Ship tracks in the East Pacific, and eddy circulations near the California coast

April 24th, 2019 |

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]

GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (above) showed a number of ship condensation trails (or “ship tracks”) over the East Pacific Ocean on 24 April 2019. Aerosols from the exhaust of ships cause a “cloud seeding effect”, which results in a higher concentration of smaller cloud droplets compared to the surrounding unperturbed clouds. These smaller cloud droplets are more effective reflectors of sunlight, leading to a warmer (darker red) 3.9 µm signature.

GOES-17 Visible images (below) revealed a few eddy circulations within the marine boundary layer stratocumulus off the coast of southern California, along with other interesting Channel Island cloud interactions — some of the eddy circulations exhibited a small cloud-free center. Surface winds were light and variable over the Channel Islands (surface analyses), with a thermal low situated well inland over the Desert Southwest (the national high temperature on 24 April was 106ºF at Death Valley, California).


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

Stereoscopic views in the Visible and Near-Infrared

February 20th, 2019 |

GOES-16 (left) and GOES-17 (right) Visible Imagery (0.64 µm) from 1422 UTC to 2257 UTC on 20 February 2019 (Click to play mp4 animation)

Stereoscopic views of Visible Imagery (from GOES-16 and GOES-17, above) allow for visualization of three dimensions, as shown in the mp4 animation above (click here for an animated gif of the same scene). The imagery captures multiple cloud layers over the western United States (a map will show up in the animation) as a potent system moved eastward.

GOES-R includes four channels in the near-visible including the Cirrus Channel at 1.37 µm. The Cirrus Channel is useful here because the water vapor absorption of 1.37 µm energy means that any near-surface signal is absorbed, so mostly high-level clouds are present (low clouds become visible in the cirrus channel in very dry atmospheres). The animation below (the animated gif is here) is a stereoscopic view created with 1.37 µm imagery and the structure of the high clouds is more apparent.

GOES-16 (left) and GOES-17 (right) Band 4 Near-Infrared Imagery (1.37 µm) from 1422 UTC to 2257 UTC on 20 February 2019 (Click to play mp4 animation)

Stereoscopic views of a small storm over the North Pacific Ocean

January 16th, 2019 |

Himawari-8 AHI and GOES-17 ABI Band 13 (10.41 µm and 10.35 µm, respectively) at 0400 UTC on 16 January 2019 (Click to enlarge)

GOES-17 Data in this post are preliminary and non-operational.

The toggle above shows clean window imagery from the Advanced Himawari Imager (Band 13, 10.41 µm) on Himawari-8 (data courtesy JMA) and clean window imagery from the Advanced Baseline Imager (ABI, Band 13, 10.3 µm) on GOES-17 (GOES-17 data are non-operational). There is a small developing storm between the Hawai’ian Islands and Alaska that is resolved by both satellites.  The storm is in between the two satellites and therefore ideal for stereoscopic views created from Visible 0.64 µm imagery (Band 3 for AHI, Band 2 for GOES-17).  That is shown below.  Thirty-minute timesteps are used because GOES-17 scans a full disk every 15 minutes (in Mode 3 that is currently operational; Mode 6, if used, scans a Full Disk every 10 minutes; and Mode 4, continuous Full Disk, the highest data rate for the GOES-R series, scans a Full Disk every 5 minutes). Himawari scans a Full Disk every 10 minutes. The three-dimensional representation facilitates the identification of warm conveyor belts associated with this developing storm. (This link shows the same animation but with the imagery flipped so it can be viewed in Google Daydream).

GOES-17 non-operational Visible (0.64 µm) imagery (left) and Himawari-8 Visible (0.64 µm) imagery (right), every half-hour from 2000 UTC on 15 January to 0400 UTC on 16 January (Click to animate)

Thanks to Mary Ellen Craddock, Northrop-Grumman, for the reminder that stereo imagery is possible with GOES-17 and Himawari.  (It should be even better with Himawari-8 and South Korea’s GEOKOMPSAT-2A!)

Stereoscopic Views of a storm on the West Coast of the United States

January 14th, 2019 |

GOES-16 (left) and GOES-17 (non-operational, right) Visible Imagery (0.64 µm) at 15-minute timesteps from 1500 to 2245 UTC on 14 January 2019 (Click to animate)

GOES-17 images shown here are preliminary and non-operational

When GOES-17 was in the test position at 89.5 degrees W Longitude, GOES-16 and GOES-17 in satellite projections could be used to create stereoscopic imagery (example 1; example 2; example 3); the human brain could correct for any projection differences to create 3-dimensional imagery (as explained here, for example). Because GOES-17 is now in its operational position at 137.2 degrees W Longitude, the perspective differences are too great. However, a simple remap of the imagery to the same native projection (Mercator in this case) allows for the construction of animations that show three dimensions, as shown above for the storm making landfall over southern California on 14 January 2019. The coastlines of Washington and Oregon are apparent in the imagery, as is Baja California. Multiple cloud layers become apparent in the imagery.