SAR views of ice over the Great Lakes

January 24th, 2022 |
SAR estimates of wind speed/ice on 20 January at 1124 UTC and 24 January at 1124 UTC (Click to enlarge)

In addition to its use in detecting wind fields over water (link 1, link 2), SAR data can also be used to detect ice. An example is shown above: similar domains on 20 and 24 January 2022 (from this website; this image on 20 January 2022 and this on one 24 January 2022) are toggled. There is a general increase in Lake Michigan shore ice off shore of southwestern Lower Michigan. Ice concentrations have also increased in western Lake Erie, Lake St Clair, Saginaw Bay in Lake Huron, and along the southwestern shore of Lake Huron. Strong winds were occurring over Lake Huron on the 20th as denoted by the yellow enhancement over the Lake.

SAR data are best used by viewing them each day. The imagery below shows views on different days in December 2021 and January 2022 over Lakes Erie (below) and Michigan (bottom). Note how ice cover can diminish (for example, over Saginaw Bay between 16 and 20 January) in response (typically) to strong winds that can move ice to the middle of the lake where it will melt.

A similar occurrence is shown in Lake Michigan (bottom): there is a filament of near-shore ice on 21 January that had detached from the shoreline under strong southwesterly flow. On 1200 UTC on 22 January, when strong southwesterlies continued, the ice is gone. It’s also not present on 1208 UTC on 23 January, when winds shift back to northerly. Detachment of ice from the shore can be a hazard to fishermen! The Lake Michigan cases also include very strong southwesterly winds (denoted by the yellow enhancements).

Views of Lakes Erie, St Clair, and Huron, dates as indicated. (Click to enlarge)
Views of Lake Michigan, dates as indicated.

Note that ice in a cloud can also cause strong returns that can be misinterpreted as strong winds. Ice will strongly reflect the microwave signals from the RCM (RADARSat Constellation Mission) satellites. That’s the case in this image over Lake Ontario, and this summertime convection view of Lake Superior. Use caution when you see very strong winds; ask: could this be ice in the cloud, or in the lake?

GOES-16 Visible imagery, below, from 21 January 2022 (more imagery from this date is available here), shows challenges in monitoring ice in single-banded imagery. The detached shoreline ice noted in the SAR imagery becomes more faint with time, suggesting melting. The ice over southern Lake Michigan is apparent. Clouds over western Lake Erie make it very hard to interpret ice coverage there.

GOES-16 Visible imagery, 1601-2156 UTC on 21 January 2022 (Click to enlarge)

Very cold air is forecast to overspread the Great Lakes this week. Check to see if ice coverage increases at this link!

Atmospheric River affecting Alaska

January 21st, 2022 |
MIMIC Total Precipitable Water estimates, 1800 UTC on 20 January – 1700 UTC on 21 January 2022 (Click to enlarge)

MIMIC Total Precipitable Water fields for the 24 hours ending 1700 UTC on 21 January, above, show abundant moisture flowing into southern Alaska. Hourly GOES-17 infrared imagery (Band 13 clean window infrared imagery at 10.3 µm), below, shows a large cyclonic circulation to the south and west of Alaska that is helping to draw moisture towards the state. Level 2 Total Precipitable Water (TPW) is overlain on the imagery and two things stand out: because it is a clear-sky only product, and because the north Pacific Ocean is very cloudy on the 21st, there is little TPW information. Also, GOES-R Total Precipitable Water is not completely Full Disk; TPW is computed to a Local Zenith Angle of 67o (ATBD) and you can see the cut-off for the product in northwestern Canada. Those two things argue for the utility of microwave detection of moisture over Alaska, as shown above.

