Transitory Solar Reflectance in GOES-R Series Imagery

March 5th, 2018 |

GOES-16 Visible (0.64 µm) animation, 1637-1732 UTC on 5 March 2018 (Click to enlarge)

Animations of GOES-16 Visible, near-Infrared and shortwave Infrared over North America shortly before the Vernal Equinox, and shortly after the Autumnal Equinox, (that is, when the Sun is overhead in the Southern Hemisphere) show bright spots that propagate quickly from west to east (these features were first noted by Frank Alsheimer of the National Weather Service). The animation above shows the visible imagery (0.64 µm) over the Continental United States on 5 March 2018 (Click here for a slower animation speed). Brightening over regions between 30 and 40 N between 1637 UTC and 1732 UTC is apparent. The animation below of the shortwave infrared (3.9 µm) shows slight warming (Click here for a slower animation), as might be expected with reflected solar energy. The brightening is also apparent in the Band 4 “Cirrus”  (1.37 µm) — in fact, a closer look at southern Colorado reveals the bright signature of sunlight reflecting off solar panels at the Alamosa Solar Generating Facility (Google maps).

GOES-16 Shortwave Infrared (3.9 µm) animation, 1637-1732 UTC on 5 March 2018 (Click to enlarge)

The increased reflectance can cause the ABI Clear Sky Mask to mis-characterize clear regions as cloudy (See the animation below; click here for a slower animation). Thus, Cloud properties (Cloud-top Height, Temperature, Pressure, etc.) can be identified in clear regions.

GOES-16 Clear Sky Mask (White: Clouds ; Black : No Clouds) from 1637 UTC – 1732 UTC on 5 March 2018 (Click to enlarge)

The bright spots in the visible, and warms spots in the shortwave infrared, occur when the Earth’s surface, the GOES Satellite and the Sun are aligned on one line. If you were within the bright spot with a powerful telescope trained on the Sun, you would see the GOES Satellite transecting the solar disk. The location of these bright spots changes with season: they appear in the Northern Hemisphere shortly before the (Northern Hemisphere) vernal equinox and shortly after the (Northern Hemisphere) autumnal equinox. Similarly, they appear in the Southern Hemisphere shortly before the (Southern Hemisphere) vernal equinox and shortly after the (Southern Hemisphere) autumnal equinox. On the Equinox, the bright spots are centered on the Equator.

This animation (courtesy Daniel Lindsey, NOAA/CIRA and Steve Miller, CIRA) shows where the reflection disk moves during the days around the Northern Hemisphere Autumnal Equinox; a similar animation for the Northern Hemisphere vernal equinox would show a disk starting at the North Pole and moving southward with time.

The animation below (from this link that is used for calibration exercises), shows the difference in reflectance (Bands 1-6) or Brightness Temperature (Bands 7-16) between 1657 and 1652 UTC on 3 and 5 March 2018. Two things are apparent: The centroid of the largest difference in solar reflectance has moved southward in those two days, as expected; the effect of this solar backscatter is most obvious in the visible, near-infrared and shortwave infrared channels (that is, bands 1-7 on the ABI).  The effect is most pronounced in clear skies.

Time Difference in each of the 16 ABI Channels (1657 – 1652 UTC) on 3 and on 5 March 2018 (Click to enlarge)

This reflectance feature is also detectable in legacy GOES Imagery. However, the great improvements in detection and calibration in the GOES-R Series ABI (and AHI on Himawari-8 and Himawari-9) and the better temporal resolution with the GOES-R Series allows for better visualization of the effect.

The feature also shows up in “True Color” Imagery, shown below (from this site). Geocolor imagery (shown here), from CIRA, also shows the brightening.

CIMSS Natural True Color Animation ending 1757 UTC on 5 March 2018 (Click to enlarge)

Thanks to Daniel Lindsey and Tim Schmit, NOAA/ASPB, Steve Miller, CIRA and Mat Gunshor, CIMSS, for contributions to this blog post.

Temporary transition from Himawari-8 to Himawari-9

February 13th, 2018 |

Himawari-8 and Himawari-9

Himawari-8 and Himawari-9 “Clean” Infrared Window (10.4 µm) images [click to play Animated GIF | MP4 also available]

Himawari-9 temporarily took over for Himawari-8 beginning at 0250 UTC on 13 February 2018, as Himawari-8 underwent a 2-day scheduled maintenance. “Clean” Infrared Window (10.3 µm) images of Category 4 Cyclone Gita in the South Pacific Ocean during the satellite transition is shown above.

