Group for Earth Observation

The Independent Amateur Quarterly Publication for
Earth Observation and Weather Satellite Enthusiasts

53
March 2017
Inside this issue . .
This issue of GEOQ marks amajor reappraisal of thesatellite imagery currently
available. With ESA’s
Copernicus mission now wellestablished, both Sentinel 2Aand Sentinel 3A satellites are
now fully commissioned andproviding amazing colour
imagery of Earth. Our pages
are replete with primeexamples of the output of bothsatellites. The image at left,from Sentinel 2A, clearlypicks out shipping in theStrait of Gibraltar.
Imagery from both thesesatellites is available via
EUMETCast, and many of ourreaders are already enjoying
this option. Bur don’t despair
if you are not a EUMETCast
user: you can now to obtainthe very same products fromthe Internet.
The emphasis this issue is on
Sentinel 2A, with an article
which describes how to
obtain the data, and anotherwhich introduces you to new
software from David Taylor
which can process the files
into colour images.
Other topics covered include
NASA’s Operation IceBridge,
Mapping the speed ofglaciers, Kerguelen island,
Snow on the summits of
Hawaii, and an eruption at
Erta Ale in Ethiopia.

GEO MANAGEMENT TEAMLes Hamilton

Director and Public Relations
Francis Bell,
Coturnix House, Rake Lane,
Milford, Godalming, Surrey GU8 5AB,
England.
Tel:
01483 416 897
email: francis@geo-web.org.uk
General Information
John Tellick,email: information@geo-web.org.uk
GEO Quarterly Editor

geoeditor@geo-web.org.uk

T

his issue of GEO Quarterly could justifiably be described asa ‘Sentinel Special’ edition as our pages are replete with fullcolour images from both Sentinel-2A and Sentinel-3A. Apart from the
EUMETCast data streams, data from both the above satellites is now
freely available from the internet.

T

Membership and Subscriptions

o start you off, we concentrate on Sentinel-2A, which provides
stunning images at a resolution of just ten metres per pixel. The
front cover illustrates the detail available by revealing shipping in theStrait of Gibraltar. Such imagery is available from the Land Viewer
website, described in our article on page 28.

David Anderson,
35 Sycamore Road,
East Leake, Loughborough LE12 6PP,
England, UK.
email: members@geo-web.org.uk
Tel:01509 820 067

eaders who enjoy creating coloured satellite images from scratch
can download individual channel data for Sentinel-2A and combine
them using new software from David Taylor. An extensive guide to thisrelatively simple procedure is to be found on page 31.

Technical Consultant (Hardware)

avid Taylor has produced a ‘starter’ guide to EUMETCastView,
software for viewing images disseminated via EUMETCast,
including those from Sentinel-3A. At the end of last year I spread theword to quite a number of parties that I hoped someone would produce
a guide for this rather complex program. Disappointingly, no-one
obliged, and I am grateful to David Taylor—who has far better things to
do—who stepped in at short notice to produce the article you can readon page 41.

Les Hamilton,
8 Deeside Place,
Aberdeen AB15 7PW, Scotland UK.
email: geoeditor@geo-web.org.uk
GEO Quarterly Despatch
Peter GreenDavid Simmons
email: tech@geo-web.org.uk
Webmaster and Website Matters
Alan Banks,e-mail: webmaster@geo-web.org.uk
GEO Shop Manager
Nigel Evans (Assistant: David Simmons),
email: shop@geo-web.org.uk
International Liaison
Rob Denton,
email: liaison@geo-web.org.uk
Management Committee Members
Clive Finnis
Carol Finnis

Publisher
Published by The Group for Earth
Observation Limited, a company in Englandand Wales, limited by guarantee and nothaving share capital.
The Company Number is 4975597.
The registered office is Coturnix House,
Rake Lane, Milford, Godalming,
Surrey GU8 5AB, England.
Printing (December Issue)
Hedgerow Print,
16 Marsh Lane,
Crediton, Devon EX17 1ES.
Tel: 01363 777 595
Responsibility
Every effort is made to ensure that thetechnical and constructional articles
published in this Quarterly are correct.
However, the ultimate responsibility iswith the reader to ensure the safety of
constructions and for any interfacing withother equipment. GEO cannot accept liability
for shortcomings in any published design or
any constructions carried out by members orother third parties.
Copyright GEO © 2017
The contents of this Quarterly remain theintellectual property of the Group for Earth
Observation Limited and its contributors.
Copying of text or images, either from theprinted Quarterly or from any electronicallystored source, is forbidden without
permission from the Editor.

R
DC

opy deadline for the June issue of GEO
Quarterly is Sunday, May 28, 2017.

Contents
GEO Report
Cover Image Details
International Space Station Images
Quarterly Question
Panama Canal
Sentinel 3A Images UK and Netherlands
Operation Ice Bridge
Ship Wave Cloud Formations
Mapping the Speed of Ice in Earth’s Glaciers
ISS Images the Namib Sand Sea
Kerguelen Island
Snow-Capped Summits in Hawaii
Cloud Vortices off Cheju Do, South Korea
Land Viewer
SentineltoJPEG Image Creation Software
Muted La Nina follows Potent El Nino
EUMETCastView
French Storms
From Drought to Overﬂow
Blue Jets
Snow and Ice above Katmai
Sicilian Snow
Fission Eruptions on Erta Ale
Satellite Status
GEO Helplines and Internet Discussion Groups
GEO Membership Application FormGEO Shop Catalogue and Price List

Francis Bell
Francis Bell
Francis BellDavid Taylor
Gerard Boon
NASA Earth Observatory
NASA Earth Observatory
NASA Earth Observatory
NASA Earth Observatory
Les Hamilton
NASA Earth Observatory
Modis-WebLes Hamiton
Les Hamilton
NASA Earth Observatory
David Taylor
John Tellick
European Space Agency
John Tellick
NASA Earth Observatory
John Tellick
NASA Earth Observatory

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March 2017

Francis BellI’m looking forward to the coming year, perusing myinterests in Earth observation further, triggered by theavailability of the high resolution satellite images from the
new Sentinel satellites. As usual I’m lagging a little behindwith the technology relating to the reception of these newimages, but with the help and advice from our talented
GEO members and the ever helpful EUMETSAT ‘Ops’
team, I hope to regularly receive for myself a selection ofthese ultra high resolution Earth images.
There are superb examples of these Sentinel images
included elsewhere in this Quarterly, and a comparison
can be made between the ground resolution of Sentinel
images which are several orders of magnitude higher thanthe ISS’s HDTV images which I have used in the Quarterly
Question. However, this will not diminish my interest in
the ISS and in receiving their HDTV from time to time.
Symposium 2017?
My report in the previous GEO Quarterly asked readers
for suggestions relating to a venue for our GEO annual
meeting. I have only received three responses, hence a
decision is still pending on this topic and the issue about
a possible annual meeting has yet to be resolved. I havebeen in touch with EUMETSAT and they are quite willingto send one of their senior staff to our meeting bringing us
up to date with the latest image reception but, because of
their current increased workload related to the Sentinel
programme, they would prefer to send a representative to
our meeting rather that hold the meeting at their HQ.
One interesting idea suggested by a member is to overlap
our own meeting, or run it in parallel, with the RSGB’s
annual conference at Milton Keynes in October 2017. I am
currently researching this suggestion.
Widening the Management Team
Likewise there was a poor response about widening the
GEO Management Team (MT) membership to include
an individual interested in promoting the educational
interests in Earth observation, plus another to promotetechnical interests in the reception of satellite images.
Our current MT believe that one or two addition people
promoting these areas would be of great benefit to bothcurrent and potentially new members. The invitation for
addition people to broaden our membership is ongoing—please respond if you can.
Membership Numbers
I will ask our membership secretary to give us a broad
report about membership numbers for our next Quarterly
publication, but in the meantime I think total membershipis about 276 (as of November last year). Of course I would
like to see this number double, not just for the sake of
numbers but primarily to bring new interests and skills
into our fast moving hobby of Earth observation.
Finances
I usually produce a financial report for our annual meeting
but, because the time and place for a 2017 meeting is still2

unresolved, I will produce a financial report for publicationin our next Quarterly. In the meantime we are financiallysecure, mainly due to the reserves created by shop sales
over the past years.
Future Events
30th April 2917
The West London Radio and Electronics Show is to be held
at Kempton Park, West London on April 30, 2017. GEO
have again booked a stand at this popular busy show andI hope to meet up with many GEO members there.
On June 14, GEO will be giving an evening presentation at
the Farnborough Amateur Radio Club’s meeting.
October 14-15 is the weekend of the RSGB’s annual
convention, which will be held at Kents Hill Park
Conference Centre, Milton Keynes. Watch the RSGB web
site for details of this event as they become available. GEO
hopes, for the first time, to have a presence at this eventwith a stand, perhaps even contributing to the programmeof presentations. However, these details still have to bearranged.
On November 5, GEO will again be attending the West
London Radio and Electronics Show at Kempton with ourstand.

