No 82 - June 2024

Group for Earth Observation

Located some million miles from Earth, NASA’s EPIC (Earth Polychromatic Imaging
Camera) imager aboard the DSCOVR (Deep Space Climate Observatory) satellite,
captured this view of the April 8 total solar eclipse over the North American continent.
Image: NASA

GEO MANAGEMENT TEAM

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Copy for the Newsletter

GEO Quarterly Back-issue Archive

The Editor is always delighted to receive material for
inclusion in the GEO Quarterly Newsletter. These canrelate to any aspect of Earth Imaging, especially• Technical articles concerning relevant hardware andsoftware• Construction projects• Weather satellite images• Reports on weather phenomena• Descriptions of readers’ satellite imaging stations• Activities from overseas readers• Letters to the Editor• Problems and Queries for our experts to answer

GEO Quarterly has been in continuous publication since2004, and all previous issues are available on-line as
PDF copies from:https://leshamilton.co.uk/GEO/archive.htm

Contributions should of course be original and besubmitted to the editor by e-mail not later than the
middle of the month preceding publication.
If your article submission contains embedded images
and diagrams, please note that you must also submit
copies of the original images as separate attachments:
these are essential for page make-up purposes.
Materials for publication should be sent to the editor,
Les Hamilton, at

There is also a searchable index to all titles fromprevious years, and this can be downloaded from:https://leshamilton.co.uk/soft/geoindex-setup.exe

geoeditor@geo-web.org.uk

www.geo-web.org.uk

2

Les Hamilton

The cover image this month shows the recent total eclipse of the sun over the
USA as observed by DISCOVR, NOAA’s Deep Space Climate Observatory, whichmonitors space weather and climate, as well as providing deep space imagery of
the Earth’s surface from the L1 orbit, that neutral gravity point between the Earthand Sun, approximately one million miles from Earth. Read more on page 4.
Nearer home, Russia’s Meteor M 2-4 launched successfully on schedule—see
details on page 11—and transmitted its first visible images within 24 hours:
examples appear on pages 13, 21 and 38 thanks to Joachim Scharrer.
Recently, while delivering a presentation to a NOAA user group, Carl Reinemannwas challenged as to whether combining different satellite channels into colour
composite images was science or art. You can read Carl’s justification for his
process in an illustrated article on page 22. If any reader has thoughts on this, feel
free to contact the Editor with a contribution to the debate.

Contents
Total Solar Eclipse darkens North America
NASA Earth Observatory
Sau Reservoir Dries Up
NASA Earth Observatory
Wind-shaped sea ice in Antarctica
Copernicus Image of the Day
Gravity Waves off the West Coast of the United States
MODIS Web Image of the Day
Antarctica Unpinned
NASA Earth Observatory
Meteor M No 2-4
Les Hamilton
Aldabra Atoll: an outpost for evolution
NASA Earth Observatory
Aurora Borealis viewed from the ISS
NASA Earth Observatory
Making Sense of Holes in the Clouds
NASA Earth Observatory
The Amazon Plume
European Space Agency
Australia’s Channel Country
MODIS Web Image of the Day
A Blanket of Ash from Ruang
NASA Earth Observatory
Iceberg A 23a Continues Northward Drift
MODIS Web Image of the Day
The Science and Art of Post-processing Satellite Imagery
Carl Reinemann
Fresh Flows Spread Across IcelandNASA Earth Observatory
Death Valley flooded after Heavy Rain
Copernicus Image of the Day
Shrinking Lake Tharthar
MODIS Web Image of the Day
A Climate Archive Melts
NASA Earth Observatory
Tulips bloom in the Netherlands
Copernicus Image of the Day
Mining Lithium in Argentina
NASA Earth Observatory
Galapagos Island Volcano Lava Flow
European Space Agency
Ship Tracks over the Pacific
MODIS Web Image of the Day
One of the Largest Batteries in the World
NASA Earth Observatory
Low Pressure Systems surround Australia
David Sale
Montgomery Reef Revealed
NASA Earth Observatory
Secrets of the Maude Rise Polynya revealed
MODIS Web Image of the Day
Satellite Status		

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3

Total Solar Eclipse Darkens North America
NASA Earth Observatory
Story by Emily Cassidy

On April 8, 2024, millionsof Americans saw day turn
temporarily to night as theMoon passed between the Sun
and Earth to create a total solar
eclipse.
As people in the 185-kilometrewide path of totality looked up andsaw the Moon conceal the brightorb of the Sun and obscure all but
its wispy corona, Earth-observing
satellites captured imagery of
the Moon’s shadow as it raced
eastward over North America.
About 1 million miles from Earth,NASA’s EPIC (Earth Polychromatic
Imaging Camera) imager on the
DSCOVR (Deep Space Climate
Observatory) satellite, captured
this above view of Earth between
16:02 and 20:32 Universal Time.
DSCVR is a joint NASA, NOAA,
and U.S. Air Force satellite built toobserve our planet from Lagrange
Point 1, the gravitationally stable
position between the Sun andEarth.
The Moon’s shadow swept over
North America, from the Pacificcoast of Mexico, through Texas,
and over the Great Lakes before
crossing the Atlantic coast of
Newfoundland, Canada.
Observers on the ground had
a rare view of the Sun’s active
outer atmosphere, or corona.
Glowing loops of plasma called
solar prominences could also beseen extending into the corona.
Plasma is super-hot ionized gas
which flows along the tangled andtwisted structure of the Sun’smagnetic fields.
“This view of the corona will never
happen again, ever,” said Michael
Kirk, a research scientist in the
Heliophysics Division at NASA’s
Goddard Space Flight Center
during a live broadcast of theeclipse from Dallas, Texas. During
the broadcast, Kirk noted that the

The Lunar Shadow over North America on April 8, 2024
NASA Earth Observatory image by Michala Garrison and
Wanmei Liang, using data from DSCOVR EPIC

spiky and asymmetrical natureof the corona was a sign that theSun’s magnetic field was active
and approaching solar maximum.
As the Moon’s shadow moved
east across North America, the
NOAA‑20 satellite orbiting the
Earth from pole to pole captured
images of Earth from east to west.
The image overleaf is a mosaic
comprised of swaths of images
collected by the satellite at threedifferent times on April 8.
The right hand third of the image
shows the eastern United States
at about 17:10 Universal Time,
before the eclipse had begun.
The middle part was captured
at about 18:50 Universal Time,www.geo-web.org.uk

when the eclipse was in progressin the centre of the country.
Even outside of the path of
totality, skies were much darker
throughout the U.S.
The left third of the image wascollected at about 20:30 Universal
Time, after the Moon’s shadow
had moved out over the Atlantic
Ocean.
The path of totality included
portions of Texas, Oklahoma,
Arkansas, Missouri, Illinois,
Kentucky, Indiana, Ohio,
Pennsylvania, New York, Vermont,
New Hampshire, and Maine.
The next total eclipse to travel
across the lower 48 states fromcoast to coast will be in 2045.

4

This is a composite of three images taken during the April 8 total solar eclipse
NASA Earth Observatory images by Michala Garrison and Wanmei Liang, using VIIRS data fromNASA EOSDIS LANCE, GIBS/Worldview, and the Joint Polar Satellite System (JPSS).

www.geo-web.org.uk

55

Sau Reservoir Dries Up
NASA Earth Observatory
Story by Emily Cassidy

Three successive years of record
low precipitation have taken a toll on
northeastern Spain’s Catalonia region.
Satellite images show one of theregion’s largest reservoirs dried to atrickle in March 2024.
According to the Meteorological
Service of Catalonia, 2023 was thesecond-driest year on a record that
goes back 110 years, second only
to 2022. The past three years inCatalonia have all seen the least
amount of rain since 1914. In themeteorological agency’s annual
climate bulletin for 2023, the drought
was described as the ‘worst on
record.’ And parched conditions
have continued into 2024: Parts ofCatalonia received less than half of
the average (1991-2000) rainfall fromJanuary through early March, andcrops and reservoirs have dried up.

Sau Reservoir imaged by Landsat 9 on March 3, 2023
NASA Earth Observatory images by Wanmei Liang, using Landsat datafrom the U.S. Geological Survey.

On February 1 this year, the Catalan
government declared a drought
emergency, which placed restrictions
on water consumption for the region’s
six million residents, as well as
businesses and farmers. Such an
emergency is typically declared once
reservoir levels drop below 16%. The
average water levels of Catalonia’s
reservoirs stood at 14%t on March
8. In Barcelona, the Catalan capital,
public fountains and beach side
showers were turned off. Restrictions
were also been placed on residential
water, limiting daily use to about 210
litres per person.
The Pantà De Sau (Sau Reservoir),located 80 kilometres inland from
Barcelona, is the region’s secondlargest reservoir. It was created in1966 by damming the Ter River andflooding an old village, called Santa
Romà de Sau. The reservoir serves
as a water source for numerous towns
in the area, including Barcelona.
The images opposite show the
Sau Reservoir on March 3, 2023
on March 4, 2024. They wereacquired by Landsat 9 and Landsat
8, respectively. Receding water has
exposed bare ground at the bottom of

Sau Reservoir imaged by Landsat 8 on March 4, 2024
NASA Earth Observatory images by Wanmei Liang, using Landsat datafrom the U.S. Geological Survey.

the reservoir. Although not visible in
the images, the lack of water has also
exposed structures of the old village
of Santa Romà de Sau, including
an 11th-century church, which now
stands on dry land. Over the past
three years, the water level in thisreservoir has decreased substantially.
In April 2023, its capacity dipped towww.geo-web.org.uk

7% but continued drought throughwinter 2023 caused water levels torecede further, and by early March2024 capacity had dropped to just
1%. This time of year, the reservoir
capacity typically stands at about
65%. According to news reports, if thelack of rain continues, Barcelona may
begin importing water from Valencia.

