VIIRS Dust product captures Mount Pavlof’s Plume

Author: Emily Berndt

Mount Pavlof, one of Alaska’s most active volcanoes, has been erupting since last week. The plume has caused some disruption of flights and ash fallout in nearby communities. The Alaska Volcano Observatory has been closely monitoring it’s activity (http://www.avo.alaska.edu/activity/Pavlof.php). The steam, ash, and gas plume is continually created as hot lava contacts snow and ice. The steam, ash, and gas plume has occasionally reached up to 20,000 ft and has been carried downwind as much as 100 km to the northeast, east, and southeast  before dissipating. This graphic from the Alaska Volcano Observatory shows the location of Mount Pavlof within the Aleutian Island Chain.

The plume can be seen in the VIIRS RGB Dust product. Let’s first look at the VIIRS true color product. Inside the red circle, you can see a faint brown plume, but it’s not easy to see (click on the images).

VIIRS True Color Image 2135 UTC 18 May 2013

Now take a look at the VIIRS RGB Dust product. On the three images below there is a pink/red streak (inside the purple circle) emanating from the location of Mount Pavlof.

This is an excellent example of the utility of multichannel RGB products to obtain a clearer view of the location and extent of volcanic plumes.

VIIRS RGB Dust Imagery 2135 UTC 18 May 2013

VIIRS RGB Dust Imagery 1138 UTC 18 May 2013

VIIRS RGB Dust Imagery 2332 UTC 17 May 2013

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Experimental VIIRS DNB Outage Composite for Moore, Oklahoma

During the afternoon of May 20, 2013, the city of Moore, Oklahoma was struck by a large, violent tornado that caused widespread damage and numerous fatalities.  Some aspects of the tornado and the resulting damage are observable from space.  As with Superstorm Sandy and Hurricane Isaac, the VIIRS day-night band can be used to monitor changes in light resulting from a variety of features, such as moonlight reflection off of cloud tops or the surface, lightning from thunderstorms, fires, or human activity.  The images below show day-night band imagery prior to the major tornado as observed in the early morning of May 20 and an image obtained in the early morning of May 21.  In the May 21 image, thunderstorms continued east of Oklahoma City.  Reflected moonlight provides imaging of ongoing thunderstorms and the DNB captures a few lightning flashes.  Clearing skies over the Oklahoma City area help to identify the outages resulting from the tornado several hours earlier.  When pre- and post-event imagery are combined in a 24-bit RGB image, reductions in light output appear in shades of light yellow across the Moore, OK area.  Changes in cloud cover between the two days result in other shades of blue to identify cloud contamination where the RGB change product is not applicable.  A zoomed-in portion for Oklahoma City is shown in the final image.

Many SPoRT team members have spent time in the Oklahoma City area as students at the University of Oklahoma in Norman, or through collaborations with other scientists at the National Weather Center.  Our thoughts are with our colleagues in Moore and the citizens of Oklahoma during their recovery efforts.

Day-night band imagery from the VIIRS sensor aboard the S-NPP satellite show city lights, cloud cover, and lightning during the early morning hours of May 20 prior to the storms over Moore, OK and the Oklahoma City area.

VIIRS DNB imagery during the early morning of May 21 show city lights in the Oklahoma City area, but reduced light output in Moore, OK as a result of the major tornado that occurred during the afternoon of May 20. Storms from earlier in the day had shifted eastward, still visible in the DNB imagery.

When pre- and post-storm imagery are combined in a 24-bit composite, power outages in the Moore, OK area are evident in shades of yellow. Other areas appear yellow, such as Tulsa, OK, but this is a result of changes in cloud cover between the two scenes.

Zoomed in area of the outage composite focusing on the Oklahoma City area.

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Full Moonlight Observations with the VIIRS Day-Night Band Imagery

I wanted to point out a couple of Day-Night Band (DMB) observations from the VIIRS instrument aboard the Suomi NPP satellite since we are at full moon.  Yesterday, smoke from firest could easily be seen in GOES 4-km visible imagery.  However, the loss of visible at nighttime with conventional geostationary imagery makes it nearly impossible to detect smoke plumes at night.  The DNB imagery, while just a snapshot from a polar orbiter, at least allows for a check of how phenomena have evolved since the loss of standard daytime visible imagery.  Notice the plumes of smoke in the loop of GOES imagery below.

Image 1. GOES visible imagery and METAR observations loop 2231-0045 UTC March 26-27 2013.

