Nearshore ice along the Bering Sea coast of Alaska

November 20th, 2021 |

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

GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) showed the motion of pack ice away from the southwest coast of Alaska on 20 November 2021. Strong offshore winds (gusting in excess of 30 knots at times) were causing the ice motion away from the coast into the Bering Sea — although some landfast ice was also evident.

During the subsequent nighttime hours, a sequence of 3 Suomi-NPP VIIRS Day/Night Band (0.7 µm) images (below) allowed sea ice motion to be monitored during the long night, when GOES-17 Visible imagery was not available — providing that there is ample illumination from the Moon, which there was in this case (since it was in the Waning Gibbous phase, at 99% of Full).

Suomi-NPP VIIRS Day/Night Band (0.7 µm) images [click to enlarge]

This ice growth was being promoted by colder than normal Sea Surface Temperatures in that portion of the Bering Sea — along with the offshore flow of very cold air that had been in place across much of Alaska during the previous days. In fact, Interior Alaska recorded its first -40ºF/-40ºC temperatures of the winter season on this day.

Total Lunar Eclipse in the Day Night Band

November 19th, 2021 |
NOAA-20 Day Night Band, 19 November 2021 (Click to enlarge)

NOAA-20 Day Night Band imagery from early morning (from the VIIRS Today website at CIMSS) on 19 November 2021 shows the impact of the total lunar eclipse on Day Night Band imagery. A lunar eclipse will always occur during a Full Moon; ample lunar illumination off the east coast accompanied that descending NOAA-20 pass between about 0635 and 0640 UTC (as shown in this orbital path image from this website) — just as the lunar eclipse was starting. By the time NOAA-20 overflew the central US (0815 to 0825 UTC), near totality was occurring. The overflight on the west coast (0955 to 1005 UTC) occurred as the eclipse was starting to wane, so a bit more lunar illumination was available.

A similar Day Night Band image from Suomi-NPP (also from the VIIRS Today website) is below, and it shows similar differences in swath illumination. The west coast overpass by Suomi-NPP occurred around 1050 UTC; by then the eclipse had ended. Suomi NPP Day Night Band imagery is also available at the NASA Worldview site.

Suomi-NPP Day Night Band imagery from early morning 19 November 2021 (Click to enlarge)

Actinoform cloud in the East Pacific

November 16th, 2021 |

GOES-17 True Color RGB images [click to play animated GIF | MP4]

GOES-17 (GOES-West) True Color RGB images created using Geo2Grid (above) showed a cyclonically-rotating actinoform cloud feature that was moving west-southwestward across the East Pacific Ocean (about midway between Hawai’i and California) on 16 November 2021.

In GOES-17 Day Cloud Phase Distinction RGB images (below), the increasing shades of green exhibited by the curved bands of shallow convection suggested that those features were likely mixed-phase clouds — composed of a combination of liquid/supercooled water droplets and ice particles. 

GOES-17 Day Cloud Phase Distinction RGB images [click to play animated GIF | MP4]

Similarly, in a toggle between NOAA-20 VIIRS True Color and False Color RGB images viewed using RealEarth (below), darker shades of cyan suggested the presence of mixed-phase banded cloud elements within the core of the actinoform feature.

NOAA-20 VIIRS True Color and False Color images at 2218 UTC [click to enlarge]

Other examples of actinoform clouds can be examined by scrolling through this link.

ACSPO SSTs on 9 November

November 9th, 2021 |
ACSPO SSTs over the northern Gulf of Mexico derived from NOAA-20 VIIRS data, 0800 UTC 09 Nov 2021 (Click to enlarge)

The Advanced Clear Sky Processor for Ocean algorithm is part of the Community Software Processing Package (CSPP), CIMSS-maintained software that can be applied to Direct Broadcast data, such as those data from NOAA-20 and Suomi-NPP (and other satellites) downloaded at two antennae at CIMSS. CSPP will create AWIPS-ready tiles so that SST information can be viewed within AWIPS (as shown above and below) and the AWIPS-ready tiles are available via LDM feed from CIMSS (images — rather large — are also routinely available online: here for the image above, here for the Suomi-NPP-derived image below).

Both SST images show remarkable gradients in sea surface temperature: upper 60s (cyan) to low 80s (yellow) just south of Louisiana in less than 20 miles (above); low 60s (blue) to 80 (chartreuse) to the east of the Outer Banks, also in less than 20 miles (below). The warmest water in the Gulf of Mexico is around 83º F, and shelf water is in the mid-60s. Warmest Gulf Stream waters are around 81º F. Magenta values correspond to temperatures in the 50s.

ACSPO SSTs over the northern Gulf of Mexico derived from Suomi-NPP VIIRS data, 0710 UTC 09 Nov 2021 (Click to enlarge)