Icebreaking in Whitefish Bay on Lake Superior

March 24th, 2018 |

GOES-16 ABI Band 2 “Red” (0.64 µm) Visible imagery, 2202 UTC on 22 and 23 March 2018 (Click to enlarge)

Dan Miller, the Science and Operations Officer (SOO) in Duluth sent the imagery above. Constant icebreaking has been ongoing on Whitefish Bay prior to the opening of the SOO Locks this weekend. A faint black line representing open water is apparent in the 22 March imagery, and it’s even more apparent in the 23 March imagery.

A toggle below, from 24 March 2018, shows the Band 2 “Red” (0.64 µm) Visible and the Band 5 “Snow/Ice” (1.61 µm) Near-Infrared images. The open water is apparent in both images — dark in contrast to the white snow and lake ice in the visible, darker than the adjacent ice in the 1.61 µm. Recall that horizontal resolution in Band 2 is 0.5 km at the sub-satellite point (nadir), and in Band 5 it is 1 km.

GOES-16 ABI Band 2 “Red” (0.64 µm) Visible and Band 5 “Snow/Ice” (1.61 µm) near-infrared imagery, 2202 UTC on 22 and 23 March 2018 (Click to enlarge)

Suomi NPP and NOAA-20 also viewed the icebroken path on 24 March, and favorable orbit geometry for NOAA-20 and Suomi NPP on 24 March (orbit paths from this site) meant 2 sequential passes from both satellites both viewed Whitefish Bay. The 4 images are shown in an animation below, with imagery from NOAA-20 first, then Suomi NPP (the labels all say Suomi NPP erroneously). Note that NOAA-20 data are provisional, non-operational, and undergoing testing still).

VIIRS Visible (0.64 µm, I1) Imagery from NOAA-20 (1708, 1846 UTC) and Suomi-NPP (1756, 1937 UTC) on 24 March 2018 (Click to enlarge)

The break in the ice was also visible in Day Night Band Imagery from VIIRS at 0722 UTC (from NOAA-20) on 24 March 2018.  It is also apparent in the shortwave Infrared imagery from both GOES-16 (very subtly) and from VIIRS (which offers better spatial resolution).

The icebreaking track was also apparent on 250-meter resolution Terra MODIS True-color and False-color Red-Green-Blue (RGB) images from the MODIS Today site (below). In the False-color image, ice and snow (in areas of sparse vegetation) show up as shades of cyan.

Terra MODIS True-color and False-color RGB images [click to enlarge]

Terra MODIS True-color and False-color RGB images [click to enlarge]

2 structural fires: Beaver Dam, Wisconsin and San Francisco, California

March 17th, 2018 |

GOES-16 Shortwave Infrared (3.9 µm, left) and

GOES-16 Shortwave Infrared (3.9 µm, left) and “Red” Visible (0.64 µm, right) images, with hourly surface reports plotted in yellow [click to play animation]

As documented by NWS Milwaukee/Sullivan, the controlled burn of an apartment building occurred during the late morning hours on 15 March 2018. A comparison of GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) and “Red” Visible (0.64 µm) images (above) displayed subtle “hot spot” signatures (darker red pixels, circled) as well as an occasional hint of a small smoke plume during the early phase of the fire. At the bottom of the images, note the appearance of a few larger and hotter fires (black pixels) in northern Illinois — likely agricultural fires to prepare fields for Spring planting.

2 days later, another structure fire occurred in the San Francisco area during the early evening hours of 17 March 2018:

Hot spot signatures were observed on the 0247 UTC and 0252 UTC (7:47 and 7:52 PM local time) Shortwave Infrared (3.9 µm) images, along with subtle lighter gray pixels on the Near-Infrared (2.24 µm) images (below).

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared (2.24 µm, right) images, with station identifiers plotted in cyan [click to play animation]

GOES-16 Shortwave Infrared (3.9 µm, left) and Near-Infrared (2.24 µm, right) images, with airport identifiers plotted in cyan [click to play animation]

A timely overpass of the NOAA-15 satellite scanned the fire at 02:43:50 UTC (7:43:50 PM local time), showing a well-defined hot spot (darker red enhancement) on the 1-km resolution Shortwave Infrared (3.7 µm) image (below).

NOAA-15 Shortwave Infrared (3.7 µm) image [click to enlarge]

NOAA-15 Shortwave Infrared (3.7 µm) image [click to enlarge]

Silt at the mouth of the Mississippi River

March 13th, 2018 |

CIMSS Natural True Color Imagery, 1515 – 1830 UTC on 13 March 2018 (Click to animate)

The CIMSS Natural True Color RGB, above, from 13 March 2018, shows the motion of alluvial sediment in the Gulf of Mexico in the outflow from various rivers. Muddy plumes from the Atchafalaya River in central Louisiana, the Mississippi River, and the Mobile River in Alabama are apparent. In particular, there is distinct northward motion during the 3 hours shown in this animation along the northern edge of the Mississippi River Delta.

