Tag Archives: clouds
By now, you probably know the drill: a little bit of discussion about a particular subject, throw in a few pop culture references, maybe a video or two, then get to the good stuff – high quality VIIRS imagery. Then, maybe add some follow-up discussion to emphasize how VIIRS can be used to detect, monitor, or improve our understanding of the subject in question. Not today.
You see, VIIRS is constantly taking high quality images of the Earth (except during orbital maneuvers or rare glitches). There isn’t enough time in a day to show them all, or go into a detailed discussion as to their relevance. And, nobody likes to read that much anyway. So, as we busily prepare for the upcoming holidays, we’re going to skip the in-depth discussion and get right to the good stuff.
Here then is a sample of interesting images taken by VIIRS over the years that weren’t featured on their own dedicated blog posts. Keep in mind that they represent the variety of topics that VIIRS can shed some light on. Many of these images represent topics that have already been discussed in great detail in previous posts on this blog. Others haven’t. It is important to keep in mind… See, I’m starting to write too much, which I said I wasn’t going to do. I’ll shut up now.
Without further ado, here’s a VIIRS Natural Color image showing a lake-effect snow event that produced a significant amount of the fluffy, white stuff back in November 2014:
As always, click on the image to bring up the full resolution version. Did you notice all the cloud streets? How about the fact that the most vigorous cloud streets have a cyan color, indicating that they are topped with ice crystals? The whitish clouds are topped with liquid water and… Oops. I’m starting to discuss things in too much detail, which I wasn’t going to do today. Let’s move on.
Here’s another Natural Color RGB image using the high-resolution imagery bands showing a variety of cloud streets and wave clouds over the North Island of New Zealand:
Here’s a Natural Color RGB image showing a total solar eclipse over Scandinavia in 2015:
Here’s a VIIRS True Color image and split-window difference (M-15 – M-16) image showing volcanic ash from the eruption of the volcano Sangeang Api in Indonesia in May 2014:
Here’s a VIIRS True Color image showing algae and blowing dust over the northern end of the Caspian Sea (plus an almost-bone-dry Aral Sea):
Here is a high-resolution infrared (I-5) image showing a very strong temperature gradient in the Pacific Ocean, off the coast of Hokkaido (Japan):
The green-to-red transition just southeast of Hokkaido represents a sea surface temperature change of about 10 K (18 °F) over a distance of 3-5 pixels (1-2 km). This is in a location that the high-resolution Natural Color RGB shows to be ice- and cloud-free:
Here’s a high-resolution infrared (I-5) image showing hurricanes Madeline and Lester headed toward Hawaii from earlier this year:
Here are the Fire Temperature RGB (daytime) and Day/Night Band (nighttime) images of a massive collection of wildfires over central Siberia in September 2016:
Here is a 5-orbit composite of VIIRS Day/Night Band images showing the aurora borealis over Canada (August 2016):
Here is a view of central Europe at night from the Day/Night Band:
And, finally, for no reason at all, here’s is a picture of Spain wearing a Santa hat (or sleeping cap) made out of clouds:
There you have it. A baker’s ten examples showing a small sample of what VIIRS can do. No doubt it will be taking more interesting images over the next two weeks, since it doesn’t stop working over the holidays – even if you and I do.
(What’s the Story) Middle-of-the-Night Glory?
A Morning Glory is a lot of things: a flower, a town in Kentucky, a popular choice for song and album titles, and – what is most relevant for us – it’s a rare atmospheric phenomenon that is both beautiful and potentially deadly.
For glider pilots, it’s the atmospheric equivalent to catching a 40-wave off the North Shore of Oahu. Like surfing the North Shore, the thrill is in catching a powerful wave and going for a ride, which only happens if you position yourself in the right spot. And, just like surfing a monster wave, one misstep can result in being crushed downward into a pile of jagged rocks and swept out to sea. The difference is, a North Shore wave is 10-12 m high and only travels a 100 m or so until it hits land and stops. A Morning Glory wave is 500-1000 m high and can travel hundreds of kilometers over a period of several hours. Here’s a picture of one:
Simply put, a Morning Glory is a solitary wave, or “soliton“. We talked about mesospheric bores before, which are another kind of soliton. In this case, however, the soliton propagates through (or along the top of) the atmosphere’s boundary layer. Sometimes, it produces a cloud or series of clouds that came to be known as a “Morning Glory” because these clouds commonly occur near sunrise in the one place on Earth where this event isn’t rare.
