Aircraft dissipation trails over southern Wisconsin and northern Illinois

October 6th, 2019 |

GOES-16

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

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images (above) revealed a series of aircraft “dissipation trails” drifting northeastward across southern Wisconsin and northern Illinois on 06 October 2019. 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 jet engine exhaust acted as ice condensation nuclei to cause the small supercooled water droplets to turn into larger ice crystals (many of which then often fall from the cloud layer, creating “fall streak holes“).

A comparison of Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below) helped to confirm the presence of ice crystals within the aircraft dissipation trails: a darker appearance in the 1.61 µm image (since ice is a strong absorber of radiation at that wavelength), and a colder (brighter white) signature in the 3.74 µm image. In the enhancement applied to the 3.74 µm and 11.45 µm images, colors are applied to infrared brightness temperatures of -30ºC and colder — and the shades of yellow represent cloud-top brightness temperatures in the -30 to -39ºC range.

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Several of the “fall streak” clouds were seen in time-lapse videos of west- and east-facing AOSS rooftop cameras (below).

Time lapse of west-facing AOSS rooftop camera images [click to play YouTube video]

Time lapse of west-facing AOSS rooftop camera images (courtesy of Pete Pokrandt, AOSS) [click to play YouTube video]

Time lapse of east-facing AOSS rooftop camera images [click to play YouTube video]

Time lapse of east-facing AOSS rooftop camera images (courtesy of Pete Pokrandt, AOSS) [click to play YouTube video]

Orphan anvil over the Atlantic Ocean

October 3rd, 2019 |


The interesting east-to-west moving cold (brighter white) infrared signature mentioned above was determined by another Twitter user to be the convective debris of an isolated orphan anvil that developed over the Atlantic Ocean east of Florida (and north of the Bahamas) toward sunset on 03 October 2019. A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images is shown below.

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.35 µm, bottom) images [click to play animation | MP4]

The convective tower producing the orphan anvil was still dimly illuminated by the setting sun at 2301 UTC (below), when cloud-top infrared brightness temperatures first became colder than -25ºC (darker blue pixel).

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 2301 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images at 2301 UTC [click to enlarge]

The coldest infrared brightness temperature exhibited by the orphan anvil was -29ºC at 2316 UTC — which closely corresponded to the 313 hPa pressure level in rawinsonde data from Cocoa Beach, Florida at 00 UTC (below). Wind speeds at that altitude were 42 knots; the 300 hPa analysis at 00 UTC showed a 50-knot wind speed maxima approaching the orphan anvil region from the northeast.

Plot of 00 UTC rawinsonde data from Cocoa Beach, Florida [click to enlarge]

Plot of 00 UTC rawinsonde data from Cocoa Beach, Florida [click to enlarge]

The orphan anvil signature was only apparent in Infrared imagery until about 2336 UTC — but since the surrounding atmosphere was fairly dry, the westward transport of moist convective debris could be tracked for another 3 hours using GOES-16 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor imagery (below).

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

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

Orphan anvils often appear shortly before the onset of significant convective development — signalling that convective inhibition is weakening — as previously  discussed here, here, here, here and here.

Decker Fire in Colorado

October 2nd, 2019 |

GOES-16 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed the afternoon/evening smoke plume and the persistent thermal anomaly (cluster of hot pixels) associated with the Decker Fire burning just southwest of Salida, Colorado on 02 October 2019.

A closer view of the fire was provided by a 4-panel comparison of GOES-16 Shortwave Infrared, Fire Power, Fire Temperature and Fire Area products (below). More information on these GOES Fire Detection and Characterization Algorithm (FDCA) products can be found here. Windy conditions on this day —  with sustained speeds of 20-30 mph and gusts to 46 mph — promoted rapid fire growth during the afternoon hours.

GOES-16 Shortwave Infrared (3.9 µm), Fire Power, Fire Temperature and Fire Area [click to play animation | MP4]

GOES-16 Shortwave Infrared (3.9 µm), Fire Power, Fire Temperature and Fire Area [click to play animation | MP4]

A sequence of VIIRS True Color Red-Green-Blue (RGB) and Infrared Window images from Suomi NPP and NOAA-20 as viewed using RealEarth (below) showed the smoke plume and the fire’s thermal anomaly (cluster of dark black pixels).

