Using GOES-16 visible and near-infrared imagery to diagnose areas of flooding

April 6th, 2017 |

Flood Warnings (green) in effect at 7:43 pm CDT on 06 April 2017 [click to enlarge]

Flood Warnings (green) in effect at 7:43 pm CDT on 06 April 2017 [click to enlarge]

** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

Following several days of heavy rainfall across northwestern Missouri, Flood Warnings remained in effect for many areas on 06 April 2017 (above).

A comparison of GOES-16 Visible (0.47 µm and 0.64 µm) and Near-Infrared (0.86 µm and 1.61 µm) images at 1507 UTC (below) shows that the Vegetation and Snow/Ice spectral bands are useful for identifying areas of swollen rivers and adjacent flooded lands (since water appears darker on those 2 images).

GOES-16 Visible (0.47 µm and 0.64 µm) and Near-Infrared (0.86 µµ and 1.61 µm) images [click to enlarge]

GOES-16 Visible (0.47 µm and 0.64 µm) and Near-Infrared (0.86 µµ and 1.61 µm) images [click to enlarge]

 

 

Cyclone Debbie makes landfall in Queensland, Australia

March 28th, 2017 |

Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images [click to play animation]

Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images [click to play animation]

Cyclone Debbie formed in the Coral Sea on 22 March 2017, and eventually intensified to a Category 3 storm (ADT | SATCON) as it moved southward toward Australia. Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images (above) showed the eye of Debbie as it was making landfall in Queensland, near Prosperpine (YBPN).

Landsat-8 false-color, with Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images [click to enlarge]

Landsat-8 false-color, with Himawari-8 Visible (0.64 µm) and Infrared Window (10.4 µm) images [click to enlarge]

The Landsat-8 satellite made an overpass of the eye at 2358 UTC (above), as a large convective burst had developed within the northern semicircle of the eyewall (which was also evident in the corresponding Himawari-8 Visible and Infrared Window images viewed using RealEarth).

Himawari-8 Infrared Window (10.4 µm) and GMI Microwave (85 GHZ) Images around 1430 UTC on 27 March [click to enlarge]

Himawari-8 Infrared Window (10.4 µm) and GMI Microwave (85 GHZ) Images around 1430 UTC on 27 March [click to enlarge]

Debbie was undergoing an eyewall replacement cycle as the storm center approached the coast — this was evident in Microwave (85 GHz) images from GMI at 1425 (above) and SSMIS at 2017 UTC (below) from the CIMSS Tropical Cyclones site.

Himawari-8 Infrared Window (10.4 µm) and DMSP-18 SSMIS Microwave (85 GHz) images around 2017 UTC on 27 March [click to enlarge]

Himawari-8 Infrared Window (10.4 µm) and DMSP-18 SSMIS Microwave (85 GHz) images around 2017 UTC on 27 March [click to enlarge]

The MIMIC Total Precipitable Water product (below; also available as an MP4 animation) showed copious tropical moisture associated with Cyclone Debbie, which led to rainfall accumulations as high as 780 mm (30.7 inches) — with rainfall rates up to 200 mm (7.9 inches) per hour — and record flooding along the coast from Brisbane to Lismore.

MIMIC Total Precipitable Water product [click to play animation]

MIMIC Total Precipitable Water product [click to play animation]

 

 

 

Heavy Rains over southern California

February 28th, 2017 |

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

The GOES-15 Water Vapor animation, above, shows a potent cold front moving through southern California late on 27 February. This front that passed through San Diego at 0500 UTC on 28 February (9 PM PST) was accompanied by abundant precipitation, the heaviest rainfall in 13 years at the San Diego airport (link), with widespread 2+-inch rains that caused power outages and flooding. The image below (from this site), shows the 24-hours precipitation ending at 1200 UTC on 28 February 2017. Values in excess of 6″ occurred in the mountains east of San Diego.

Accumulated Precipitation for 24 hours ending 1200 UTC on 28 February 2017 [click to enlarge]

Accumulated Precipitation for 24 hours ending 1200 UTC on 28 February 2017 [click to play animation]

Hourly MIMIC Total Precipitable Water estimates for the 72 hours ending 1400 UTC on 28 February 2017 [click to enlarge]

Hourly MIMIC Total Precipitable Water estimates for the 72 hours ending 1400 UTC on 28 February 2017 [click to play animation]

Satellite estimates of Total Precipitable Water (TPW) suggested that heavy rains were likely. MIMIC total precipitable water plots, above (source), show a moisture source that tapped the rich moisture of the Intertropical Convergence Zone. NOAA/NESDIS Blended Precipitable Water Percent-of-Normal plots (source, at this site), shown below, show values exceeding 200% of normal over southern California. Both MIMIC and Blended TPW products offer excellent situational awareness.