Front CoverThe 10-metre resolving power of ESA’s Sentinel 2A satellite isevident in this image of the Strait of Gibraltar, where shipping inthe strait is clearly discernible. The image dates from September
24, 2016.
Modified Copernicus data © ESA / Sentinel (2016)

Inside Front CoverThis image showing striking detail of the Aral Sea and its
environs is a vignette taken from a Suomi‑NPP image acquired byMike Stevens on November 24, 2016.
Image © EUMETSAT 2016

Inside Back CoverGerard Boon acquired this Sentinel 2A image of the Maasvlaakte
harbour at the mouth of the Nieuwe Maas near Rotterdam on
December 27, 2016. The resolution is quite staggering, thisimage section measuring approximately 12 kilometres from northto south.
Image © EUMETSAT 2016

Back CoverPeter Kinghorn recently started receiving Sentinel 3A data via
EUMETCast, and submitted this superb image of Kamchatka thathe acquired on January 18, 2017. The snow-covered mountains
stand out starkly under the oblique illumination.

www.geo-web.org.uk

Image © EUMETSAT 2017

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GEO Quarterly No 53

Francis BellIn the corner of my study I still have a 15 year old computer
which, although not today’s state of the art technology, stillworks perfectly well and has a high speed Internet connection.
Occasionally, just out of curiosity, I turn on this computer which
by default connects to the website transmitting the International
Space Station’s (ISS) High Definition Television ( HDTV) images.
The web site I usually use is
http://www.ustream.tv/channel/iss-hdev-payload
This site constantly transmits live images from the experimental
HDTV cameras on the ISS. If you want to receive these camera
images for yourself go to the above website or an attractive
alternative, which ishttps://www.nasa.gov/multimedia/nasatv/iss_ustream.html
This alternative site not only transmits Earth images but also
occasionally sends images from inside the ISS and, if your lucky,some audio between the space station and ground control.

and one offering a vertical view directly below the space station.
Although I like all the views offered by all the cameras I prefer
the image from the vertical view camera because of the higher
definition compared with the more distant views from the othercameras, which often involve the Earth’s horizon and deep
space.
When attempting to view these images it must be recognised that
there is constant switching between the operational cameras,
hence there is no guarantee that at any moment my favoured
vertical camera will be in use. It also has to be recognised that
half the ISS’s orbit will be in darkness, and from time to time
the transmissions stop because of communication links or othertechnical reasons. This means that I cannot predict whether the
ISS is transmitting images which might interest me, so my option
is reduced to turning on the system and viewing whatever it isoffering me at that moment.

There are several HDTV cameras involved in these experimental
transmissions and from time to time the position of the cameras
can be changed. Currently there seems to a camera giving aforward view from the space station, another giving a rear view

It so happened that, when I turned on my system one day in
February 2017, I was greeted with images from the ISS’s verticalviewing camera; so I quickly checked the location of the spacestation from its orbital prediction which showed it to be crossing
eastern Brazil, then the central Atlantic and on to overﬂy theThis is a near north / south image of the Canary Islands with mainland
Africa to the right. I picked this image partly for nostalgic reasons having
visited four of the major islands in the group during several holidays overthe past few years. Currently I’m particularly interested in the island of
Lanzarote with its volcanic lunar like landscape, hence an invitation toanyone who has a high resolution image of this island please send it to me
or our editor for potential publication in our next Quarterly.

This image shows the Cape Verde Islands just visible among traces ofwhat looks like high level clouds. This island group is located in the Atlantic
ocean about 200 miles off the coast of Senegal. A recent Sentinel 2A
image of the main island, São Domingos, appears on page 19.

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March 2017

Strait of Gibraltar. This part of the orbit was in full daylightwith only a little cloud present, so I recorded some of thepleasing images I received, three of which are shown
below. To record the images I press the ‘Print Screen’
key on my keyboard and then paste the image in to theprogram ‘Paint’. I also use the program ‘IrfanView64’
to view the images. If anyone knows a better way ofrecording and processing ISS images please let meknow as I’m always on a learning curve in these matters.
[If you are using the IrfanView program, forget
about Paint. Just paste your ‘PrintScreen’ image
directly into IrfanView and save it - Ed]
Having been alerted to the vertical image views beingtransmitted by the space station, I continued to takean interest in the transmissions for the next two orbits
and recorded some more images, two of which are thesubject of the Quarterly Question.
Please remember that when viewing images fromthe ISS cameras that their orientation could be in any
direction, and not particularly related to a definedcompass direction. North is not necessarily at the topof an original image; however, subsequent processing
can orientate the image to an almost conventional view,which I certainly prefer.
The scale of the images from the vertical viewing camera
seems to be approximately 200 miles square.

The Outer Banks
The image to the right shows the Atlantic coast of the USA sateof North Carolina. I think the area is called the Outer Banks for
obvious reasons. I have flown over this area in a commercial
aircraft and photographed some of the area. I was surprised
how busy it was for an exposed coastal region with recreational
harbours and marinas lining much of the outer coast. Just to thesouth and not quite appearing in the image is town of Wilmington
the location for the Wright brothers first aircraft flight.

Francis Bell
Quarterly Question 52
The previous Quarterly Question asked for theidentification of two major European cities from twosatellite images, one from a camera on board the ISS,the other from the Earth observation satellite EnviSat.
My thanks to those GEO members who responded to thequestion and gave me their answers.
All those who responded were correct and identified
Lisbon, the capital city of Portugal and St. Petersburg,
which was once the capital of Russia. I was reminded that
St. Petersburg previously had other names: Petrograd(1914-24) and Leningrad (1924-91).
The image showing St Petersburg also showed much of the
Gulf of Finland which is an inlet of the larger Baltic Sea.
Also identifiable in this second image were Helsinki, thecapital city of Finland, and Tallinn the capital of Estonia.

4

I know that one GEO member was initially confused by
the different scales of the two images in spite of the scales
being quoted; however, there will be no such issue withthis quarter’s question because, although again there are
two images featured in the question, both are the from thesame camera on the ISS and hence have the same scale.
Quarterly Question 53
This Quarterly Question relates two images I captured live
from an ISS HDTV camera. In each case the challenge is
to identify the main body of water shown in each image.
To help with the identification, the following backgroundinformation might be useful. The scale of each image
should be the same at about 200 miles (320 kilometres)
across. The images appear on page 5.
Further help may be the fact that in figure 1, the tropic ofCancer (not shown) just touches the bottom of the image.
Another clue here might be the fact that in spite of the

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The Group for Earth Observation

GEO Quarterly No 53

Figure 1 - Note that the two land masses to the left and right are joined beyond the image’s range.

casual assumption that there are twoland masses shown, in fact the land to
the left and to the right are joined out of
the image’s range. There are some small
islands shown in the image but the twomain land masses are conjoined. I guessfor some historical reason the name ofthe sea area and the name of the left partof the land mass seems to conflict with
the name on the country to which they
currently belong. It is often the case thatmy interest in an image of a particulararea is reinforced if I have been there, inthis case I spent two days in the regionand still have the hat to prove it!
Figure 2 was also recorded from the ISS,
this time while it was overflying North
America’s Great Lakes. I have to say it
took me some time to identify exactly
which lake was shown in the image
because the image’s orientation was alittle unconventional and some of thelake’s outline was masked by ice cover—the image was received in February 2017.
To give you a further idea of scale, theimage shows about half the area of
the Great Lake in question. To makeidentification a little easier the original
image has been rotated 90 degrees toshow an approximately conventional
north-south orientation.
Answers please, tofrancis@geo-web.org.uk
before Sunday, May 28. All you need giveis the name of the main body of waterin each image but interesting additional
background details would also be
welcome.

Figure 2 - This image has been rotated to yield an approximate N/S orientation.

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5

6This image of Storm Doris was acquired by the Copernicus Sentinel‑3 satellite between 10:21 and 10:27 UT on the morning of
February 23, 2017 as the storm was at its height across the British Isles. England sits entirely within the ‘eye’ of the storm while
Southern Norway (top) and the snow-clad Pyrenees (bottom) give scale to the scene.
Image: Modified Copernicus data © ESA / Sentinel (2017)

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GEO Quarterly No 53

David Taylor
Noting Francis Bell’s request for images of specifictargets in the December issue, I thought readers would
be interested in these images of the Panama Canal,
acquired by ESA’s Sentinel-2A satellite last year.

Sentinel 2A satellite. These were then combined in
my Sentinel2toJPEG program to produce a full-colour
JPEG image as described by Les Hamilton elsewhere inthis issue.

I had actually created these images before I saw that
Francis had requested them, as my wife was taking
a trip which included the Panama Canal and manyof the interesting neighbouring locations. The images
were first downloaded from the Land Viewer website ofCalifornia-based company EOS Data Analytics at

As two separate tiles were needed for the north andsouth parts of the image, I used Autopano Pro (as Les
suggested) and produced a single large image fromwhich the three images shown were cropped. On theoriginals of the two detailed images of the lock areas
for the canal, you can easily see ships of a varietyof colours either waiting to enter or sailing off after
passing through the canal. I guess that everyone
knows that you travel from west to east on the canalwhen sailing from the Atlantic to the Pacific (shouldn’t
it be the other way round?).

https://lv.eosda.com
as three separate files corresponding the red, green
and blue bands on the OLCI sensor on the Copernicus

This image of the Panama Canal zone was created from two Sentinel 2A tiles using Autopano Pro stitching software.
Modified Copernicus data © ESA / Sentinel (2016), processed by David Taylor

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Detail showing the northeastern (Gatun) end of the Panama Canal as imaged by the Sentinel 2A satellite.
Modified Copernicus data © ESA / Sentinel (2016), processed by David Taylor

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www.geo-web.org.uk

The southwestern (Perdo Miguel and Mirflores) end of the 65 kilometre long Panama Canal is seen in this 10 metre/pixel Sentinel 2A image, as
shipping abounds in the waters of Panama Bay. Also visible is the Bridge of the Americas a little above left-centre, and Panama City at top right.
Modified Copernicus data © ESA / Sentinel (2016), processed by David Taylor

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March 2017

Sentinel 3A Images UK and Netherlands
Gerard Boon
This image is a high resolution segment of Sentinel 3A datingfrom December 4, 2016. It was received with an Ayecka
SR1 connected to an iMac running Windows 7 32‑bit using
BootCamp assistant. Data from the EUMETCast HVS service
was acquired by Tellicast 12.2.1 software followed by further
image segment processing using Hugo van Ruyskensvelde’s
EUMETCastView v 1.1.7.

