Daniel, Emilia and Fabio, oh my!
It’s been a while since we last looked at some tropical cyclones with VIIRS. If you don’t keep up to date on tropical activity, you might not know there that have been a few. Granted, since Debby dumped a bunch of rain on Florida three weeks ago, the Atlantic basin has been pretty quiet. The East Pacific basin, however, has had one storm after another. The national media has largely ignored them since they have posed no threat to any landmasses. See this article from the L.A. times. Boring! Unless you can capture video of Jim Cantore struggling to stand upright, it isn’t a hurricane, right?
Wrong! First of all, eastern Pacific hurricanes affect some major shipping lanes. Second, and this is true of all hurricanes: they transport energy and moisture and help moderate the temperature imbalance between the tropics and mid-latitudes. They are important components of global energy transport.
In this post, we are going to compare the view of hurricanes provided by VIIRS against the view provided by GOES (specifically GOES-15). On 9 July 2012, there were two storms in the East Pacific: Daniel and Emilia.
GOES-15 visible image (channel 1) of Hurricane Daniel, taken 22:45 UTC 9 July 2012. Image courtesy John Knaff.
There isn’t a big difference between the two VIIRS channels, although you can see a bit more detail in the higher resolution (I-05) image.
GOES-15 visible image (channel 1) of Hurricane Emilia, taken 21:00 UTC 9 July 2012. Image courtesy John Knaff.
In addition to the resolution differences, there is also a time difference of ~15 minutes between the VIIRS images and the GOES images. If you were to overlap these images, you would see that Emilia rotated a bit during that time. Emilia was not willing to hold the same pose for that long when having her picture taken. Once again, the M-15 image from VIIRS looks pretty similar to the I-05 image, so there’s no pressing need to show it.
Finally, let’s compare GOES-15 with VIIRS on Hurricane Fabio, which formed about a week after Daniel and Emilia were hurricanes.
GOES-15 visible image (channel 1) of Hurricane Fabio, taken 20:30 UTC 15 July 2012. Image courtesy John Knaff.
The GOES and VIIRS images of Fabio were taken only 6 minutes apart, so there is less movement to impede the comparison.
According to legend, Popocatépetl was a great warrior whose girlfriend, Iztaccíhuatl, died because her father was a jerk who lied. (An alternate story is that it was a rival warrior who was a jerk who lied.) Either way, Iztaccíhuatl was erroneously told that Popocatépetl died in battle, which caused her to die of grief. When Popoca, as he was known to his buddies, returned to find out that she was dead, he was very sad. Reports on what followed differ, but Popoca either died of grief himself, or committed suicide at the thought of living without Iztaccíhuatl. To commemorate these events, the gods turned them both into mountains. To this day, the mountain Popocatépetl spews out rock and ash and fire either because he’s still mad at what happened, or because it is his way of looking out for his girlfriend.
The name Iztaccíhuatl literally means “White Woman,” and is the name of the snow-covered mountain ~40 miles southeast of Mexico City. Popocatépetl literally means “Smoking Mountain,” and is the name given to the volcano just to the south of Iztaccíhuatl. It is one of Mexico’s most active volcanoes. Ole’ Popoca has recently begun to remind us that he is mad (or eternally vigilant).
The above image is a false-color RGB composite of VIIRS channels I-01, I-02 and I-03 taken at 19:53 on 23 April 2012. The volcanoes and nearby urban centers have been identified and labelled. Pico de Orizaba, Popocatépetl, and Iztaccíhuatl are the first, second and third tallest mountains in Mexico, respectively, and are normally the only mountains in Mexico to be snow-covered year-round. The snow on top of Pico de Orizaba and Iztaccíhuatl is clearly visible in the image. Popocatépetl lost its snow during the 1990s when it became more active. But, you can see the cloud of ash and steam from the volcano in the image, which is not being blown around in the wind as much on this day. In fact, you can watch a time-lapse video of the steam and ash cloud from a Mexican government webcam from around the time of the Suomi-NPP overpass where you can see the clouds produced/influenced by The Smoking Mountain.
In the above images, the red arrows are pointing to the same spot – the top of Popocatépetl. The upper image is from the DNB at 07:58 UTC on 20 April 2012, the lower image is from I-01 at 19:53 UTC on 23 April 2012 (the same time as the RGB composite). If you were to overlay the images on top of each other, you would see that the light source visible in the DNB image is right at the top of the volcano. Since there are no towns up there, and people surrounding the volcano have been evacuated, the light is coming from the erupting lava.
The upper image is the I-04 image. Channel I-04, at 3.74 µm, is very sensitive to hot spots such as wildfires or, in this case, volcanic eruptions. The dark (warm) spot identified is the heat signature of the molten rock that is erupting from the volcano. The cooler (brighter) ash cloud is visible in the I-04 image, but it shows up more clearly in the I-05 (11.45 µm) image underneath it.
Someone compiled a time-lapse series of images (14 April – 22 April) of Popocatépetl from a “NASA satellite” (presumably GOES-13) and posted the video to YouTube, which you can watch here.
Given its proximity to Mexico City, Popocatépetl is on the list of dangerous volcanoes to watch out for. The folks at WIRED are keeping their eye on it. Hopefully, Ole’ Popoca is just letting off a little steam, and not planning to get real violent. His girlfriend died a long time ago – it’s time to just let it go already.