6Wind-shaped sea ice in Antarctica
Copernicus Image of the day

Credit: European Union, Copernicus Sentinel-2 imagery

The katabatic winds in Antarctica are among themost remarkable meteorological phenomena on ourplanet. These winds are a result of gravity pullingdenser air downwards towards lower density air.
Katabatic winds can reach astonishing speeds,
sometimes blowing at the speed of a hurricane.
These winds shape the landscape of some regions of
Antarctica by decreasing air humidity and influencing

the distribution of ice and snow. This image was
acquired by one of the Copernicus Sentinel-2
satellites on 6 March. It shows sea ice shaped bykatabatic winds near Inexpressive Island in the Terra
Nova Bay, in Antarctica. Copernicus data informs
studies of katabatic winds, which provide valuable
insights into the complex dynamics of the Earth’s
atmosphere and our planet’s climate systems.

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77

Gravity Waves off the West Coast of the United States
Modis Web Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

On March 14, 2024, the Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terra satelliteacquired this stunning true-colour image showing gravity
waves off the California coast. Two sets of waves arevisible, one north of the mud-coloured San Francisco Bay
and another set south of the Bay.
Atmospheric gravity waves are similar to waves that occur
when the surface layer of a pond is disturbed, creating
rolling waves that can be seen from above. However,gravity waves form when the atmosphere, not water, isdisturbed. When air is forced upward by hills or mountains
into a layer of stable air, it sets up rolling waves of air,creating a ripple effect on the water surface. This can also

occur when different air masses interact, such as when
air flows off land surfaces and over the relatively warm,
moist air mass formed over bodies of water. Gravity waves
typically form perpendicular to the wind as it blows offcoastlines.
Atmospheric waves are usually invisible, both to humaneyes on Earth and in satellite imagery. An opticalphenomenon called sunglint, which is present in thisimage, often makes such waves visible. Sunglint occurs
when light is reflected directly back into the satellite
sensor. This creates a silvery-toned patch, such as seen inthis image, which can reveal air the motion of air within thesunglint area.

www.geo-web.org.uk

8Antarctica Unpinned
NASA Earth Observatory
Story by Kathryn Hansen

For many ice shelves around
Antarctica the 1970s was a bumpy
decade. Fast forward, and satellite
images show that many of thebumps once prominently visibleon the surface of ice shelves havesmoothed—implying that the
shelves have become thinner andless stable.
An ice shelf is the extension ofland-based ice—a tongue of a
glacier that has stretched out fromthe coast and on to the surfaceof the ocean. Most of the planet’s
ice shelves fringe Antarctica,
where they play an important rolein holding back, or buttressing,
the flow of ice from inland andupstream. Such buttressing canslow the discharge of ice into
the ocean and limit sea levelrise. Thick, stable ice shelves
perform this buttressing role mosteffectively.

Several bumpy areas are visible on the ice surface of Pine Island Glacier in thisimage acquired by the Landsat‑1 satellite in January 1973.
NASA Earth Observatory image by Wanmei Liang, using Landsat data from the
U.S. Geological Survey and pinning point data from B Miles R Bingham

Using satellite altimetry datacollected since the 1990s,
scientists previously foundsignificant thinning on ice shelvesin West Antarctica, the western
Antarctic Peninsula and partsof East Antarctica. Now Bertie
Miles and Robert Bingham of the
University of Edinburgh havelooked even further back in time,using 50 years of imagery fromLandsat satellites to extend ourview of the changing continent.
Their research shows that thethinning under way between
1973 and 1989 was limited tosmall regions within ice shelves,
mostly in the Amundsen Sea
Embayment and the Wilkes Land
coastline of East Antarctica. Then,from the 1990s onward, thinningspread rapidly. Their results were
published in the February 22
issue of Nature [1].
The extended look back in timeshows that the 1990s was aturning point. ‘While many
previous studies have reported

When the same area was imaged by Landsat 7 in 2001, several of the bumpy
areas have largely smoothed over.
NASA Earth Observatory image by Wanmei Liang, using Landsat data fromthe U.S. Geological Survey and pinning point data from B Miles R Bingham

ongoing ice shelf thinning around
Antarctica since the 1990s, we
didn’t previously know that a lot of
it started around then,’ Bingham
said.
Satellite altimetry data—

www.geo-web.org.uk

measurement of the height ofland and ice surfaces—was notavailable prior to the 1990s, so
Miles and Bingham instead used
optical images to track variationsin the bumps on the ice surface.

9

These bumps are surface
expressions of pinning points—
places where the floating ice shelf
is anchored onto a high pointof the sea floor. Pinning points
are a useful indicator of ice shelf
thickness: Bumps that become
smaller or even smoothed out
entirely over time indicate thatan ice shelf had thinned and had
possibly become unpinned.
“Bertie’s novel use of Landsat tomap the de-anchoring of pinningpoints serves as a proxy for ice
shelf thickness change, alongside
the more sophisticated altimetry
methods the community has
generally used,” stated Bingham.
The image pair on page 9 show
Pine Island Glacier, one of theregions in the Amundsen Sea
Embayment where thinning was
already underway in the 1970s.
Several bumpy areas visible on
the ice surface in January 1973
(upper image) are seen to be mostly
smooth in December 2001 (lower
image). These images were acquiredwith the MSS (Multispectral
Scanner) on Landsat 1 and theETM+ (Enhanced Thematic Mapper
Plus) on Landsat 7. Note that theimages use a grayscale palette toachieve a closer match between the
different sensors.

By then, the smooth, thinning shelf had lost additional ice along its
front and northern margin, and fractured ice was visible along thesouthern edge.
With Pine Island Glacier at or near the point of being completely
unanchored, its ability to buttress ice has already been minimised.
The ‘greater concern,’ Miles and Bingham pointed out in their paper,might be the other major ice shelves that are still heavily anchored but
showing signs of quickly losing their pinning points.
Reference

1 https://www.nature.com/articles/s41586-024-07049-0.pdf‘These images show the pinningpoints getting smaller through time
as warm ocean currents melt the ice
shelves, causing them to thin andsubsequently unanchor from the sea
floor highs,’ Miles said.
Miles and Bingham’s findings
confirmed that Pine Island Glacier
was thinning sooner than most
Antarctic ice shelves. Out ofroughly 600 pinning points thatthe researchers tracked, only 15
percent shrank in size from 1973
to 1989, including those on Pine
Island Glacier. That number grewto 25 percent between 1990 and
2000, and 37 percent between
2000 and 2022.
The image opposite, acquiredwith the OLI-2 (Operational Land
Imager-2) on Landsat 9, shows
Pine Island Glacier’s ice shelf inJanuary 2024.

When Pine Island Glacier was images by Landsat‑9 in January 2024, thesmooth, thinning shelf had lost additional ice along its front and northern margin,
and fractured ice was visible along the southern edge.
NASA Earth Observatory image by Wanmei Liang, using Landsat data from the
U.S. Geological Survey and pinning point data from B Miles R Bingham

www.geo-web.org.uk

10

Meteor M No 2-4
Les Hamilton

This photograph captures the moment that the Soyuz2.1b carrier launched with the Meteor M2-04 satellite aboard
Photo: Sergey Mamontov / RIA Novosti

The Meteor-M No 2-4 hydrometeorological satellite was
successfully launched from Vostochny cosmodrome
aboard a Soyuz-2.1b launch vehicle in the early hours
of February 29, 2024. Just 59 minutes and 46 seconds
following takeoff, the 3.2 tonne satellite successfully
separated from the rocket’s upper stage into its target
sun-synchronous orbit at an approximate altitude of
820 kilometres. During operation, Meteor-M No 2-4 will be
powered by electricity provided by solar arrays with a total
area of 31.5 square metres. The satellite’s design lifetime
is five years.
The upper stage of the launcher then continued on it way
to deliver an additional 18 Russian and foreign associatedsmall satellites into target orbits.
Meteor-M No 2-4 was manufactured by the VNIIEM
Corporation (part of the Roscosmos State Corporation)and has been designed to solve problems related to• Hydrometeorological support• Climate and environmental monitoring• Study of the Earth’s natural resources• Control of the heliogeophysical situation in near-Earthspace• Obtaining information from automatic measuring
platforms for data collection• Relaying signals from emergency beacons of the
COSPAS-SARSAT international satellite search andrescue system.
The ultra modern equipment aboard Meteor‑M No 2-4 also
includes an on-board radar complex based on an active
phased array antenna and heliogeophysical instruments(short-wave reflected radiation meter and radio frequency
mass spectrometer) which will enable it to provide allweather radar monitoring of the Northern Sea Routeand expand its range of controlled heliogeophysicalparameters. This data will be used for regular operational
mapping of ice conditions on internal and external seas.
Following a commissioning phase of in-flight testing, whicha Russian news outlet states could last up to six months,
continued overleaf ...