I also use David Taylor’s software for MSG-1 and AVHRR but
the discussions on the forums regarding scripts, Python andLinux are beyond me. So far the images are limited with regards
to tweaking, SNAP provided by EUMETSAT is great and works
natively on a Mac but the learning curve is steep and I have yet
to attempt stitching segments together. So a big ‘Thank You’ toHugo for EUMETCastView.

The original Sentinel 3A segment showing much of Great Britain and the Netherlands
Image © EUMETSAT 2016

The resolution of Sentinel 3A is evident in this segment of the main image showing Scotland’s northwest highlands.

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Image © EUMETSAT 2016www.geo-web.org.uk

This is another section from the Sentinel 3A image, showing the Netherlands.
Image © EUMETSAT 2016www.geo-web.org.uk

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GEO Quarterly No 53

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March 2017

NASA Earth Observatory
Scientists and crew with NASA’s
Operation IceBridge, which makes
annual aerial surveys of polar ice,made another series of science flights
over the Arctic between late August
and mid September 2016. These latesummer flights followed a previous
series during April and May. Data
from the start and end of the summer
melt allows scientists to observe howeach season affects the Greenland Ice
Sheet.
‘Earlier in IceBridge’s history, weonly surveyed the elevation ofthese glaciers once a year,’ stated
IceBridge deputy project scientist
Joe MacGregor. ‘But these glaciers
experience the climate year-round.
Now we’re starting to complete thepicture of what happens to them as
the year goes on—especially after
most of the summer melting has
already occurred—so that we canmeasure their cumulative response tothat melt.’
The image opposite, taken during
a high-priority flight that IceBridge
carried on August 29, shows Helheim
Glacier, with its characteristic
wishbone-shaped channels, as seenfrom about six kilometres altitude.
Helheim is one of Greenland’s largest
and fastest-melting glaciers. During
the first week of the summer land
ice campaign, IceBridge has also
flown over glaciers along Greenland’s
northwest, southeast and southwest
coasts, and also over lines that theIce, Cloud, and land Elevation Satellite(ICESat) flew over Greenland during
its 2003-2009 period of operations, toobserve how ice elevation has evolved
since then. Future flights will covercritical areas in central and southern
Greenland, such as the world’s fastest
glacier, Jakobshavn Isbræ.
The photographs overleaf show
some glaciers observed from the
HU-25A Guardian aircraft on
September 2, 2016. The upper
photograph shows the Brückner andHeim glaciers, where they flow into
Johan Petersen Fjord in southeastern
Greenland. The lower photograph

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Helheim Glacier, with its characteristic wishbone-shaped
channels, as seen from about 6,000 metres in the sky.
Credits: NASA/Operation IceBridge

shows a tributary of Heimdal glacier.
The dark brown thread through thecentre is a medial moraine—a ridgeof debris that forms where ice fromtwo glaciers merge. The IceBridge
team also surveyed glaciers draining
ice from Greenland’s western side.
The images provide a visual reference
to help researchers understandbetter the data collected by other
instruments during the flights.
Data collected during IceBridge
campaigns have contributed to arange of discoveries since the mission
began eight years ago. Under thesnow and ice, scientists have mappeda canyon and observed an aquifer.
They have estimated the extent offrozen and thawed areas on thebottom of the ice sheet, and haveobserved variations in the thickness ofArctic sea ice.
For this short, end-of-summer
campaign, the IceBridge scientists are
flying aboard an HU-25A Guardian
www.geo-web.org.uk

aircraft from NASA's Langley ResearchCenter in Hampton, Virginia. The
Guardian is a version of an earlygeneration Falcon 20 business jet,modified for service with the US Coast
Guard and later acquired by NASA.
The plane carries a laser instrumentthat measures changes in the ice
elevation, a high-resolution camera
system to image the surface, andan instrument to infer the surface
temperature. Due to the Guardian’s
limited range, the flights werecurtailed to just 3.5 hours long,compared with the 8-hour missions
carried during IceBridge’s spring
Arctic campaign, but the team flew
twice daily whenever possible.
Operation IceBridge maintains thecontinuity of polar measurements
between ICESat satellites. The original
ICESat mission having ended in
2009, and its successor satellite notscheduled for launch until 2018.

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The Brückner and Heim glaciers where they flowing into Johan Petersen Fjord in southeastern Greenland
Image: Jeremy Harbeck/NASA Goddard

The dark brown streak across this photograph is a medial moraine in a tributary of the Heimdal glacier
Image: Jeremy Harbeck/NASA Goddard

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Francis BellThe GEO stand at the HARS Didcot rally. The photograph was taken at the start of the day as the first wave of visitors approached the stand.

GEO already have a number of rallies and presentations toamateur radio groups—and other interest groups—lined up
for 2017. These events tend to be in the southeast of England
because its difficult and expensive for myself, often with David
Simmons, to extend the areas we are prepared to cover for these
events. However, I know there are other willing GEO members
in other parts of the country ready to support such activities
so, if you know of any technical interest group which is looking
for a presentation related to GEO’s activities and technicalachievements I recommend you to contact us with potential
details. You could contact a member of the GEO Management
Team directly: see the inside cover of this publication or consult
our website at this URL

knowledgeable in their own areas but also keen to learn about
GEO and the potential which our membership offered: together
with the inevitable enquiries about us making a presentation totheir own clubs or groups.
It was a most satisfying day and I owe a big ‘thank-you’ to David
Simmons for giving up a day of his time to be with us on the GEO
stand.

http://www.geo-web.org.uk/contacts.php
A recent rally, held at Didcot on Sunday, February 12, 2017, washosted by the Harwell Amateur Radio Society, Oxfordshire. This
was not our first attendance at this venue, which takes place ina local sports centre. As usual the rally filled most of the centre’s
main sports hall with stands, as well as several squash courts
and other areas. The GEO stand was located in the busy main
sports hall , where we displayed our own literature, promotional
materials from EUMETSAT and set up three computers runningslide shows showing polar orbiting and geostationary weather
satellite images. Most of the time just two of our Management
Team, myself and David Simmons, manning the stand. But
brieﬂy, during the day, that number increased when we welcomedGEO Shop Manager Nigel Evans and his wife Michele.
It proved to be a busy day, particularly between 10.00 am and1.00 pm, but visitors then coordinated their departure earlier thanusual, I suspect because of the cold weather outside. It’s always
rewarding to meet people, and as usual visitors to the stand had
a wide spectrum of interests. Without exception they seemed

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www.geo-web.org.uk

David Simmons, right and Francis Bell manning
the GEO stand at the HARS rally, Didcot.

March 2017

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GEO Quarterly No 53

NASA Earth Observatory

Ship Waves spawned by the South Sandwich Islands on November 15, 2016
Image: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC

Sometimes, when viewed from space, the South Sandwich
Islands can appear much like a ﬂeet of fishing boats cutting
through foamy waves. Appearances can be deceiving,
however. In reality, the ‘moving islands’ are merely an illusion
created by low clouds and strong winds blowing past therugged—and solidly stationary—islands. The Moderate
Resolution Imaging Spectroradiometer (MODIS) aboard
NASA’s Aqua satellite captured such a moment as it passed
over the southern Atlantic Ocean on November 15, 2016 andacquired this true-colour image.
When strong winds slam into tall, immobile objects (called‘bluff bodies’), the wind ﬂow is disrupted, creating turbulencein the motion of the air as it passes by the object. On a clear
day, such turbulence would remain unseen. But when thesky is filled with clouds, the motion of the wind moves thecloud cover, making it visible to the human eye. The resulting
patterns of turbulence can take many forms, including
V-shaped waves that appear to be similar to wakes behindmoving ships.
The South Sandwich Islands sit in a location where westerly
winds blow frequently and with substantial strength. Cloud
cover is frequent, with only slightly more than a thousand
hours of sunshine annually on average. The islands arevolcanic in origin, with tall mountains and rugged terrain—
making them formidable bluff bodies. These features combine
to make the appearance of these ship-wave shaped clouds, acommon occurrence in this remote location.
Reference
Ship Waves - GEO Quarterly 11, page 10 (2006)

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NASA Earth Observatory
Earth’s ice is changing: frommountain glaciers to ice sheets to
ice shelves. For the most part, landbased ice has been shrinking, andthe very definition of a ‘glacial pace’has changed within our lifetimes.
Now researchers have the tools to see
those changes every few weeks and at
scales as small as 5 metres.
Using freely available data fromthe Landsat 8 satellite, scientists areworking to provide a near-real-timeview of every large glacier and ice
sheet on Earth. A group of scientists
from the National Snow and Ice Data
Center (NSIDC), the University of
Alaska–Fairbanks, the Universityof Bristol, and the Jet Propulsion
Laboratory (JPL) have started the
Global Land Ice Velocity Extraction
project (GoLIVE), a NASA-funded effort
to better understand how ice flow ischanging worldwide.
‘We are now able to map how theskin of the ice is moving,’ said
Ted Scambos, senior researchscientist at NSIDC and lead for
the GoLIVE project. ‘From now on,
we’re going to be able to track allof the different types of changes inglaciers. There’s so much science
to extract from the data.’
The effort was described at the2016 fall meeting of the American
Geophysical Union.
Evidence strongly suggests that theloss of ice from glaciers and ice sheets
has been the largest contributor
to sea level rise over the past three
decades, with waters rising at a
global average rate of 3.3 millimetres
per year. By examining changes in
ice flow in combination with dataon ocean and atmospheric changes,
the researchers hope to determine
what causes ice masses to change
and how much ice will flow into
the ocean. The satellite-based
approach is particularly valuable inremote landscapes, where groundand airplane-based observations
are expensive, dangerous, andintermittent.
In Alaska and Canada’s Yukon
Territory, for instance, most glaciers

