Single-Purpose Flour

Posted on November 16, 2016 by Curtis_Seaman

Think of a snowflake. What happens when that snowflake hits the ground? Now, picture other snowflakes – millions of them – all hitting the ground and piling up on top of each other, crushing our first poor snowflake. Skiers love to talk (and dream) about “fresh powder.” But, what happens when the “powder” isn’t so fresh?

Those delicate, little snow crystals we imagine (or look at directly, if we click on links included in the text) undergo a transformation as soon as they hit the ground. Compression from the weight of the snow above, plus the occasional partial thaw and re-freeze cycle (when temperatures are in the right range), breaks up the snow flakes and converts the 6-pointed crystals into more circular grains of snow. As more and more snow accumulates on top, the air in between the individual snowflakes/grains (which is what helps make it a good insulator) gets squeezed out, making the snow more dense. If enough time passes and enough snow accumulates, individual snow grains can fuse together. These bonded snow grains are called “névé.” If this extra-dense snow can survive a whole summer without melting, then a second winter of this compaction and compression will squeeze out more air and fuse more snow grains, creating the more dense “firn.” After 20 or 30 years of this, what once was a collection of fragile snowflakes becomes a nearly solid mass of ice that we call a “glacier.” Glaciers can be made up of grains that are several inches in length.

But, you don’t need to hear me say it (or read me write it), you can watch a short video where a guy in a thick Scottish accent explains it. (Did you notice his first sentence was a lie? Snow is made of frozen water, so glaciers are made of frozen water, since they are made of snow. I think what he means is that glaciers aren’t formed the same way as a hockey rink, but the way he said it is technically incorrect.) At the end of the video, the narrator hints at why we are looking at glaciers today: glaciers have the power to grind down solid rock.

When a glacier forms on a non-level surface, gravity acts on it, pulling it down the slope. This mass of ice and friction from the motion acts like sandpaper on the underlying rock, converting the rock into a fine powder known as “glacial flour” or, simply, “rock flour.” In the spring and summer months, the meltwater from the glacier collects this glacial flour and transports it downstream, where it may be deposited on the river’s banks. During dry periods, it doesn’t take much wind to loft these fine particles of rock into the air, creating a unique type of dust storm that is not uncommon in Alaska. One that can be seen by satellites.

And, wouldn’t you know it, a significant event occurred at the end of October. Take a look at this VIIRS True Color image from 23 October 2016:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (21:24 UTC 23 October 2016)

See the big plume of dust over the Gulf of Alaska? Here’s a zoomed in version:

Zoomed in version of above image.

That plume of dust is coming from the Copper River delta. The Copper River is fed by a number of glaciers in Wrangell-St. Elias National Park, plus a few in the Chugach Mountains so it is full of glacial sediment and rock flour (as evidenced by this photo). And, it’s amazingly full of salmon. (How do they see where they’re going when they head back to spawn? And, that water can’t be easy for them to breathe.)

Notice also that we have the perfect set-up for a glacial flour dust event on the Copper River. You can see a low-pressure circulation over the Gulf of Alaska in the above picture, plus we have a cold, Arctic high over the Interior shown in this analysis from the Weather Prediction Center. For those of you familiar with Alaska, note that temperatures were some 30 °F warmer during the last week in October in Cordova (on the coast) than they were in Glennallen (along the river ~150 miles inland). That cold, dense, high-pressure air over the interior of Alaska is going to seek out the warmer, less dense, low-pressure air over the ocean – on the other side of the mountains – and the easiest route to take is the Copper River valley. The air being funneled into that single valley creates high winds, which loft the glacial flour from the river banks into the atmosphere.

Now, depending on your preferences, you might think that the dust shows up better in the Natural Color RGB composite:

VIIRS Natural Color RGB composite of channels I-1, I-2 and I-3 (21:24 UTC 23 October 2016).

But, everyone should agree that the dust is even easier to see the following day:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (21:01 UTC 24 October 2016)

VIIRS Natural Color RGB composite of channels I-1, I-2 and I-3 (21:01 UTC 24 October 2016)

You can also see a few more plumes start to show up to the southeast, closer to Yakutat.

