An RGB computed using the GOES-16 Cirrus Channel

November 3rd, 2017 |

Cloud Type RGB at 1502 UTC on 3 November 2017 (Click to enlarge)

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

Red-Green-Blue (RGB) Composite Images are a handy way of showing information from multiple satellite bands (or band differences) at once. The image above shows an RGB created by NOAA Scientist Andy Heidinger that uses the GOES-16 Visible Band (0.64 µm) as the green component, Snow-Ice Band (1.61 µm) as the blue component and Cirrus Band (1.38 µm) as the red component to tease out information about Cloud Type.  The Cirrus Channel (unique to GOES-16 as far as Geostationary Satellites are concerned) is a handy channel to use in an RGB because it discriminates very well between high clouds and low clouds.  In a moist environment, low clouds are not apparent at all in the Cirrus Band.  The toggle below shows the Visible, Snow/Ice and Cirrus Channels at 1502 UTC.  Low clouds over Kansas have no signal in the Cirrus channel — there are other differences as well, of course.

In the RGB, Thin cirrus clouds (for example, the contrails over Illinois) are red, opaque ice clouds (over the western Atlantic) are yellow (having a contribution from both Red and Green Components), Low Clouds (over the southern Plains) are Cyan (having a contribution from Blue and Green), snow is Green, and lofted water clouds are white (having a contribution from all three). As the atmosphere dries, the amount of lofting necessary for the Cirrus channel to view a cloud composed of water droplets (and therefore white in the RGB) decreases.

GOES-16 Imagery at 1502 UTC on 3 November 2017: Snow/Ice (1.61 µm), Visible (0.64 µm) and Cirrus Channels (1.38 µm) (Click to enlarge)

The Day Land Cloud RGB (sometimes called ‘Natural Color’) can also be used to estimate cloud type. The toggle below shows how the Cloud Type RGB has more gradations between ice cloud type because of the use of the Cirrus Channel.  The Cloud Type RGB also highlights the contrails and thin cirrus more effectively, again because of the use of the Cirrus Channel

Cloud Type RGB (1.38 µm, 0.64 µm, 1.61 µm) and Day/Land/Cloud RGB (1.61 µm, 0.86 µm, 0.64 µm), 1502 UTC on 3 November 2017 (Click to enlarge)

 

Three toggles below show the Snow/Ice and Visible and Cirrus channels zoomed in over Illinois (where contrails are present), over the western Atlantic (where strong convection is occurring) and over the southwestern United States.

GOES-16 Imagery at 1502 UTC on 3 November 2017: Cirrus Channel (1.38 µm), Visible (0.64 µm) and Snow/Ice (1.61 µm) (Click to enlarge)

GOES-16 Imagery at 1502 UTC on 3 November 2017: Cirrus Channel (1.38 µm), Visible (0.64 µm) and Snow/Ice (1.61 µm) (Click to enlarge)

GOES-16 Imagery at 1502 UTC on 3 November 2017: Cirrus Channel (1.38 µm), Visible (0.64 µm) and Snow/Ice (1.61 µm) (Click to enlarge)

GOES-16 also has a Baseline Product that shows Cloud Type. That is shown below. The 1502 UTC Image was incomplete, so the 1507 UTC image is shown.

GOES-16 Cloud Phase, Baseline Product, 1507 UTC on 3 November 2017 (Click to enlarge)

Power Outages in the wake of a strong Nor’easter

October 31st, 2017 |

Suomi NPP Day Night Band Visible Imagery (0.70 µm) on 4 October 2017 (2:43 AM EST) and on 30 October 2017 (2:38 AM EST) (Click to enlarge)

The toggle above includes nocturnal visible Suomi NPP VIIRS  Day Night Band (0.7 µm) imagery over New England after a strong storm (blogged here), compared with a reference image from 04 October 2017.  The primary nighttime light source for the Day Night Band over land on 31 October was cities (since the Moon was below the horizon), thus a comparison between the latest image with one earlier in the month having different lunar illumination (from October 4th) highlights regions that experienced significant power outages due to high winds.  Clouds will affect the interpretation of the Day Night Band imagery, and a reference Infrared Window (11.45 µm) image from 31 October at 2:38 AM EST is here.  The Day Night Band image with only cloud outlines is here.  (VIIRS imagery courtesy of Will Straka, CIMSS).