A similar animation for 9 March 2018 is available here (courtesy Tim Schmit, NOAA and Mat Gunshor, CIMSS). Close monitoring of where the outflow from rivers is mixing with the Gulf of Mexico waters is a capability of GOES-16 Imagery when skies are clear.

Natural True Color is computed from GOES-16 Reflectance imagery using the “Blue” band (0.47 µm), the “Red” band (0.64 µm) and the “Veggie” band (0.86 µm), that latter being used to give information that in True Color Imagery from MODIS or Suomi NPP (for example) is supplied by a true “Green” band (0.55 µm).

The animation below shows True-Color imagery from MODIS for clear days between 30 January and 13 March 2018. The superior resolution of MODIS (on the Terra and Aqua spacecraft) and the presence of a 0.55 µm channel (in addition to 0.47 µm and 0.64 µm) allows for crisper imagery than from GOES-16; however, the ability to animate at small time scales over the Gulf of Mexico is a capability reserved for GOES-16 (and GOES-17, when it becomes operational). Terra and Aqua imagery are not useful if the overpass of the Polar Orbiters coincide with clouds; on days with variable cloud cover, GOES Imagery is more likely to provide useful information.

MODIS True Color Imagery for select dates between 30 January and 13 March 2018 (Click to animate)

Blowing Dust in Kansas

March 6th, 2018 |

GOES-16 Band 1 (“Blue Visible”) 0.47 µm Imagery, 1502 – 2132 UTC on 6 March 2018 along with surface METAR observation plots (Click to animate)

Strong northwesterly winds over the Great Plains to the west of a storm system over the mid-Mississippi River Valley have resulted in Red Flag Warnings over Oklahoma, and High Wind Warning and Dust Storm Warnings — including the closing of I-70 over Kansas. Visible Imagery in the “Blue Band”, above, shows little indication of the blowing dust (Click here for an animation without surface observations); dust is difficult to observe when sun angle are high. The higher-(spatial) resolution “Red Visible” animation, shown below, similarly struggles to identify with clarity where the dust is occurring.

The ‘Blue Band’ does detect plumes of smoke that develop over southern Kansas during this animation, plumes that originate over ‘hot spots’ in the 3.9 µm shortwave infrared imagery (not shown).

GOES-16 Band 2 (“Red Visible”) 0.64 µm Imagery, 1502 – 2132 UTC on 6 March 2018 along with surface METAR observation plots (Click to animate)

Infrared Imagery can be used to detect dust, both during the day and at night. This is because dust selectively absorbs energy. For example, energy at 10.3 µm that is emitted by the surface, and destined to be observed by the satellite, will be absorbed (and re-emitted from a higher, cooler level in the atmosphere) as it passes through the dust layer. Energy with a longer wavelength (12.3 µm), passes through dust mostly unaffected. Thus, a difference field between the two — the so-called Split Window Difference — will show negative values in regions where lofted dust is present in the atmosphere. An animation is shown below. As with imagery in this blog post, the colormap in the AWIPS display was changed to “Grid/Lowrange Enhanced”; dust regions are highlighted in yellow.  Dust is first detected in central Nebraska before it shows up in central and western Kansas. A closer view of the area where Interstate 70 was closed (between Goodland and Colby in northwestern Kansas) can be seen here.

GOES-16 Split Window Difference Field (10.3 µm – 12.3 µm) Imagery, 1502 – 2132 UTC on 6 March 2018 along with surface METAR observation plots (Click to animate)

The Cloud Phase Channel Difference field in AWIPS (Currently 10.3 µm – 8.5 µm, shortly to transition in AWIPS to 11.2 µm – 8.5 µm) can also detect dust (as was shown in this blog post), and that animation is shown below. Blowing Dust in this field is a bright green — and this Difference field (compared to the Split Window Difference) better identifies sources of plumes over western Kansas.

GOES-16 Cloud Phase Brightness Temperature Difference Field (10.3 µm – 8.5 µm) Imagery, 1502 – 2132 UTC on 6 March 2018 (Click to animate)

The Dust RGB, below, combines both the Split Window Differerence (the ‘Red Gun’) and the Cloud Phase Brightness Temperature Difference (the ‘Green Gun’), as well as the Clean Window (10.3 µm, ‘Blue Gun’, not shown). Dust in this RGB is typically bright pink, and its presence is notable over western Kansas.

GOES-16 Dust Red-Green-Blue (RGB) Composite Imagery, 1502 – 2132 UTC on 6 March 2018 (Click to animate)

Closer to sunset, at 2252 UTC on 6 March, the Dust Plume is readily apparent in the Band 1 and Band 2 imagery, shown below in a toggle with infrared channel differences and the Dust RGB.

GOES-16 Band 1 (“Blue Visible”) 0.47 µm Imagery, Band 2 (“Red Visible”) 0.64 µm Imagery, Split Window Difference (10.3 µm – 12.3 µm), Cloud Phase (10.3 µm – 8.5 µm) Brightness Temperature Difference and Dust RGB, all at 2252 UTC on 6 March 2018 (Click to enlarge)

Hat tip to Jeremy Martin, the SOO in the Goodland KS National Weather Service Office, for alerting us to this case!