Nantahala National Forest Wildfires 11-11-16

Above average temperatures have been persisting over a great portion of the United States, bringing drought-like conditions. One of the areas that have been experiencing the lack in precipitation is the Nantahala National Forest located in Western North Carolina. In Figure 1, the U.S. Drought Monitor shows the severity of the drought, highlighting areas of the Nantahala National Forest under Extreme (red) and Exceptional (purple) drought. More statistics of the drought can be seen and evaluated through the U.S. Drought Monitor website.


Figure 1: The U.S. Drought Monitor of the state of North Carolina and the criteria for drought intensity (right). Currently, one can see that Eastern North Carolina is experiencing no drought, however, Western North Carolina increases in drought intensity, seen by the black circle in the figure.

The extreme drought in Western North Carolina has prompted several wildfires in the Nantahala National Forest. To monitor these wildfires not only during the day but during the night-time hours one can utilize the Near-Constant Contrast (NCC) which is a derived product of the Day/Night Band (DNB) sensor on-board Suomi-NPP, a polar orbiting satellite. The NCC utilizes a sun/moon reflectance model that helps illuminate atmospheric features (i.e., clouds, lightning) and recognizes emitted lights sources (i.e., wildfires and city lights) around the globe.

To infer the current locations of the wildfires in Western North Carolina, an NCC image of a clear-sky atmosphere, during the full moon stage of the lunar cycle is utilized. Figure 2 below highlights a static image of the emitted city lights in Western North Carolina on 17 October 2016 at 0640Z.


Figure 2: NCC image of the emitted city lights located in Western North Carolina on 17 October 2016. In the top-left corner of the figure is the approximate percent visibility of the moon (~full moon) and the corresponding moon elevation angle (in degrees) above the horizon.

Figure 2 will now be compared to Figure 3 (below). Figure 3 consists of the current locations of the wildfires in North Carolina, denoted by the white circles, as of 0710Z on 11 November 2016.


Figure 3: NCC image of the emitted city lights and the wildfires in Western North Carolina on 11 November 2016. In the top-left corner of the figure is the approximate percent visibility of the moon (~full moon) and the corresponding moon elevation angle (in degrees) above the horizon.

An additional tool to complement the NCC is the GOES Infrared (IR) 3.9 um satellite imagery (Figure 4) that can dictate hotspots; areas within the imagery that are very hot, such as wildfires. One can use the same domain, that has been utilized in Figure 2 and 3 and overlay it with the IR imagery. One can see some of the hotspots, expressed in brightness temperature (dark grey to black colors), are located in the same white circles that were seen in Figure 3, verifying the location of the wildfires.


Figure 4: A corresponding GOES IR 3.9 um satellite imagery at 0710Z, 11 November 2016, showing the brightness temperatures (in degrees Celsius) of the hotspots. The same white circles that were used in Figure 3 were overlayed in this figure to complement and verify that the wildfires are located in these specific areas. 

For more information on the wildfires click the link, and to see the animation of the fires discussed above, click Figure 5 below.


Figure 5: An animated composite of Figures 2, 3 , and 4, please click on this figure.

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11 November 2016 Himawari imagery around Japan

In this blog entry, we look at imagery from the AHI instrument on Himawari-8 with  anticipation for GOES-R over the USA as the ABI instrument is very similar to AHI.

We start with the 0.64 micron (visible) band during the daytime hours of 11 November:

North of Japan, we observe a circulation (as depicted below) associated with a surface low with convection to the east and southeast of it along a frontal boundary.



Also note the islands that appear to be blocking the flow (as depicted above).

Next, we look at the 1.6 micron band, which will be one of the new GOES-R bands:

The 1.6 micron band is useful for cloud top phase discrimination.  Ice clouds are relatively absorbing at 1.6 microns, therefore glaciated clouds appear darker.  As the deeper convective clouds in the vicinity of the circulation and east of it along the front grow in vertical extent, they become darker, which indicates cloud top glaciation associated with vertical growth.  This information is in addition to many of the features we already viewed in the visible imagery at 0.64 microns.

Next we’ll look at 2 of the 3 water vapor bands that will be available on GOES, the 7.3 micron low-level tropospheric water vapor band:

and the 7.0 micron mid-level tropospheric water vapor band:

Looking at multiple water vapor bands with GOES-R will allow a better 3-dimensional perspective of the scene of interest.

The weighting function profile for the 7.3 micron band sees a lower layer (in altitude) relative to the 7.0 micron band.  The 7.3 micron band still shows some of the low-level clouds we observed in the visible imagery, along with numerous waves.  This channel also clearly delineates the upward and downward vertical motions around the surface low circulation.  Subsidence is associated with warmer brightness temperatures while lift is associated with cooler brightness temperatures.  We also see colder cloud tops being enhanced where convection develops.

The 7.0 micron band depicts even fewer low-level clouds compared to the 7.3 micron band due to the weighting function seeing a higher layer (in altitude), note the brightness temperatures are overall colder.  The circulation can still be seen in the imagery, which provides evidence for how deep the circulation is.  As you gain experience in viewing circulations with the 3 water vapor channels on GOES-R, you will get a better idea of the intensity and vertical extent of these circulations which can lead to better anticipation of trends observed in the imagery.

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