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This composite Meteor M2-4 image comprising three successive passes on April 6 was produced by Joachim Scharrer

development work on the creation of the Meteor-3M spacecomplex will be complete.
In the future, such spacecraft of the Meteor-M series will
be mass-produced. ‘Meteor-M’ No 2-4 is the sixth deviceof this series, created by order of the Roscosmos State
Corporation, which will make it possible to provide allweather radar monitoring of the Northern Sea Route. Afterthe constellation is completed with the eventual launchesof Meteor-M No 2-5 and Meteor M No 2-6, potentiallyduring 2025, these craft will be followed by the newgeneration of Meteor-MP satellites.

Just like its predecessor, Meteor M 2-4 started totransmit visible imagery the very day following launch,
and a fine early example appears on the following page.
Disappointingly, imaging ceased between April 4 andApril 11, but have been fairly regular since.
After three successive problematic Meteor launches(M2‑01 ditched into the sea during launch, M2‑02 suffereda meteor strike that completely disabled its LRPT service,and M2‑03’s antenna failed to fully deploy), it looks as
though Russia has at last established a weather satellitethat performs exactly as planned. Long may it last!

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12

Joachim Scharrer obtained this crisp image from Meteor M2-4 on March 2, 2024, just two days following the new satellite’s launchwww.geo-web.org.uk

13

Aldabra Atoll: an outpost for evolution
NASA Earth Observatory
Story by Lindsey Doermann

Aldabra Atoll as viewed by Landsat-9 on June 24, 2022
NASA Earth Observatory image by Wanmei Liang, using Landsat
data from the U.S. Geological Survey.

Aldabra Atoll in the Indian Ocean is one of the largest
raised coral reefs in the world. This atoll, consisting ofcoral islands ringing a shallow lagoon, is known for thehundreds of endemic species—including the Aldabra giant
tortoise—that live there. According to UNESCO, Aldabra
contains ‘one of the most important natural habitats forstudying evolutionary and ecological processes.’
Located more than 400 kilometres northwest ofMadagascar and more than 600 kilometres east of
mainland Africa, Aldabra is one of the coralline outerislands of the Seychelles. In fact, the atoll, which measures
35 kilometres east-west by 13 kilometres north-south lies
a full 1300 kilometres from the Seychelles capital city ofVictoria, on Mahé island. The OLI-2 (Operational Land
Imager-2) on Landsat 9 captured this image of the remoteatoll on June 24, 2022. Tides flow in and out of the lagoon
through channels between the large perimeter islands. The
land tops out at a mere 8 meters above sea level.
Due to the islands’ isolated location, rough terrain, andscarcity of fresh water, the human footprint on the atoll isrelatively small. A research station on West Island (alsocalled Picard Island) has operated since 1971, but tourism
is limited and carefully controlled. Aldabra Atoll was
designated a UNESCO World Heritage site in 1982 and a
Ramsar site in 2009.
Though the atoll may be remote and rugged, it is not
desolate. It contains a variety of habitats that have spurred
the evolution of specially suited flora and fauna. The atoll’svaried habitats support many species, including the largest
breeding population of frigate birds in the Indian Ocean
and one of only two oceanic flamingo populations in theworld.
In one remarkable case, a bird species on Aldabra evolved
to be flightless—twice. The islands have been completely
underwater at least once in their history when global
mean sea level was higher, wiping out all life on the atoll.
The fossil record contains evidence of a flightless rail (abird in the same family as coots and crakes) before thelast submergence, and of a flying white-throated rail thatevolved to live on the ground after the islands reemerged.

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14

With the lack of terrestrial predators and an abundance offood, the bird thrived without the ability to fly.
Seven different types of wetlands, including shallow marine
waters and sea grass beds, exist at Aldabra. Mangrove
forests line much of the lagoon-facing sides of the large
islands. They provide nesting sites for wading birds, aswell as feeding grounds for turtles, sharks, and othermarine species.
On land, the mostly herbivorous Aldabra giant tortoise(above) sits atop the terrestrial food chain. The populationof this social tortoise species is estimated to exceed
100,000. Males can weigh up to 250 kilograms andmeasure 1.2 meters in length.
In 2018, a small group of Aldabra giant tortoises wasreintroduced to neighbouring Madagascar, where no giant
tortoises had lived for 600 years due to over hunting.

Photograph by Dennis Hansen, University of Zurich

Ecologists believe the lumbering creatures could promoteforest regeneration on cattle-grazed land by distributing
seeds through their dung. They may also suppress fire risk
by feeding on grasses and dry leaves.

Aurora Borealis viewed from the ISS
NASA Earth Observatory
Caption by Andrea Wenzel

Image: NASA/JSC Gateway to Astronaut Photography of EarthAn astronaut aboard the International Space Station
took this photo of eastern Canada. The image wastaken near the northernmost limit of the station’s inclined
equatorial orbit, which tops out about 52 degrees northof the equator. The perspective includes a view of spacestation’s solar panels in the foreground, Earth’s horizon
about 1,500 kilometers (930 miles) away, and celestial
objects far in the distance. Lights, snow, and clouds
brighten the winter scene on Earth.
Two of Canada’s provinces—Quebec, andNewfoundland and Labrador—are pictured along withthe territory of Nunavut on the other side of the Hudson

Strait. Toward Earth’s limb, the coast of Greenlandis faintly visible beneath the clouds. Higher in theatmosphere, airglow hugs the curvature of Earth and thelight of the aurora cuts across the scene.
Thin cloud layers cover the Atlantic Ocean, while
clearer skies prevail over the land exposing snow
cover, the lights of small settlements, and rivers flowing
toward Canada’s coast. Tucked into the frozen scene
is Mistastin Lake, which partially fills the depressionof an impact crater. The crater serves as a sitewhere astronauts are trained in geology and work ontechniques for planetary exploration.

www.geo-web.org.uk
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15

Making Sense of Holes in the Clouds
NASA Earth Observatory
Story by Adam Voiland

Cavum clouds, also called hole-punch
clouds and fallstreak holes, look so
odd that people sometimes argue thatthey are signatures of flying saucers
or other unidentified anomalous
phenomena. Seen from below, they
can look as though like large circles or
ellipses have been cut neatly from theclouds, with feathery wisps remaining
in the middle of the hole.
They are equally impressive when
seen from above. This image showsa cluster of cavum over the Gulf of
Mexico off of Florida’s west coast on
January 30, 2024. It was capturedby the MODIS (Moderate Resolution
Imaging Spectroradiometer) on
NASA’s Terra satellite.
Otherworldly explanations are notrequired to explain the eye-catching
cloud formation. While scientists
have periodically mentioned thephenomenon in scientific journals andspeculated about its cause since the1940s, a pair of studies publishedin 2010 and 2011, led by University
Corporation for Atmospheric Research(UCAR) scientists, laid out an
explanation that put other theories torest. These cvum clouds are causedby airplanes as they move throughbanks of altocumulus clouds.
These mid-level clouds are composedof liquid water droplets that aresupercooled: that means that the
droplets remain liquid even whentemperatures are below the typicalfreezing point of water (zero degrees
Celsius). Supercooling happens whenwater droplets are exceptionally pureand lack those small particles—suchas dust, fungal spores, pollen, or
bacteria—around which ice crystals
typically form.
Supercooling may sound exotic,
but it occurs routinely in Earth’s
atmosphere. Altocumulus clouds,
which cover about 8% of Earth’s
surface at any given time, are mostly
composed of liquid water droplets
supercooled to a temperature ofaround -15°C.

NASA Earth Observatory image by Michala Garrison
using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview.

But even supercooled clouds havetheir limits. As air moves aroundthe wings and past the propellersof airplanes, a process known as
adiabatic expansion cools the waterby an additional 20°C or more. This
cooling can push the supercooled
liquid water droplets to the point offreezing even without the help of
airborne particles.
Ice crystals beget more ice crystals
as the liquid droplets continue tofreeze. The ice crystals eventuallygrow heavy enough that they begin
to fall out of the sky, leaving a void in
the cloud layer. The falling ice crystals
are often visible in the center of theholes as wispy trails of precipitationthat never reach the ground—features
called virga.
Unlike previous attempts to
explain the phenomena, the UCAR
researchers, with colleagues fromseveral other institutions, including
NASA’s Langley Research Center,made use of a combination of aircraft

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flight data, satellite observations,and weather models to explain how
the cavum clouds form and to track
how long they lasted. When planes
passed through clouds at a fairly
sharp angle, the researchers foundthat small, circular cavum appeared.
If they passed through the clouds at
a shallow angle, longer ‘canal clouds’
with lengthy virga trails, like the one
shown above, became visible.
Other factors that can affect the lengthof these clouds include the thicknessof the cloud layer, the air temperature,and the degree of horizontal wind
shear, the researchers reported. Their
analysis showed that a full spectrumof aircraft types—including large
passenger jets, regional jets, private
jets, military jets, and turboprops—canproduce cavum and canal clouds.
With more than 1,000 flights arriving
at Miami International Airport eachday, there are many opportunities forplanes to encounter the atmosphericconditions needed to produce cavum
clouds.