Himawari-9 was launched on 02 November 2016.

First Imagery from Himawari-9

January 24th, 2017 |

Visible Band 3 (0.64 µm) Full Disk Imagery from Himawari-9 at 0240 UTC on 24 January 2017 [click to enlarge]

The Japanese Meteorological Agency (JMA) has released the first imagery from the Advanced Himawari Imager (AHI) on Himawari-9. The image above, from 0240 UTC on 24 January 2017, is from Band 3 (the “Red” Band) that detects reflected solar radiation near 0.64 µm in the visible part of the electromagnetic spectrum. This band has the highest spatial resolution of the 16 AHI channels: 0.5 km at the sub-satellite point. (A similar image from Himawari-8 at 0250 UTC on 24 January 2017 is here; Himawari-8 does not produce imagery at 0240 UTC or 1440 UTC; satellite housekeeping occurs at those times).

Additional Himawari-9 band imagery from 0240 UTC on 24 January 2017 is available here. All imagery courtesy of JMA.

Himawari-9 Launches

November 2nd, 2016 |
Himawari-8 imagery of all 16 AHI Channels, as indicated, bracketing the launch time of Himawari-9 (Click to enlarge)

Himawari-8 imagery of all 16 AHI Bands, as indicated, bracketing the launch time of Himawari-9 (Click to enlarge)

Japan successfully launched the Himawari-9 satellite from the Tanegashima Space Center (near the southern tip of Tanegashima in the Osumi Islands south of Kyushu), a back-up to Himawari-8, shortly after 3:20 PM local time (0620 UTC) on 2 November 2016 (News Link 1, 2, 3, 4). Images showing all 16 Himawari-8 AHI spectral bands bracketing the 0620 UTC launch time are shown above; signatures of the warm thermal anomaly (from the burning of the solid rocket boosters) as well as the moisture of the rocket condensation cloud plume were evident in the Shortwave Infrared (3.9 µm) and Water Vapor (6.2 µm, 6.9 µm and 7.3 µm) bands, but a signal was also detectable in the Infrared 8.6 µm, 12.2 µm and 13.3 µm bands. The Himawari-8/9 AHI instrument is nearly identical to the ABI instrument on GOES-R — so similar imagery will be routinely available once GOES-R becomes operational in 2017.

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Himawari-8 Band 4 (0.86 µm) Visible Imagery for times bracketing the launch of Himawari-9 on 2 November 2016 (Click to enlarge)

The animation above shows the rocket plume in the Band 4 (0.86 µm) imagery (Band 4, the so-called “Veggie Band”, better discriminates between land and water so that the island of Tanegashima is more distinct) from Himawari-8, in the image at 0622 UTC. (Annotated 0622 UTC Image is here). The plume appears north of the launch site (which is located at the southern tip of the island).

A true-color image, below, that includes the three visible channels from Himawari-8 (Band 1 at 0.47 µm, Band 2 at 0.51 µm and Band 3 at 0.64 µm, with the Band 2 “Green Band” boosted by information in the Veggie Band at 0.86 µm) shows a plume, perhaps, emerging from the cloud field at the southern tip of the island.

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True-color imagery from Himawari-8 at 0620 UTC on 2 November, 2016 (Click to enlarge)

Another view of the 3.9 µm Shortwave Infrared imagery, below, shows a short-lived hot-spot near where the Band 4 imagery shows the plume. Note: due to parallax, the location of the high-altitude hot spot appears farther north than its actual location.

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Himawari-8 Band 7 (3.9 µm) Shortwave Infrared Imagery for times bracketing the launch of Himawari-9 on 2 November 2016 (Click to enlarge)

Visible Imagery for the same three times, below, suggests a plume may be present (toggle between Visible and Shortwave Infrared images).

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Himawari-8 Band 3 (0.64 µm) Imagery for times bracketing the launch of Himawari-9 on 2 November 2016 (Click to enlarge)

As mentioned above, signatures of the warm thermal anomaly and the moisture of the rocket condensation cloud plume were also evident on the three Himawari-8 Water Vapor bands, shown below — strong westerly winds aloft (satellite | model) quickly transported the high-altitude portion of the rocket plume eastward.

Himawari-8 6.2 µm (top), 6.9 µm (middle) and 7.3 µm (bottom) Water Vapor images (Click to enlarge)

Himawari-8 6.2 µm (top), 6.9 µm (middle) and 7.3 µm (bottom) Water Vapor images [click to enlarge]

A video of the launch is here, with the launch itself at 44 minutes.