Northeast US heavy rain and high wind event

October 30th, 2017 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly precipitation type symbols plotted in red [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly precipitation type symbols plotted in red [click to play MP4 animation]

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

GOES-16 Mid-level Water Vapor (6.9 µm) images with hourly surface weather symbols plotted in red (above) showed the large-scale evolution of a storm system that deepened rapidly as it moved across the Northeast US during the 29 October30 October 2017 period (surface analyses). This storm produced widespread high winds and heavy rain (WPC storm summary | NWS Boston PNS | NWS Caribou PNS). Record low sea level pressures for the month of October were set in New York at Albany (977.7 hPa) and Fort Drum (977.5 hPa), and in Massachusetts at Nantucket (982.6 hPa) — a map of the minimum sea level pressures from the New York State Mesonet can be seen here.

Closer views of the Northeast US using images from the GOES-16 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm) and Low-level Water Vapor (7.3 µm) bands are shown below, with hourly surface wind gusts (knots) plotted in red. The high winds caused extensive damage to trees and power lines, leading to power outages in some areas — and also contributed to coastal storm surge.

GOES-16 Upper-level Water Vapor (6.2 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

GOES-16 Upper-level Water Vapor (6.2 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

GOES-16 Lower-level Water Vapor (7.3 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

GOES-16 Lower-level Water Vapor (7.3 µm) images, with hourly surface wind gusts (in knots) plotted in red [click to play MP4 animation]

One interesting aspect of this rapidly-deepening storm was the absorption/merging of the northward-moving remnants of Tropical Storm Philippe (storm track), which was shown by the CIMSS 850 hPa relative vorticity product (below).

850 hPa Relative Vorticity product [click to play animation]

850 hPa Relative Vorticity product [click to play animation]

Additional details of this event can be found on the Satellite Liaison Blog.

Detection of low clouds on “Cirrus band” imagery

October 29th, 2017 |

GOES-16 Visible (0.64 µm, top), Cirrus (1.37 µm, middle) and Infrared Window (10.3 µm, bottom) images [click to play animation]

GOES-16 Visible (0.64 µm, top), Cirrus (1.37 µm, middle) and Infrared Window (10.3 µm, bottom) images [click to play animation]

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

The ABI “Cirrus” (1.37 µm) band is centered in a strong water vapor absorption spectral region — therefore it does not routinely sense the lower troposphere, where there is usually substantial amounts of water vapor. Hence, its main application is the detection of higher-altitude cirrus cloud features.

However, in areas of the atmosphere characterized by low amounts of total precipitable water, the Cirrus band can sense clouds (and other features, such as blowing dust) in the lower troposphere. Such was the case on 29 October 2017, when a ribbon of dry air resided over the northern Gulf of Mexico in the wake of a strong cold frontal passage; low-level stratocumulus clouds were very apparent on GOES-16 Cirrus band images (above). Also of note: cloud features associated with Tropical Storm Philippe could be seen east of Florida.

The three GOES-16 Water Vapor bands (Upper-level 6.2 µm, Mid-level 6.9 µm and Lower-level 7.3 µm) highlighted the pocket of dry air that was moving across the northern Gulf of Mexico on that day (below).

GOES-16 Upper-level Water Vapor (6.2 µm, top), Mid-level Water Vapor (6.9 µm, middle) and Lower-level Water Vapor (7.3 µm, bottom) images [click to play animation]

GOES-16 Upper-level Water Vapor (6.2 µm, top), Mid-level Water Vapor (6.9 µm, middle) and Lower-level Water Vapor (7.3 µm, bottom) images [click to play animation]

The MODIS instrument on Terra and Aqua has a 1.37 µm Cirrus band as well; 1619 UTC Terra images (below) also revealed the stratocumulus clouds (especially those over the northeastern Gulf, where the driest air resided). Conversely, note how the low cloud features of Philippe were not seen on the Cirrus image, since abundant moisture within the tropical air mass east of Florida attenuated 1.37 µm wavelength radiation originating from the lower atmosphere.

In addition, the VIIRS instrument — on Suomi NPP, and the upcoming JPSS series — has a 1.37 µm Cirrus band.

Terra MODIS visible (0.65 µm), Cirrus (1.375 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Terra MODIS visible (0.65 µm), Cirrus (1.375 µm) and Infrared Window (11.0 µm) images [click to enlarge]

Hourly images of the MIMIC Total Precipitable Water product (below) showed the ribbon of very dry air (TPW values less than 10 mm or 0.4 inch) sinking southward over the northern Gulf of Mexico. This TPW product uses microwave data from POES, Metop and Suomi NPP satellites (description).

http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2017/10/tpw_17z.png

MIMIC Total Precipitable Water images [click to play animation]