NOAA/NESDIS Blended Total Precipitable Water Percent-of-Normal, times as indicated [click to play animation]

NOAA/NESDIS Blended Total Precipitable Water Percent-of-Normal, times as indicated

An interesting aspect of the GOES-15 Water Vapor animation, at the top of this post, is the appearance of land features. The spine of the mountains over Baja California appears throughout the animation, for example, as does the Front Range of the Rockies from Colorado southward to New Mexico. Should land features be visible in water vapor imagery? An answer to that lies in computed weighting functions, shown below (from this site), that describe from where in the atmosphere energy at a particular wavelength is being detected by the satellite.

At the start of the water vapor animation, near 0000 UTC, thick clouds cover southern California (and the sounding from San Diego shows saturated conditions); dry layers in the sounding appear by 1200 UTC. The 7.4 µm weighting function shows that information is detected by the satellite from lower down in the atmosphere; energy detected at 6.5 µm comes from higher in the atmosphere. This difference arises because of the better absorptive qualities of water vapor gas for 6.5 µm radiation vs. 7.4 µm radiation. By 1200 UTC, sufficient drying has occurred that the 7.4 µm Sounder Channel is detecting radiation that emanates from sea level. Note also at 1200 UTC that each individual moist layer influences the weighting function — but there is insufficient moisture at 1200 UTC in those moist layers that they are opaque to energy at either 6.5 µm or 7.4 µm.

Note: GOES-R Series satellites, including GOES-16, have ‘water vapor’ channels at 6.2 µm, 6.9 µm and 7.3 µm.

Water Vapor Weighting Functions at 72293 (San Diego) for GOES Imager (6.5 µm) (Black Line) and GOES Sounder (7.4 µm) (Red Line) at 0000 UTC 27 February (Left) and 1200 UTC 28 February (Right). The Sounding for San Diego is also indicated [click to enlarge]

Water Vapor Weighting Functions at 72293 (San Diego) for GOES Imager (6.5 µm) (Black Line) and GOES Sounder (7.4 µm) (Red Line) at 0000 UTC 27 February (Left) and 1200 UTC 28 February (Right). The Sounding for San Diego is also indicated [click to enlarge]

Atmospheric river events bring heavy precipitation to California

January 13th, 2017 |

MIMIC Total Precipatable Water product [click to play MP4 animation]

MIMIC Total Precipatable Water product [click to play MP4 animation]

A series of 3 atmospheric river events brought heavy rainfall and heavy snowfall to much of California during the first 10 days of January 2017 (NWS San Francisco/Monterey | WeatherMatrix blog). Hourly images of the MIMIC Total Precipitable Water product (above; also available as a 33 Mbyte animated GIF) showed the second and third of these atmospheric river events during the 06 January11 January 2017 period, which were responsible for the bulk of the heavy precipitation; these 2 events appear to have drawn moisture northeastward from the Intertropical Convergence Zone (ITCZ)..

Terra MODIS Visible (0.65 µm) and Near-Infrared

Terra MODIS Visible (0.65 µm) and Near-Infrared “Snow/Ice” (2.1 µm) images [click to enlarge]

A relatively cloud-free day on 13 January provided a good view of the Sacramento Valley and San Francisco Bay regions. A comparison of Terra MODIS Visible (0.65 µm) and Near-Infrared  “Snow/Ice” (2.1 µm) images (above) showed that snow cover in the higher terrain of the Coastal Ranges and the Sierra Nevada appeared darker in the Snow/Ice band image (since snow and ice are strong absorbers of radiation at the 2.1 µm wavelength) — but water is an even stronger absorber, and therefore appeared even darker (which allowed the areas of flooding along the Sacramento River and its tributaries to be easily identified). A similar type of 1.6 µm Near-Infrared “Snow/Ice” Band imagery will be available from the ABI instrument on the GOES-R series, beginning with GOES-16.

Better detail of the flooded areas of the Sacramento River and its tributaries was seen in 250-meter resolution false-color Red/Green/Blue (RGB) imagery from the MODIS Today site — water appears as darker shades of blue, while snow appears as shades of cyan (in contrast to supercooled water droplet clouds, which appear as shades of white). In the corresponding MODIS true-color image, rivers and bays with high amounts of turbidity (tan shades) were evident; the offshore flow of sediment from a few rivers could also be seen.

Terra MODIS true-color and false-color RGB images [click to enlarge]

Terra MODIS true-color and false-color RGB images [click to enlarge]