Smoke and Fog in the VIIRS Day/Night Band

July 2nd, 2015
Suomi NPP VIIRS 0.70 µm visible Day/Night Band and 11.45 µm - 3.74 µm Brightness Temperature Difference images, and Ceilings and Visibilities, ~0800 UTC (click to enlarge)

Suomi NPP VIIRS 0.70 µm visible Day/Night Band and 11.45 µm – 3.74 µm IR Brightness Temperature Difference images, and Ceilings and Visibilities, ~0800 UTC (click to enlarge)

July’s first Full Moon occurred at 0219 UTC on 2 July (a second full moon occurs later this month on 31 July). Strong illumination from the moon showed river valley fog in several tributaries of the Mississippi River (for example, the Wisconsin River in southwest Wisconsin; the Upper Iowa River in Iowa) across the Upper Midwest. The Suomi NPP VIIRS Day/Night Band also shows a plume of Canadian wildfire smoke aloft, stretching from central Iowa northwestward to western Minnesota. This smoke (visible on 1 July in Aqua true-color imagery from the MODIS Today site) is not apparent in the IR Brightness Temperature Difference field, although the river valley fog certainly is. Smoke is transparent to most infrared channels and detection at night is very difficult if visible information such as that provided by the Day/Night Band is not present.

The VIIRS Day/Night Band also enabled detection of the dense plume of Canadian wildfire smoke as it moved off the US East Coast and over the adjacent offshore waters of the western Atlantic Ocean at 0614 UTC  (below). Again, note that the smoke aloft does not exhibit a signature on the corresponding VIIRS Infrared imagery.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm Infrared images (click to enlarge)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm Infrared images (click to enlarge)

Hourly Infrared Animation for June 2015

July 1st, 2015


The video embedded above shows GOES-13 Water Vapor imagery each hour for all of June. Water vapor imagery (6.5 µm) is handy for tracking features in the atmosphere, and various circulations are plain in the animation, including Tropical Storm Bill and Pacific Hurricanes Blanca and Carlos. The 10.7 µm window channel animation is shown below.


Fires in Alaska, Canadian smoke over the Lower 48

June 29th, 2015
Suomi NPP VIIRS 3.74 µm infrared channel images, times as indicated (click to enlarge)

Suomi NPP VIIRS 3.74 µm infrared channel images, times as indicated (click to enlarge)

Suomi NPP 0.64 µm visible channel images, times as indicated (click to enlarge)

Suomi NPP 0.64 µm visible channel images, times as indicated (click to enlarge)

The 2015 Wildfire Season is off to a quick start in Alaska (continuing an observed trend). This map (from this site) shows more than 300 active fires over Alaska at 2000 UTC on 29 June 2015. This graph (from the Alaska Climate Info Facebook page) compares early burn acreage in 2015 to that in 2004 (the year with the most acreage burned — see this graph, courtesy of Uma Bhatt, University of Alaska-Fairbanks).

Soumi NPP VIIRS 3.74 µm infrared imagery from early morning on 29 June 2015 (top) shows numerous wildfire hot spots (dark black pixels) in the region surrounding the Yukon River (the middle portion of the imagery, south of Kotzebue Sound). VIIRS visible imagery from the same time, above, shows an extensive pall of smoke over much of central Alaska.

GOES-13 Visible (0.63 µm) imagery (click to play animation)

GOES-13 Visible (0.63 µm) imagery (click to play animation)

Meanwhile, thick smoke from fires burning over northern Canada (comparison of VIIRS visible and shortwave IR images from 28 June) was drifting southward over central portions of the Lower 48 states. The smoke plume on 28 June (above) was fairly narrow; however, a much broader and thicker plume was seen moving south on 29 June (GOES visible imagery below, then MODIS/VIIRS true-color RGB imagery as displayed using the SSEC RealEarth web map server). SSEC MODIS Today true-color imagery of this smoke plume is also available here. Pilot reports placed the lower and upper bounds of the thick smoke at 5000 and 17500 feet, with flight visibilities as low as 2 miles at 5000 feet. Some of the smoke subsided to the surface in southeastern South Dakota, restricting the surface visibility at Sioux Falls to 5 miles and raising the Air Quality Index there into the Unhealthy category. In fact, the smoke was so thick over far eastern South Dakota that it had the effect of reducing surface heating and slowing the rise of afternoon temperatures, such that convective temperatures were not being reached and probabilities of precipitation had to be scaled back:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
356 PM CDT MON JUN 29 2015