VIIRS True Color RGB and Infrared Window (11.45 um) images from Suomi NPP and NOAA-20 [click to enlarge]

VIIRS True Color RGB and Infrared Window (11.45 µm) images from Suomi NPP and NOAA-20 [click to enlarge]

A time series of surface observation data from the Salida Airport (identifier KANK, located just northwest of the fire) revealed southwesterly winds gusting to 20-29 knots as the dew point dropped to the -1 to -11ºF range — creating Relative Humidity values as low as 4% — during the afternoon hours (below).

Time series of surface observation data from Salida, Colorado [click to enlarge]

Time series of surface observation data from Salida, Colorado [click to enlarge]

===== 03 October Update =====

GOES-17 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

The Decker Fire continued to burn on 03 October, as seen using 1-minute Mesoscale Domain Sector GOES-17 “Red” Visible and Shortwave Infrared images (above). Although surface winds were still gusting as high as 30 knots at Salida, additional boundary layer moisture (dew points were in the 20s F) helped to slow the rate of fire growth compared to the previous day. The southeasterly winds transported some low-altitude smoke toward Salida, reducing the visibility to 5-7 miles at times (below).

Time series of surface observation data from Salida, Colorado [click to enlarge]

Time series of surface observation data from Salida, Colorado [click to enlarge]

A comparison of GOES-16 (GOES-East) and GOES-17 (GOES-West) Shortwave Infrared images with topography (below) demonstrated the effect of large satellite viewing angles on apparent fire location in areas of rugged terrain — note the offset in the position of the Decker Fire thermal anomaly between the 2 satellites (the viewing angle of the fire from each satellite is about 53 degrees).

GOES-16 and GOES-17 Shortwave Infrared (3.9 µm) images, with topography [click to play animation | MP4]

GOES-16 and GOES-17 Shortwave Infrared (3.9 µm) images, with topography (highways are plotted in cyan) [click to play animation | MP4]

GOES-17 ABI Temperature Data Quality Flags (TDQF) thresholds updated

October 2nd, 2019 |

Top: Thumbnails of GOES-17 and GOES-16 ABI Band 12 (9.6 µm) on August 1, 2019. Bottom: Time series of GOES-17 minus GOES-16 brightness temperature for a region located between the two satellites. Also plotted is the GOES-17 Focal Plane Temperature. The reduced duration of the GOES-17 data to be flagged is highlighted. [click to enlarge]

As of 19:45 UTC on August 8, 2019, the new Look-Up-Table (LUT) went into operations for use in the GOES-17 ABI Temperature Data Quality Flags (TDQF). These hotter thresholds are possible due to the recent implementation of the Predictive Calibration algorithm.  Note that the image also includes the percent good (and conditionally usable) values (flagged 0 or 1) for both GOES-16 and GOES-17 ABI. Recall there are 5 Data Quality Flags for ABI data:

  • DQF:percent_good_pixel_qf = 1.f ;
  • DQF:percent_conditionally_usable_pixel_qf = 0.f ;
  • DQF:percent_out_of_range_pixel_qf = 0.f ;
  • DQF:percent_no_value_pixel_qf = 0.f ;
  • DQF:percent_focal_plane_temperature_threshold_exceeded_qf = 0.f

The last one, DQF:percent_focal_plane_temperature_threshold_exceeded_qf, reports what percentage of the images pixels are warmer than the threshold value. Note that the thresholds on both the increasing and decreasing temperatures are also reported in the meta-data.

Near realtime brightness temperature comparisons between GOES-16 and GOES-17, as well as historical comparisons for a region centered on the equator and half way between the two satellites.

From the NOAA Notification:

Product(s) or Data Impacted: GOES-17 ABI auxiliary field change

Date/Time of Initial Impact: August 8, 2019 1945 UTC

Details/Specifics of Change:

The GOES-17 ABI Temperature Data Quality Flags (TDQF) thresholds for the thermal bands have been updated to the values in the table below.  This update will make utilizing the TDQF more effective for flagging saturated data caused by the GOES-17 ABI cooling system anomaly. There will be no impacts to distribution caused by this update.

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]

Update (10/02/2019)

On October 2, 2019, at 17:04 UTC, updates for a number of the ABI GOES-17 DQF thresholds were implemented in the operational system. NOAA Notification: https://www.ospo.noaa.gov/data/messages/2019/MSG2751954.html

Table of updated Temperature Quality Data Flag thresholds

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]. The bold numbers are those values that were updated on October 2nd.