16

The Amazon Plume
European Space Agency

Image contains modified Copernicus Sentinel data (2022), processed by ESA / License CC BY-SA 3.0 IGO

Originating in the Andes, the Amazon River flows east,
traversing six South American countries before reaching
the northeast coast of Brazil, where it empties into the
Atlantic. The sediment-laden river appears brown as it
flows to the open ocean in the upper centre of the image.
The coast is surrounded by a muddy-brownish plume ofsuspended sediment, carried from upstream to the mazeof channels constituting the 270 kilometre wide mouthof the Amazon. Discharge from the Amazon River, theAmazon plume, accounts for around 20% of the global
input of freshwater into the ocean from Earth’s land
surfaces.
The Amazon has over 1000 tributaries, some of which arevisible as thin, winding lines entering the river from thesouth, including the Tapajos River to the west and, further
downstream, the Xingu River. The dark colour of thesesediment-poor tributaries contrasts with the brownish
sediment-rich Amazon waters. The Tapajós-Xingu area isan important moist forest ecoregion. The colour of the landvaries, ranging from the deep green of dense, untouchedvegetation to various tones of brown, highlighting thecontrast between the rainforest and sprawling cultivation—
the fishbone-like patterns particularly visible along the
highway. Light green hues across the image denoteagricultural areas, which were once covered by rainforest.
The somewhat geometric shapes, which appear darkgreen and brown, result from forest clear-cutting.
Rainforests worldwide are disappearing at an alarming
rate, a matter of great concern owing to their pivotal role in
the global climate, and their status as habitats for a wide
range of plants, animals and insects.
With their unique view from space, Earth observation
satellites like Copernicus Sentinel-3 are instrumental inhighlighting the vulnerability of rainforests by documenting,on a large scale, the extent and damage due todeforestation, particularly in remote regions.

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Australia’s Channel Country
MODIS Web Image of the Day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

In Queensland, fierce storms in January 2024 brought
stunning greening to Australia’s Channel Country in April.
In late January and early February, Queensland
received a major drenching from Tropical Cyclone Kirrily.
According to the Queensland Government website,a metre of rain fell over the northern part of the statenear landfall on January 25. Then, between January
29-30, more than 300 mm fell in southeast Queensland.
Additional soaking occurred from the storm’s remnants
and from moisture-laden low pressure systems in theregion through late February.
Since mid-February, stormwater has been moving slowly
southward through Australia’s Channel Country, covering
about 8-10 kilometres per day, according to the Australia
Bureau of Meteorology (BoM), ultimately heading toSouth Australia’s Lake Eyre. The Channel Country
bioregion is made up of a vast area of arid and semi-arid land across parts of Queensland, South Australia,
Northern Territory, and New South Wales, with about
seventy percent found in southwestern Queensland.
Most of the crisscrossing channels are ephemeral, fillingwith water only during heavy flood conditions.
On April 10, 2024, the Moderate Resolution Imaging
Spectroradiometer (MODIS) acquired this true-colour
image of greening along the Georgina, Diamantina, andCoopers Creek Rivers in the Queensland portion ofAustralia’s Channel Country.
Floodwaters had reached these rivers by March 19,
according to the BoM and continued to creep southward.
By April 9, water had reached the northern tip of Kati
Thanda-Lake Eyre (not visible but located south of
this image). Meanwhile, the arid lands surrounding the
Channel Country rivers had burst forth in glorious green
vegetation.

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18

A Blanket of Ash from Ruang
NASA Earth Observatory
Story by Adam Voiland

Ruang is a small volcanic island in
the Sangihe Islands arc in North
Sulawesi, Indonesia, home to about
800 people. Late on April 16, 2024,
the mountain roared to life, unleashinga series of explosive eruptions that,at times, sent plumes of ash and gas
billowing high into the stratosphere.
The eruption also bombarded theisland with tephra, small pebbles oflapilli, and fine shards of pulverizedrock called ash.
This pair of Landsat satellite images
above highlights how the eruption
transformed the landscape. The OLI-2(Operational Land Imager-2) captured
the image in figure 1 on April 12 thatshows Ruang’s lush green vegetation
before the eruption. The OLI image
in figure 2, acquired on April 20,
shows the same area after volcanic
debris had blanketed the island. The
image also shows signs of pyroclastic
flows—destructive torrents of hot ash,rock, soil, and gas—that poured down
the mountain’s slopes and left thickdeposits at the base.

Figure 1 - Landsat OLI-2 image of Ruang on April 12, four days prior to the eruption

Settlements on the north side of theisland were among the hardest hit
with volcanic debris. On the west side,
tephra also blanketed Laingpatehi,
the island’s largest village. The brightwhite features obscuring parts of
the island are likely passing clouds,
though some of them could be
volcanic plumes emitted by the stillactive volcano.
According to initial assessments by
Badan Nasional Penanggulangan
Bencana (BNPB), Indonesia’s disastermanagement agency, heavy ashfall
and volcanic rock fragments severely
damaged or destroyed more than
500 houses. It also damaged crops
and farms.
The ash posed a hazard toaviation, prompting widespreadflight cancellations and diversions.
Authorities closed the Sam RatulangiInternational Airport in the nearby
provincial capital of Manado dueto the ash, disrupting travel forthousands of people.

Figure 2 - Landsat OLI-2 image of Ruang on April 20, four days after to the eruption
NASA Earth Observatory images by Michala Garrison
using Landsat data from the U.S. Geological Survey

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19

The airport reopened on April 22, after rainfall washedaway ash on the runway, and after BNPB had loweredthe volcanic alert level.

April 17, according to Simon Carn, a volcanologist at
Michigan Technological University. The following day,other satellites measured about 0.3 teragrams.

A geostationary satellite operated by the Japan
Meteorological Agency and polar-orbiting satellites
operated by NASA and NOAA all observed ash and sulfur
dioxide streaming from Ruang as the volcano erupted.

“The actual sulfur dioxide emission was probably
between 0.3 and 0.5 teragrams, well below thethreshold for significant climate impacts,” statedCarn.

According to Ghassan Taha, an atmospheric scientist
at NASA’s Goddard Space Flight Center, data from the
Ozone Mapping and Profiler Suite (OMPS) Limb Profiler(LP) show that the volcanic plume reached an altitude
of about 20 kilometres into the stratosphere, the second
layer of the atmosphere above the ground. Atmosphericscientists monitor the quantity of particles and gases that
volcanoes inject into the stratosphere because material
reaching this altitude can spread widely and have global
effects on the climate.

The 1991 eruption of Mount Pinatubo in the Philippines,
which caused a global cooling of about 0.5°C for abouta year, released approximately 20 teragrams of sulfur
dioxide into the stratosphere. More recently, the 2022
Hunga Tonga-Hunga Ha’apai eruption injected an
estimated 0.5 to 1 teragrams.

“We expect to see aerosol particles circulating in thestratosphere for weeks, if not months,” Taha said.
In recent decades, volcanic eruptions have injectedmaterial into the stratosphere about once a year.
However, the injection of at least 5 teragrams (1teragram equals 1 million tonnes) of sulfur dioxide is
generally required to produce enough aerosol particles
to temporarily change the reflectivity of the upper
atmosphere, according to climatologists. In most cases,
the amount of material reaching the stratosphere has
been modest and below that threshold.
After the eruption at Ruang, an infrared sensor on
the geostationary Himawari satellite measured a total
emission of about 0.5 teragrams of sulfur dioxide on

Ruang, whose name means ‘space’ or ‘room’ in the local
Bugis language, has a long eruptive history and is one
of Indonesia’s most active and dangerous volcanoes.
Major explosive eruptions have occurred in 1634, 1670,
1843, 1871, 1904, 1956, and 2002, according to the
Global Volcanism Program. The 1871 eruption triggered atsunami that devastated a village on a nearby island andcaused hundreds of deaths.
Officials warned the 2024 eruption could trigger lahars—
volcanic mudflows—as rain intermingles with fallen ash
in the coming days and weeks. The eruption also raised
fears of potential tsunamis from volcanic flows entering
the sea, prompting multiple tsunami warnings, thoughno significant tsunamis have occurred, according to the
local volcanic survey (PVMBG) and BNPB. Indonesianauthorities coordinated the evacuation of over 16,000
residents from areas most at risk of pyroclastic flows, ash
falls, and tsunamis. Since the eruption began, no deaths
or injuries have been reported.

Iceberg A 23a Continues Northward Drift
MODIS Web Image of the Day
On April 11, 2024, theModerate Resolution Imaging
Spectroradiometer (MODIS) on
NASA’s Terra satellite captured atrue-colour image of a decades-old
and immensely large iceberg drifting
slowly northwards into warmer
waters.
Iceberg A23a broke from the Filcher
shelf in Antarctica in 1986 and quickly
grounded on the seafloor of thesouthern Weddell Sea, only about
200 km from its calving location.
The berg became unstuck from theseafloor in the early 2020s, likely due
to melting from below the waterline.
Since beginning to drift freely, it has
made slow progress northward.

First, it took its time exploring theWeddel Sea, riding the currents of
the Weddel Sea Gyre for most of
the summer of 2023. Then, from
November 2023 to February 2024 it
took a lengthy spin on the currents
off the tip of the Antarctic Peninsula,
performing a full pirouette before
capturing a more northerly current toride.
On April 12, the U.S. Ice Center
reported that A23a was locatedroughly half-way between the tip of
the Antarctic Peninsula and South
Georgia Island. Icebergs in thisregion usually drift eastward around
South Georgia where they begin tofind warmer waters and ultimately
melt.

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Image Credit: MODIS Land Rapid Response
Team, NASA GSFC

20

When Meteor M2-4 initiated a test mode by simultaneously transmitting all three of its infrared channels on April 24,
Joachim Scharrer produced this interesting MCIR false-colour composite image by processing the data SATDUMP.

