06 October MODIS Visible Image

High pressure over the eastern United States on October 6th allowed a rare view of the (almost) cloud-free Great Lakes, above, from the MODIS instrument on board Terra. The clear skies also allowed observations of lake surface temperatures over the entire Lake system, shown below. (Click here for an animation between the Visible and Lake Surface Temperatures). Note that the region of turbulent, sediment-laden waters over southern Lake Michigan — (link for blog post) — are warmer than adjacent waters. The default AWIPS Lake-surface temperature enhancement shows little variations in temperature, when in fact the temperature ranges from 46 F in Lake Superior to 74 F in Lake Erie (near the mouth of Sandusky Harbor). An image with a stretched enhancement that more clearly shows the temperature variability is here. Lakes Michigan, Huron and Ontario continue to show the effects of persistent easterly winds associated with a series of cut-off lows that have passed south of the Great Lakes in the past weeks: cold near-shore temperatures associated with upwelling in the eastern part of the basins.

06 October MODIS Sea Surface Temperature Image

Screenshot of AWIPS including MODIS True-color image, 06 October

MODIS multi-channel data can be combined to produce a true-color image in the AWIPS environment. In this case, above, the sediment-laden lake waters over southern Lake Michigan jump out. Fall colors over northern Wisconsin and the southern Upper Peninsula of Michigan are also evident. More true-color imagery is available at the MODIS today site: Link.

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GOES-11 + GOES-15 + GOES-13 visible channel images

Strong southerly winds (gusting as high as 50 mph) helped a large grassland fire (named the Okreek fire) spread rapidly northward across south-central South Dakota during the afternoon hours on 05 October 2011. The light gray smoke plume and the dark burn scar grew very quickly, which could be seen on GOES-11 (GOES-West),  GOES-15, and GOES-13 (GOES-East) visible channel images (above). Each of the 3 sets of images is displayed in the native projection of the respective satellite.

The corresponding 3.9 µm shortwave IR images from each satellite (below) showed the large and intense “hot spot” (dark black to yellow pixels) associated with the Okreek fire. Note there were also a few other smaller fires burning in other parts of central South Dakota during that time period, which also exhibited very intense hot spot signatures.

GOES-11 + GOES-15 + GOES-13 shortwave IR images

A comparison of 250-meter resolution false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site from before (04 October), during (05 October), and after (07 October) the Okreek fire revealed the development and growth of the 26 mile long burn scar (which appears as the light brown line). The bright pink feature on the 05 October image was the heat signature of the active front line of the fire, which was rapidly advancing northward on that day.

MODIS false-color RGB images from 04 October, 05 October, and 07 October 2011

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MODIS and GOES-13 fog/stratus product images

Strong nocturnal radiational cooling beneath a large area of high pressure centered over the Ohio River Valley led to the formation of widespread areas of fog and stratus on 05 October 2011. AWIPS image comparisons of the 1-km resolution MODIS and the 4-km resolution GOES-13 fog/stratus products at 03:30 UTC or 11:30 pm local time (above) and 07:45 UTC  or 3:45 am local time (below) demonstrated the clear advantage of having improved spatial resolution to detect the more subtle features such as river valley fog.

MODIS and GOES-13 fog/stratus product images

To compliment the improved fog/stratus detection capabilities offered by higher spatial resolution, other products are being developed (as part of the CIMSS participation in GOES-R Proving Ground activities) that provide more quantitative information about areas of fog and/or low cloud: for example, Fog Depth, Marginal Visual Flight Rules (MVFR) Probability, and Instrument Flight Rules (IFR) Probability (below). In this case, the 07:45 UTC products indicated that the Fog Depth values were as high as 1231 feet (cyan color enhancement) over parts of northern West Virginia, where there were also MVFR Probabilities greater than 90% and IFR Probabilities greater than 75% (brighter red color enhancement).

GOES-13 fog/stratus product, Fog Depth, MVFR Probability, and IFR Probability

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MODIS true color images: 02 October (left) and 03 October (right)

As was highlighted in news stories posted by the National Weather Service forecast offices at Chicago and Milwaukee, a large amount of sediment was seen in southern Lake Michigan following a strong wind event which produced very large waves. A comparison of 250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed one particularly large sediment feature protruding northward from the southeastern part of Lake Michigan on 02 October and 03 October 2011.

A comparison of AWIPS images of 1-km resolution MODIS 0.65 µm visible channel data with the corresponding 1-km resolution MODIS Sea Surface Temperature (SST) product on 03 October (below) showed that while the prominent sediment feature was embedded within a larger scale area of warmer waters (SST values in the lower 60s F, darker red color enhancement) in the far southern part of the lake, there was not necessarily a 1:1 correspondence between the sediment pattern and the sea surface temperature pattern.

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

GOES-13 0.63 µm visible channel imagery (below; click image to play animation) indicated that the prominent sediment feature was moving slowly northward early in the day on 03 October — however, once the northwesterly winds reported by the mid-lake buoy began to increase and gust to 16 knots later in the day, the northward motion of the sediment feature appeared to slow somewhat.

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

===== 06 October Update =====

A sequence of daily 250-meter resolution MODIS true color RGB images from 02, 03, 04, 05, and 06 October (below) show the changes in shape and location of the large sediment feature in the southeastern part of Lake Michigan.

MODIS true color images from 02, 03, 04, 05, and 06 October

In addition, daily 15-minute interval GOES-15 0.63 µm visible channel images from that same period (below; click image to play 5-day animation) further show how the sediment patterns were transported and morphed by the Lake Michigan water currents.

GOES-15 0.63 µm visible channel images (click image to play 5-day animation)

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