GOES-17 Clean Window (10.3 µm, Band 13), hourly from 1200 – 1700 UTC on 21 January 2022, overlain with GOES-17 Level 2 Total Precipitable Water (Click to enlarge)

Much of Alaska Southeast from Yakutat to Wrangell is under a Flood Watch. (Image, taken from this site)

Using CSPP Software to view Level 2 GOES-R Products

January 20th, 2022 |
Level 2 Cloudtop Phase product, 1401 UTC on 20 January 2022 (Click to enlarge)

The Community Satellite Processing Package (CSPP) Algorithm Integration Team (AIT) has released a new version of processing software that creates (using updated Enterprise algorithms) Level 2 GOES-R products from radiance products. It also includes processing to provide Quick Look imagery for those products; that is, if you have the processed Level 2 product files, you can display them. One example is shown above, Cloud Top Phase from 1401 UTC on 20 January 2022.

The processing package is available here (a quick easy registration may be required): Look for “AIT Framework V2.0beta4 Software for Linux” and download the gzipped tar file. Note also that documentation is also available (link). Per that documentation, I downloaded the software into a directory that I changed directories to, and I put that directory at the front of my unix PATH, i.e., export PATH=”$PWD:$PATH”. Then I used the aitf-ql (“ql” for quick-look) command:

aitf-ql /path/to/directory/holding/L2products/ACTPC/*s20220201401*.nc --image_size 2560.0 1920. -o /home/scottl/

I have specified both the image size, and the output directory. If you have access to L2 imagery (in NOAA CLASS, for example), this is an easy way to view the imagery. Note that this software will also create QuickLooks from ABI radiance files, as the GOES-17 example below shows. You can create imagery for computed brightness temperature (Bands 7-16) or reflectance (Bands 1-6).

GOES-17 Band 13 (Clean Window, 10.3 µm) at 1401 UTC on 20 January 2022 (Click to enlarge)

Hunga Tonga erupts again

January 13th, 2022 |

GOES-17 imagery revealed another explosive eruption of Hunga Tonga-Hunga Ha?apai in the south Pacific Ocean between 1500 and 1530 UTC on 13 January 2022; an eruption in December 2021 is discussed here. The brightness temperatures in this volcanic plume cooled from -9.4o to -66.7o between 1520 and 1530 UTC. This 1308 UTC NUCAPS profile from 20.5oS / 175.5o W (the profile location is shown here) suggests the plume rose from 445 mb to 188 mb in those 10 minutes (or from 20 thousand to 39 thousand feet).

GOES-17 Clean Window*(see below) (Band 13, 10.3 µm) Infrared Imagery, 1500-1940 UTC on 13 January 2022 (Click to enlarge)

Imagery at 2100 UTC, below, shows the extent of the plume in the visible.

GOES-17 Visible (Band 2, 0.64 µm) Imagery, 2100 UTC on 13 January 2022 (Click to enlarge)

Computed Ash/Dust Cloud Heights, below, from 1510-1600 UTC on 13 January, available at the CIMSS Volcanic Cloud Monitoring Web Portal (link, search under the Wellington VAAC for Hunga Tonga), shows the rapid increase in height, to above 16 km, as well.

Retrieved Cloud Heights, 1510 – 1600 UTC on 13 January 2022 (Click to enlarge)

An animation of GOES-17 visible imagery, below, (courtesy Scott Bachmeier, CIMSS) shows the evolution of the pulsing eruption throughout the day on 13 January.

GOES-17 Visible (0.64 µm) imagery, 1700 UTC 13 January – 0010 UTC 14 January 2022 (Click to enlarge)

* You might notice that this AWIPS Full Disk imagery is at full resolution! In NWS Forecast Offices, full-disk imagery in AWIPS is degraded to 6-km resolution, meaning that interesting events outside of GOES-16 CONUS (or GOES-17 PACUS) that do not fall within a mesoscale sector can only be shown such that they’re zoomed out (as in this tweet from WFO Seattle about this event). The full-res imagery herein was created by inputting the full-resolution full-disk imagery (obtained at CIMSS from the GRB datastream) into AWIPS, replacing the subsected data.