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Figure 1 - Ice velocity in southeastern Alaska

are so remote that speedup events
can go unnoticed for months until apilot flies over the region and reports
disrupted ice. Figure 1, based on an
analysis by GoLIVE investigators,
shows the velocity of ice insoutheastern Alaska near Malaspinaand Hubbard glaciers.
‘By measuring ice ﬂow all thetime, we can identify a surge as it
starts, providing an entirely new
way to follow this phenomenon,’stated Mark Fahnestock of the
University of Alaska. ‘We can also
follow large seasonal swings intidewater glaciers as they respondto their environment. Scientists
need to see all of this variability inorder to identify trends.’
Automation has been key to thisice velocity mapping effort. Landsat 8
collects images of roughly 700 sunlit
parcels of the planet’s surface every
day, and during the course of 16 days,
the satellite observes the entire land
surface of Earth in multiple visible
and infrared wavelengths. This meansthat scientists can view changes inthe same spot on Earth every 16 days(or 32, 48, 64, etc. days as cloud coverallows).
www.geo-web.org.uk

This also means that there is ahuge amount of data to process andanalyse. Between 2013 and 2016,
Landsat 8 collected thousands ofimages from Antarctica alone. The
globes in figure 2 illustrate how manytimes Landsat 8 passed over a givenicy parcel in 2015 alone. As many as
150 to 200 images were collected overthe brightest yellow and green areas,
while purple areas had just a handfulof useful images because of frequent
cloud cover and fewer orbital passes.
Due to the nature of the satellite’spolar orbit, areas in the far north andsouth can be imaged more frequently(when there is sunlight).
The imaging system aboard Landsat 8
is far more sensitive than previous
Landsat sensors, distinguishing far
more subtle differences in shading
and surface texture. The GoLIVE
team has written software thatallows researchers to follow thesesubtle features, like bumps ordune-like patterns on ice surfaces.
By comparing images of thesame location on different dates,
researchers can track individualfeatures and determine the speed of
the surface flow.

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Figure 2 - Frequency of Landsat 8 passes over Antarctica in 2015

‘The question is: how sensitive are these ice sheets tochanges in the atmosphere and the ocean?’ said Alex
Gardner of JPL. ‘We could wait and see, or we could
look to the past to help inform what is most likely tohappen in the future.’

You can view a speeded-up animation showing the motionof Greenland’s Heimdal Glacier on YouTube athttps://www.youtube.com/watch?v=EahiP3Qa7QY

Gardner has been looking closely at Antarctica, with ice
velocities represented in the map below (figure 3). He is
working to combine the new Landsat 8 ice-flow data withprior maps of the continent’s glacier flow in the hope ofunderstanding decadal changes across the entirety of theice sheet. Almost 2,000 cubic kilometres of ice flow into
the Southern Ocean from Antarctica each year.
Twila Moon, an ice scientist at the University of Bristol,is using the global maps to expand her research inGreenland. With the new database, she can study the
movements of more than 240 glaciers, nearly all of theoutlets from the ice sheet. And with Landsat 8 making an
overpass every 16 days, she has the opportunity to detectseasonal changes and cyclical patterns.
While most glaciers speed up in the warmer summer
months, Moon has found several that slow down
dramatically in the mid- to late-summer.
‘We can group these glaciers by looking at thesimilarities in their behaviour,’ Moon said. ‘It’s
providing an opportunity to get at the underlying driversof why they change.’
With measurements of what the seasonal shifts do to
glacier speed, scientists can extrapolate what might
happen to those glaciers as global temperatures continue
to climb.

Figure 3 - Ice velocities in Antarctica(For colour key, see figure 1)

NASA Earth Observatory images by Joshua Stevens, using
Landsat-derived ice velocity data courtesy of Alex Gardner, NASA
Jet Propulsion Laboratory/California Institute of Technology and
ASTER GDEM data from the NASA/GSFC/METI/ERSDAC/
JAROS, and U.S./Japan ASTER Science Team.
Caption by Kate Ramsayer and Mike Carlowicz.

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This Sentinel 2A image depicts São Domingos, the main island of the Republic of Cabo Verde (Cape Verde), acquired on February 6, 2017.
The island measures 55 kilometres from north to south, and its capital city, Praia, can be seen clearly at the far south.

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NASA Earth Observatory

An astronaut aboard the International Space Station (ISS) used along lens to document what crews have termed one of the mostspectacular features of the planet: the linear sand dunes of the
Namib Sand Sea.
Looking inland (from an ISS position over the South Atlantic) nearsunset, the highest linear dunes show smaller linear dunes riding
along their crests. Linear dunes are generally aligned parallel tothe formative wind—in this case, strong winds from the south.
Southerly winds explain the parallel north-aligned linear dunes on
the left side of the image.
But this simple pattern is disrupted near the Tsondab valley,
which acts as a funnel for winds from the east. These lessfrequent but strong winter winds are channelled down the valley
and usually carry large amounts of sand, similar to the Santa Ana
winds in California. These strong easterly winds significantly
deﬂect all the linear dunes near the valley so that they point
downwind.
Further inland (right), the north-pointing and west-pointing
patterns appear superimposed, making a rectangular pattern.

Because the Namib Desert is very old—dating from the time
when the cold, desert-forming Benguela ocean current started
to ﬂow about 37 million years ago—wind patterns and dune
patterns have shifted over time. North-oriented dunes haveshifted north and east with drier climates and stronger winds,
overriding but not removing earlier dune chains, thus creating therectangular dune network we see today.
The Tsondab, an ephemeral dry river in the west of Namibia, isblocked by linear dunes (just outside the left margin of the image)
100 kilometres from the Atlantic Ocean. Research has shown
that, during wetter times, it did reach the ocean. The name
Tsondab means ‘that which is running is suddenly stopped’ in thelocal Khoisan language.
Along the edge of the dune-free Tsondab River valley, you cansee star dunes, which are smaller and display multiple arms (topleft).
Astronaut photograph ISS047-E-23405 was taken by a member of the Expedition
47 crew on March 27, 2016, with a Nikon D4 digital camera using a 500 millimetrelens, and is provided by the ISS Crew Earth Observations Facility and the Earth
Science and Remote Sensing Unit, Johnson Space Center. Caption by M. Justin
Wilkinson, Texas State University, Jacobs Contract at NASA-JSC.

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André T’Kindt submitted this finely detailed NOAA 18 APT image he decoded from the satellite’s 18.17 UT pass on November 22, 2016,
and which shows the British Isles in a ridge of high pressure which drove freezing winds south over the North Sea.

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Les Hamilton
Formed over millions of years by a series of lava flows,
the Kerguelen Archipelago is a group of islands locatedin the southern Indian Ocean roughly midway between
Africa, Australia, and Antarctica. The Kerguelen
Islands experience a fierce climate, with incessant,howling winds accompanied by rain or snow nearly
every day. At a latitude of about 49° south, they lie
in the path of the ‘Furious Fifties’, the belt of westerly
winds that whips around the Southern Hemisphere,
mostly unimpeded by land.
These islands are among the most isolated placesof Earth, being located 450 kilometres northwest of
the uninhabited Heard Island and McDonald Islands
and more than three thousand kilometres from thenearest populated location, on Madagascar. The
Kerguelen islands, along with the Crozet Islands andthe Amsterdam and Saint Paul Islands were officiallyannexed by France in 1893 and were included as
possessions in the French constitution in 1924: they
are now part of the French Southern and Antarctic
Lands and are administered as a separate district.
The main island, Grande Terre, its perimeter carved by
fjords, has an area of 6,675 km2 and is surrounded byan archipelago of 300 smaller islands and islets with a
total area of 7,215 km2. The climate is raw and chilly
throughout the year with frequent high winds and thesurrounding seas are generally rough though they
do remain ice-free all year. There are no indigenous
inhabitants, but France has maintained a permanent
presence of between 50 and 100 scientists, engineers
and researchers since 1950. There is also a Frenchsatellite tracking station. There are no airports on theislands, so all travel and transport from the outside
world is conducted by ship.

Figure 1 - A rare cloud-free image of Kerguelen island, acquired by NASA’s Terra satellite on October 28, 2016
Image: LANCE Rapid Response/NASA/GSFC

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The islands were officially discovered by the Frenchnavigator Yves-Joseph de Kerguelen-Trémarec on
February 12, 1772 and, the following day, Charles deBoisguehenneuc landed and claimed the island for the
French crown. A number of other expeditions briefly
visited the islands, including that of Captain James
Cook in December 1776. Following their discovery, thearchipelago was regularly visited by whalers and sealers(mostly British, American and Norwegian) who hunted theresident populations of whales and seals to the point ofnear extinction.
In 1825, the British sealer John Nunn and three crew
members from the Favourite, were shipwrecked on
Kerguelen for almost three years until they were rescued
in 1827. Nunn related his experiences in a book: Narrativeof the Wreck of the ‘Favourite’ on the Island of Desolation.
During their time on Kerguelen, the men built a wooden
cottage in which to live (figure 2) and a cart for collecting
and transporting king penguin eggs, which formed an
important part of their diet (figure 3).

Figure 3 - The Egg Cart, another engraving from Nunn’s book.
Source: Wikimedia Commons

biology. A former sounding rocket range to the east of Portaux-Français is currently the site of a SuperDARN radar.
Since 1992, the French Centre National d’Études Spatiales(CNES) has operated a satellite and rocket tracking station
which lies four kilometres east of Port-aux-Français. CNES
needed a tracking station in the Southern Hemisphere,
and the French government required it to be located on
French territory, rather than in a populated, but foreign,place like Australia or New Zealand.