Since Alaska is far enough north, we get more than one daytime overpass every day. Here’s the same scene on the very next orbit, about a 100 minutes later:

VIIRS Natural Color RGB composite of channels I-1, I-2 and I-3 (22:42 UTC 24 October 2016)

Notice that the dust plume appears darker. What is going on? This is a consequence of the fact that glacial flour, like many aerosol particles, has a tendency to preferentially scatter sunlight in the “forward” direction. At the time of the first orbit (21:01 UTC), both the sun and the dust plume are on the left side of the satellite. The sunlight scatters off the dust in the same (2-dimensional) direction it was traveling and hits the VIIRS detectors. In the second orbit (22:42 UTC), the dust plume is now to the right of the satellite, but the sun is to the left. In this case, forward scattering takes the sunlight off to the east, away from the VIIRS detectors. With less backward scattering, the plume appears darker. This has a bigger impact on the Natural Color imagery, because the Natural Color RGB uses longer wavelength channels where forward scattering is more prevalent. Here’s the True Color image from the second orbit:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (22:42 UTC 24 October 2016)

The plume is a little darker than the first orbit, but not by as much as in the Natural Color imagery. Here are animations to show that:

Animation of VIIRS True Color images (24 October 2016)

Animation of VIIRS Natural Color images (24 October 2016)

There are many other interesting details you can see in these animations. For one, you can see turbid waters along the coast in the True Color images that move with the tides and currents. These features are absent in the Natural Color because the ocean is not as reflective at these longer wavelengths. You can also see the shadows cast by the mountains that move with the sun. Some of the mountains seem to change their appearance because VIIRS is viewing them from a different side.

The dust plumes were even more impressive on 25 October 2016, making this a three-day event. The same discussion applies:

VIIRS True Color composite of channels M-3, M-4 and M-5 (20:43 UTC 25 October 2016)

VIIRS True Color composite of channels M-3, M-4 and M-5 (22:26 UTC 25 October 2016)

VIIRS Natural Color RGB composite of channels I-1, I-2 and I-3 (20:43 UTC 25 October 2016)

VIIRS Natural Color RGB composite of channels I-1, I-2 and I-3 (22:26 UTC 25 October 2016)

Full disclosure, yours truly drove through a glacial flour dust storm along the Delta River on the north side of the Alaska Range back in 2015. Even though it was only about a mile wide, visibility was reduced to only a few hundred yards beyond the hood of my car. It felt as dangerous as driving through any fog. The dust event shown here was not a hazard to drivers, since it was out over the ocean, but it was a hazard to fisherman. Being in a boat near one of these river deltas means dealing with high winds and high waves. To forecasters, these dust plumes provide information about the wind on clear days (when cloud-track wind algorithms are no help), which is useful in a state with very few surface observing sites to take advantage of.

The last remaining issue for the day is one of terminology. You see, “glacial flour dust storm” is a mouthful, and acronyms aren’t always the best solution. (GFDS, anyone?) “Haboob” covers desert dust. “SAL” or “bruma seca” covers Saharan dust specifically. So, what should we call these dust events? Something along the lines of “rock flour”, only more proactive! And, Dusty McDustface is right out!

Watch for Falling Rock

Posted on July 11, 2016 by Curtis_Seaman

Q: When a tree falls in the forest and nobody is around to hear it, does it make a sound?

A: Yes.

That’s an easy question to answer. It’s not a 3000-year-old philosophical conundrum with no answer. Sound is simply a pressure wave moving through some medium (e.g. air, or the ground). A tree falling in the forest will create a pressure wave whether or not there is someone there to listen to it. It pushes against the air, for one. And it smacks into the ground (or other trees), for two. These will happen no matter who is around. As long as that tree doesn’t fall over in the vacuum of space (where there is nothing to transmit the sound waves and nothing to crash into), that tree will make “a sound”. (There are also sounds that humans cannot hear. Think of a dog whistle. Does that sound not exist because a human can’t hear it?)

What if it’s not a tree? What if it’s 120 million metric tons of rock falling onto a glacier? Does that make a sound? To quote a former governor, “You betcha!” It even causes a 2.9 magnitude earthquake!

That’s right! On 28 June 2016, a massive landslide occurred in southeast Alaska. It was picked up on seismometers all over Alaska. And, a pilot who regularly flies over Glacier Bay National Park saw the aftermath:

If you didn’t read the articles from the previous links, here’s one with more (and updated) information. And, according to this last article, rocks were still falling and still making sounds (“like fast flowing streams but ‘crunchier'”) four days later. That pile of fallen rocks is roughly 6.5 miles long and 1 mile wide. And, some of the rock was pushed at least 300 ft (~100 m) uphill on some of the neighboring mountain slopes.