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21

The Science and Art of Post-processing Satellite Imagery
By Carl G. Reinemann, USRadioguy.com (https://usradioguy.com)

Figure 1 - A GOES 16 image rendered in color by the author

At the most recent NOAA user group meeting, after I had finished my presentation, I received a coupleof questions regarding my last slide, pictured above, which was a full disk image of planet Earth derived
from the GOES-16 satellite which I had subsequently processed further using using bands 02 and 13. The
question was: ‘How much of this is science, and how much of this is art?’
To answer this question, I will fall back on the adage: Beauty is in the eye of the Beholder.
Science and art, though reaching distinct destinations, share surprising common ground in their journeys.
Science strives to demystify the world, building knowledge and solutions. In contrast, artists ‘paint’ withemotions, aiming to evoke beauty or a stir within the viewer, expressed through any artistic medium.
Figure 1 contains significant scientific aspect and also an artistic aspect.
The Base Imagery
I created Figure 1 from two images I received from the GOES 16 satellite using my HRIT receiver: Band O2
from the near infrared region of the spectrum (0.60 ‑ 0.68 μm) and Band 13 from the longwave infrared(10.2 ‑ 10.5 μm). Band 02 is located near the red portion of the visible spectrum and has the highest ground
resolution (2-kilometers) among the GOES-R series of satellites. Band 13 is considered ‘clean’ because it isless sensitive than other infrared window channels to water vapor.

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This helps to improve corrections to atmospheric moisture and is useful for the estimation of cloud particle
sizes. Channel 13 will be used in many composite and band differences views.
There is no ‘green’ channel on any GOES satellite. That is important, as all three RGB colors—red, green,
and blue—are needed to produce a ‘true color’ image. So, every satellite image that appears in color is, inreality, a false representation of what the Earth’s colors would look like from space. Figure 1 was createdby merging these two channels into a single image by using ImageMagick software [1], then enhancing justthe cloud detail. This has the added benefit of also preserving the land mass detail apparent in the band 02
imagery. So far everything is still very science-based.
How is color created from greyscale imagery?
Since the satellite has no sensor that can detect any green color, which is needed to create RGB, or a color
image, we need to work out how to do that. Some software, like Goestools and Satdump for instance, use apredefined Color LookUp Table (CLUT) to apply a set of colors to the albedo based on
an average range of temperatures.
I created the 256×256 pixel CLUT, shown opposite, to apply color, based on visible
and infrared radiance from channels 02 and 13. Visible reflectance is represented on
the Y axis as color brightness between black and white, while infrared radiance isrepresented on the X axis as a range of color temperature. It is in this way that color
can be painted on to visible imagery as informed by infrared-sensed temperature andvisible channel reflectance.
This does have many limitations, and this can be readily seen during different times of the year: for instance,in the winter months over North America, the cold regions have a distinct bluish cast, and during thesummer months they appear to be more accurate, showing the greens, browns and tan colors of Earth.
(Again, it is just coloring the image based on an averaged CLUT). This is the same way, though in a more
complicated process, that NOAA and most processors of satellite imagery use to create TrueColor, or
GeoColor using three bands, 01,02, and 13.
GeoColor is a multispectral product composed of True Color (using a simulated green component) during
daytime, and an Infrared product that uses bands 7 and 13 at night.
So, even though the colors are ‘False Color’, science is still used as the basis for color representation.
The Process
The technique which I adapted to my needs is used by many weather satellite agencies such as NOAA,
CIRA, SSEC, EUMETSAT and even your local TV weather station. It involves the use of pre-made, predefined
underlays—or images—of the Earth. These images are typically compiled by using imagery from Low Earth
Orbit (LEO) Satellites. These representations are created and published in a NASA Collection called The
Blue Marble (Figure 2) [2]. The Blue Marble: Next Generation offers a year’s worth of monthly composites at
a spatial resolution of 500 meters. These monthly images reveal seasonal changes to the land surface: thegreen-up and dying-back of vegetation in temperate regions such as North America and Europe, dry andwet seasons in the tropics, and advancing and retreating Northern Hemisphere snow cover. By using an
underlay such as this and selecting the appropriate month to match the correct imagery, a very realistic
rendering of the Earth can be created.
To this rendering of the Earth, I further refine the static underlay, using several items of software. In thiscase I utilised an older piece of software, Xplanet [3] to generate topographical information via a global‘bump map’ showing valleys, mountains, and other elevation data, to create a more realistic representationof the planet (Figure 3). This is pieced together from the USGS DEM database. It contains landmass
elevations only, with the ocean at zero and the top of Mount Everest at 255. This is used as a bump map
to give the appearance of the Earth’s rugged surface features. I also used this data in POV Ray tracing as
a displacement map on a very finely divided sphere to produce a ‘true’ 3D version of the Earth showing
shadows at the correct point during that day. For instance, in a late afternoon view of North America,shadows are just apparent to the east of the Rocky Mountains, while in the early morning views, theshadows appear to the west of the Rockies.
The second step is to use a specular lighting algorithm. Specular lighting identifies the bright specular
highlights that occur when light hits object surfaces such as lakes, rivers and oceans and reflects light backtoward the viewpoint of the imager. A specular map of Earth is complex to render. There are large land areasand vast areas of open water that are both specular and reflective, including small areas of reflective watersuch as lakes and rivers. I use a specular map that is derived from USGS DEM data (Figure 4) with theaddition of the Arctic ice areas which do not show up on USGS data (since they are not solid land masses.)... continued on page 25

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Figure 2 - A basic equi-rectangular Blue Marble image of the Earth for the month of August

Figure 3 - The topographical ‘bump’ map used for elevation detail.

Figure 4 - Equi-rectangular Specular Map. The white areas are the areas that are considered to be reflective.

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This is then used to add specular reflectance of theocean surface, and glints of sunlight from lakes,
rivers, and streams, all accurately based on theposition of the sun in relation to the orbital positionof the satellite. Figure 5 is a crop from the specularmap of Earth showing South American rivers, inparticular the Amazon, which shows up quite well in
the imagery from space.
My third step, if I choose to enable it on an image,is to apply a ‘night side’ view of the Earth. Since
current geostationary satellites do not possess the
wavelengths necessary to capture the human-madelights of Earth at night, again I use a map generated
by LEO Satellites, the ‘Earth at Night’ imagery data
sets from the NASA Blue Marble collection previously
mentioned (Figure 6).
Now, the software I employ uses an algorithm based
upon the longitude of the satellite (derived from TLEdata) and the date and time in UTC-hours, minutes
and seconds. It then processes the static image
underlay, combining the bump map with elevation
data giving the ‘Earth’ a realistic topography. I use
the specular map to apply specular lighting showing
glints of light from rivers, lakes and the ocean,and then if enabled, create a day/night view of theplanet.
The finished rendered and enhanced planet image
has now been created. I now need to apply Advanced
Baseline Imager (ABI) data from the satellite to theequirectangular static image of the Earth (Figure 2).
In the fourth step, using band 13, I create a typeof bump map for the cloud layer, using it to create
slight elevation changes of the cloud layer basedon changes in the grey scale pixel brightness. The
combined band 02 and 13 imagery is reprojected
into an equirectangular static image using an open-

Figure 5 - Specular rivers in South America

source software named Sanchez [4]. This is thenprocessed to enhance the cloud details for the next
step. Using Sanchez again, the static underlay of‘Earth’ and the reprojected Band 02/13 imagery arecomposited together, creating a flat equirectangularimage of Earth with the cloud layer added.

Figure 6 - Blue Marble Day//Night imagery prior to adding the satellite imagery

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25

With the addition of band 02, the land masses are overlaid with the actual satellite’s 2-kilometer resolution
imagery of the Earth, enhancing the detail accurately from orbit. The final step in the processing again relies
on Sanchez to reproject the static imagery from the viewpoint of exactly 75.2° longitude from geostationary
orbit into a globe representation and add atmospheric hazing, some tinting, and some histogram equalization
to the rendered image.

Figure 7 - The final processing

The Final Result
The first pass of processing is on the left of Figure 7 and the final processing is on the right. Looking closely
you can see the river valleys on the west coast of Africa, some greens in Portugal, and the blue waters of theAtlantic.
Many other options can be added, such as changing the view of the planet by altering the longitude, adding
LEO Satellite Orbit Tracks using current TLE data, adding stars to the background using data from the YaleStar Catalog, or even adding the sun in the correct place in space. This method can also be applied to GOES
Rebroadcast Imagery (GRB). Figure 8 (next page) shows some of the extraordinary cloud details.
Conclusion
So, in conclusion, is it more art than science? I don’t think so. Science is used to make every layer andattribute of the image from scientifically derived data sets. The combination of these is left to me (the artist?).
The same processing technique has been applied to Himawari 9, GOES-18, and GOES-16 (Figure 9). Despite
their contrasting approaches, both science and art rely heavily on keen observation as a springboard for
creativity. Scientists meticulously observe natural phenomena and meticulously record details to identify
patterns and relationships. Artists, too, are keen observers of the world around them, drawing inspirationfrom the natural world, human behavior, and the complexities of the human condition. These observations
fuel their creative processes, shaping artistic expression and interpretation.
While Figure 8 might evoke a sense of beauty, the entire process adheres to scientific principles. The
selection of bands, data analysis and manipulation techniques are all rooted in scientific knowledge andmathematics. The artistic aspect lies in the choices made during processing, such as color enhancement
and the use of underlays which influence the final aesthetic. Ultimately, postprocessing satellite imagery
exemplifies the fascinating convergence of science and art, where scientific data is transformed into avisually compelling representation of our planet.
References

1 Imagemagick
https://imagemagick.org/index.php
2 Blue Marble
https://visibleearth.nasa.gov/collection/1484/blue-marble

3 Xplanet
https://xplanet.sourceforge.net/
4 Sanchez
https://github.com/nullpainter/sanchez

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Figure 8 - The final processed GOES-16 image using GRB Band 01 imagery

Figure 9 - The same processing technique as applied to (left to right) Himawari 9, GOES-18, and GOES-16

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27

Fresh Flows Spread Across IcelandNASA EArth Observatory
Story by Lindsey Doermann

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey.