Figure 2 - Hope Cottage, an engraving from John Nunn’s book showing
the refuge they built on Courbet Peninsula in 1825.
Source: Wikimedia Commons

Grand Terre
The main island of the archipelago is called La GrandeTerre, and measures 150 kilometres from east to west and
120 km from north to south. The scientific base is known
as Port-aux-Français, and is located on the eastern shoreof the Gulf of Morbihan. Facilities there include scientificresearch buildings, a satellite tracking station, dormitories,
a hospital, a library, a gymnasium, a pub, and the chapelof Notre-Dame des Vents.
The highest point is Mont Ross in the Gallieni Massif,
thought to be Kerguelen’s youngest volcano, which rises
along the southern coast of the island to an elevation of1850 metres. No eruptive activity has been recorded inhistoric times although some fumaroles are still active inthe southwest of Grande-Terre.

Agricultural activities were limited until 2007 to raising
sheep (about 3,500 Bizet sheep—a breed of sheepthat is rare in mainland France) on Longue Island for
consumption by the occupants of the base, as well as
small quantities of vegetables in a greenhouse within theimmediate vicinity of the main French base. There are also
feral rabbits and sheep that can be hunted, as well as wild
birds.
There are also five fishing boats and vessels, owned byfishermen on Réunion Island (a department of France
about 3,500 km to the north) who are licensed to fish
within the archipelago’s Exclusive Economic Zone.
ClimateKerguelen’s climate is oceanic, cold and extremely
windswept and is classified as tundra. The averagetemperature in the warmest month is below 10 °C,
comparable with Alaska’s Aleutian Islands, Iceland, theGlaciers are scattered across the island and the Cook Ice
Cap—France’s largest glacier with an area of about 403
km2—lies to its west-centre. Overall, the glaciers of the
Kerguelen Islands cover just over 500 km2. Grande Terre
has numerous bays, inlets, fjords, and coves, as well as
several peninsulas and promontories.
EconomyThe French supply ship Marion Dufresne makes regularcalls at the Kerguelen Islands and typically carries a small
contingent of tourists. Principal activities on the Islands
focus on scientific research—mostly Earth sciences and22

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Figure 4 - The south rim of Cook Glacier andMount Ross on Kerguelen Island
Photo: B.navez (1983) / Wikimedia

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GEO Quarterly No 53

Figure 3 - Port-aux-Français, the French Station located at Golfe du Morbihan on Grand Terre in the Kerguelen Archipelago
Image: Daniel Delille / Wikimedia

northern Kamchatka Peninsula, Labrador and Tierradel Fuego. All climate readings come from the Port-auxFrançais base, which has one of the more favourable
climates in Kerguelen due to its proximity to the coast andits location in a gulf sheltered from the wind.
The average annual temperature is 4.9 °C with an annual
range of around 6 °C. The warmest months of the year
include January and February, with average temperatures
between 7.8 and 8.2 °C. The coldest month of theyear is August with an average temperature of 2.1 °C.
Annual high temperatures rarely achieve 20 °C, whiletemperatures in winter have never been recorded below-10 °C at sea level.
Kerguelen receives frequent precipitation, with snow
throughout the year as well as rain. Port-aux-Français
receives a modest 708 millimetres of precipitation per year,
compared to the west coast which receives an estimatedthree times as much. The mountains are frequently
covered in snow but can thaw very quickly in rain. Overthe course of several decades, many permanent glaciers
have shown signs of retreat, with some smaller ones
having disappeared completely.
The west coast receives almost continuous wind at an
average speed of 35 km/hour, due to the islands’ location
between the Roaring Forties and the Furious Fifties. Wind
speeds of 150 km/hour are common and can even reach
200 km/hour.
Flora and Fauna
Despite the challenging climate, several animals and birds
make their homes at Kerguelen or use it as a stopping overpoint in their migrations or during breeding. Among theindigenous wildlife on the Kerguelen Islands are several
species of penguins, elephant and fur seals, plus dozensof species of sea birds, including terns and albatrosses.
It is the sea that makes this ‘wildlife sanctuary’ possible
because the islands are located along the Antarctic
Convergence Zone, where the icy waters of the Southern
Ocean meet the warmer waters of the Indian Ocean. The
waters in this mixing area are very rich in nutrients, which
support the phytoplankton which are the foundation of theocean food web.

Plant life in this rocky landscape is mainly limited
to tussock grass (Poa cookii), mosses (Azorella selago
and Acaena adscendens), lichens and the famous
Kerguelen cabbage (Pringlea
antiscorbutica). This latter
species, belongs to thebrassica family (as does thecommon cabbage), and has
evolved a unique methodof cross-pollination which
relies on the wind, since
there are no flying insects
on the island. The leaves
Kerguelen Cabbageof the cabbage contain a
Photo: Wikimedia Commons / Share
Alike 3.0
pale-yellow, highly pungent
essential oil which is rich inascorbic acid (vitamin C) which made it a useful dietary
supplement against scurvy for early sailors.
The wildlife on Kerguelen is particularly vulnerable tointroduced species and one particular problem has beencats. The main island is home to a well-established feral
cat population, descended from ships’ cats, which survive
on a diet of sea birds and the feral rabbits that wereintroduced to the islands by the whalers. All these cats
are black-and-white because the original three cats on theisland were black-and-white.
There are also populations of moufflon sheep (Ovis aries
musimon) and reindeer introduced by the French. The
reindeer have now become wild, and impossible to remove
from the island and probably number in excess of 3,000
head.
Tourism
Tourists can book a cabin in the base support ship Marion
Dufresne for €8,300 per person for a double cabin, or€16,500 for a single cabin. There are apparently four trips
open to tourists per year. The trip leaves from Réunion andtakes about 28 days
Acknowledgements
Much of the information contained in this article wasgleaned from Wikipedia, and from reports from NASA
Earth Observatory.

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NASA Earth Observatory
Snow may not be the first thing thatcomes to mind when you think of
the Hawaiian Islands. But nearly
every year, the volcanic peaks of
Mauna Kea and Mauna Loa become
temporarily dusted with white. The
Operational Land Imager (OLI) on theLandsat 8 satellite captured thesenatural-colour images of the snowy
peaks on December 25, 2016. A storm
a week earlier brought not only snow,
but bouts of thunder and lightning.
While snow in Hawaii is not unusual,and can even fall in summer,
thundersnow is less common.
The storm was reportedly associatedwith a Kona low. This low-pressure
system brought a change in winddirection, such that winds thattypically blow out of the northeast
shifted to blow from the southwest.
The winds from the leeward or ‘Kona’side drew moisture from the warm,
tropical Pacific that ultimately fell assnow over the high elevations.
Detailed views give a closer look at thesnowy summits. Mauna Kea rises to
4,205 meters (35 meters higher than
Mauna Loa) and is one of Hawaii’s
older dormant volcanoes, with steep,
irregular terrain marked by numerous
cones. Mauna Loa, in contrast, isrelatively active and topped with threecircular depressions that compose
the Moku‘aweoweo caldera. Mauna
Loa is less steep, with gentle slopes

Snow capping Mauna Loa and Mauna Kea, Hawaii on Christmas Day 2016.

NASA Earth Observatory images by Jesse Allen, using Landsat data from the US Geological Surveythat block the view of its snow cappedsummit from sea level. Satellites
offer views of both summits. Naturalcolour visible imagery from satellites,
however, can be obscured by the

The summit of Mauna Kea showing its numerous cones
Image: NASA24

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presence of clouds. That was the caseearlier in December when a storm wasreported to have dropped more than
60 cm of snow on the peaks.

Moku‘aweoweo caldera Mauna Loa
Image: NASA

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MODIS-Web Image of the Day

NASA’s Terra satellite captured this image of Van Karman vortices being shed by the island of Cheju Do, South Korea
Image Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC

On January 31, 2017, the Moderate Resolution Imaging
Spectroradiometer (MODIS) ﬂying aboard NASA’s Terrasatellite captured a stunning true-colour image of cloud
vortices induced by the island of Cheju Do, South Korea.
The swirling patterns are being formed by the turbulencecreated when southward-ﬂowing air strikes the broad faceof Mount Halla—a tall, broad-faced mountain that rises
to 1,950 metres. The turbulent wind causes the clouds to
ﬂow in the large, spinning eddies seen in this image.

Known as von Karman vortex streets, such patterns
occur in many situations, such as the vibration of a carantenna at specific speeds, or wind impacting buildings.
The size and shape of the eddies formed by the unsteady
ﬂow of a ﬂuid around blunt bodies can be predictedwith good accuracy via mathematical formulas, andthis aspect of ﬂuid dynamics is important in science,
meteorology, and engineering. Only when clouds arepresent, however, is this beautiful pattern visible in theatmosphere.

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This image of North America’s Great Lakes comes from a February 9 Meteor M2 image posted on the GEO-Subscribers YAHOO Group by Jeff Kelly.

26
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Periodically, Russia’s Meteor M2 satellite transmits three visible light channels, as here, on February 11. This segment comes from an image
submitted by Enrico Gobbetti, and the cyan colouration highlights areas covered by snow, frost or ice.

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Les Hamilton
ESA’s Sentinel-2A satellite, launched in June 2015, has thecapability of imaging the Earth at a resolution of ten metres
per pixel. Thanks to cloud-based GIS analysis service
EOS Data Analytics, it is now possible for anyone to inspect the
Earth’s surface in exquisite detail by means of their Land Viewer
website athttps://lv.eosda.com/
Visit this URL and click the prominent ‘Open Land Viewer’ button.