Of course, who needs pilots with video cameras? All we need is a satellite instrument known as VIIRS to see it. (That, and a couple of cloud-free days.) First, lets take a look at an ultra-high-resolution Landsat image (that I stole from the National Park Service website and annotated):

Glacier Bay National Park as viewed by Landsat (courtesy US National Park Service)

Of course, you’ll want to click on that image to see it at full resolution. The names I’ve added to the image are the names of the major (and a few minor) glaciers in the park. The one to take note of is Lamplugh. Study it’s location, then see if you can find it in this VIIRS True Color image from 9 June 2016:

VIIRS True Color RGB composite image of channels M-3, M-4 and M-5 (20:31 UTC 9 June 2016), zoomed in at 200%.

Anything? No? Well, how about in this image from 7 July 2016:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (21:42 UTC 7 July 2016), zoomed in at 200%

I see it! If you don’t, try this “Before/After” image overlay, by dragging your mouse from side to side:

That dark gray area in the image from 7 July 2016 that the arrow is pointing to is the Lamplugh Glacier landslide! If the “Before/After” overlay doesn’t work, try refreshing the page, or look at this animated GIF:

Animation of VIIRS True Color images highlighting the Lamplugh Glacier landslide

Of course, with True Color images, it can be hard to tell what is cloud and what is snow (or glacier) and with VIIRS you’re limited to 750 m resolution. We can take care of those issues with the high-resolution (375 m) Natural Color images:

Animation of VIIRS Natural Color images of the Lamplugh Glacier landslide

Make sure you click on it to see the full resolution. If you want to really zoom in, here is the high-resolution visible channel (I-1) imagery of the event:

Animation of VIIRS high-resolution visible images of the Lamplugh Glacier landslide

You don’t even need an arrow to point it out. Plus, if you look closely, I think you can even see some of the dust coming from the slide.

That’s what 120 million metric tons of rock falling off the side of a mountain looks like, according to VIIRS!

Remote Islands V: St. Helena and Ascension

Posted on May 2, 2016 by Curtis_Seaman

You may have missed it in the news, but history was made last week:

A plane landed! Wow!

But, that’s not any old plane – that’s the first commercial airliner to land on St. Helena Island, which just completed the construction of their very first airport. That means there may be no more commercial sailing to this tiny island.

People prone to seasickness may be cheering the news. People afraid of flying might not. Did you notice it took three attempts to land that plane in the video above? The first pass was getting everything all lined up with no intention of landing. The landing gear wasn’t even down. The second – which looked like a roller coaster – was waived off due to the heavy crosswinds. The third time was the charm. However, it was such a shaky first landing, they’ve postponed the official opening of the airport.

So, where is St. Helena (pronounced Ha-LEEN-a), anyway? And why should I care?

Well, to answer the first question, it’s somewhere in this image:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (12:45 UTC 26 April 2016).

Did you find it? To help you with your bearings, Africa is just outside this VIIRS swath on the right side of the image. Two hints: click on the image to bring up the full resolution version. St. Helena is just northwest of the center of the image. It’s the only island in the image not covered by clouds. Fun fact: every island within this VIIRS swath is part of the British Overseas Territory of St. Helena, Ascension and Tristan da Cunha. We already looked more closely at Tristan da Cunha, so let’s take a look at the other two.

We can get a higher resolution look if we use the I-band Natural Color RGB composite:

VIIRS Natural Color RGB composite of channels I-01, I-02 and I-03 (12:45 UTC 26 April 2016).

Notice the island appears green in the center, surrounded by a ring of brown – just the way it looks on a really high resolution satellite image. VIIRS has the resolution to pick this out!

As for why you should care, I don’t know if I can answer that. If your first thought is to ask that question, you probably don’t care. But, there are a few interesting things to note about St. Helena (besides its new airport):

– It was once an important stopping point for ships sailing from Europe to India in search of spices. At least, until the Suez Canal opened.

– It later became a prison, housing those who fought against the British government and lost, including Napoleon Bonaparte, Dinuzulu, King of the Zulu Nation, and POWs from the Boer War.

– Along with Ascension Island, St. Helena helped inspire the modern environmental movement. And it was here that the first large scale experiments in weather modification took place. (Not counting rain dances, of course.)

