Deadly Smog in India and Pakistan

November 9th, 2017 |

Suomi NPP VIIRS Day Night Band Visible Imagery (0.70 µm) at Night, 05, 07 and 08 November 2017 (Click to enlarge).

Suomi NPP VIIRS Visible Imagery at Night (the Day Night Band Visible Image (0.7 µm) from 5 November, 7 November and 8 November), above, and Infrared Channel Brightness Temperature Difference  (11.45 µm – 3.9 µm) on 5 November, 7 November and 8 November), below, both show the presence of fog/smog over northern Pakistan and northwestern India from 05-08 November 2017 (Suomi NPP VIIRS Imagery courtesy of William Straka, CIMSS). The Smog led the Government of Punjab to ban burning of stubble; schools in Delhi were closed.  Vehicle crashes linked to reduced visibilities have killed at least 10 people (source).  Air Quality in the region is very poor as shown in this Screen Grab from this site.

Suomi NPP VIIRS Infrared channel Brightness Temperature Difference (11.45 µm – 3.9 µm) on 05, 07, and 08 November 2017 (Click to enlarge)

An animation of Meteosat-8 Visible Imagery, below, from 03-09 November, shows little improvement in conditions in the past week.

Meteosat-8 Visible Imagery (0.6 µm) at 0300 UTC from 03 to 09 November 2017 (Click to enlarge)

Daily composites of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from RealEarth, below, showed the areal coverage of the smog during the 03-09 November period. Surface observations at New Delhi’s Indira Gandhi International Airport indicated that the visibility remained below one statute mile — with zero visibility at times — during the 72-hour period spanning 07 November, 08 November and 09 November (animation).

Daily composites of Suomi NPP VIIRS true-color RGB images (click to enlarge)

Daily composites of Suomi NPP VIIRS true-color RGB images (click to enlarge)

Worth noting on a nighttime comparison of Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Day/Night Band (0.7 µm) images, below, was the appearance of a cloud shadow being cast by moonlight onto the top of the boundary layer smog/fog.

Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Dat/Night Band (0.7 µm) images [click to enlarge]

Suomi NPP VIIRS Infrared Brightness Difference (11.45-3.74 µm) and Day/Night Band (0.7 µm) images [click to enlarge]

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).

GOES-16 and Fog Detection

October 18th, 2017 |

GOES-16 Brightness Temperature Difference (10.3 µm – 3.9 µm) “Fog Product” from 0202 – 0357 UTC on 18 October 2017 (Click to animate)

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

Stratus and Fog formed over the valleys of Kentucky (and in surrounding states) early on 18 October 2017 (It was there on 17 October as well). When was the fog first obvious from Satellite imagery? It very much depends on the spatial resolution of the Satellite viewing the scene. The Brightness Temperature Difference field (10.3 µm – 3.9 µm) from GOES-16, shown above, can be used to identify regions of stratus clouds that are made up of water droplets. Carefully examine the animation; the time when fog is definitively present over valleys of eastern Kentucky (around 84º W Longitude) is around 0327 UTC.

GOES-16 has 2-km resolution (at the sub-satellite point — 89.5º W Longitude during GOES-16 Check-out); this is superior to GOES-13’s nominal 4-km resolution at the subpoint (75º West Longitude). The GOES-13 Brightness Temperature Difference Field (10.7 µm – 3.9 µm) at 0330 UTC shows no distinct indication of Fog/Stratus over eastern Kentucky. A series of animations of the GOES-13 Brightness Temperature Difference field, from 0215-0345 UTC, from 0415-0500, from 0545-0700 and from 0700-0815 suggest GOES-13 identified the region of fog about 4 hours after GOES-16, at 0730 UTC.

The GOES-13 vs. GOES-16 toggle below, from 0700 UTC on 18 October 2017, shows how the resolution improvement with GOES-16 facilitates earlier detection of fog and stratus as it develops overnight.

Toggle between 0700 UTC 18 October 2017 Brightness Temperature Differences from GOES-13 (10.7 µm – 3.9 µm) and GOES-16 (10.3 µm – 3.9 µm) (Click to enlarge)