Figure 2 - The grid that is displayed as soon as a satellite is selected

Figure 1 - The opening Land Viewer screen

Land Viewer’s opening screen (ﬁgure 1) displays two panels: a
scrollable/zoomable map of the Earth and ‘Select Satellite’. To
use the software, select the desired satellite (which, from theperspective of this article is Sentinel-2A), then drag/zoom the
map to the desired location with the mouse. Zooming can also
be achieved using the +/- buttons at the left of the display or by awheel-mouse.
As soon as you select a satellite, a grid is superimposed overthe map (though it is not visible until you have zoomed in threetimes). This grid, based on the NATO Military Grid Reference
System [1], consists of 100 kilometre squares, each of which may
relate to a tile of Sentinel-2A imagery. Figure 2 shows this grid
overlain upon The Netherlands.

Figure 3 - Select the Tile of interest

Click on a square to highlight it (ﬁgure 3) and a panel of images
will appear in the right-hand panel. Be patient as it may takeseveral seconds for the images to download. The default images
shown all contain excellent land detail with at maximum, 10%
cloud cover. Grid squares wholly over the sea do not containimagery.
Finally, click on the image of choice to load it into the grid square(ﬁgure 4). You can zoom into this image and scroll around as
described above. You can hide the right-hand panel and view thisimage full-screen by clicking the ‘Toggle Panel’ icon at theright of the screen.
Program Options
Once you have loaded a satellite image, the column of icons to
the right of the right-hand panel all become active.

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Figure 4 - Select an image from the scrollable side panel

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Figure 5 - A zoom into the Amsterdam canal system

GEO Quarterly No 53

Figure 6 - The same scene with channel 8 replacing the red component

Satellite: Select between Landsat-8 and Sentinel-2A data.
Scene Search: removes any image displayed on the map
and displays the grid
Scene View: displays the selected thumbnail image on the
map and hides the gridBand Combinations: by default, a true colour image isdisplayed by combining channels 2, 3 and 4 (the blue,
green and red channels from the satellite). But Sentinel‑2
images in thirteen distinct frequency ranges, and thisoption allows you to vary the combinations used. Figure 6
shows channels 3, 4 and 8 in combination (vegetation).
Contrast and Stretching: a panel appears with controls thatallow you to adjust the contrast of the displayed scene.
Scene Downloading: this reveals the Download Options
from which you can download full-resolution original
images. As explained in the following article, David
Taylor has developed software that can, specifically,
combine the red, green and blue Sentinel 2A tiles into acoloured image. To download, hover the mouse over the‘B02 ‑ Blue’ option and a down-pointing arrow appears
at the right: click this to start the download. Repeat forthe ‘B03 ‑ Green’ and ‘B04 ‑ Red’ bands. All three can be
downloaded simultaneously.

Figure 7 - The download screen showing the blue tile selected

Labels: Clicking this icon adds labels to the image, as
appropriate. Applied to figure 7, main roads in the city arehighlighted along with the caption ‘Amsterdam’. Figure 8
shows how the full tile responds to the ‘Labels’ button.
Other Options
The final three buttons offer, respectively:• Feedback on the map• Map sharing• Log in/out

Figure 8 - Labelling applied to the entire tile

It goes without saying that, with 10‑metre resolution available,
the main value of Sentinel 2A images comes when you zoom into small regions: cities, oceanic islands, mountains, lakes andman-made structures all provide fascinating viewing.

bottom left margin of the Land Viewer screen is a display of thelatitude and longitude of the cursor. These change as you scan
the map with your mouse. I started by looking up the coordinatesof St Helens on the internet than placed the cursor as close tothis on the World Map. Successive double-clicks on this spot tozoom into the map coupled with repositioning of the cursor eachtime soon brought St Helena into view. The result can be seen
overleaf.

But how can you locate a tiny island, St Helena for example,
which is simply a tiny dot in a vast expanse of ocean? At the

1 https://en.wikipedia.org/wiki/Military_Grid_Reference_System

Although you must log in to use Land Viewer, usage is free.
Locating Areas of Interest

Reference

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The Atlantic Island of St Helena, imaged by ESA’s Sentinel-2A satellite on April 2, 2016. The island measures just 16 × 10 kilometres.
Image: Modified Copernicus data © ESA / Sentinel (2016)30

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Les Hamilton
As explained in the previous article, high-resolution
imagery from ESA’s Sentinel-2A satellite is now
available on the Land Viewer internet site. It is perfectly
feasible to view image tiles within Land Viewer, butwouldn’t it be much more satisfying to be able todownload the individual red, green and blue datachannels and combine them into colour composites
yourself? Well, now you can!
David Taylor has produced the Sentinel2toJPEG
program which, in addition to allowing the user tocreate colour composite images of individual Sentinel
tiles, also affords control over the extent of histogram
equalisation and gamma correction, as well as theability to define cropping areas. The software isavailable in both 32- and 64-bit versions.
Sentinel Tiles
Segments of imagery from Sentinel 2A passes areavailable as ‘tiles’, each of which contains a scene
measuring 100 × 100 km. These tiles correspond withsquares on the NATO Military Grid Reference System,
which covers the entire surface of Earth. Not all tiles
contain Sentinel imagery however: many of those above
land and some (but not all) small oceanic islands do so.
Of the thirteen spectral bands sensed by Sentinel 2A,
those for blue (490 nm), green (560 nm) and red(665 nm) are realised at the maximum 10 metres per
pixel ground resolution of the satellite’s multi-spectral
instrument (MSI). It is these three channels that areprocessed by Sentinel2toJPEG.
Once you have selected a tile, download the three RGB
images as explained in the preceding article. Although
every tile has a specific descriptor which includes thedate and tile name, the files you download always havethe following basic names:
B02.jp (blue)
B03.jp (green)
B04.jp (red)Bay of Gibraltar on September 24 - Gibraltar is the peninsula on the east
Modified Copernicus data © ESA / Sentinel (2016)

The south end of Lake Mead with the Hoover Dam
Modified Copernicus data © ESA / Sentinel (2016)

David Taylor recommends that you should immediately
rename these by prefixing them with the tile descriptor.
For the Amsterdam tile used earlier, this would give:
S2A_tile_20160501_31UFO_0-B02.jp
S2A_tile_20160501_31UFO_0-B03.jp
S2A_tile_20160501_31UFO_0-B04.jp
I prefer to name images after a prominent feature in thetile itself, e.g.
Gibraltar_20160924-B02.jp
Gibraltar_20160924-B03.jp
Gibraltar_20160924-B04.jp
The choice is yours. But it is vital that the names are
identical, with the sole exception of the respective
suffixes ‘B02.jp’, B03.jp’ and ‘B04.jp’. Without these,
the software cannot identify the three channels
correctly, and processing will not take place.
... continued on page 33

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Mount Saint Helens in Washington State

Modified Copernicus data © ESA / Sentinel (2016)31

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The cross-Channel Ferry terminal at the port of Zeebrugge, Belgium.
Modified Copernicus data © ESA / Sentinel (2016)

San Francisco Bay on March 26, 2016, with the Golden Gate bridge at left and Alcatraz the small Island to its right.
Modified Copernicus data © ESA / Sentinel (2016)32
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The volcanic South Atlantic island of Tristan da Cunha, only 12 kilometres wide and with a population of 265 hardy souls.
Modified Copernicus data © ESA / Sentinel (2016)

The files you download are losslessly coded in the
JPEG2000 [1] format, one, alas, that most current viewing
and graphics programs do not recognise. Hence theimpetus to create a software package that would not
merely load these tiles, but could combine them into a true
colour images like the segments illustrated on these pages.
You can read David’s own web article on this topic at
http://www.satsignal.eu/wxsat/Sentinel/Sentinel-2A.html
Sentinel tiles measure 10980 pixels in both dimensions,which works out at a nominal resolution of 10 kilometres
per pixel at nadir. Consequently, the files you download
are large, even with JPEG2000 compression, and typicallymeasure between 90 MB and 130 MB each. This meansthat processing is a relatively lengthy process, and evenwith a fairly fast computer, Sentinel2toJPEG will take aroundninety seconds to produce an image from a set of three
Sentinel 2A JPEG2000 image tiles.
The Sentinel2toJPEG Software

Figure 1 - The Sentinel2toJPEG program interface

If so, you must download and install Microsoft’s Visual
C++ Redistributable Package for Visual Studio 2013 fromhttps://www.microsoft.com/en-us/
download/details.aspx?id=40784

This program comes as a zip file which contains both the
32- and 64-bit versions. Also included is a copy of theessential FreeImage.dll library file for each version.

The 32-bit version does not require this file.

The first time you attempt to run the 64-bit version
of Sentinel2toJPEG, you may be confronted by an error
message stating that the library file VCOMP120.DLL is
missing.

This new software comes with a refreshingly simple
interface which can be resized from full-screen right down
to the size of a postage stamp: and the only controls are
the three buttons you can see in figure 1.