Enough talk. The Day/Night Band (DNB) on VIIRS just saw a one. Let’s see if you can see it:
This really is like “Where’s Waldo?” because the image covers a much larger area than the Morning Glory. Even I didn’t see it at first. But, zoom in to the corner of the image over the Gulf of Carpentaria. (You can click on any of these images to see the full resolution version.) Now do you see it?
Once more on the zoom, and it’s obvious:
But, this happened at ~1:30 AM local time – depending on where in that image you are looking – so maybe it’s a Middle-of-the-Night Glory instead of a Morning Glory. (Fun fact: Northern Territory and South Australia are on a half-hour time zone, GMT+9:30. Queensland and the rest of eastern Australia are at GMT+10:00. But, the southern states have Daylight Saving Time while the north and west do not. That means almost every state has it’s own time zone.)
The Gulf of Carpentaria is where Morning Glory clouds are most likely to form. And, this is the peak season for them. (The season runs from late August to mid-November.) What is rare is seeing them so clearly at night.
Since this image was taken one night before a full moon, there was plenty of moonlight available to the DNB to see the “roll clouds” that are indicative of the Morning Glory. You can even see ripples that extend beyond the endpoints of the clouds, which might be some kind of aerosol plume affected by the waves.
There is another way to see this Morning Glory, and it’s what we call the “low cloud/fog product”. The low cloud/fog product is simply the difference in brightness temperature between the longwave infrared (IR) (10.7 µm) and the mid-wave IR (3.9 µm). For low clouds, this difference is positive at night and negative during the day. Here is an example of the low cloud/fog product applied to a new geostationary satellite, Himawari-8:
The Advanced Himawari Imager (AHI) on Himawari-8 is similar to VIIRS, except it has water vapor channels in the IR and it doesn’t have the Day/Night Band. It also stays in the same place relative to the Earth and takes images of the “full disk” every 10 minutes. That’s what allows you to see – in impressive detail – the evolution of this Morning Glory. The low, liquid clouds switch from white to black after sunrise because, as I said, the signal switches from positive (white) to negative (black) at sunrise. Ice clouds (e.g. cirrus) always look black in this product.
Here’s a zoomed in version of the above animation:
Of course, once the sun rises, the standard visible imagery from AHI captures the tail end of the Morning Glory:
And, once again, zoomed in:
At this point, it really is a Morning Glory, since it appeared at sunrise. Of course, at night, only the VIIRS Day/Night Band under full moonlight can show it in “all of its glory”. (Pun definitely intended.)
Pilots take note: the waves can still exist even when the clouds evaporate, and they are a source of severe turbulence.
If you want to know more about the phenomenon, watch this video with a lot of information or this video with a lot of pretty pictures. And, while a lot of people believe the cause of the Morning Glory is still a mystery, one scientist in Germany thinks the cause is now known. You can read all about his and other’s research into the science behind these solitary waves at this webpage.
UPDATE (12/16/2016): We’ve seen more examples of Morning Glory waves and clouds with Himawari-8. The formation of two Morning Glory waves may be seen on our Himawari Loop-of-the-Day webpage here and here. Plus, there is an extended loop covering a two day period shown in this very large animated GIF (83 MB).
Investigating Mysteries of the Deep, Dark Night
Conspiracy theorists will tell you that conspiracies exist everywhere; that they’re part of daily life; and that most people are ignorant of all the attempts by various governments around the world to covertly control every facet of your life. Only they know the truth. But, that’s just what they want you to believe! Conspiracy theorists are simply manipulating you in order to control you and create a New World Order! Wake up!
Full disclosure: I am subsidized by the U.S. government to inform people of the capabilities and uses of the satellite instrument called VIIRS and today I’ll show you how that satellite instrument can help separate fact from fiction when it comes to the latest conspiracy theory. (Of course, working for the government means I could be part of the conspiracy! Mwa ha ha!)
