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

A GOES-13 (GOES-East) North/South Station Keeping maneuver was performed on Wednesday, February 19, 2014, beginning 1145 UTC, and ending at 1945 UTC (Link). During this time, the navigation of the satellite degraded mostly in the north-south direction. At 1945 UTC, after the maneuver ended, the navigation snapped back to normal. (Compare the 1932 and 1945 UTC images).

Navigation error tracking is available online for some geostationary satellites. For example, this link, off this page, shows landmark errors from MTSAT. NOAA’s OSPO maintains a site for GOES satellites; however, results are posted weekly. (Link).

View only this post Read Less

MODIS 6.7 µm water vapor channel image, with pilot reports of turbulence

United Airlines flight 1676 enroute from Denver, Colorado KDEN to Billings, Montana KBIL (flight track) encountered severe turbulence at an altitude of 34,000 feet over Wyoming on 17 February 2014. Three crew members and two passengers were injured, and taken to hospitals upon landing in Billings. An AWIPS image of 1-km resolution Aqua MODIS 6.7 µm water vapor channel data (above) showed a number of pilot reports of moderate turbuence over Wyoming between the altitudes of 33,000 and 45,000 feet around that time; the United 1676 pilot report of severe turbulence is highlighted in red.

On the MODIS water vapor image, note the appearance of distinct signatures of non-parallel mountain waves just to the east of that turbulence plot (in the vicinity of KIDV) — these closely-spaced bands of descending dry air (darker blue to yellow color enhancement) and ascending moist air (lighter blue to pale white color enhancement) were just east (downwind) of the Bighorn Mountains. The corresponding MODIS 0.65 µm visible channel and 11.0 µm IR channel images (below) showed that there were no cloud features associated with the entire extent of these mountain waves — they were were essentially occurring in “clear air”. This example demonstrates the value of high spatial resolution water vapor imagery for helping to identify signatures of potential clear air turbulence.

MODIS 0.65 µm visible channel, 11.0 µm IR channel, and 6.7 µm water vapor channel images

An animation of 4-km resolution GOES-13 6.5 µm water vapor channel images (below; click image to play animation) showed that there were numerous other reports of moderate and even severe turbulence over Wyoming between about 20:00 UTC and 23:40 UTC. On the final 23:40 UTC image, there was a pilot report of severe turbulence as high as 47,000 feet in that same general area. The mountain wave signature to the lee of the Bighorn Mountains was not stationary, but was seen to exhibit some meandering during that time period.

GOES-13 6.5 µm water vapor channel images, with pilot reports of turbulence (click to play animation)

View only this post Read Less

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

AWIPS images of GOES-13 0.63 µm visible channel data (above; click image to play animation) displayed a number of interesting Lake Michigan features on 16 February 2014: (1) the motion of lake ice in the northern and far eastern portions of the lake, (2) the formation of parallel cloud streets over the ice-free waters of the central part of lake, and (3) the development of a mesoscale vortex (or “mesovortex”) over the southern end of the lake.

Northerly winds were blowing down the long axis of Lake Michigan in the wake of a departing area of low pressure; Metop ASCAT surface scatterometer wind speeds were as high as 35 knots at 15:26 UTC (below).

GOES-13 0.63 µm visible channel image with ASCAT surface scatterometer winds

False-color Red/Green/Blue (RGB) images created from Suomi NPP VIIRS 0.64 µm visible and 1.61 µm “snow/ice channel” data (below) helped to disctiminate between snow cover and ice fearures (which appeared as varying shades of red) and supercooled water droplet cloud features (which appeared as brighter shades of white). Even in the relatively short 1.5 hour period separating the two VIIRS RGB images, a significant amount of ice motion could be seen.

Suomi NPP VIIRS false-color “snow/ice vs cloud discrimination” RGB images

As an aside, another feature of interest seen in the GOES-13 visible images included arc-shaped aircraft dissipation trails (or “distrails”), created by air traffic that was likely circling upon approach or departure from the Chicago O’Hare or Midway airports (below; click image to play animation). Partcles in the aircraft exhaust acted as ice condensation nuclei, glaciating a trail as they penetrated the supercooled water droplet cloud deck.

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

View only this post Read Less

MTSAT-1R 10.8 µm IR channel images (click to play animation)

McIDAS-X images of MTSAT-1R 10.8 µm IR channel data (above; click image to play animation; also available as an MP4 animation) showed the rapid expansion of the volcanic umbrella cloud resulting from the eruption of Kelut (aka Kelud) on the Indonesian island of Java on 13 February 2014. The MTSAT-1R satellite was in rapid scan mode, providing images at 10-minute intervals (with some gaps). The initial signal of a volcanic cloud appeared as a small cluster of cold pixels on the 16:09 UTC (11:09 PM local time) IR image.

