portion of Lake Michigan in the Milwaukee, Wisconsin and Chicago, Illinois area (below). Snow cover and ice appear as shades of cyan on the MODIS false color images, in contrast to supercooled water droplet clouds (which appear as much brighter features on the imagery).

MODIS true color and false color Red/Green/Blue (RGB) images (Milwaukee WI and Chicago IL region)

=============== 23 JANUARY UPDATE ===============

With continued cold temperatures across the Great Lakes region, ice coverage increased along the nearshore waters of southern Lake Michigan. A comparison of 250-meter resolution MODIS true color RGB images on 23 January 2011 (below) revealed some northward movement of the ice during the time between the 16:22 UTC overpass of the Terra satellite and the 19:42 UTC overpass of the Aqua satellite (due to southerly winds pushing the ice away from the shore). Features appear somewhat “blurred” on the later Aqua MODIS image due to the fact the the scene was near the edge of the scan swath.

250-meter resolution MODIS true color Red/Green/Blue (RGB) images

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

A long lake effect snow band became well-organized and stretched nearly the entire length of Lake Ontario on 20 January 2011. The cloud band was very evident on McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation). As the lake band moved onshore, it produced light to occasionally moderate snow at a few inland locations across central New York. In addition, if you look closely in the far northeastern portion of the lake you can also see ice floes that were drifting slowly eastward.

An AWIPS image of 1-km resolution MODIS 0.65 µm visible channel data (below) showed a more detailed view of the lake effect snow band feature. On the corresponding 1-km resolution MODIS Sea Surface Temperature (SST) product, relatively warm SST values as high as 40º F (lighter blue color enhancement) could be seen on either side of the cloud band.

MODIS 0.65 µm visible channel image + MODIS Sea Surface Temperature product

A comparison of the MODIS 0.65 µm visible image with the corresponding 3.7 µm shortwave IR image (below) indicated that there was a significant amount of solar reflection off the center portion of the cloud band, suggesting a cloud composed of supercooled water droplets (darker gray enhancement) — perhaps with a very thin veil of cirrus cloud spreading out over the top of the supercooled water droplet clouds. At the time of the MODIS images, Fulton, New York (station identifier KFZY) was reporting moderate snow with a reduction in surface visibility to 0.5 mile.

MODIS 0.65 µm visible image + MODIS 3.7 µm shortwave IR image

However, the 4-km resolution MODIS Cloud Phase product (below) indicated that a good portion of the center of the cloud band had glaciated (salmon color enhancement), although this thin area of ice cloud was surrounded by a great deal of mixed phase (darker gray) or uncertain (lighter gray) and also water phase (blue color enhancement) cloud.

MODIS Cloud Phase product

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GOES-13 6.5 µm water vapor images (click image to play animation)

AWIPS images of GOES-13 6.5 µm ‘water vapor channel” data (above) showed a large area of dry air aloft moving southward across the state of Utah behind a shortwave trough axis on 19 January 2011. The 500 hPa wind fields from the RUC80 model indicated that winds turned more northerly and increased in speed behind the trough axis.

At 20:01 UTC, a comparison of the GOES-13 6.5 µm water vapor image with the corresponding 1-km resolution MODIS 6.7 µm water vapor image (below) demonstrated the value of higher spatial resolution for detecting the presence of widespread mesoscale mountain waves that covered a good deal of the state of Utah. Such a mountain wave signature on water vapor imagery can indicate the presence of a potential for turbulence — however, in this case there were no pilot reports of turbulence that showed up over Utah during that particular time period.

There was also an obvious northwestward parallax shift in the image features on the GOES-13 image, due to the large viewing angle from that geostationary satellite (which was positioned over the Equator at 75 degrees West longitude).

GOES-13 6.5 µm water vapor image + MODIS 6.7 µm water vapor image

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GOES-11 10.7 µm IR and POES AVHRR 12.0 µm IR images

The surface air temperature at Watson Lake in the southern Yukon Territory of Canada (station identifier CYQH) fell to -56º F (-49º C) at 16 UTC on 14 January 2011. About 2 hours later, a comparison of AWIPS images of 4-km resolution GOES-11 10.7 µm IR and 1-km resolution POES AVHRR IR data (above) showed the signature of cold air that had settled into the valleys across that region — this signature was naturally much clearer on the higher resolution POES AVHRR image. The coldest surface IR brightness temperature on the POES AVHRR IR image was -52º C (-62º F) just to the southeast of Watson Lake. Also note the northeastward “parallax shift” of the warmer cloud features on the GOES-11 image, due to the high viewing angle from that geostationary satellite (which was situated over the Equator at 135º West longitude).

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