During the last week of August 2014, I was sent this link to a story from a pilot/photographer who captured “the creepiest thing so far” in his long flying career. I’ll quote his initial post again in its entirety here (for those of you too lazy to click on the links):
Last night [24 August 2014] over the Pacific Ocean, somewhere South of the Russian peninsula Kamchatka I experienced the creepiest thing so far in my flying career. After about 5 hours in flight we left Japan long time behind us and were cruising at a comfortable 34.000ft with about 4,5 hours to go towards Alaska.
We heard via the radio about earthquakes in Iceland, Chile and San Francisco, and since there were a few volcanos on our route that might or might not be going off during our flight, we double checked with dispatch if there was any new activity on our route after we departed from Hongkong.
Then, very far in the distance ahead of us, just over the horizon an intense lightflash shot up from the ground. It looked like a lightning bolt, but way more intense and directed vertically up in the air. I have never seen anything like this, and there were no flashes before or after this single explosion of light.
Since there were no thunderstorms on our route or weather-radar, we kept a close lookout for possible storms that might be hiding from our radar and might cause some problems later on.
I decided to try and take some pictures of the night sky and the strange green glow that was all over the Northern Hemisphere. I think it was sort of a Northern Lights but it was much more dispersed, never seen anything like this before either. About 20 minutes later in flight I noticed a deep red/orange glow appearing ahead of us, and this was a bit strange since there was supposed to be nothing but endless ocean below us for hundreds of miles around us. A distant city or group of typical Asian squid-fishing-boats would not make sense in this area, apart from the fact that the lights we saw were much larger in size and glowed red/orange, instead of the normal yellow and white that cities or ships would produce.
The closer we got, the more intense the glow became, illuminating the clouds and sky below us in a scary orange glow. In a part of the world where there was supposed to be nothing but water.
The only cause of this red glow that we could think of, was the explosion of a huge volcano just underneath the surface of the ocean, about 30 minutes before we overflew that exact position.
Since the nearest possible airport was at least 2 hours flying away, and the idea of flying into a highly dangerous and invisible ash-plume in the middle of the night over the vast Pacific Ocean we felt not exactly happy. Fortunately we did not encounter anything like this, but together with the very creepy unexplainable deep red/orange glow from the ocean’s surface, we felt everything but comfortable. There was also no other traffic near our position or on the same routing to confirm anything of what we saw or confirm any type of ash clouds encountered.
We reported our observations to Air Traffic Control and an investigation into what happened in this remote region of the ocean is now started.
If you go back and click on the link, you’ll see he posted several pictures of the mysterious red lights along with more detailed information about where and when this occurred. To save you some time, here is a representative picture (taken at 11:21 UTC 24 August 2014). And here is the location of the aircraft when they saw the lights.
There are three parts to this story: 1) the bright flash of light that looked like lightning coming up from the surface; 2) the aurora-like features in the sky; and 3) the red and orange lights from the clouds below that appeared to be larger than ordinary ship lights.
Since the story was first posted, people from all over commented on what they thought the lights were and the pilot has been updating his webpage to cover the most common and/or most likely explanations. The media picked up the story and used it to claim the world was coming to an end. Existing theories range from UFOs (unidentified flying objects) and UUSOs (unidentified under-surface objects) operated by space aliens to covert military operations to spontaneously-combusting methane bubbling out of the ocean to “earthquake lights“. The pilot himself initially thought it was an underwater volcanic eruption.
So, can VIIRS shed light on what was going on? Yes – at least, on #2 and #3. VIIRS passed over the area in question at 15:35 UTC on 24 August, which is about 4 hours after the pilot took his pictures. This means VIIRS can’t say anything about the lightning-like flash that was observed. So #1 is unexplained.
As for #2 – the aurora-like features in the sky – those are simply airglow waves. We’ve discussed airglow and airglow waves before here and here.
Now, onto #3 where VIIRS is most informative: the mysterious surface lights. I mentioned the VIIRS overpass at 15:35 UTC on 24 August. Here’s what the Day/Night Band (DNB) saw:
Look at 47.5°N latitude and 159°E longitude. (You can click on the image, then on the “4329 x 2342” link below the banner to see the full resolution image.) Those are the lights the pilot saw! (Note also that this night was near new moon, so any illumination of the clouds in that area comes from airglow. Light in the northeast corner of the image is twilight from the approaching sunrise.)