A few of the smoke plumes really stand out: one in SW Arkansas at site KDEQ, one west of McComb, MS and another between Jackson and Hattiesburg, MS.  Notice that the smoke plume from the fire in far SE OK was reducing visibility at KDEQ in SW Arkansas.  At times, visibility was reduced to 1 3/4 SM, which is within IFR conditions.  If this was a Terminal Aerodrome Forecast (TAF) site, this would cause potentially large aviation impacts and a forecaster would want to know about the evolution of the fire and smoke after sunset.  Granted, while only serving as a snapshot, the DNB imagery (images 2 and 3 below) show that the fires and smoke in the region had essentially dissipated by the satellite pass at approximately 0751 UTC Mar March 27.

Image 2. VIIRS DNB Reflectance image valid 0752 UTC 27 March 2013.

Image 3. VIIRS DNB Radiance RGB product valid 0752 UTC 27 March 2013.

Now, the question might remain, did the smoke actually disappear/dissipate or are the smoke plumes simply not showing up in the imagery?  It seems more likely that the smoke/fires had dissipated.  Early morning daytime visible imagery just after sunrise (not shown) indicated that the fires indeed had burned out.

Now, for another type of phenomenon…snow.

During the day, clouds may linger over recent snowfall and it can be difficult for forecasters to discern the true extent of the snow.  Sure, observations allow forecasters a sense of the extent of snow cover, but may not allow for a sufficient assessment of its true extent.  Notice in the short loop below, the clouds moving across recent snow in sections of the Midwest.

Image 4. GOES visible image loop valid 2315 – 0015 UTC March 26-27 2013.

In the imagery above, a trained eye can differentiate snow on the ground in portions of eastern Missouri and western Illinois from cloud cover.  However, forecasters and others would want to know the extent of snow cover on the ground over the area.  The VIIRS DNB Radiance RGB combined with the VIIRS Nighttime Microphysics RGB later that night after clouds had cleared somewhat helped to answer that question.

Imager 5. VIIRS DNB Radiance RGB valid 0752 UTC 27 March 2013.

Image 6. VIIRS Nighttime Microphysics image valid 0752 UTC 27 March 2013.

In the DNB RGB image above (image 5), the snow field is relatively easy to see extending from eastern Missouri into western Ohio.  Some clouds still obscure the view and SPoRT’s Nighttime Microphysics RGB product (image 6 above) makes it very easy to distinguish clouds from areas of snow.  The low/mid clouds in the area appear as yellows/oranges, while higher, colder clouds appear as deeper magenta/reds.  Toggling the two images (as shown in image 7 below) makes the ease of detecting snow vs. clouds apparent.

Image 7. Toggle of Nighttime Microphysics RGB with DNB radiance RGB, both images valid 0752 UTC March 27 2013.

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Classic Mid-Latitude Dynamic Dry Slot Event for New Mexico

NWS ABQ continues to research the MODIS RGB airmass imagery and its potential to improve prediction of significant fire weather, wind, and dust events across New Mexico.  The MODIS satellite captured a stunning example of a dynamic dry slot within the base of a strong mid latitude cyclogenesis over the central Rockies.  Blowing dust in association with the strong jet core sliding directly over eastern NM produced very hazardous conditions for much of the afternoon.  The lead meteorologist from Cannon Air Force Base reported visibilities down to around 100 yards at times with the sky completely obscured for roughly 5 hours.  This was the worst dust storm for the region that he could remember going back to 2006.  He also mentioned the region is about as close to the Dust Bowl as he can imagine with essentially no top soil left after multiple strong wind events already this season and persistent severe to extreme drought.

MODIS RGB Airmass 240pm March 23, 2013.

MODIS/VIIRS Blowing Dust 240pm March 23, 2013.

 

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The Demise of a Snow Field

The MODIS-VIIRS Snow-Cloud RGB product has been fun to watch over the past week as the two main snow fields from our blizzard of February 24-25 disappeared.  Check out these two neat animated gifs from Quay and Torrance counties for the period February 27th – March 2nd.  Click the images to animate.  The previous post from February 27th showed these two areas on the MODIS true color images.  It took roughly a week for the snow fields to melt but they are finally gone after above normal temperatures impacted the region.  Only very minor differences are still occurring with temperature and humidity forecasts as soil moisture dries out across this area.

The gradual demise of a snow field over Quay County, New Mexico February 27 – March 2 as seen from MODIS-VIIRS Snow-Cloud RGB products.  Click the image to animate.