The dramatic signature of a distinct circular-shaped warm core (shades of red, around -60º C) surrounded by a ring of colder (shades of white, -75º to -80º C) cloud-top IR brightness temperatures possibly indicated that a portion of the cloud plume associated with the explosive eruption rose well into the lower stratosphere, and was therefore radiating at the warmer temperatures that existed far above the tropopause. The leading edge of the top of the cloud plume eventually exhibited IR brightness temperatures colder than -80º C (shades of violet) as it drifted toward the west-southwest, with a minimum of -84.5º C on the 19:29 UTC image. Along the upwind (eastern) portion of the volcanic cloud, a signature of “bow shock waves” was evident: an indication that the massive and dense volcanic cloud was acting as a barrier to the ambient easterly flow across the region. Volcanic lightning was also generated by the rising ash plume (see photos on the Wired Science “Eruptions” blog posts 1 and 2).

Suomi NPP VIIRS 11.45 µm IR channel and 0.7 µm Day/Night Band images

A more detailed view was provided by McIDAS-V images of Suomi NPP VIIRS 375-meter resolution 11.45 µm IR channel and 750-meter resolution 0.7 µm Day/Night Band data (above; images courtesy of William Straka, CIMSS). A ring of gravity waves could be seen around the periphery of the volcanic cloud shield; the coldest IR brightness temperature within the small cluster of “overshooting tops” was 175 K or -98º C (closer view). Since the Moon was in the Waxing Gibbous phase at 98% of full, it provided ample illumination for a “visible image at night” using the VIIRS Day/Night Band — note how the ash-laden volcanic cloud exhibited a darker gray appearance compared to the surrounding brighter white meteorological clouds.

Surabaya/Juanda rawinsonde data (12 UTC on 13 February)

A plot of the 13 February/12:00 UTC rawinsonde data from the nearby (map/IR image comparison) Surabaya/Juanda International Airport (above) showed that a very moist and marginally unstable (Lifted Index of only  -1.7) atmosphere existed over the region about 4 hours prior to the eruption — the tropopause was located at 105 millibars (mb), at an altitude of 16.29 km where the air temperature was -84.5º C. According to the volcanic ash advisory issued by the Darwin VAAC at 00:43 UTC on 14 February, the top of the volcanic ash extended to 55,000 feet or 16.76 km — somewhere between 100 mb and 87.1 mb on the Surabaya sounding. The warmest temperature recorded in the stratosphere by the sonde instrument was -71.3º C at 64.9 mb or 19.02 km.

A GOES-R Volcanic Ash Height product (VISITview lesson | PowerPoint) — derived using MTSAT-2 data — indicated that downwind portions of the ash cloud reached the 18-20 km ASL range (black color enhancement), with a maximum ash height value of 22 km (below; click image to play animation). CALIOP data from a CALIPSO overpass of the Kelut volcanic cloud just around 18:13 UTC on 13 February showed that the top of the volcanic cloud was generally at an altitude of 18-19 km, with some cloud/ash material reaching a maximum height of 26 km; taking that data source into consideration, a subsequent volcanic ash advisory issued by the Darwin VAAC at 17:09 UTC on 14 February revised the maximum ash height to 65,000 feet or 19.8 km.

MTSAT-2 Volcanic Ash Height product (click to play animation)

With the arrival of early morning daylight, MTSAT-1R 0.68 µm visible channel images (below) showed the dense volcanic ash plume drifting west-southwestward; there was also a subtle signature of the “bow shock waves” seen along the eastern edge of the ash plume, similar to what was observed on the IR imagery.

MTSAT-1R 0.68 µm visible channel images

Back to the topic of the 26 km height seen on the CALIPSO data: on the 10-minute interval MTSAT-1R 10.8 µm IR imagery, the warmest cloud-top IR brightness temperature within the “circular warm spot” of the volcanic cloud was -56ºC at 17:19 UTC. The 13 February/12 UTC Surabaya/Juanda rawinsonde only made it up to 64.9 mb or 19.02 km (where it was -71.3ºC) — however, the 14 February/00 UTC rawinsonde ascended all the way to 10 mb (below). So using this later sounding, the air temperature of -56ºC corresponded to an height somewhere between 24.9 mb (24.8 km) and 20 mb (26.2 km) — which roughly agrees with the 26 km height seen on the CALIOP data.

Surabaya/Juanda rawinsonde data (00 UTC on 14 February)

Additional satellite products showing details of the Kelut volcanic eruption can be found on Nicarnica Aviation blog posts (1 | 2).

View only this post Read Less