Now, VIIRS also has bands in the short-, mid- and long-wave infrared (IR). Surely, they must have seen the heat signature put out by a volcanic eruption, right? Not necessarily. The pilot’s photographs clearly show the lights shining through a layer of clouds, and it doesn’t take much cloud cover to obscure heat signatures at these wavelengths. But, for completeness, here are the observed brightness temperatures at 3.7 µm (channel M-12) and 10.7 µm (channel M-15):
I don’t see any hotspots in either of those images near the location of the lights. But, as I said, this doesn’t disprove the presence of flaming methane or volcanic activity because of possible obscuration by clouds. (Note that the clouds are easier to see in the DNB image than either of the IR images because there is no thermal contrast between the clouds and the open ocean for the IR images to take advantage of. There is, however, reflection of airglow light available to provide contrast in the DNB.)
What about the night before? The night after? Were the lights still there?
Here’s the DNB image from 15:54 UTC 23 August 2014 (aka the night before):
The light is there in pretty much the same place, although it looks like one big circle instead of a number of smaller lights. What is going on? Once again, it’s clouds. This time, the longwave IR shows we have optically thicker and/or an additional layer of high clouds over the lights:
Optically thicker clouds scatter and diffuse the light more, and what you are seeing in the DNB image is the area of clouds surrounding the light source that scatter the light to the satellite. See how clouds scatter the city lights of the U.S. Midwest in this comparison between the DNB and M-15 from 07:42 UTC 2 September 2014:
(You may have to refresh the page if this before/after image trick doesn’t work.)
It’s not that Chicago, Illinois and Gary, Indiana extend that far out into Lake Michigan or that the map is not plotting correctly. It’s that the optically thicker clouds over the southern end of the lake scatter more of the light back to the satellite (and over a larger area than the lights themselves), making it appear that the light is coming from over the lake.
Similarly, scattering in the clouds makes the individual “mystery lights” over the Pacific Ocean appear to be one large area of light, instead of a number of smaller lights.
How do the lights look on 25 August 2014 (aka the night after)? Here’s the DNB image:
Did you notice that? The lights aren’t in the same place as before. They moved. In fact, I tracked these lights in the DNB for two weeks. And I got this result:
Do volcanoes move around from day to day? I think we can safely say the pilot was not observing a volcanic eruption.
Now, I don’t know much about spontaneously combusting methane bubbles in the ocean, but I doubt they are this frequent. The pilot found another pilot’s report of methane burning over the ocean from 9 April 1984 (which also occurred during a flight from Japan to Alaska) but, that was during the day and it was the resulting cloud that was spotted, not the actual flames. There is no evidence of clouds being produced by these lights over this two week period. There also isn’t much evidence from seismic activity over this period to justify earthquake lights.
Another theory put forth was meteorites but, again, it seems highly improbable that VIIRS would be capturing this many meteorites hitting this localized area of the Pacific Ocean every night for two weeks. Plus, they would have to be pretty large meteors to appear as large as these lights.
Unless you believe in UFOs (or UUSOs), that leaves only one question: why were the pilots of this flight so quick to dismiss ships? The DNB has seen ships on the ocean before, and they look a lot like this. (You can find examples of individual boats observed by the DNB here and an example of larger squid boat operations here.)
It is true that most squid boats use white or greenish light and the pictures clearly show red and orange lights coming up through the clouds. But military ships are known to use red lights at night, at least, according to Yahoo! Answers.
If it looks like a fleet of ships and moves like a fleet of ships, I’m guessing it’s a fleet of ships. Unless, of course, it’s a gam of sharks with freakin’ laser beams attached to their heads.
Hell Froze Over (and the Great Lakes, too)
This has been some kind of winter. The media has focused a lot of attention on the super-scary “Polar Vortex” even though it isn’t that scary or that rare. (I wonder if Hollywood will make it the subject of the next big horror movie in time for Halloween.) Many parts of Alaska have been warmer than Georgia, with Lake Clark National Park tying the all-time Alaskan record high temperature for January (62 °F) on 27 January 2014. (Atlanta’s high on that date was only 58 °F.) Sacramento, California broke their all-time January record high temperature, reaching 79 °F three days earlier. In fact, many parts of California had record warmth in January, while everyone on the East Coast was much colder than average. Reading this article made me think of an old joke about statisticians: a statistician is someone who would say: if your feet are stuck in a freezer and your head is stuck in the oven, you are, on average, quite comfortable.