The gradual demise of a snow field over Torrance County, New Mexico February 27 – March 2 as seen from MODIS-VIIRS Snow-Cloud RGB products. Click the image to animate.

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Blizzard Impacts East Central NM

The heaviest snowfall from the blizzard of February 24-25, 2013 can still be seen on satellite imagery across portions of east central NM.  The 1km True Color imagery shows a very well defined area where the heaviest snowfall occurred and the 500-meter Visible imagery from this same area details some interesting terrain features. The satellite images were posted as a Graphicast today and shared via Facebook.  The snow pack is still having a significant influence on humidity and temperature forecasts in this area and forecasters continue using the imagery to provide greater accuracy.  The snow cover imagery validated the 12 hour snowfall forecast during the heart of blizzard conditions with exceptional accuracy.  Snowfall amounts were slightly less than forecast however the areal coverage was pinpointed very well.

High temperature observation February 27, 2013. Snow pack has a major regulating factor on temperature and boundary layer moistening.

Minimum humidity observation February 27, 2013. Snow cover has a major regulating factor on temperatures and boundary layer moistening.

Snowfall forecast for the 12hour period of blizzard conditions across eastern NM.

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Early February Northeast Blizzard

The Northeast is bearing down for a blizzard as two storm systems are expected to merge off the East Coast early Saturday morning. Currently, one low pressure center is near Lake Erie and the other one is off the Virginia coast (see surface map below). Once the two systems phase off the East Coast, the new system is expected to rapidly deepen to 970 mb. Blizzard conditions will result as 1-2 feet of snow falls and winds gust to as high as 70 mph.

HPC 1500 UTC Surface Analysis Feb. 8, 2013

From a satellite perspective, how can some of the new GOES-R imagery and AIRS profiles help identify significant features associated with this unique synoptic set up? Below is an RGB Air Mass image from 0634 UTC this morning. The image gives a clear view of the coastal storm. Notice the green colors to the south of the main cloud shield, indicated by a blue arrow. The green colors represent warm, moist tropical air that is being drawn into the storm.  This air mass will provide abundant moisture to produce the robust snow fall amounts expected. A VIIRS/CRiS RGB Air Mass image from 0733 UTC this morning gives a broader view of the Eastern United States and shows the structure of both storms. The storm situated over the Great Lakes will usher cold air into the Northeast. There are also green colors to the north and northwest of the Great Lakes storm however they indicate cold, moist air.

NASA SPoRT Aqua MODIS RGB Air Mass Image  0634 UTC Feb. 8, 2013.
Yellow arrow points to ozone rich stratospheric air and Blue arrow points to warm, moist tropical air.

NASA SPoRT VIIRS/CRiS RGB Air Mass Image     0733 UTC Feb. 8, 2013.
Yellow arrow points to ozone rich stratospheric air

Stratospheric intrusions are commonly associated with rapidly developing cyclones and may be responsible for transporting higher momentum air to the surface to produce damaging winds at the surface. If we piece together information from the RGB Air Mass imagery, AIRS total column ozone, and a 300 mb map, can we find an explanation to why this system will be associated with strong wind gusts?  The 1200 UTC 300 mb observations, pictured below, show a 125 kt jet streak north of Maine. The red/orange colors in the MODIS RGB Air Mass imagery indicate the presence of a jet streak and high potential vorticity air.  The AIRS total column ozone, pictured below, indicates higher values of ozone in the same vicinity. The presence of high potential vorticity air and larger amounts of ozone signify higher momentum stratospheric air intruding into the troposphere. Some of this stratospheric air is being drawn into the Great Lakes storm, shown by the yellow arrows on the VIIRS/CRiS RGB Air Mass image. Unfortunately  there was not an AIRS pass to the east of the storm system to further confirm ozone-rich stratospheric air. As the system continues to progress, more AIRS data and RGB Air Mass data will be investigated to watch how stratospheric air is drawn into the storm and how it relates to the production of surface wind gusts.

