Suomi NPP VIIRS 0.7 µm Day/Night Band, 11.45 µm IR, and 11.45-3.74 µm “fog/stratus product” images

A comparison of AWIPS images of the Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB), the 11.45 µm IR channel, and the 11.45-3.74 µm “fog/stratus product” (above) showed well-defined signatures of the aurora borealis (or “Northern Lights”) across central Canada on 09 August 2012. Comparison with the corresponding 11.45 µm IR channel image and the 11.45-3.74 µm “fog/stratus product” confirmed that the brighter DNB features (the wide west-to-east oriented band that stretched across Saskatchewan, Manitoba, and Ontario, as well as the separate more complex feature over northern Manitoba) were indeed signatures of the aurora, and not high-level or low-level cloud features.

The Auroral Oval map from the Space Weather Prediction Center  (below) showed that the southern edge of the auroral oval extended far southward across Canada at that time.

Space Weather Prediction Center auroral oval map

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Suomi NPP VIIRS 0.64 µm visible channel + 11.45 µm IR channel images

An unusually strong area of low pressure moved northward into the Arctic Ocean and intensified during the 05 August – 08 August 2012 time period — a storm this deep (965 hPa central pressure) is exceptional for the Arctic Ocean region, especially during the summer month of August. A comparison of AWIPS images of Suomi NPP VIIRS 0.64 µm visible channel and 11.45 µm IR channel images with an overlay of the surface pressure analysis  (above) showed the cloud patterns associated with the storm around 00 UTC on 08 August.

Suomi NPP VIIRS 0.64 µm visible channel images (click image to play animation)

Animations of Suomi NPP VIIRS 0.64 µm visible channel images (above; click image to play animation) and 11.45 µm IR channel images (below; click image to play animation) showed the evolution of the storm over the Arctic Ocean during the 06 August – 08 August period.

Suomi NPP VIIRS 11.45 µm IR channel image (click image to play animation)

McIDAS images of Terra MODIS 11.0 µm IR channel data (below; click image to play animation; images courtesy of Dave Santek, SSEC) showed the storm moving poleward during the 05 August – 08 August time period. Barrow, Alaska was in the warm sector of the storm on 05 August, and recorded a daily high temperature of 60º F (with a peak wind gust from the southwest at 41 mph). Two days later, strong cold air advection in the wake of the storm (with a peak westerly wind gust of 33 mph) kept the daily high temperature at Barrow down to 39º F.

Terra MODIS 11.0 µm IR channel images (click image to play animation)

The circulation of the deep low could be easily identified using atmospheric motion vectors (cloud-tracked winds) derived from a variety of polar-orbiting satellites (below).

IR images and atmospheric motion vectors from a variery of polar-orbiing satellites

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

McIDAS images of 4-km resolution GOES-13 10.7 µm IR channel data (above; click image to play animation) showed Category 1 Hurricane Ernesto as it approached the far southeast coast of Mexico during the late afternoon and eary evening hours on 07 August 2012. The GOES-13 satellite had been placed into Rapid Scan Operations mode, providing images as frequently as every 5-10 minutes (vs the standard 15-minute image interval). Cloud top IR brightness temperatures of -80º C and colder were highlighted by the violet color enhancement.

AWIPS images of the 1-km resolution POES AVHRR Cloud Top Temperature (CTT) product indicated that CTT values were as cold as -87º C at 02:12 UTC and -86º C at 03:27 UTC (below).

POES AVHRR Cloud Top Temperature product

The 1-km resolution POES AVHRR Cloud Top Height (CTH) product showed that the highest cloud tops were around 16 km (below).

POES AVHRR Cloud Top Height product

Much of the highest cloud top area was denoted as “overshooting” (violet color enhancement) on the 1-km resolution POES AVHRR Cloud Type product (below).

POES AVHRR Cloud Type product

According to the 00:00 UTC / 08 August rawinsonde data from Belize City (below), the height of the tropopause was 15.8 km, with the air temperature at and just above the tropopause around -82º C. Note the nearly saturated profile of the tropical air mass, with a total precipitable water value of 2.58 inches.

Belize 00 UTC rawinsonde data

===== 08 August Update =====

Since the Moon was in the Waning Gibbous phase (61% of full), there was enough reflected moonlight to allow a Suomi NPP VIIRS Day/Night Band image (below) to reveal the well-defined circulation of Ernesto as it was moving inland across the Yucatan Peninsula of Mexico at 06:54 UTC (1:54 am local time). Note the bright areas of city lights along the coastal areas (most notably Campeche, Merida, and Cancun) that could be seen through the relatively thin edges of the cirrus canopy.

Suomi NPP VIIRS 0.7 µm Day/Night Band

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Tongariro Ash Plume as seen by VIIRS Day-Night Band on Suomi/NPP

Mount Tongariro in New Zealand (on the North Island) erupted on Monday, August 6th, for the first time in a century. A Suomi-NPP overpass at 12:52 UTC, approximately one hour after the eruption, allowed the day-night band to capture an image of the volcanic plume as it moved eastward across the central part of the North Island. The 3.74 µm shortwave IR image and the 11.45 µm longwave IR image show that the height of the plume is fairly high: brightness temperatures in the 11.45 µm image are around 218 K or -55º C. (VIIRS Imagery courtesy of William Straka, UW-Madison/CIMSS). The minor eruption did disrupt air travel, with some flights cancelled in Gisborne, Taupa, Rotorua and Palmerston North.

MTSAT Enhanced Brightness Temperature Difference between 10.8 µm and 12 µm (click image to play animation)

Volcanic Ash has different emissivity properties at 11 and 12 µm; hence, the heritage method for detecting Volcanic Ash uses the difference in brightness temperatures at those two wavelengths. The loop above shows MTSAT-2 imagery; Note the spike in signal in the 1232 UTC image (about 30 minutes after the eruption) that continues to grow as it crosses the coast at 1332 UTC; it then moves rapidly eastward over the ocean.

MTSAT Visible Imagery at 1932 UTC on 6 August 2012

Visible imagery from MTSAT at 1932 UTC, above, approximately 8 hours after the eruption, shows the ash cloud over the ocean east of New Zealand.

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