POES AVHRR 0.86 µm visible channel + POES AVHRR 12.0 µm IR channel images

A surge of cold air brought the first measurable snowfall to parts of the Pacific Northwest states on 14 January – 15 January 2012. The Seatle-Tacoma aiport received 2.4 inches of snow on 15 January. A comparison of 1-km resolution POES AVHRR 0.86 µm visible channel and 12.0 µm IR channel data (above) displayed a classic example of “open cell convection” — this type of open-cell mesoscale convective cloud pattern is a signature of strong instability (via boundary layer cold air advection over relatively warmer waters) in an environment of cyclonic flow.

A sequence of 1-km resolution POES AVHRR 12.0 µm IR channel images (below) showed the inland progression of the open cell convection, eventually producing snowfall at Seattle, Washington (station identifier KSEA) and Portland, Oregon (station identifier KPDX).

POES AVHRR 12.0 µm IR channel images

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GOES-5 Visible Imagery of Hurricane Dennis over Florida in August 1981

The University of Wisconsin served as the official National Satellite Archive for many years before the National Climatic Data Center took over that responsibility. The original operational GOES satellite archive was acquired at the UW-SSEC Data Center onto Sony U-Matic tapes starting in 1978. When these data were converted from U-Matic tapes to IBM 3590 tapes in the mid-1990s through the early 2000s, notable gaps in the satellite record were obvious. (Click here for the image shown above in its originally ingested form).

Recent work at the SSEC Data Center has started to fill in those missing gaps using newly written software that reconciles redundant data and interrogates any anomalies found. Errors that arise from mis-tracking on the U-Matic tape, for example, can be corrected. Similarly, Ingest/signal transmit errors on the U-Matic tape can be rectified. It is important to note that no data are changed, averaged or otherwise manipulated in this processing; rather, data are uncovered by correcting errors in previous processing.

Playback from the U-Matic tapes in the 1990s and 2000s for one image may have occurred multiple times if the Engineer determined that tracking or other errors could be mitigated by adjusting the playback. Usually this involved manual tracking working with an oscilloscope. Present-day recovery involves reprocessing data saved on 3590s (originally pulled from U-Matic tapes), effectively re-ingesting all images, possibly resulting in multiple different ingested images (If an image was played back more than once from the U-Matic tape) that can be merged together into one image that is far more complete than its separate pieces. In a second type of recovery, the playback is redone only once, but smarter ingest software corrects tracking noise, signal noise and tape deterioration. All of the signal (including the noise) was saved onto the 3590s.

More examples of the correction results are shown below. In each case, the original version saved on 3590 is on the left, and the cleaned version is on the right.

About 2800 Mode-A images thought to be completely lost have been recovered by this processing. Nearly 8100 images had corrections to at least 95% of their lines. More than 25000 images had framing errors that were corrected, which errors affected every visible scan in the image. In sum, about 2 full years of data have been recovered from the archive by the smarter re-processing.

GOES-1 Visible Imagery from March 1979

GOES-1 Visible Imagery from May 1979

GOES-5 IR Window Channel Imagery from August 1981

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

Snowfall amounts as high as 10-15 inches fell across parts of west Texas and southeast New Mexico on 09 January 2012 as a strong upper level disturbance moved across that region (NWS Lubbock TX storm summary). On the following morning, a comparison of GOES-15 (GOES-West) and GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation) showed the areal coverage of the snow cover that remained on the ground. Note how the patch of snow began to melt from the outer edges inward as the full day of sunshine warmed the ground surface. Also note the curious “donut hole” of bare ground on the northern end of the main snow cover — this feature rapidly disappeared, as the snow depth associated with this feature was not very high.

A comparison of 250-meter resolution MODIS true color and false color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed greater detail in the snow cover (snow on the ground appears as darker shades of cyan on the false color image) at 18:02 UTC.

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

A comparison of AWIPS images of MODIS 0.65 µm visible channel data and the corresponding false color RGB image (below) offered another tool that can be used to discriminate between snow cover (which in this example appears as darker shades of red on the false color image) and supercooled water droplet clouds (which appeared as varying shades of white).

MODIS 0.65 µm visible image + MODIS false color RGB image

A comparison of the MODIS 0.65 µm visible image with the corresponding MODIS Land Surface Temperature (LST) product (below) revealed how the deep snow cover was helping to keep surface air temperatures significantly colder than adjacent regions with bare ground. MODIS LST values were in the low to middle 30s F across the deeper snow cover, in the upper 40s to low 50s F in the “donut hole” region where the snow had just melted, and in the 60s F to the north over bare ground. Also note how the urban areas of Midland and Odessa stand out in the LST image, with LST values in the low to middle 40s F.

MODIS 0.65 µm visible image + MODIS Land Surface Temperature product

The mechanism for the creation of the “donut hole” snow cover feature is unclear at this point. A comparison the MODIS Land Surface Temperature product with the regional topography (below) seems to suggest that this feature was not topographically-driven.

MODIS Land Surface Temperature product + Topography

The MODIS true color image viewed using Google Earth (below) showed that the community of Brownfield (which did received about an inch of snowfall the previous day) was aptly named, being located within the brown-colored snow-free region at 18:02 UTC.

MODIS true color image (viewed using Google Earth)

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MTSAT-2 6.75 µm water vapor channel images (click image to play animation)

A large area of low pressure over the Southern Ocean between Australia and Antarctica on 07 January – 08 January 2012 (surface analyses) exhibited a beautiful signature of an occluding cyclone on 5-km ressolution MTSAT-2 6.75 µm water vapor channel imagery (above; click image to play animation). This storm prompted the issuance of Gale Warnings for widespread areas of winds of 30-45 knots producing high seas.

A closer view of the MTSAT-2 water vapor imagery (below) revealed very intricate detail to the plume of dry air wrapping into the ceter of the storm, along with several small vortices of dry air that became cut off and isolated along the periphery of the system as it began to decay just southwest of the island of Tasmania.

MTSAT-2 6.75 µm water vapor channel images

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