300 mb Heights (dm) and Isotachs (kts) 1200 UTC Feb. 8, 2013. Image from NCAR RAL Real Time Weather Data website

AIRS Total Column Ozone 0630-0636 UTC            Feb. 8, 2013

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January 12, 2013 Dense Fog Event over Central North Carolina

By Ryan Ellis NWS WFO Raleigh, NC

On January 12th, a dense fog event over central NC prompted a Dense Fog Advisory across the CWA. This was the second night in a row where an extremely warm and moist airmass by January standards was in place over the region ahead of a strong cold front that brought significant rain to western NC and southern VA. This is the first time since having access to the VIIRS RGB Nighttime Microphysics Imagery that fog has shown up this widespread. The fog is clearly indicated with a blue color. This makes sense because dense amount of blue in the image is directly related to the 10.8 micron thermal channel which is related to the temperature of the surface. This is the first opportunity we have had to see fog with the micro physics imagery with a warm surface. Usually the fog appears as a light green color and it is tougher to tell between fog and low stratus. Since this was a slam dunk fog event there was no doubt about what we were seeing.
As a forecaster it was helpful to know which interstate corridors had the worst conditions. For our CWA this turned out to be the I-85 corridor north of Raleigh and the northern half of the I-95 corridor. In fact, later that morning a multi-vehicle accident was reported on I-95 southbound near Wilson that shut down the southbound lanes for several hours. While not exactly in the dense fog at the time of these images, this location is in the general area. According to these images, this location might have had some higher clouds over the area that were masking the fog. It is also conceivable that the fog had moved southward in the several hours between the time the image was captured and the time that the accident was reported. Either way, this was a great situational awareness tool to let us know that these two interstates in particular were in more danger than some of our other high traffic corridors.
Also in these images it is very easy to tell where fog ends and higher level debris clouds associated with the approaching cold front begin. This is clearly evident in southern VA where the higher red clouds quite definitively end and the blue color representing the fog begins. This is a big advantage over the general visible satellite imagery and the 11-3.9 micron channel that we usually use to forecast fog. While this imagery is only available a couple of times per morning, it has still proven to be a useful tool in operations.

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MODIS-VIIRS Night-time Microphysics RGB and 11-3.9um Imagery to Distinguish Cloud Heights

A semi-permanent large scale trough and its associated cold temperatures have  plagued much of the western US since Friday, January 11th.  Shortwave troughs embedded within the large scale feature periodically rotated in and out of New Mexico sending the occasional back door front into the eastern plains.  One such front slid southward on Saturday, January 12th before stalling just shy of Roswell.  Later that night, low clouds formed behind the front across much of the area.  Per area observations, no fog was reported at the time of the images below.

Another shortwave trough was approaching New Mexico from the north. The MODIS-VIIRS Night-time Microphysics RGB satellite image (left) clearly showed the difference between low-level clouds associated with the back door front (lime green) and the mid-level clouds associated with the approaching shortwave (brownish).  Interestingly, the imagery also captured low clouds present over the Zuni Mountains, an area void of surface observations, but did not show low clouds over any of the adjacent high terrain.  Low clouds nestled up against the west slopes of the northern mountains also showed up quite well.

To further distinguish the low clouds from the mid level clouds, the MODIS-VIIRS 11-3.9um imagery was used in conjunction with the aforementioned image.  In the 11-3.9um imagery, the low clouds clearly stand out in bright yellow, though in northwest New Mexico, there is very little, if any, indication of cloud cover.

Graphicast showing how night-time cloud cover was depicted on the MODIS-VIIRS Night-time Microphysics RGB and 11-3.9um imagery.

For reference, cloud ceilings per area observations across the eastern plains ranged from 1500 to 3500 feet, while ceilings across northwest NM were approximately 8000 feet.

The graphicast above was posted to NWS Albuquerque’s webpage and facebook page early Sunday morning, January 13th.

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MODIS-VIIRS 11micron Inversion Detection

The 1km MODIS-VIIRS 11micron product valid 0932UTC January 6, 2013 showed very high resolution temperature inversion patterns across northern NM and southern CO.  The 11micron product is overlaid with the surface observation network across the area on the graphicast example below.   High resolution details are captured well by the temperature observation network…including a well defined warm region where Ute Mountain sits within the San Luis Valley south of Alamosa.  Minimum temperatures are ingested into GFE to provide fine resolution details for the following nights forecast in persistence.  The black outlines in the temperature grid are public zone boundaries which capture the general topography quite well and focus where colder valley temperatures would occur.  The maximum temperature forecast also captures these strong inversion effects where weak mixing forces high temperatures to be warmer over mid slope areas than in valley areas.  While no major operational impact outside of improved high temperature forecasts is expected, it would be interesting to see how the extent of the cold pool over southern CO impacts the strength of drainage winds in the Rio Grande Valley for airport locations from Taos south to Santa Fe and Albuquerque.

Graphicast depiction of temperature inversions detected by MODIS-VIIRS 1km 11micron product.

Minimum Temperature Grid January 6, 2013

Maximum Temperature Forecast January 6, 2013

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