Lava flow from Kilauea in Hawai’i

June 6th, 2018 |

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Shortwave Infrared (3.9 µm) images, with hourly plots of surface reports [click to play MP4 animation]

The Kilauea volcano on the Big Island of Hawai’i continued to be active into early June 2018 — and GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) imagery (above) showed the thermal anomaly or “hot spot” (black to yellow to red enhancement) associated with lava flows from active fissures in the East Rift Zone on 06 June.

GOES-15 Visible (0.63 µm) images (below) showed clouds of steam from the East Rift Zone drifting to the south-southwest; a hazy plume of volcanic fog or “vog” was also evident, which was being transported farther to the southwest by the northeasterly trade wind flow.

GOES-15 Visible (0.63 µm) images, with hourly plots of surface reports [click to play MP4 animation]

GOES-15 Visible (0.63 µm) images, with hourly plots of surface reports [click to play MP4 animation]

A Suomi NPP VIIRS Visible (0.64 µm) image at 2307 UTC (below) showed clear skies over Kapoho on the eastern tip of the Big Island, with steam plumes from the active East Rift Zone fissures flowing southwestward.

Suomi NPP VIIRS Visible (0.64 µm) image [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) image [click to enlarge]

The corresponding VIIRS Shortwave Infrared (3.74 µm) image (below) helped to discriminate between the hot brightness temperatures of recent (and old) lava flows and the cooler brightness temperatures exhibited by regions of vegetation.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

A closer look at the Kilauea East Rift Zone (below) provided a detailed view of the recent lava flow and active fissures, including the lava field that entered and covered Kapoho Bay a few days earlier. Note the appearance of numerous multi-colored pixels in the center of the lava field — the 3.74 µm I04 band detectors on the VIIRS instrument saturate around 385 K, so the hottest lava features which exceeded that brightness temperature threshold ended up being displayed as cold pixels (the so-called “wrap-around” effect). There is a Moderate-resolution M13 band (4.05 µm) on VIIRS which saturates at a much hotter 700 K; while it is a lower spatial resolution (750 meters, vs 375 meters for the I04 band), the M13 band can be useful for sampling the actual temperature of very hot features such as lava flows or wildfires.

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Suomi NPP VIIRS Shortwave Infrared (3.74 µm) image [click to enlarge]

Thanks to Jordan Gerth (CIMSS) and Eric Lau (NWS Pacific Region Headquarters) for providing the VIIRS imagery for this case.

Update: This link shows Landsat-8 and Sentinel-2 imagery before and after the Kapoho Bay lava flow.

Why Mesoscale Sectors matter: Tropical Storm Aletta

June 6th, 2018 |

GOES-16 Visible (0.64 µm) Imagery, 1422-1741 UTC on 6 June 2018 (Click to animate)

The first Tropical Storm, Aletta, of the eastern Pacific Ocean basin has been named. One-minute imagery from a moveable Mesoscale Sector, above as an animated gif (or here as an mp4), shows a distinct low-or mid-level circulation center moving out from under higher clouds in the northeast quadrant of the storm at about 1621 UTC, being even more obvious at 1636 UTC.

The GOES-16 CONUS Sector scans at 5-minute intervals. The southern boundary of the CONUS sector (15º N Latitude), however, bisects this tropical storm, as shown at this link, and is therefore unhelpful for center diagnostics. Full Disk imagery captures the storm evolution at a 15-minute time step that is too coarse to provide a smooth animation. (Just two years ago, the time resolution for this storm formation would have been every 3 hours, as that was the time cadence for a Full Disk from GOES-13! GOES-16 really is life-changing for those who view satellite animations.)