After witnessing the effect of deforestation on the island in the late-1700s and early-1800s, it was believed that re-foresting would help keep moisture on the island, which would lead to more clouds and more rainfall. Ascension Island, which was essentially a barren wasteland when first discovered, was also planted with trees, creating it’s Green Mountain, which is clearly visible on very high resolution satellites.

Speaking of Ascension Island – where is that located? In the first image above, showing most of the Southern Atlantic, Ascension is near the upper left corner. It’s hard to see because it is covered by clouds. Just follow the 8 °S latitude line in from the left edge of the image.

Here it is at high resolution during a clear day:

VIIRS Natural Color RGB composite of channels I-01, I-02, and I-03 (14:03 UTC 20 April 2016).

If you look closely, you’ll see that there is a small cloud or two right over Green Mountain, so maybe the efforts of the early environmentalists paid off!

For completeness, Tristan da Cunha is in the lower left of the True Color image I posted at the top. While it is covered by clouds, you can tell it’s there because it is creating its own waves. Here it is on the next orbit, where it is closer to satellite nadir:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (15:24 UTC 26 April 2016).

If I’ve inspired you to visit these islands, ask the government to give me a commission. But, seriously, don’t forget to say “Hi!” to Jonathan. Or see the many other plants and animals that are found nowhere else on Earth.

UPDATE (16 October 2017): Reuters has reported that the airport is now officially open to commercial flights (only a year and half after I wrote the original blog post)!

The Sirocco and the Giant Bowl of Dust

Posted on March 14, 2016 by Curtis_Seaman

As mentioned before on this blog, there are typhoons, hurricanes, and cyclones, and they’re all basically the same thing. They’re just given a different name depending on where they occur in the world. Similarly, there are many different names for winds (not counting the classification of wind speeds developed by a guy named Beaufort). There’s the Chinook, the Santa Ana, the bora, the föhn (or foehn), the mistral, the zonda, the zephyr and the brickfielder. (A more complete list is here.) Some of these winds are different names for the same phenomenon occurring in different parts of the world, like the föhn, the chinook, the zonda and the Santa Ana. Others are definitely different phenomena, with different characteristics (compare the mistral with the brickfielder), but they all have the same basic cause: the atmosphere is constantly trying to equalize its pressure.

The Mediterranean is home to wide variety of named winds, one of which is the sirocco (or scirocco). (Europe is home to wide variety of languages, so this wind is also known as “ghibli,” “jugo” [pronounced “you-go”], “la calima” and “xlokk” [your guess is as good as mine].) Sirocco is the name given to the strong, southerly or southeasterly wind originating over northern Africa that typically brings hot, dry air and, if it’s strong enough, Saharan dust to Europe. Of course, after picking up moisture from the Mediterranean, the wind becomes humid, making life unpleasant for people along the north shore. Hot, humid and full of dust. Perhaps it’s no surprise that the sirocco is believed to be a cause of insomnia and headaches.

Now, I don’t know how hot it was, but an intense low pressure system passed through the Mediterranean around Leap Day and, out ahead of it, strong, southerly winds carried quite a bit of dust from northern Africa into Italy. Here’s what it looked like in Algeria. And here’s what it looked like in Salento. See if you can see that dust in these True Color VIIRS images:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (12:09 UTC 28 February 2016).

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (11:48 UTC 29 February 2016)

No problem, right? With True Color imagery, the dust is usually easy to identify and distinguish from clouds and the ocean because it looks like dust. It’s the same color as the sky over Salento, Italy in that video I linked to. The top image shows multiple source regions of dust (mostly Libya, with a little coming from Tunisia) being blown out over the sea. The second image shows one concentrated plume being pulled into the clouds over the Adriatic Sea, headed for Albania and Greece.

By the way, this storm system brought up to 2 meters (6.5 feet) of snow to northern Italy, and even brought measurable snow to Algeria! Africa and Europe made a trade: you take some of my dust, and I’ll take some of your snow.

But, this wasn’t the worst dust event to hit Europe recently. Here’s what the VIIRS True Color showed over Spain and Portugal on 21 February 2016:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (12:40 UTC 21 February 2016).

And VIIRS wasn’t the only one to see this dust. Here’s a picture taken by Tim Peake, an astronaut on the International Space Station. Again, it’s easy to pick out the dust because it almost completely obscures the view of the background surface. But, what if the background surface is dust colored?