One consequence of the cold air in the eastern United States is that Hell froze over. No, not the Gates of Hell in Turkmenistan. This time I’m talking about Hell, Michigan. Hell is a nice, little town whose residents never get tired of people telling that joke.
It has been so cold in the region around Hell that the Great Lakes are approaching a record for highest percentage of surface area covered by ice. This article mentions some of the benefits of having ice-covered Lakes, including: less lake-effect snow, more sunshine and less evaporation from the Lakes, which would keep lake levels from dropping. Although, that is at the cost of getting ships stuck in the ice, and reducing the temperature-moderating effects of the Lakes, which allows for colder temperatures on their leeward side.
This article (and many other articles I found) uses MODIS “True Color” images to highlight the extent of the ice. Why don’t they show any VIIRS images? Well, I’m here to rectify that.
First off, I can copy all those MODIS images and show the “True Color” RGB composite from VIIRS:
While it was a rare, sunny winter day for most of the Great Lakes region on 11 February 2014, it’s hard to tell that from the True Color imagery. I mean, look at this True Color MODIS image shown on NPR’s website. Can you tell what is ice and what is clouds?
There are ways of distinguishing ice from clouds, which I have talked about before but, it doesn’t hurt to look at these methods again and see how well they do here. First, let’s look at my modification of the EUMETSAT “Snow” RGB composite:
This “Snow” RGB composite differs by using reflectances at 2.25 µm in the place of the 3.9 µm channel that EUMETSAT uses. (Their satellite doesn’t have a 2.25 µm channel.) It’s easy to see where the clouds are now. Of course, now the snow and ice appear hot pink, which you may not find aesthetically pleasing. And it certainly isn’t reminiscent of snow and ice.
If you don’t like the “Snow” RGB, you may like the “Natural Color” RGB composite:
This has the benefit of making snow appear a cool cyan color, and has the added benefit that you can use the high-resolution imagery bands (I-01, I-02 and I-03) to create it. There is twice the resolution in this image than in the Snow and True Color RGB images. Here’s another benefit you may not have noticed right away: the clouds, while still white, appear to be slightly more transparent in the Natural Color RGB. This makes it a bit easier to see the edge of the ice on the east side of Lake Michigan and the center of Lake Huron, for example.
If you’re curious as to how much ice is covering the lakes, here are the numbers put out by the Great Lakes Environmental Research Laboratory (which is about a 25 minute drive from Hell) from an article dated 13 February 2014:
Lake Erie: 96%; Lake Huron: 95%; Lake Michigan: 80%; Lake Ontario: 32% and Lake Superior: 95%. This gives an overall average of 88%, up from 80% the week before. The record is 95% set in 1979, although it should be said satellite measurements of ice on the Great Lakes only date back to 1973.
Why does Lake Ontario have such a low percentage? That last article states, “Lake Ontario has a smaller surface area compared to its depth, so it loses heat more slowly. It’s like putting coffee in a tall, narrow mug instead of a short, wide one. The taller cup keeps the coffee warmer.” Doesn’t heat escape from the sides of a mug as well as the top? And isn’t Lake Superior deeper than Lake Ontario? Another theory is that “Lake Ontario’s depth and the churning caused by Niagara Falls means that it needs long stretches of exceptionally cold weather to freeze.” Does Niagara Falls really have that much of an impact on the whole lake?
So, what is the correct explanation? I’m sorry, VIIRS can’t answer that. It can only answer “How Much?” It can’t answer “Why?”
BONUS UPDATE (17 February 2014):
It has come to my attention that the very next orbit provided better images of the Great Lakes, since they were no longer right at the edge of the swath. Here, then, are the True Color, Snow and Natural Color RGB composite images from 19:07 UTC, 11 February 2014:
UPDATE #2 (18 March 2014): The Great Lakes ice cover peaked at 92.2% on 6 March 2014, just short of the all-time record in the satellite era. March 6th also happened to be a clear day over the Great Lakes, and VIIRS captured these images: