GOES-14 SRSO-R: aircraft “hole punch clouds” in North and South Carolina

February 9th, 2016 |

GOES-14 Visible (0.63 µm) images [click to play MP4 animation]

GOES-14 Visible (0.63 µm) images [click to play MP4 animation]

1-minute interval GOES-14 Super Rapid Scan Operations for GOES-R (SRSO-R) Visible (0.63 µm) images (above; also available as a large 71 Mbyte animated GIF) revealed the formation of clusters of aircraft “hole punch clouds” over central North and South Carolina on the morning of 09 February 2016. These types of cloud features form when aircraft fly through a layer of clouds composed of supercooled water droplets; cooling from wake turbulence (reference) and/or the particles from the jet engine exhaust which may act as ice condensation nuclei cause the small water droplets to turn into larger ice crystals (which then often fall from the cloud layer, creating “fall streak holes“). Similar features have been discussed in previous blog posts.

A comparison of GOES-14 Visible (0.63 µm, 1-km resolution) and Shortwave Infrared (3.9 µm, 4-km resolution) images (below; also available as a large 71 Mbyte animated GIF) offered evidence that the cloud material within each “hole punch” was composed of ice crystals, which exhibited colder (lighter gray) IR brightness temperatures than the surrounding supercooled water droplet clouds. It is likely that many of the hole punch features were caused by aircraft ascending from or descending to the Charlotte Douglas International Airport in North Carolina (KCLT).

GOES-14 Visible 0.63 µm (left) and Shortwave Infrared 3.9 µm (right) images [click to play MP4 animation]

GOES-14 Visible 0.63 µm (left) and Shortwave Infrared 3.9 µm (right) images [click to play MP4 animation]

In a comparison 1-km resolution POES AVHRR Visible (0.86 µm) and Infrared (12.0 µm) images (below), the cloud-top IR brightness temperatures in the vicinity of the hole punch features were only as cold as -20 to -24º C (cyan to blue color enhancement), which again is supportive of the cloud layer being composed of supercooled water droplets.

POES AVHRR Visible 0.86 µm) and Infrared (12.0 µm) images [click to enlarge]

POES AVHRR Visible 0.86 µm) and Infrared (12.0 µm) images [click to enlarge]

Aircraft dissipation trails and “hole punch clouds” over Florida

December 12th, 2014 |
GOES-13 0.63 µm visible channel images (click to play animation)

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

McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (below; click image to play animation; also available as an MP4 movie) revealed numerous aircraft dissipation trails and “hole punch clouds” which formed over southern Florida and the adjacent waters of the Atlantic Ocean on 12 December 2014. These features are formed when an aircraft penetrates a supercooled cloud layer — the particles in the exhaust act as ice nuclei which allow the supercooled water droplets to transform into ice crystals.

A comparison of 250-meter resolution Terra MODIS true-color and false-color Red/GreenBlue (RGB) images from the SSEC MODIS Today site (below) confirmed that the clouds within the dissipation trails and the hole punch features had glaciated — ice crystal clouds appear as shades of cyan in the false-color image, in contrast to supercooled water droplet cloud which appear as varying shades of white.

Terra MODIS true-color and false-color images

Terra MODIS true-color and false-color images

Lake Michigan: ice motion, cloud streets, and a mesovortex

February 16th, 2014 |
GOES-13 0.63 µm visible channel images (click to play animation)

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

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

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)

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

Aircraft dissipation trails over the Lake Ontario region

November 4th, 2013 |
GOES-13 0.63 µm visible channel images (click to play animation)

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

Hat tip to NWS Buffalo NY forecasters Jon Hitchcock and David Zaff for letting us know about a number of aircraft dissipation trails (also known as “distrails” or “hole punch clouds”) over the Lake Ontario region on 04 November 2013. A series of McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation) showed these features as they drifted eastward during the day.

A comparison of AWIPS II images of 375-meter resolution Suomi NPP VIIRS 0.64 µm visible channel data and the corresponding false-color”Snow Cloud Discrimination” Red/Green/Blue (RGB) product at 18:17 UTC (below) indicated that the cloud layer penetrated by the aircraft was composed of supercooled water droplets (which appear brighter on the RGB image) — but the particles in the aircraft exhaust acted as ice nuclei and caused the cloud to glaciate (ice crystal clouds appear as varying shades of red on the RGB image).

Suomi NPP VIIRS 0.64 µm visible channel and

Suomi NPP VIIRS 0.64 µm visible channel and “Snow Cloud Discrimination RGB” images

AWIPS images of the POES AVHRR CLAVR-x Cloud Type product confirmed that the cloud layer over the Lake Ontario region was a supercooled water droplet cloud (green color), with the Cloud Top Height product indicating tops in the 7-9 km range (below). However, higher-altitude cirrus clouds were beginning to overspread the region from the west (cirrus=orange; thick ice=yellow; overlap=violet).

POES AVHRR 0.86 µm visible channel image, Cloud Type product, and Cloud Height produc

POES AVHRR 0.86 µm visible channel image, Cloud Type product, and Cloud Height product