Bore feature in SAR winds over Lake Michigan

June 6th, 2022 |
RCM2 Wind Speeds, 1152 UTC on 6 June 2022 (Click to enlarge)

Color-enhanced wind speeds observed from Synthetic Aperture Radar (SAR) data on the second RADARSAT Constellation Mission satellite (RCM-2), shown above in AWIPS (Click here for a similar image online at this website) show parallel lines of enhanced wind speeds, a wind structure suggestive of a bore (click here for many previous blog posts on this phenomena), over southern Lake Michigan. Peak wind values (in yellow over the water) are near 14 m/s, with minima in between the lines showing winds around 5-6 m/s. (Note that SAR wind information over land is invalid). When this kind of event happens under mostly clear skies, parallel lines of clouds (that are perpendicular to the observed wind) develop. In this case, widespread clouds prevented satellite detection of cloud bands. The toggles below show Visible (Band 2, 0.64 µm) and Infrared (Band 13, 10.3 µm) at the time of the SAR observations.

GOES-16 Band 2 visible (0.64 µm) and RCM Winds, 1152 UTC on 6 June 2022 (Click to enlarge)
GOES-16 Band 13 infrared (10.3 µm) and RCM Winds, 1152 UTC on 6 June 2022 (Click to enlarge)

Modest convection (cloud tops are only around -48oC) over central Lake Michigan likely generated the bore. For a bore to propagate, a strong inversion is required. Soundings at Green Bay WI and Gaylord MI likely are unrepresentative of the environment over southern Lake Michigan. The sounding at White Lake Michigan — near Detroit — (from this website) does show a surface inversion, as does the sounding at Davenport IA. The cool late-Spring waters of Lake Michigan will serve to anchor a similar low-level inversion over the Lake; bore features travel along those inversions.

SAR Wind data off the Pacific Coast

May 19th, 2022 |
SAR Winds over the Pacific Ocean, 0237 UTC on 19 May 2022, and GOES-17 Visible Imagery, 0240 UTC (Click to enlarge)

Synthetic Aperture Radar imagery can give very high-resolution observations of winds in regions where wind observations are otherwise sparse (or non-existent). The image above and below show data from an ascending pass of Canada’s RADARSAT Constellation Mission 2 (RCM2) satellite. These data are available online (click here for the image above, and here for the image below), but netcdf files can also be inserted into AWIPS for a direct comparison to other satellite imagery. The image above shows the increase in wind speeds (about 11 m/s) associated with a broken line of cumulus clouds, with stronger winds over the northwest part of the SAR domain. The later image, below, farther north, shows generally stronger winds, and it also shows local wind maxima out in front of cloud formations (in the southeast corner of the SAR domain).

SAR Winds over the Pacific Ocean, 0238 UTC on 19 May 2022, and GOES-17 Visible Imagery, 0240 UTC (Click to enlarge)

SAR data over Hawai’i

May 5th, 2022 |
Sentinel-1 SAR data around 0430 UTC overlain on top of GOES-17 ABI Shortwave IR (3.9 µm) at 0430 UTC on 5 May 2022 (Click to enlarge)

This NOAA/OSPO website shows regions where SAR data are available each day. SAR data can also be imported into AWIPS, as shown in the animation above, which animation has the SAR data overlain on top of GOES-17 Band 7 (Shortwave IR, 3.9 µm) data. Note that SAR winds are not valid over the land — the stronger returns over the islands are instead telling you something about the surface. (Compare this image to a Landsat image — there’s a good correlation!)

A zoomed-in version of the imagery over the ?Alenuih?h? Channel between the Big Island of Hawai’i and Maui is shown below as a toggle between the 3.9 µm and the winds. The significant funneling between the two islands is readily apparent, with winds increasing from about 15 knots northeast of the Big Island to closer to 25 knots within the channel.

GOES-17 Band 7 shortwave infrared (3.9 µm) imagery with SAR winds overlain, 0430/0431 UTC on 5 May 2022 (click to enlarge)

A zoom-in over Maui and Molokai, below, details winds around those islands as well, with strong winds between Molokai and Lanai, and an apparent col to the lee of Maui.

GOES-17 Band 7 shortwave infrared (3.9 µm) imagery with SAR winds overlain, 0430/0431 UTC on 5 May 2022 (click to enlarge)

Farther north, over the open Pacific to the north of the Hawai’ian Islands, SAR data shows enhancements in wind underneath structures that are apparent in the Band 7 imagery!

GOES-17 Band 7 shortwave infrared (3.9 µm) imagery with SAR winds overlain, 0430/0432 UTC on 5 May 2022 (click to enlarge)

SAR Observations of Red River of the North Flooding

May 5th, 2022 |
RCM3 NRCS footprints from south to north, 00:13:28 through 00:13:55 on 5 May 2022 (click to enlarge)

Data on this website (if you click through to 5 May 2022) shows regions where the RCM constellation has produced data. There are very small footprint scenes (shown below) over the Red River of the North, where flooding is ongoing (blog post 1; blog post 2). The Normalized Radar Cross Section (NRCS) imagery within those small footprints is shown sequentially, from south to north, above. The NRCS imagery gives very high-resolution snapshots of flooded regions. This NRCS image from 00:13:39 has the largest extent of flooding within it.

A single image that shows the 6 scenes, aligned from south to north, is available here. (Warning: It’s large)

SAR Wind Imagery site, zoomed in over the North Dakota/Minnesota border (Click to enlarge)

Data were also available from earlier in May. Compare this RCM2 NRCS image from 00:29:27 on 3 May to this RCM3 NRCS image from 00:05:41 on 4 May to this RCM3 NRCS from 00:13:39 on May 5th. Flooding has expanded slightly over the two days.