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 10.7 µm 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 NESDIS are working to find the source of this difference.

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Update, 17 November 2014

A software fix has been identified and tested. Link.

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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)

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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

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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.

(Update, 4 June 2012: An Imager Electronics Side Swap is scheduled for June 6, 2012, for GOES-12 (GOES-South America) based on the Manufacturer’s Recommendation as a potential remedy to mitigate the ongoing Cycle Slips. The side switch will be performed at 1615 UTC on 6 June 2012. The duplicate sensors that will now be used have not yet been used during GOES-12’s life. Because new sensors are being used, new look-up tables and calibration coefficients have been computed and are available here. Also, see page 29 in this pdf for more information on the two detector sets. Here is the notification of coming changes.)

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