Contrails off the coast of Southern California

April 23rd, 2018 |

As pointed out by NWS San Diego, an interesting pattern of contrails formed off the coast late in the day on 23 April 2018. A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Cirrus” (1.37 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed signatures during the daylight hours — Visible images revealed contrail shadows being cast upon the low-altitude cloud tops at 0142 and 0147 UTC — with an Infrared signature persisting after sunset. These contrails were likely caused by military aircraft performing training exercises, since chaff was seen with radar in that same area on the previous day.

GOES-16

GOES-16 “Red” Visible (0.64 µm, left), Near-Infrared “Cirrus” (1.37 µm, center) and “Clean” Infrared Window (10.3 µm, right) images [click to play animation | MP4]

A better post-sunset signature was seen on a NOAA-15 Infrared Window (10.8 µm) image at 0212 UTC (below). A comparison with the corresponding GOES-16 “Clean” Infrared Window (10.3 µm)  image displayed a significant northwestward GOES-16 displacement due to parallax — and the 1.1 km spatial resolution of AVHRR data resulted in a clearer contrail signature.

NOAA-15 AVHRR Infrared Window (10.8 µm) and GOES-16 ABI

NOAA-15 AVHRR Infrared Window (10.8 µm) and GOES-16 ABI “Clean” Infrared Window (10.3 µm) images [click to enlarge]

The pattern of contrails could also be followed after sunset using GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) imagery (below).

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

GOES-16 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images [click to play animation | MP4]

The GOES-16 Water Vapor weighting function plots (below) displayed a bi-modal distribution for all 3 spectral bands, with peaks near 300 hPa and 500 hPa. The absence of a distinct contrail signature on the 6.2 µm imagery suggests that these features were located closer to the 500 hPa pressure level.

GOES-16 Water Vapor weighting functions, calculated using rawinsonde data from San Diego CA [click to enlarge]

GOES-16 Water Vapor weighting functions, calculated using rawinsonde data from San Diego CA [click to enlarge]

Blowing dust in Texas and Oklahoma

January 21st, 2018 |

GOES-16

GOES-16 “Moisture” Infrared brightness temperature difference (10.3-12.3 µm) images, with hourly surface reports plotted in cyan [click to play animation]

Strong winds in the wake of a cold frontal passage created large areas of blowing dust across the Panhandle Plains of northwestern Texas after 16 UTC on 21 January 2018. GOES-16 “Moisture” or “split-window difference” (10.3 µm12.3 µm) images (above) showed that the leading edge of this airborne dust moved over far southwestern Oklahoma after 20 UTC. (Note to AWIPS users: the default enhancement for this GOES-16 “Moisture” Channel Difference product was changed to “Grid/lowrange enhanced” to better highlight the dust with shades of yellow)

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Cirrus” (1.37 µm) images (below) also displayed blowing dust signatures; the surface visibility was restricted to 2-3 miles at some locations, with Big Spring briefly reporting only 1/4 mile from 20-21 UTC. The dust signature was apparent on the Cirrus imagery because this spectral band can be used to detect any airborne particles that are effective scatterers of light (such as cirrus ice crystals, volcanic ash, dust/sand or haze).

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with hourly reports of surface weather plotted in red and surface visibility (miles) plotted in red [click to play animation]

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm) images, with hourly reports of surface weather plotted in red and surface visibility (miles) plotted in red [click to play animation]

A Cirrus band is also available with the MODIS instrument on the Terra and Aqua satellites (as well as the VIIRS instrument on Suomi NPP and NOAA-20) — a comparison of Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images from Terra and Aqua (below) highlighted the differing appearance of the blowing dust features as sensed by each of those spectral bands. The airborne dust exhibited a darker signature in the Shortwave Infrared images since the small dust particles were efficient reflectors of incoming solar radiation, thus appearing warmer at 3.7 µm.

Terra MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Terra MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Aqua MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Aqua MODIS Visible (0.65 µm), Cirrus (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images, with surface reports plotted in cyan [click to enlarge]

Pilot reports within 20-45 minutes after the Terra overpass time (below) revealed Moderate to Severe turbulence at an elevation of 8000 feet, just southeast of the most dense dust plume feature (highlighted by the cooler, lighter gray infrared brightness temperatures) — this was likely due to strong wind shear in the vicinity of the rapidly-advancing cold front. Farther to the southwest, another pilot report indicated that the top of the blowing dust was at 7000 feet, with a flight-level visibility of 3 miles at 10,000 feet.

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of turbulence highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of turbulence highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of dust layer top and flight level visibility highlighted in red [click to enlarge]

Terra MODIS Infrared Window (11.0 µm) image, with a pilot report of dust layer top and flight level visibility highlighted in red [click to enlarge]

Severe turbulence over Hawai’i

January 12th, 2018 |

GOES-15 Water Vapor (6.5 µm) images, with hourly pilot reports of turbulence [click to play animation]

GOES-15 Water Vapor (6.5 µm) images, with hourly pilot reports of turbulence [click to play animation]

Numerous pilot reports of moderate to severe turbulence were received over the Hawai’i area on 12 January 2018 — and GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above; also available as an MP4) showed the development of a quasi-stationary gravity wave train over the northwestern portion of the island chain which appeared to be associated with many of these pilot reports.