Lava poured from a volcanic fissure near the town of
Grindavík, Iceland, in spring 2024. The eruption, whichbegan on March 16 and remained active over two weeks
later, was the largest in a string of four volcanic events on
the Reykjanes peninsula starting in December 2023.
The OLI (Operational Land Imager) on Landsat 8
captured this image of the ongoing eruption on March 30,
2024. The natural colour scene is overlaid with an infrared
signal to help distinguish the lava’s heat signature. The
active part of the fissure and the origin of a volcanic
plume are apparent.
According to the Icelandic Met Office, the eruption began
at 8:23 pm local time on March 16 when a fissure nearly
three kilometers long quickly opened in a similar location
to the February 2024 eruption. Hundreds of people at theBlue Lagoon, as well as a small number in Grindavík,
were evacuated within about 30 minutes of the eruption
starting.
In the days that followed, lava flowed toward infrastructuresuch as water pipes and roads, the town of Grindavík,
and the ocean. Human-constructed barriers of earth androck diverted lava away from the town, although a flow did
extend across one road. Officials were initially concernedthat lava would reach the coast and cool rapidly upon

contacting water, which could have posed additional
hazards such as the production of hydrogen chloride gas.
But the flow stopped short.
Like the eruptions that preceded it, the spring 2024 event
was effusive, not explosive. Effusive eruptions tend toemit minimal ash, and their plumes typically contain water
vapour, sulfur dioxide, carbon dioxide, and small amountsof other volcanic gases.
This eruption did not disrupt air travel, but sulfur dioxide
emissions proved locally hazardous at times. Workers
evacuated the power plant north of Grindavík on March 18
due to gas pollution. The SO2 emissions from this eruption
were forecast to drift across the United Kingdom andnorthern Europe, according to models based on satellite
observations, but at an altitude too high to affect surface
air quality.
Unlike the other recent eruptions in this region, thespringtime event stretched out over weeks rather than acouple of days. The reason for the relatively prolonged
eruption may be that magma now has an easier path tothe surface, experts suggested in news reports. Others
think that magma is no longer accumulating in the shallow
magma chamber beneath the area and that this eruption
could be the last in the longer cycle.

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Death Valley flooded after Heavy Rain
Copernicus Image of the Day

Credit: European Union, Copernicus Sentinel-2 imagery

After last year’s historical deluge, Death Valley
National Park, renowned for its extreme heat andarid landscape, recently gone through an unusually
heavy rainfall episode. The rainwater transformed
parts of the park into temporary lakes, allowing
adventurous kayakers to paddle through the usually
dry landscape of the park. The event showcases the
dynamic nature of this desertic environment andprovides a unique recreational opportunity amidst
the typically harsh conditions of Death Valley. This
image of Badwater Basin was acquired on 8 Marchby one of the Copernicus Sentinel-2 satellites.
The Copernicus Sentinel satellites provide valuable
data for identifying and delineating the extent offlooded areas after heavy rainfall.

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Shrinking Lake Tharthar
MODIS Web Image of the Day

Figure 1
Lake Tharthar and its environs on April 17, 2024
Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Figure 2
Lake Tharthar and its environs on April 11, 2004
Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Located in the Middle East between Iran andKuwait, Iraq is dominated by a dry desert landscapetraversed by two ancient rivers: the Tigris and the
Euphrates. These rivers flow southeastward fromthe northern highlands across Iraq’s alluvial plains
until they reach the Persian Gulf. Many lakes, bothman-made and natural, dot the plains between thesemajor rivers, including Lake Tharthar, which was
created in 1956, primarily for water storage and to
hold floodwater from the Tigris River.

has profoundly affected water levels in many lakes,
including Lake Tharthar. Two true-color images
acquired by the Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terra satellite,
acquired twenty years apart, show the changes inwater levels in the lakes and rivers north of Baghdad
over time.

The many lakes, as well as the rivers, provide
livelihoods as well as water for drinking, agriculture
and other uses for most of Iraq’s population. Overseveral decades, the country has experienced
significant changes to the climate, including asignificant reduction in rainfall and increasing
evaporation rates, spurred by rising temperatures.
According to ReliefWeb, Iraq is one of the fivecountries in the world most vulnerable to climatechange. Desertification affects 39% of Iraq’s territory,
with very high temperatures more common, drought
more frequent, and dust storms becoming more
intense. These environmental stresses and increasing
demands for water for agricultural and other uses

Figure 1, acquired on April 17, 2024, centers on
Lake Tharthar. The Euphrates river and Haditha
Dam Lake can be seen running across the image
weat of Lake Tharthar. Both are surrounded bydesert. The Tigris River lies northeast of the lake,with little water visible within its banks, a green
flood plain, and what appear to be agricultural fields
surrounding it. In centre left of the image, gray pixels
mark the city of Baghdad, the capital of Iraq whichsits on the Tigris River. Lake Habbaniyah sits southof Lake Tharthar and west of Baghdad.
Figure 2 is a true-color Terra MODIS image acquired
twenty years earlier on April 11, 2004. All threelakes are seen to be much larger and the Tigris Riverappears to also be wider and more visible, including
the region flowing through Baghdad. The agricultural
regions near the Tigris are also notably smaller.

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30

A Climate Archive Melts
NASA Earth Observatory
Story by Emily Cassidy

Glaciers are natural archivesof past climate. In their frozen
layers lies evidence of Earth’schanging temperature andatmospheric composition. But as
the climate warms, some of thelongest records of our changing
planet are melting away.
One such archive is the
Corbassière glacier in
Switzerland. This high-altitude
glacier is situated on the flanksof Grand Combin, one of thehighest peaks in the western
Alps. It has suffered the same
fate as many alpine glaciers in
Switzerland, which collectively
have lost more than half of theirvolume since the 1930s. Someof the more recent changes at
Corbassière glacier are visible inthese images, captured in August
2001 (upper) and in August2023 (lower). They were acquiredby Landsat 5 and Landsat 8,
respectively. In just over two
decades, Corbassière has shrunkin area and surface mass. The
glacier was darker in 2023 dueto lack of snow, and the glacier’s
tongue had retreated.
A research team from Switzerland
and Italy took cores of ice from
Corbassière glacier in 2018and 2020 to reconstruct past
concentrations of the region’s
aerosols, those tiny airborne
particles that were suspended
in the atmosphere and thendeposited on the ice. Suchinformation from glaciers aroundthe world can provide clues aboutpast environmental conditions
thousands of years ago.
Ice cores contain ammonium,
nitrate and sulfate ions,signatures of aerosols lacing
the snow that’s deposited on
glaciers year after year. Ion
concentrations are lower inwinter than in summer because
less polluted air can rise from thevalley when the air is cold.

Corbassière glacier imaged by the Landsat-5 satellite on August 23, 2001
NASA Earth Observatory images by Wanmei Liang, using Landsat datafrom the U.S. Geological Survey.

Corbassière glacier imaged by the Landsat-8 satellite on August 20, 2023
NASA Earth Observatory images by Wanmei Liang, using Landsat datafrom the U.S. Geological Survey.

The team analysed a core drilledfrom the glacier in 2018 andfound seasonal fluctuations in theamount of ion deposits throughout
the ice core, as expected.
“But when we went to core
the glacier in 2020, we
noticed melting on the surface
right away,”

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stated Margit Schwikowski, who isan environmental chemist at Paul
Scherrer Institute in Switzerland.
Schwikowski led the team ofresearchers that analysed theice cores with PhD student Carla
Huber.
In the 2020 core, seasonal
fluctuations of ions were only31Margit Schwikowski and Theo Jenk taking a core sample from the Corbassière glacier
Photo: Riccardo Selvaticopresent in the upper three or four annual layers.
Deeper in the ice (and farther back in time), thescientists noticed fewer ions overall and that theiramounts fluctuated less than expected.
As reported in Nature Geoscience, the team foundevidence that previous melting of the glacier’s surface
between 2018 and 2020 most likely penetrated theglacier layers below and carried away the aerosolions. This melting rendered the core unusable in
the team’s research, and other attempts to core theglacier had the same result. The valuable information
stored in the ice was destroyed.

Schwikowski and other ice core experts from aroundthe world are part of an effort to preserve cores fromthe last remaining glaciers. The initiative, led by theIce Memory Foundation, aims to obtain ice cores from20 endangered glaciers around the world in 20 years
and collect them in a global climate archive.
“Glaciers are retreating worldwide, and we
may find similar issues at other sites,” said
Schwikowski. Even at the highest altitudes in
the Alps, she added, “glaciers are on the verge of
becoming unsuitable as natural paleo-archives.”

