GOES-16 visible images of a squall line moving across Virginia

March 1st, 2017 |

GOES-16 Visible (0.64 µm) images [click to play MP4 animation]

GOES-16 Visible (0.64 µm) images [click to play MP4 animation]

Note: GOES-16 data shown on this page are preliminary, non-operational data and are undergoing on-orbit testing.

A strong pre-cold-frontal squall line produced widespread severe weather (primarily damaging winds: SPC storm reports) across the eastern US on 01 March 2017. A GOES-16 Mesoscale Sector provided imagery at 60-second intervals during a portion of the day — and ABI 0.5-km resolution Visible (0.64 µm) images (above; also available as a 79 Mbyte animated GIF) showed the well-defined squall line cloud band as it moved across Virginia.  Behind the squall line, note the presence of semi-stationary mountain wave rotor clouds downwind of the Appalachian Mountains. A larger-scale animation is available here.

The GOES-16 ABI Veggie channel at 0.86 µm

March 1st, 2017 |

GOES-16 Red Visible (0.64 µm) and Veggie (0.86 µm) bands over Florida, 21:11 UTC on 01 March 2017 (Click to enlarge)

Note: GOES-16 data shown on this page are preliminary, non-operational data and are undergoing on-orbit testing.

The ABI Band at 0.86 µm (Fact Sheet) allows superior land/sea discrimination. This occurs because land is more reflective to radiation at 0.86 µm than to radiation at 0.64 µm. The toggle above shows Florida in the standard visible (0.64 µm) and at 0.86 µm. Coastal boundaries and islands (such as the Keys and the Bahamas) are far more distinct in the near-infrared so-called ‘veggie’ channel at 0.86 µm. Inland lakes are also better defined with the 0.86 µm channel. Because the land is so bright, land/cloud contrast is reduced in the 0.86 µm imagery, so clouds over land appear more distinct in the 0.64 µm imagery.

The toggle below shows a similar scene over the Tidewater region of southeast Virginia and points to the south.  Again, inland lakes and rivers and the coastal boundary is more apparent in the 0.86 µm imagery than in the 0.64 µm imagery.

GOES-16 Red Visible (0.64 µm) and Veggie (0.86 µm) bands over the mid-Atlantic States, 20:01 UTC on 01 March 2017 (Click to enlarge)

Use the 0.86 µm band when land/water distinction is important!

Because ABI does not have a spectral band in the ‘green’ part of the electromagnetic spectrum (Band 1 at 0.47 µm is in the blue, Band 2 at 0.64 µm is in the red), information from the 0.86 µm band is used in construction of simulated ‘true color’ imagery (as discussed here).

In addition, the 0.86 µm channel provides useful burn scar information in ‘False Color’ imagery (that combines 2.2 µm, 0.86 µm and 0.64 µm imagery) because burn scars appear dark in 0.86 µm imagery.

The GOES-16 ABI Cirrus Channel

March 1st, 2017 |

GOES-16 Band 4 (1.37 µm) Imagery from 1236-1406 UTC on 1 March 2017 [click to animate]

Note: GOES-16 data shown on this page are preliminary, non-operational data and are undergoing on-orbit testing.

The Advanced Baseline Imager (ABI) on the GOES-R Series of satellites (including GOES-16) includes a band that detects radiation at 1.37 µm (Fact Sheet Link). This 2-km resolution band is unique to GOES-16 among geostationary satellites. The animation above shows a subset of Full-Disk imagery at 15-minute intervals (GOES-16 produces a full disk every 15 minutes, in contrast to GOES-13/GOES-15’s 3-hour Full Disk cadence). The Cirrus channel highlights only the highest clouds associated with the wave cyclone over the central part of the United States. Clouds are not initially obvious early in the animation over the northern Plains: this band detects reflected solar radiation and therefore gives little information at night.

The Band 4 Cirrus Channel to the Band 2 visible (0.64 µm) toggle, below, enables an observer to distinguish between low/middle cloud levels and high clouds quite easily. Water vapor in the atmosphere above the low clouds in Illinois and Missouri (and elsewhere) is absorbing any reflected radiation at 1.37 µm there. If precipitation is being produced by a seeder/feeder mechanism, the presence of high clouds as detected in the Cirrus channel could help refine analyses of falling precipitation.

GOES-16 Band 2 (0.64 µm) and Band 4 (1.37 µm) Imagery from 1447 UTC on 1 March 2017 [click to enlarge]

A similar band (with 1-km resolution) is present on Terra and Aqua as part of MODIS and there are numerous CIMSS Satellite Blog Posts that incorporate snapshots from this MODIS cirrus-detection channel:  Detecting thin cirrus and contrails over Arkansas and Tennessee; Thin Cirrus over the Midwest; Cirrus associated with Haloes; The Cirrus Canopy of Hurricane Matthew; Transverse Banding, for example.

Although this band on ABI is called the Cirrus Channel, it has other uses.  It can be used to detect any highly reflective aerosol, such as volcanic ash or blowing dust, as long as the features are not obscured by water vapor.  It can also view the surface if the atmosphere is sufficiently dry:  Research suggests that a total precipitable water of about 12 mm is sufficient to attenuate the radiation.