We switch now to the other side of the world and the Takla Makan desert in China, where the dust has been blowing for the better part of a week:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (07:11 UTC 4 March 2016).

Can you tell what is dust and what is the desert floor? Can you see the Indian Super Smog on the south side of the Himalayas? Here is the same scene on a clear (no dust) day:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (07:49 UTC 2 March 2016).

There is a subtle difference there, but you need good eyesight to see it. It might be easier to see if you loop the images:

Animation of VIIRS True Color images (1-7 March 2016)

Animation of VIIRS True Color images of the Takla Makan desert (1-7 March 2016).

You’ll have to click on the image to see it animate.

Did you notice the dark brown areas surrounding the Takla Makan? Those are areas that have green vegetation during the summer. Notice how they become completely obscured by the dust as the animation progresses. That’s one one way to tell that there’s dust there. But, as we have seen before, there are other ways to see the dust.

There’s EUMETSAT’s Dust RGB composite applied to VIIRS:

Animation of VIIRS EUMETSAT Dust RGB images (1-7 March 2016)

Animation of VIIRS EUMETSAT Dust RGB images of the Takla Makan desert (1-7 March 2016).

That’s another animation, by the way, so you’ll have to click on it to see it animate. The same is true for the Dynamic Enhanced Background Reduction Algorithm (DEBRA), which we also talked about before:

Animation of VIIRS DEBRA Dust Product images (1-7 March 2016)

Animation of VIIRS DEBRA Dust Product images of the Takla Makan desert (1-7 March 2016)

But, there’s one more dust detection technique we have not discussed before: the “blue light absorption” technique:

Animation of VIIRS Blue Light Dust images (1-7 March 2016)

Animation of VIIRS Blue Light Dust images of the Takla Makan desert (1-7 March 2016).

The Blue Light Dust detection algorithm keys in on the fact that many different kinds of dust absorb blue wavelengths of light more than the longer visible wavelengths. It uses this information to create an RGB composite where dust appears pastel pink, clouds and snow appear blueish and bare ground appears green. Of course, other features can absorb blue light as well, like the lakes near the northeast corner of the animation that show up as pastel pink. But, depending on your visual preferences and ability to distinguish color, the Blue Light Dust product gives another alternative to the hot pink of the EUMETSAT Dust RGB, the yellow of DEBRA, and the slightly paler tan of the True Color RGB.

One question you might ask is, “How come DEBRA shows a more vivid signal than the other methods?” In the True Color RGB, dust is slightly more pale than the background sand, because it’s made up of (generally) smaller sand particles (which are more easily lofted by the wind) that scatter light more effectively, making it appear lighter in color. In the EUMETSAT Dust RGB, dust appears hot pink because the “split window difference” (12 µm – 10.7 µm) is positive, while the difference in brightness temperatures between 10.7 µm and 8.5 µm is near zero and the background land surface is warm. In DEBRA, the intensity of the yellow is related to the confidence that dust is present in the scene based on a series of spectral tests. DEBRA is confident of the presence of dust even when the signals may be difficult to pick out in the other products, either because it’s a superior product, or because its confidence is misguided. (Hopefully, it’s the former and not the latter.)

By the way, the Takla Makan got its name from the native Uyghurs that live there. Takla Makan means “you can get in, but you can’t get out.” It has also been called the “Sea of Death.” I prefer to call it “China’s Big Bowl of Dust.” It’s a large area of sand dunes (bigger than New Mexico, but smaller than Montana) surrounded on most of its circumference by mountains between 5000 and 7000 m (~15,000-21,000+ feet!). The average annual rainfall is less than 1.5 inches (38 mm). That means when the wind blows it easily picks up the dusty surface, but that dust can’t go anywhere because it’s blocked by mountains (unless it blows to the northeast). The dust is trapped in its bowl.

The Takla Makan is also important historically, because travelers on the original Silk Road had to get around it. Notice on this map, there were two routes: one that skirted the northern edge of the Takla Makan and one that went around the southern edge. This part of Asia was the original meeting point between East and West.

CIRA produces all four imagery products over the Takla Makan desert in near-real time, which you can find here. And, in case you’re curious, you can check out how well DEBRA and the EUMETSAT Dust products compare for the dust-laden siroccos over southern Europe and northern Africa by clicking here and here (for the first event over Spain and Portugal) or here and here (for the second one over Italy and the Adriatic Sea).

