GOES-13 10.7 µm IR images + surface frontal analysis (click image to play animation)

AWIPS images of 4-km resolution GOES-13 10.7 µm IR data (above; click image to play animation) showed a variety of cloud features across the central and southern US between 07:01 UTC and 09:30 UTC on 19 January 2012. In particular, note (1) the darker gray (warmer) low clouds streaming northward from the Gulf of Mexico into Texas, signalling a northward return flow of low-level moisture (Total Precipitable Water values of 15-25 mm); (2) a large lighter gray (colder) banner cloud extending downwind of the Rocky Mountains, due to northwesterly flow aloft interacting with the high terrain; and  (3) a long lighter gray (colder) cloud band exhibiting some transverse banding, associated with a strong 165-knot core jet stream flowing southeastward from Nebraska to Tennessee.

Below are corresponding examples of 1-km resolution IR images from polar-orbiting satellites from the 08:22 to 08:43 UTC time period. The oldest “legacy” instrument is the AVHRR, carried on the constellation of NOAA POES satellites. A newer instrument is the MODIS, carried on the NASA Aqua and Terra satellites. The most recently-launched satellite is the NASA NPP, which carries the VIIRS instrument.

POES AVHRR 12.0 µm IR image

Aqua MODIS 11.0 µm IR image

NPP VIIRS M15 10.763 µm IR image

NPP VIIRS 10.763 µm IR image (viewed using Google Earth)

Images such as these from polar-orbiting satellites are available less frequently that those from GOES, but they offer a more detailed view of cloud features due to improved spatial resolution. The more modern instruments such as MODIS and VIIRS also contain many more channels (or spectral bands) than are available from the current generation of GOES satellites. These additional bands allow the creation of a variety of quantitative satellite products.

For example, if we focus our attention on the low cloud features in Texas, using MODIS data we can be more descriptive in terms of the Cloud Type (water), Fog Depth (as deep as 1300 feet), and Probability of Marginal Visual Flight Rules MVFR (as high as 70-80%) or Probability of Instrument Flight Rules IFR (as high as 50-60%).

View only this post Read Less

GOES-13 10.7 µm IR channel images (click image to play animation)

A strong cold front moved southward across the south-central US on 17 January 2012, dropping temperatures as much as 20 degrees F in 1-2 hours with wind gusts of 30-40 knots. The cold air behind the front (lighter gray enhancement) was clearly evident on AWIPS images of 4-km resolution GOES-13 10.7 µm IR channel data (above; click image to play animation).

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

As the cold front moved southward, a lee-side cold frontal gravity wave was seen along its leading edge on 4-km resolution GOES-13 6.5 µm water vapor channel images (above; click image to play animation). Note the very complex wave structure that was displayed on a 1-km resolution MODIS 6.7 µm water vapor channel image at 08:34 UTC (below). In addition, the MODIS water vapor image showed great detail in the mountain waves across parts of New Mexico and far southwestern Texas, as strong westerly flow was interacting with the terrain in that region.

MODIS 6.7 µm water vapor channel image + Surface frontal analysis

Jayton, Texas NOAA Wind Profiler time series

As the cold front passed the Jayton, Texas NOAA wind profiler site (station identifier JTNT2) after about 12 UTC, the transition to a northeasterly flow of cold air was evident (above). Even though the depth of the cold air was not more than about 1.5 km, the lee-side cold frontal gravity wave was able to be seen on the water vapor imagery due to the fact that the cold, dry air mass shifted the peak of the GOES-13 water vapor weighting function down to within the 700-500 hPa pressure level — much lower than the height of the water vapor weighting function of the US Standard Atmosphere air mass (below).

Amarillo, Texas water vapor weighting function vs US Standard Atmosphere water vapor weighting function

View only this post Read Less

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

View only this post Read Less

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

View only this post Read Less