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Windows 10 64-bit
4 core Intel i5-4460
8 GB RAM

Windows 7 64-bit
4-core AMD A6-6310
8 GB RAM

March 2017

Windows 7 64-bit
2-core Intel i7-620M
4 GB RAM

Windows 7 64-bit
2-core Intel Duo E4600
4 GB RAM

32-bit64-bit32-bit64-bit32-bit64-bit32 bit64 bit3 × JPEG2000 files

96.6 sec

86.2 sec

201.1 sec

192.8 sec

116.1 sec

105.2 sec

190.6 sec

180.4 sec

1 × 48-bit PNG file

12.3 sec

10.9 sec

27.2 sec

25.1 sec

15.5 sec

14.4 sec

22.9 sec

23.2 sec

1 × 48-bit TIFF file

6.4 sec

6.2 sec

14.4 sec

14.3 sec

12.8 sec

12.7 sec

12.6 sec

13.4 sec

3 × Landsat TIFF files

4.0 sec

4.0 sec

8.3 sec

8.7 sec

5.9 sec

6.3 sec

10.54 sec

10.2 sec

Table 1Comparative processing times for both versions of Sentinel2toJPEG on various computers

To process your first Sentinel image, just load any oneof the Sentinel RGB files, either by dragging it on to theinterface, or by clicking the ‘Open’ button and navigating
to its folder and double-clicking the one of your choice.
Note that you only have to load one of the three files:
the software will then automatically load all three (theopen dialogue normally displays only the ‘Blue’ B02 tile.
However, if you load the ‘Near Infrared’ B08 tile, thisshows up as well - see Appendix on page 32).
From this point you will face a delay until the image isready. The bulk of this time is required to decipher the
wavelet-based coding within the JPEG2000 files: once
that is achieved, the final RGB image follows swiftly andis automatically saved in standard jpg format in the same
folder as the original files. Do not panic if a ‘Program not
responding’ message appears in the title bar: this may
occur because the program is hogging the computer’s
resources—but processing is continuing. Just be patient
for a while and check the progress messages at the lower
left of the Sentinel2toJPEG interface as it decodes the red,green and blue images in sequence. Table 1 shows timings
for various processes using both the 32-bit and 64‑bit
versions of Sentinel2toJPEG.
I have tested both the 32- and 64-bit versions of
Sentinel2toJPEG using four different computer systems,
one running Windows 10 Home and three Windows 7
Home. The top line of the table shows the times taken tocompletely process the same set of three JPEG2000 files.
The 64-bit version of the software is marginally faster thanthe 32‑bit compilation, but the overall processing timedepends mainly on the speed of the processor (all otherthings being equal).
ThreeJP2toPNG48
If you wish to process a particular set of JPEG2000
files several times—to optimise gamma and histogram
stretching for example—this could turn out to be a lengthy
exercise.

Figure 2 - The ThreeJP2toPNG48 interface

The solution to this problem comes via a small ‘helper’
application named ThreeJP2toPNG48. This utility canprocess a set of JPEG2000 files into a single 48-bit PNG
file, a common format that can be read quickly (or, if you
prefer, as a 48-bit TIFF file). Although it can take several

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minutes to create these files, both the PNG and TIFF files
process rapidly in Sentinel2toJPEG: see Table 1 for details.
Options
When you click the ‘Options’ button on the programinterface, the Sentinel2 Reader Setup panel appears.
Figure 3 displays the default settings.

Figure 3 - The default Setup panel

Here you find options to process a cropped section of a
Sentinel tile, crop the extremities of its histogram andadjust the gamma to optimise the brightness of theprocessed image.
Crop to Region
When processing an image—such as that of Tristan da
Cunha shown on the previous page—the area of interest
is an island just twelve kilometres wide in an image tile
stretching one hundred kilometres along each side. The
first time I processed this Sentinel tile, I ended up with theimage shown in figure 4, where the island is highlighted in
the white square.
If you wish to image a specific region regularly, it would bemuch more manageable if the software could process justthe immediate area of interest and save that alone. This iswhat the ‘Crop to Region’ options are designed to achieve.
On completion of tile processing in Sentinel2toJPEG —oncethe ‘Saved as’ message appears at the lower left of thescreen—the X- and Y-coordinates of the position of the
cursor above the final image are shown in the bottom
left-hand corner of the display. By scrolling the image andpositioning the cursor successively above, left, below andto the right of the area required, appropriate Y-values canbe established and entered into the ‘top’ and ‘bottom’ fieldsof the Setup panel; similarly, the X-values can be enteredinto the ‘left’ and ‘right’ fields (figure 5). Now, when the tile
is reprocessed, only the desired area appears on screen,
and in the saved image.
The Sentinel2toJPEG zip archive contains a file named‘Sentinel2toJPEG-sample.ini’ which contains a list ofpresets for the program, Tristan da Cunha among them.
If you copy this file into the Sentinel2toJPEG folder andwww.geo-web.org.uk

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Setting the Crop to Default Values
If, after setting a cropping preset, you wish to prepare animage of a complete tile, the crop values can be returnedto their defaults by clicking ‘- default -’, the top item in thedrop-down menu.’
Delay Display
This option, when ticked, prevents the red, green and blue
images from appearing on screen during the processing
operation. Only the final RGB composite is displayed. This
could be of benefit if your processor struggles handling thethree JPEG2000 files.
Note that this change requires that the program be closed
down and run afresh (a warning message appears).
Log Events
If this box is ticked, the program produces a log file thatdetails precisely how long is taken over each task during
the processing of an RGB image. Again, a restart isrequired to enable a change in status.
JPEG Save Quality
Figure 4 - The complete Sentinel 2 tile containing Tristan da Cunha
with the volcanic island highlighted in the white square.

This selector allows three save options: normal, good andsuperb. Personally, I can only just detect the difference
between these, but of course the better the quality thelarger the file size. If file size is important, the ‘normal’option will serve you well.
Troubleshooting
As you build up a list of presets for Sentinel2toJPEG, a time
may come when you discover that a particular preset nolonger works as expected: the main area of interest could
lie off-centre or, if quite small, off screen altogether.
This had me puzzled for a while until I looked more closely
at Land Viewer. Although a given tile will most commonly
offer just one Sentinel image on a given date, sometimes
there are two: one each from the satellite’s northboundand southbound passes. As the satellite track will differ
for each pass, the exact location of features within the tile
will alter slightly between the two image. Not serious, butsomething to be aware of.

Figure 5 - Tristan da Cunha crop parameters

Creating Composite Images
Frequently, a feature of interest such as a city or island
straddles the boundaries of two or even four Sentinel tiles.
A typical case is the island Majorca, illustrated in figure 7.

Figure 6 - The crop drop-down list

rename it to ‘Sentinel2toJPEG.ini’, a drop-down list
containing all these presets becomes available. This issimply a text file, which you can edit in any way you wish.
Just ensure that the [CROP] line is present at the startof the list otherwise the program will not recognise theentries.
ReprocessProvided you do not close the Sentinel2toJPEG program, the‘Reprocess’ button allows you to make alterations to the‘Histogram’ and ‘Gamma’ settings and quickly process thesame Sentinel tile multiple times (this saves having to keep
reloading the files). This can be a great help in producing
images with the optimum range of tones and brightness.
www.geo-web.org.uk

Figure 7 - Majorca straddles four Sentinel tiles

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A glance at the figure shows that there is considerable
overlap between adjacent tiles, approximately nine
percent, in fact: so joining the four sections should befeasible.
For my first effort, I searched for the appropriate
set of four tiles from the same Sentinel pass (notalways possible) and discovered what I required on
August 26, 2016. I prepared appropriate presets forthe four sections and prepared the coloured composite
images, which proved easy to slide together in
Photoshop. But there was a problem: the brightness
characteristics of the four segments were slightly
different, as is clear in the resulting composite image ofMajorca (figure 8).
Many photographers these days are in the habit ofstitching together series of photographs to create
panoramic views. I do this with Autopano Pro [2].
Because this software caches its workspace on thehard drive, it easily copes with the full-size tile images,saving the bother of creating presets for the four
quadrants of Majorca. The program also intelligently
compensates for any differences in illumination
between photographs. To my delight, my first effort
was perfect: there was absolutely no indication of
the joins (figure 9). Because the original images wererather bright for my taste, both those illustrated were
initially processed with a gamma value of 100.
Locating Small Target Areas
One of the problems of locating the correct tile forsmall islands is that they are hard to spot until you

Figure 8
The initial Majorca composite image, compiled using Photoshop,
which showed brightness variations between quadrants.

zoom a long way into the world map. This was true of
Tristan da Cunha, for example. But there is an easy way
to locate it because, at the very bottom left of the Land
Viewer screen there is a display line showing the latitude
and longitude beneath the mouse cursor. I looked up thelatitude/longitude of Tristan da Cunha in Wikipedia andmoved the mouse as close to this as possible. There wasas yet no sign of the island but, by successively zooming
the map and correcting the mouse to these coordinates,
it eventually came into view, allowing me to select theappropriate tile.

... continued on page 38

Figure 9 - The Majorca composite image, compiled using Autopano Pro, which produced a perfectly balanced result.

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Modified Copernicus data © ESA / Sentinel (2016)www.geo-web.org.uk

The Caribbean holiday island of Aruba, imaged by Sentinel 2A on May 16, 2016
Modified Copernicus data © ESA / Sentinel (2016)www.geo-web.org.uk

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But a word of caution: whether this is an arcane American
way of denoting coordinates, or is simply an error, I do
not know. But the coordinates at the foot of the screen arealways suffixed by ‘N’ for latitude and ‘W’ for longitude:
never ‘S’ or ‘E’. Latitudes south of the equator are negative
and those north positive; longitudes west of Greenwich arealways negative and those to the east of it positive.
So, the correct location of Tristan da Cunha is:
Latitude 37°04’ south, Longitude 12°19’ west
Land Viewer quotes it as:
Latitude -37.15°N, Longitude -12.26°W
I know this is absolutely bonkers, but that’s the way itworks (at present anyway).
As yet, all small islands in the ocean have not been viewed
by Sentinel 2A (e.g. Ascension island), so these are worth
looking out for as the image bank builds up in future.
Landsat-8 Images
Finally, as an ‘optional extra’, you can also process theLandsat‑8 tiles offered by Land Viewer. These, however,
have a ground resolution of only 30 metres/pixel. The
process is similar, but Landsat tiles are in TIFF format andyou must load them into Sentinel2toJPEG by dragging, orusing the ‘All files (*.*)’ option.