HNL UA /OV 2115N16010W/TM 2241/FL320/TP B767/TB CONT MOD TURB

HNL UUA /OV 2115N16048W/TM 2255/FL340/TP H/B747/TB MOD-SEV TURB

HNL UUA /OV BOARD/TM 2350/FL370/TP H/B772/TB SEVERE TURB

PHNL UUA /OV 2443N 15516W /TM 2358 /FL370 /TP B737 /TB SEV 370 /RM ZOA CWSU AWC-WEB

In spite of the large satellite viewing angle, these waves were also very evident on Himawari-8 Lower-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (below; also available as an MP4). The 3 Water Vapor bands on the Himawari AHI are nearly identical to the 3 Water Vapor bands on the GOES-R series ABI.

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and 6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

Himawari-8 Low-level (7.3 µm, left), Mid-level (6.9 µm, center) and Upper-level (6.2 µm, right) Water Vapor images, with hourly pilot reports of turbulence [click to play animation]

A toggle between 1-km resolution Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and 250-meter resolution true-color Red-Green-Blue RGB images at 2106 UTC on 12 January (below) showed that no high-altitude clouds were associated with the gravity wave features — thus, these aircraft encounters were examples of Clear Air Turbulence (CAT).

Terra MODIS Water Vapor (6.7 µm) and True-color RGB images [click to enlarge]

Terra MODIS Water Vapor (6.7 µm), Infrared Window (11.0 µm) and true-color RGB images [click to enlarge]

A color-enhanced version of the Aqua MODIS Water Vapor (6.7 µm) image at 0014 UTC on 13 January is shown below (courtesy of Jordan Gerth, CIMSS).

An AWIPS screen capture (below, courtesy of Robert Bohlin, NWS Honolulu and Jordan Gerth, CIMSS) displays a High Pass filter product along with the 3 individual Himawari-8 Water Vapor band images at 0120 UTC on 13 January.

Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

Himawari-8 High Pass filter product (6.9 µm, upper left), Upper-level Water Vapor (6.2 µm, upper right), Mid-level Water Vapor (6.9 µm, lower left) and Lower-level Water Vapor (7.3 µm, lower right) images [click to enlarge]

It bears mention that the rawinsonde data from Lihue, Hawai’i at 0000 UTC on 13 January (below) indicated significant wind shear (both speed and directional) within the 200-300 hPa layer (text listing) — the layer in which many of the turbulence reports were found.

Rawinsonde data from Lihue, Hawai'i at 00 UTC on 13 January [click to enlarge]

Rawinsonde data from Lihue, Hawai’i at 00 UTC on 13 January [click to enlarge]

The packet of gravity waves was directly over Lihue (red asterisk) at that time (below).

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

GOES-15 Water Vapor (6.5 µm) image at 0000 UTC on 13 January, with pilot reports of turbulence plotted. The red asterisk denotes the location of Lihue [click to enlarge]

Aircraft hole punch and cloud dissipation features over Illinois, Indiana and Ohio

December 21st, 2017 |

Terra MODIS true-color and false-color RGB images [click to enlarge]

Terra MODIS True-color and False-color RGB images [click to enlarge]

A toggle between 250-meter resolution Terra MODIS True-color and False-color Red-Green-Blue (RGB) images from the MODIS Today site (above) revealed numerous aircraft “hole punch” and dissipation trail or “distrail” features over Illinois, Indiana and Ohio on 21 December 2017.  These cloud features were caused by aircraft that were either ascending or descending through a layer of cloud composed of supercooled water droplets — cooling from wake turbulence (reference) and/or particles from the jet engine exhaust acting as ice condensation nuclei causes the small supercooled water droplets to turn into larger ice crystals (many of which then fall from the cloud layer, creating “fall streak holes“). The ice crystal clouds appear as darker shades of cyan on the false-color image.

GOES-16 "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images over Illinois/Indiana [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images over Illinois/Indiana [click to play MP4 animation]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images showed the hole punch and distrail features over Illinois/Indiana (above) and over Indiana/Ohio (below). The glaciated (ice crystal) hole punch and distrail clouds appeared dark gray on the Snow/Ice images (since ice is a strong absorber of radiation at the 1.61 µm wavelength).

GOES-16 "Red" Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images over Indiana/Ohio [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images over Indiana/Ohio [click to play MP4 animation]

RealEarth is used to display Suomi NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.9 µm), Near-Infrared (1.61 µm), True-color and False-color RGB images at 1841 UTC (below). O ne the Shortwave Infrared images, the hole punch and distrail features are colder (brighter white) than the surrounding supercooled water droplet cloud deck — since water droplet are effective absorbers of incoming solar radiation, such clouds appear warmer (darker gray) in 3.9 µm images.

Suomi NPP VIIRS

Suomi NPP VIIRS “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), Near-Infrared “Snow/Ice” (1.61 µm), True-color and False-color RGB images [click to enlarge]