Indian Super-Smog

Posted on December 8, 2015 by Curtis_Seaman

We’ve poked a lot of fun at China and their serious smog problem. (Just this week, Beijing schools had their very first “smog day.” It’s just like a “snow day”, except you can’t go outside and write your name in it.) But, as it turns out, China is not the only country to produce super-thick smog. India does it, too. And, from the point of view of human health, India’s smog may actually be worse!

The World Health Organization just released a list of the Top 20 smoggiest cities, and 13 of them are in India (plus 1 in Bangladesh and 3 in Pakistan). Not a single Chinese city was anywhere in the Top 20! I’d consider taking back some of things I’ve said about China, except that 1) I never lied (although I did quote Brian Williams), and 2) the Chinese government is now instituting “smog days” because the smog is so bad. What I will do is stop comparing every type of air pollution to Chinese smog. From now on (at least until they start making some positive changes), India is the paragon of poor air quality on this blog.

Since VIIRS has no trouble seeing Chinese smog, it should have no problem seeing Indian smog. And it doesn’t:

VIIRS True Color RGB composite of channels M-4, M-4 and M-5 (07:14 UTC 18 November 2015).

You guessed it: all that gray area is optically thick smog! Let’s not forget, too, that India is the seventh largest country in world (2.4% of the Earth’s total surface area!), which is quite a large area to be covered by smog.

In the True Color image above from 18 November 2015, you can see that the people of Tibet are grateful for the Himalayas, which are an effective barrier to the smog. They may not get much air up there on the highest plateau in the world, but what little there is is much cleaner than what’s down below!

If your respiratory system is sensitive to this kind of thing, you might not want to read any further. Consider this your trigger warning. For those few brave enough to continue – prepare yourself, because it gets worse!

Here’s another VIIRS True Color image from 14 November 2015:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (06:50 UTC 14 November 2015).

Now it’s even harder to see the background surface along the base of the Himalayas. And, it’s easy to compare India’s pollution with Burma’s – I mean Myanmar’s – clean air.

VIIRS passed over the center of India on 11 November 2015 and saw that almost the entire country was covered by smog, with the thickest smog near Delhi:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (07:46 UTC 11 November 2015).

November 11^th was the night of Diwali, the Hindu, Sikh and Jain “Festival of Lights” celebrating the “triumph of goodness over evil and knowledge over ignorance.” If you clicked that link and thought, “that doesn’t look so bad,” then note that the first few pictures were taken in England. In India, it was much smokier. I guess lighting all those fireworks in India comes with this “pro”: they can light the way through the thick smog; and this “con”: they give off smoke that adds to the thick smog. And, while the smog didn’t stop people from celebrating Diwali, it did affect people’s plans. It also caused a huge increase in the market for air purifiers.

The super-smog was not confined to November or Diwali. It’s still going on! Here’s a VIIRS image from 5 December 2015:

VIIRS True Color RGB composite of channels M-3, M-4 and M-5 (06:56 UTC 5 December 2015).

I assure you that India and Bangladesh are under there somewhere beneath all that gray muck!

As I mentioned in the previous post, we now have access to data from the new Japanese satellite, Himawari, which can be thought of as a geostationary version of VIIRS. Himawari-8 hangs out over the Equator at a longitude of 140 °E and it takes images of the full disk every 10 minutes. From its perspective, India is right on the edge of the Earth (which, in satellite meteorology is called “the limb”). This means Himawari’s line-of-sight to India has an extra long path through the atmosphere, and that makes the smog look even worse. Here’s a True Color/Geocolor loop of Himawari images of India’s “Worse-than-China” Super-Smog. You can find this and other amazing loops on our new “Himawari Loop of the Day” webpage. We also produce a lot of other Himawari imagery products, which we post here.

Shameless plugs aside, don’t forget: India’s smog is actually worse than China’s. And, unless you live in India, you probably didn’t think that was possible! (If you do live in India, get them to clean up the air!)

JPSS (SNPP and NOAA-20)

VIIRS Imagery and Visualization Team Blog

Tag Archives: true color

Single-Purpose Flour

Watch for Falling Rock

Remote Islands V: St. Helena and Ascension

The Sirocco and the Giant Bowl of Dust

Indian Super-Smog