Tulips bloom in the Netherlands
Copernicus Image of the Day
Tulips are one of the most iconic symbols of theNetherlands.
With around two billion bulbs exported every year, thecountry is the world’s largest commercial producer of theflowers. Every spring, tulip season in the Netherlands
ushers in a colourful spectacle that delights both visitors
and locals alike. In this Copernicus Sentinel-2 image
from April 29, 2024, the multocoloured tulip fields of theNoordoostpolder are visible from 786 km above Earth.

Credit: European Union, Copernicus Sentinel-2 imagery

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32

Mining Lithium in Argentina
NASA Earth Observatory
Story by Emily Cassidy

NASA Earth Observatory image by Wanmei Liang, using Landsat data from the U.S. Geological Survey.

Some of the largest known deposits of lithium—a soft
silvery metal that powers batteries in cell phones, laptops,and electric vehicles—lie in one of the driest places on
Earth. Much of the surveyed deposits of this metal arelocated in the arid salt flats of South America, where Chile,
Argentina, and Bolivia meet.

This image, acquired by the OLI (Operational Land
Imager) on Landsat 8, shows lithium mines in northwestern
Argentina’s Jujuy province, near the country’s border with
Chile. The light blue evaporation ponds of the mines standout. The mines are located just south of a large salt flat,
known as the Salar de Olaroz.

The Altiplano-Puna Plateau is an elevated 500,000-squarekilometre area in the Central Andes, and the second
highest plateau on Earth after the Tibetan Plateau. Several
climatic and geologic factors converged in these dry plains
to create large underground lithium deposits.

To harvest the lithium, wells are tapped into the lithium-richbrine beneath the surface. They shunt the brine toward
rectangular evaporation ponds lined with plastic. Once
there, the briny mixture remains in the ponds for months at
a time, where sunshine and wind separate out lithium, salt,
and other substances through evaporation. This lithiumrich solution is then processed into lithium carbonate orlithium hydroxide.

The Altiplano-Puna sits on one of Earth’s largest known
reservoirs of active magma. Although the area receives
very little precipitation (less than 30 centimeters a year),hydrothermal fluids associated with this volcanic activity
naturally replenish underground aquifers. Over time, rocks
containing trace quantities of lithium have weathered,causing the metal to build up in the aquifers. According
to the U.S. Geological Survey, about half of the world’s
measured lithium resources are in these undergrounddeposits in Bolivia, Argentina, and Chile, an area known as
the ‘Lithium Triangle.’

Landsat images show that the mine immediately adjacent
to Salar de Olaroz has expanded several times since2016, and it is now one of the largest lithium mines inArgentina. In 2018, evaporation ponds were developed
for another mine two kilometers to the south. Global
production of lithium has increased almost ten-fold overthe last two decades, from approximately 15,000 metrictons in 2001 to 146,000 metric tons in 2022.

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33

Galapagos Island Volcano Lava Flow
European Space Agency

Image contains modified Copernicus Sentinel data (2024), processed by ESA

This image, captured on March 6, 2024 by the Copernicus Sentinel-2 mission, shows lava flowing down theflanks of the La Cumbre volcano on Fernandina Island, Galapagos. The volcano began erupting on March 2.
Although the island lacks human inhabitants, it does host diverse wildlife, including iguanas, penguins andflightless cormorants.
The image has been processed using the satellite instrument’s shortwave-infrared channels to highlight theflow of lava. The La Cumbre volcano is one of the most active in the Galapagos Island chain and the darker
shades of brown depict older lava flows.

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34

Ship Tracks over the Pacific
MODIS Web Image of the Da

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Linear clouds crisscrossed the Pacific Ocean off thecoast of California in early April 2024, each marking
the passage of a ship. The Moderate Resolution
Imaging Spectroradiometer (MODIS) acquired thistrue-colour image of the distinctive clouds known as‘ship tracks’ on April 1.

surrounding clouds, because clouds that form due toship exhaust usually have more and smaller droplets
than normal, unpolluted clouds. The smaller
droplets scatter light in many directions and it is thisincreased reflectance that makes them appear whitein satellite images.

Ship tracks are thin, narrow clouds that form whenwater vapour condenses around the tiny particles
emitted by ships in their exhausts. They don’t form
over every passing ship, but tend to be found wherethin, low-lying stratus and cumulus clouds are alsopresent. Ship tracks often appear brighter thanThis area of the North Pacific Ocean is a remarkably
busy waterway, with heavy ship traffic year-round.
The combination of a high number of ships releasing
emissions and atmospheric conditions conducive tothe formation of a variety of low-level clouds makethe North Pacific a hot spot for viewing ship tracks.

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35

One of the Largest Batteries in the World
NASA Earth Observatory
Story by Lindsey Doermann

NASA Earth Observatory image by Wanmei Liang, using Landsat data from the U.S. Geological Survey. .

This reservoir holds more than justwater. Set on a bluff hundreds offeet above Lake Michigan, it also
stores potential energy that can be
unleashed to produce hydropower.
This human-built lake is part of the
Ludington Pumped Storage Plant,
a pumped storage hydropower
facility that can be likened to a giant
battery—one that moves waterinstead of electrons.
In place of complex chemistry, thisbattery employs simple physics.
Surplus electricity from the grid isused to pump water 110 metres from
Lake Michigan to an upper reservoir,
shown above. At times of higher
energy demand, water flows backdown, turning the pump-turbines in
the opposite direction to generatehydropower. This image of the facility
and reservoir was acquired by the
OLI on the Landsat 8 satellite on
March 3, 2024.
The Ludington Pumped Storage Plant
began operating in 1973, making it
essentially a battery that still works
after 50 years. Its upper reservoir
measures approximately 4 kilometreslong by 1.6 kilometres wide. Twojetties and a breakwater protect the
intake and outflow channels fromthe waves and currents of Lake
Michigan, and a barrier is installedfrom April through October, when ice
conditions permit, to keep fish awayfrom the intake.
Water rushes through six pumpturbines concealed from view withina powerhouse. Each unit raises orlowers the reservoir’s water surface
about 30 centimetres per hour during
normal operation, according toConsumers Energy, co-owner of the
facility. At full capacity, the plant canpower about 1.7 million households.
Michigan’s electricity comes largely
from fossil fuel fired power stations
and nuclear plants. With these
relatively constant sources, theLudington plant tends to pumpovernight when customer demandon the grid is low, then switch tohydropower mode during the day until
its usable capacity is exhausted.
That schedule could shift as more
renewable energy sources come

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online in the region. The Ludington
plant may adapt to solar, for example,
by recharging during the middle ofthe day and then discharging in theevening when demand increases.
Utility-scale energy storage iscritical to the wider adoption of solar
and wind power. It enables theseintermittent sources to be used whensunlight or wind are lacking andreduces the need for back-up fossil
fuel fired plants.
The United States may need to add
hundreds of gigawatts of storageby 2050 to achieve its clean energy
goals, according to the Department ofEnergy, and it has the potential to atleast double the amount of pumped
storage capacity. In 2022, 43 pumped
storage hydropower plants accounted
for 96% of U.S. utility-scale energy
storage capacity, although newbattery storage installations surged
in 2020–2022. Most pumped storage
facilities in the U.S. were built
between 1960 and 1990, and some,including Ludington, have been
upgraded in recent years to increase
their capacity and incorporate
renewable energy sources.

36

Low Pressure Systems surround Australia
David Sale

Credit: This composite VIS/NIR/IR image was received from Himawari 9 via JCSAT-2B & Himawaricast,

The Himawaricast image above was received via the
JCSat-2B geostationary communications satellite on
April 5, 2024. Several points are worth noting.
The first is a significant rain event for the Sydneyarea (eastern Australia) with the convergence of two
low pressure troughs and an associated low pressure
area.
These systems typically form in the autumn andwinter and bring large amounts of rainfall in a shortperiod of time. In this case, many areas received inexcess of 100 millimetres in one day.
The second is the developing tropical low to thenorth-west of Australia. This developed into tropical
cyclone Olga which drifted south but failed to makelandfall.
The third is the extensive band of seasonal
vegetation (green) covering the top part of Australia.

Synoptic chart courtesy of the Australian Bureau of Meteorology.

The 2024 ‘wet’ season (monsoonal) was quite strong
and large pools of water and swollen rivers areevident.

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37

Joachim Scharrer acquired this multicoloured infrared (MCIR) image from Meteor M2-4 at 13.57 UT on
May 5, 2024, highlighting successive Atlantic depressions crossing western Europe

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38

Montgomery Reef Revealed
NASA Earth Observatory
Story by Adam Voiland

The Kimberley coast of Western Australia has one of
the largest tidal ranges in Australia and the world. At
Montgomery Reef [1], in Collier Bay, water levels drop
sharply at low tide, allowing the plateau-shaped reef toemerge several metres above the water level.
Tidal shifts are particularly noticeable in this area becauseof the flat, shelf-like terrain along the Kimberley coast.
This pair of images shows the reef when the tide was high(Figure 1) and low (Figure 2) in 2024. The high tide image
was captured by the OLI-2 (Operational Land Imager-2) on
Landsat 9 on April 21; the OLI (Operational Land Imager)
on Landsat 8 acquired the low tide image on April 29.
When the tide rises, the sandy islets and main mangrovecovered island, Yawajaba, within Montgomery Reef arevisible, but the reef is mostly underwater and out of view.
During low tides, the water level can drop by as much as
10 metres, revealing the expansive terraced structure of
the reef and the network of shallow lagoons surrounding
Yawajaba.