.SHORT TERM…(THIS EVENING THROUGH TUESDAY)
ISSUED AT 356 PM CDT MON JUN 29 2015

IN ADDITION…THICK PLUME OF SMOKE CONTINUES TO DRIFT SOUTHWARD IMPACTING NEARLY ALL OF THE FORECAST AREA…BUT MOST   NOTABLE ALONG AND EAST OF THE JAMES RIVER VALLEY. BECAUSE OF THIS…AFTERNOON TEMPERATURES ARE ABOUT 2 TO 4 DEGREES
COOLER THAN FORECAST AND WE ARE HAVING A HECK OF A TIME REACHING OUR CONVECTIVE TEMPERATURE. THEREFORE LOWERED THE LATE AFTERNOON AND EVENING POPS IN OUR EASTERN ZONES TO ONLY SLIGHT CHANCE POPS. BUT EVEN THOSE MAY BE TOO HIGH AND IF NOTHING DEVELOPS OVER THE NEXT COUPLE OF HOURS…THEY MAY NEED TO BE REMOVED ENTIRELY.

GOES-13 Visible (0.63 µm) imagery (click to play animation)

GOES-13 Visible (0.63 µm) imagery (click to play animation)

MODIS and VIIRS true-color imagery (click to enlarge)

MODIS and VIIRS true-color imagery (click to enlarge)

Daytime detection of smoke plumes is not difficult with visible (or true-color) imagery. At night, however, smoke detection is a challenge. The VIIRS Day/Night Band on Suomi NPP can detect smoke when Lunar Illumination is high (although detection is limited to one or sometimes two passes per night). Smoke is otherwise mostly transparent to infrared channels on the GOES Imager. Websites such as the NOAA/NESDIS IDEA and the GASP are helpful; however, the GASP product uses single-channel (visible) detection only.

Visible imagery from GOES-15, below, highlights the expansive region covered by smoke over northern Canada. Note that the smoke becomes less distinct with time as the sun rises higher in the sky, because forward scattering of visible light by smoke particles is more effective than backward scattering.

GOES-15 Visible (0.62 µm) imagery, times as indicated (click to animate)

GOES-15 Visible (0.62 µm) imagery, times as indicated (click to animate)

The long-lasting remnants of Tropical Storm Bill

June 21st, 2015
Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (click to enlarge)

Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images (click to enlarge)

Advisories on Tropical Storm Bill were initiated when the system organized and intensified off the coast of Texas at 03 UTC on 16 June 2015 (GOES-13 IR image animation). Bill moved inland during the afternoon hours on 16 June, as can be seen in a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1916 UTC (above).

Late in the day on 17 June, the general appearance of downgraded Tropical Depression Bill on GOES-13 6.5 µm water vapor channel imagery (below) began to suggest that the system might be undergoing an extratropical transition (intrusion of dry air in the southern quadrant, along with a blosominig comma head signature on the northern quadrant) — but Bill maintained sufficient tropical characteristics to continue being named a tropical depression.

GOES-13 6.5 µm water vapor channel images, with surface pressure and frontal analyses (click to play animation)

GOES-13 6.5 µm water vapor channel images, with surface pressure and frontal analyses (click to play animation)

The circulation of TD Bill maintained its identity on satellite imagery as the storm remained over land for the next 3+ days, curving northeastward and moving across the Ohio River Valley region. Slow-moving TD Bill dropped over 12 inches of rain at some locations in Texas and Oklahoma, with amounts exceeding 8 inches in Missouri and 6 inches in Indiana (WPC storm total rainfall totals), before being designated a post-tropical feature at 21 UTC on 20 June (WPC advisories).

GOES-13 10.7 µm IR channel images (click to play animation)

GOES-13 10.7 µm IR channel images (click to play animation)

The history of Bill can be followed in a multi-day animation of GOES-13 10.7 µm IR channel imagery (above); in addition, the lower-tropospheric circulation of Bill can be followed using the CIMSS 850 hPa relative vorticity product (below).

GOES-13 850 hPa relative vorticity product (click to play animation)

GOES-13 850 hPa relative vorticity product (click to play animation)

As the post-tropical remnants of Bill emerged over the Atlantic Ocean early in the day on 21 June, it still appeared to be associated with an arc of deep convection as seen on a comparison of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images at 1742 UTC (below). A similar comparison of Terra MODIS visible and IR images at 1514 UTC can be seen here.

Soumi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images

Soumi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images