Figure 1 - Montgomery Reef at high tide on April 21, 2004
NASA Earth Observatory images by Lauren Dauphin, using
Landsat 9 data from the U.S. Geological Survey.

As the tide pours off the structure, the outward flow ofwater can grow tumultuous. At times, whitewater cascading
off the reef forms dozens of rivulets and small waterfalls [2]that flow into deeper channels within the reef, a spectacle
for tourists and a hazard for wildlife. Fish, sea snakes,
turtles, blacktop reef sharks, dugongs, and other creatures
can be seen thrashing and tumbling off the coral platform
as the water drains. Animals are occasionally left stranded
on exposed reef during low tide.
The structure of Montgomery Reef is not entirely a productof coral. The feature was once a flat-topped terrestrial
mesa made of dolomite and sandstone that formed some
1.8 billion years ago. More recently, this ancient structure
has been encrusted with a veneer of marine life, especiallyrhodolith—a free-floating type of coralline alga that adds
much of the structure to the perimeter of the reef.
Communities of several types of hard and soft corals
cover about 20 percent of the reef’s surface, particularly
along the edges of pools and channels where the water
is deeper. Corals along the Kimberley coast, like thosefound on Montgomery Reef, are known for being unusuallyresilient compared to corals in other parts of Australia andthe world. They have adapted to withstand the swings intemperature that come with tidal variations, and to endure
the exposure to elevated ultraviolet light and winds during
low tide.
But even these rugged corals are not indestructible.
Following a marine heat wave in 2016, which was partof the third global bleaching event, scientists reported
widespread coral bleaching at Montgomery Reef and othercoral communities on the Kimberley coast.

Figure 2 - Montgomery Reef at low tide on April 29, 2004
NASA Earth Observatory images by Lauren Dauphin, using
Landsat 8 data from the U.S. Geological Survey.

In April 2024, the National Oceanic and Atmospheric
Administration (NOAA) confirmed the world’s corals
were in the midst of a fourth global bleaching event, but
local reports of bleaching at Montgomery Reef have not
emerged yet. Heat stress maps from NOAA’s Coral Reef
Watch indicate that corals to the southwest in Western
Australia and those closer to the equator faced a greaterrisk of bleaching in mid-May 2024.
References

1 https://marinewaters.fish.wa.gov.au/resource/fact-sheet-montgomery-reef/
2 https://kabardesa.my.id/blog-au/montgomery-reef-wa.html

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39

Secrets of the Maud Rise Polyna Revealed
MODIS Web Image of the day

Image Credit: MODIS Land Rapid Response Team, NASA GSFC

Each winter, the oceans around Antarctica becomeheavily encrusted with a thick layer of ice, thanks to frigid
temperatures and short daylight hours. The vast expanseof ice, which spans an area roughly twice the size ofthe continental United States, isn’t perfectly smooth:
sometimes cracks or openings form. A large area freeof ice that exposes the seawater underneath is called apolynya. Polynyas usually form close to shore, but more
rarely can form in a sheet of ice over the open ocean.
For decades, scientists have been studying just how
these state-sized gaps in otherwise solid ice are formed.
It’s been clear that a combination of ocean current andwind play a rôle in polynya formation, but that never quite
fully explained the formation of some particularly complex
ones, such as the Maud Rise polynya, which appears
only sporadically.
The Maud Rise polynya in the Weddel Sea surprised
scientists when it appeared in satellite images in the
1970s. It was estimated to be about the size of Oregon
when first discovered. Smaller versions have appearedat the same site over the years, but in the winter of
2016-2017, it showed up as a truly massive gap in theice—approximately the size of Switzerland—and it lasted
for many weeks. Scientists became even more curious
about just what mechanisms drove the formation of thisparticularly erratic polynya.
On May 1, 2024, a team of scientists published a study
in the journal ‘Science Advances’ that helps explain boththe formation and persistence of the Maud Rise polynya
in 2016-2017. The factors included not only currents andwind, but also the mountain-like formation on the sea
floor (known as the Maud Rise) beneath the polynya,
which helped trigger a spiral-like movement of salt fromthe deeper layers of the ocean upward—termed Eckman
Transport. Normally, when sea ice melts, the water
immediately beneath it becomes less saline, which inturn slows melting. But Eckman Transport kept salt levels
high at the polynya, which allowed melting to continue
and slowed refreezing, creating a massive and longlasting polynya.
On September 25, 2017, the Moderate Resolution
Imaging Spectroradiometer (MODIS) on NASA’s Aqua
satellite acquired a true-colour image of the huge Maud
Rise polynya near its historically largest size.

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40
40

Currently Active Satellites and Freqencies
Polar APT / LRPT Satellites
Satellite

Frequency

StatusFormatImage Quality

NOAA 15

137.6200 MHz

On

APT

Intermittent sync problem

NOAA 18

137.9125 MHz

On

APT

Good

NOAA 19137.1000 MHz

On

APT

Good

Meteor M N2

137.1000 MHz

Off

LRPT

FailedMeteor M N2-3

137.9000 MHz

On

LRPT

Variable [1]Meteor M N2-4

137.9000 MHz

On

LRPT

Good

Satellite

Frequency

Mode

FormatImage Quality

NOAA 151702.5 MHz

Omni

HRPT

sync problem

NOAA 18

1707.0 MHz

RHCP

HRPT

Good

NOAA 19

1698.0 MHz

RHCP

HRPT

Good

Feng Yun 3C

1701.4 MHz

RHCP

AHRPT

Inactive [2]Feng Yun 3D

7820.0 MHz

RHCP

AHRPT

Active {2}Polar HRPT/AHRPT Satellites

Feng Yun 3E

7860.0 Mz

RHCP

AHRPT

Commissioning

Metop B

1701.3 MHz

RHCP

AHRPT

Good

Metop C

1701.3 MHz

RHCP

AHRPT

Good

Meteor M N2-2

1700.0 MHz

RHCP

AHRPT

Active [8]Meteor M N2-3

1700.0 MHz

RHCP

AHRPT

ActiveGeostationary Satellites
Satellite

Transmission Mode(s)Position

Status

45.5°EIODC - On

Meteosat 9

HRIT (digital)

Meteosat 10

HRIT (digital)

LRIT (digital)

0°W

Off [4]

Meteosat 11

HRIT (digital)

LRIT (digital)

9.5°E

On [3]

0.4°W

Commissioning

GOES-13GVAR 1685.7 MHz

LRIT 1691.0 MHz

61.6°E[5]

GOES-14GVAR 1685.7 MHz

LRIT 1691.0 MHz

105°W

Standby

MTG-l1

GOES-15 (W)GVAR 1685.7 MHz

LRIT 1691.0 MHz

135°W

Off (in storage)

GOES-16 (E)GRB 1686.6 MHz

HRIT 1694.1 MHz

75.2°W

On [7]

GOES-17

GRB 1686.6 MHz

HRIT 1694.1 MHz

104.7°W

Off

GOES 18

GRB 1686.6 MHz

HRIT 1694.1 MHz

137.0°W

On [7]

Himawari-8

No direct download

On

No direct download

Data is only available
via the HimawariCast
service140.7°E

Himawari-9

140.7°E

On

Feng Yun 2E

SVISSR (digital)

LRIT (digital)

86.5°EOff

Feng Yun 2F

SVISSR (digital)

LRIT (digital)

112.5°E

Standby

Feng Yun 2G

SVISSR (digital)

LRIT (digital)

105.0°E

On

Feng Yun 2H

SVISSR (digital)

LRIT (digital)

79.0°EOn

Feng Yun 4A

HRIT (digital)

LRIT (digital)

99.5°EOn

Feng Yun 4B

HRIT (digital)

LRIT (digital)

105°E

On

Notes
1
2
3
4
5
6
7
8
9

Currently, M2-3 transmits on 137.9 MHz but has on occasions switched to 137.1 MHz.
Transmission is currently on a Symbol Rate of 72,000 baud, though 80,000 baud has been used in trials.
These satellites employ a non-standard AHRPT format and cannot be received with conventional receiving
equipment.
Meteosat prime Full Earth Scan (FES) satellite
Meteosat prime Rapid Scanning Service (RSS) satellite.
Repurposed for use by the US Space Force
GOES 15 also transmits EMWIN on 1692.700 MHz GOES 16 also transmits EMWIN on 1694.100 MHz GOES 17
also transmits EMWIN
GOES Rebroadcast (GRB) provides the primary relay of full resolution, calibrated, near-real-time direct broadcast
space relay of Level lb data from each instrument and Level 2 data from the Geostationary Lightning Mapper (GLM).
GRB replaces the GOES VARiable (GVAR) service.
Following a collision with a micrometeorite, the power system aboard Meteor M2-2 has been compromised. AHRPTis still being transmitted when the solar panels are sunlit, but there is insufficient battery power to enable the LRPT
stream.
Japanese satellites MTSAT-1R (Himawari-6) and MTSAT-2 (Himawari-7) are no longer active and are probably
retired. Current Japanese operational geostationary satellites are Himawari-8 and Himawari-9.

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41