March 2017

Appendix - Near Infrared Sentinel Tiles
A recent addition to David Taylor’s Sentinel2toJPEG
software is the option to substitute the near-infrared band
(842 nm)—the only other of the thirteen offering 10‑metre
resolution—for the red component of composite images.
Download the following files
B03.jp (blue)
B04.jp (green)
B08.jp (red)and proceed as before. If you have also downloaded theB04.jp file, be sure that it’s the B08.jp file that you drag/load into the program.
The resulting images show vegetation cover in shades ofred, which can be useful for analysing the terrain in animage. It is recommended that the gamma be lowered
into the range 80-100 for optimum rendition. Figure 10
compares the true-colour RGB432 image with the infrared
RGB843 one for largely cultivated terrain.
References
1 JPEG2000
https://en.wikipedia.org/wiki/JPEG_2000
2 Autopano Pro
http://www.kolor.com/autopano/Figure 10 - The French port of Calais and its hinterland, imaged by Sentinel 2A on June 23, 2016. The two images illustrate the true-colour RGB432
band combination (left) and the vegetation RGB843 version (right), where rectangular fields of crops show in shades of red.

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This Sentinel 3A segment acquired on January 21, 2017 by Peter Kinghorn depicts the Aleutian Islands south of Alaska
Image © EUMETSAT 2017

This Sentinel 3A segment acquired on January 22, 2017 by Peter Kinghorn shows the plain of the River Ganges
Image © EUMETSAT 2017www.geo-web.org.uk

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NASA Earth Observatory

One year ago, the central and easternparts of the tropical Pacific Ocean
were pulsing with heat, a result of oneof the most intense El Niño events onrecord. One year later, La Niña has been
relatively quiet, and she does not seemto be staying for long.
La Niña is the cool sister pattern to El
Niño. While El Niño knocks down theeasterly trade winds and sloshes warm
water from the western Pacific to theAmericas, La Niña pulls up cool waterfrom the depths of the eastern Pacific,
energises the easterlies, and pushes thewarm water back toward Asia. Regionsthat are often drenched with rain andsnow during El Niño often go dry during
La Niña events—and vice versa—asatmospheric circulation and jet streams
shift with the changing heat and moisturesupply from the vast Pacific Ocean.

Figure 1

The maps in figure 1 compare sea
surface height anomalies in the Pacific
Ocean as observed by NASA scientists
on November 4, 2016, near the peak of
the current La Niña, and on January 18,
2016, near the peak of last winter’s El
Niño.
The measurements were made by
altimeters on the Jason‑2 and Jason‑3
satellites, and show averaged sea
surface height anomalies. Shades of red
indicate areas where the ocean stoodhigher than the normal sea level: surface
height is a good proxy for temperature
because warmer water expands to fill
more volume. Shades of blue show
where sea level and temperatures werelower than average (water contraction).
Normal sea-level conditions appear inwhite.

Figure 2‘Last year’s Niño was huge in area,
duration, and magnitude,’ said Bill
Patzert, a climatologist at NASA’s Jet
Propulsion Laboratory. ‘My take is that,
because it lasted so long and covered
such a large area, it damped the returnof the strong trade winds needed for ahealthy Niña. Note the strong positive
heat content north of the equator—theentire tropical Paciﬁc between Central
America and Hawaii—that lingered into
the fall.’In a report issued in December
2016, the NOAA Climate Prediction
Center described the latest La Niña
as ‘weak’, and probably changing toneutral conditions in early 2017. La
Niña conditions—with surface watertemperatures at least 0.5° Celsius
The patterns following the great El Niño ofbelow normal in the central and eastern 2015–16 have been starkly different from
Pacific (in the ‘Niño 3.4’ region between what occurred after the last major event.
170° to 120° west longitude)—began
In 1997-98, very warm El Niño conditions
to surface in July and August 2016.
persisted for roughly 13 months, but wereDuring last year’s El Niño, surface water then followed by roughly 32 months of welltemperatures were as much as 2.5°C
below-normal (La Niña) water temperatures
above the 1981-2010 norm. During the in the eastern Pacific. In 2015–2016, water
current La Niña, temperatures have not temperatures and sea surface heights were
dropped more than 1°C below normal. above normal for 19 months, first weakly40

www.geo-web.org.uk

and then with great gusto in late 2015. But
this event has been followed by just fivemonths of weak La Niña conditions that are
already fading.
The maps in figure 2 compare conditions in
December 2016 with December 1998, oneof the strongest La Niña events on record.
The data come from Jason‑3 and from the
TOPEX‑Poseidon mission.
Mike Halpert, deputy director of the NOAA
Climate Prediction Center, noted that thecurrent pattern is somewhat similar to
1982–83, when another strong El Niño wasfollowed by a relatively modest La Niña.
‘Just when you think you have seen
everything and think you know what toexpect, something happens that you just
can’t explain,’ he noted. ‘There are manyrhythms and natural variabilities, andnature will always keep it interesting.’March 2017

The Group for Earth Observation

GEO Quarterly No 53

David Taylor
EUMETCastView is an open source program created by
Hugo Van Ruyskensvelde, which allows the user to view andmanipulate data disseminated by the EUMETCast service. Data
included are• AVHRR images from NOAA-19 and Metops-A and -B• VIIRS images from SUOMI-NPP• OLCI EFR and ERR images from Sentinel-3A, and• HRIT/LRIT images from the Meteosat, FengYun, GOES and
Himawari-8 geostationary satellites.

Note that this cannot be placed inside C:\Program Files\ as the
program needs to write files to its own directory. When a newversion comes out, I can then rename EUMETCastViewer to,for example, EUMETCastViewer.1.2.0 so that I have a local
copy of the personalised .INI files which control the program’s
configuration. I may copy these .INI files to the new version’s
directory to save having to repeat all the setup process a secondtime.

Installation

On opening the program you are taken to what I call the Setup
View (figure 2). This is divided into three areas:• On the left is a vertical column of icons which allow you toswitch between the five views: setup, geostationary, polar
map view, polar globe view, image view.
The orange-handled spanner at the bottom of the column
allows you to show or hide the toolbox.

The home page currently ﬂags version 1.1.6 as the latest build
but in fact version, EUMETCastView_Windows_64bit_v1_2_0.zip iscurrently available, fromhttps://github.com/hvanruys/EUMETCastView/releases/
There is no setup as such. Simply extract the Zip archive to alocation of your choice, taking care to keep the directory structure
intact. Note that this is a 64bit program, and there is no32-bit version yet available.
The directory structure
created on unzipping the
EUMETCastView archive isshown below.
After decompressing
the Zip archive, I copied
the directory tree of:
DeployEUMETCastViewer
into the following directory in
my working tools:
C:\Tools\ EUMETCastViewer

Setup Screen• Next to the right is the toolbox which allows control of theother functions according to the mode in use.
• Finally, there is a big setup panel. You need to customise
a number of elements herein, particularly the segment
directories on the right-hand side, to tell the program
where to look for images. You can see that I have D:/MSG/
Images/VIIRS/ and a number of others selected.
The program will understand the usual \yyyy\mm\dd\
structure below these directories.
From the TLE list, check the boxes for the satellites whichinterest you. I found that the default ‘number of segments’
was rather low for my taste, so I upped it to the maximum
which appears to be 200.

Figure 1 - The Directory Tree

Figure 2 - The EUMETCastView Setup Screen

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Figure 3 - The EUMETCastView Setup Screen after selecting a date.

Figure 4 - The Plate Carrée map view for polar orbiting satellite selection

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Navigating the program would be somuch easier if, as with so much software,
the author gave pop-up hints on various
buttons and icons.
Now click on the date of interest. Note
that, following selection of the date (in thiscase 2017-Jan-30), some 152 DNB (daynight-band) files were found (figure 3).
Geostationary Satellite Selection
I’ve never used this option as the MSG
Toolset Plus suite gives me everything I
need.
Polar Orbiter Selection - Map View
There are two ways to select which
passes, or segments of a pass, you wantto process. Both are graphical, one on a
Plate Carrée projection, and the other ona globe view. The former is illustrated infigure 4, but I find that the globe view suits
my needs better.

Figure 5 - The Polar map view: zooming in to the region of interest

Polar Orbiter Selection - Globe View
Now you can see why you might want tolimit the number of segments! Drag theglobe with the mouse to bring the regionof interest into view, and zoom with themouse wheel (figure 5). Place the mouse
cursor somewhere near the centre of oneof the tiles, and right-click to select the tile.
Suppose I wanted to look at the UK—I’ve
made a guess and selected three tiles
covering that region (figure 6).
And no! I don’t know what the blue
rectangle is for....
Image View
Now click the large Make Image button at
the bottom-right of the panel. With thethree tiles selected it took about four
seconds for my PC to complete making
the image. Now switch to the Image View,
the icon below the globe in the left panel.
You may need to scroll the image withthe (rather faint and nonstandard) scroll
bars to see anything, but scrolling to
the bottom-right of the image I did find arecognisable coast outline - the north endof the Adriatic sea (figure 7).

Figure 6 - The Polar map view: selecting tiles

By playing with the Centre Band andWindow Band adjustments you can see
more detail (figure 8), or just the brightest
spots (figure 7).
Projections
By scrolling a little further (after making
the image brighter) I found the south coastof the UK (figure 9).
Now switch to the Projections tab in the
Toolbox. Figure 10 shows one I happen
to have used before, showing parts ofsoutheast England and the Netherlands.
By pressing on the Create Map button (atlower left) the image you just createdFigure 7 - A Suomi NPP day-night image showing the cities of Venice andChioggia as prominent white spots on the northwest coast of the Adriatic Sea.

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Figure 8 - The same Suomi‑NPP day-night image

March 2017

Figure 9 - Scrolling through the image reveals the UK

Figure 10 - A projection including southeast England and The Netherlands

will be re-projected on to the mapping you have chosen. Neat,eh? You can even see lights from the oil rigs in the North Sea(figure 11).

where you will find a selection of images which illustrate theprogram’s capabilities, as well as some hints on its use.

Saving Images

This article is not intended as a comprehensive review of the
EUMETCast Viewer, but just a ‘first look’ to help the newcomer
begin exploring its features to view some more unusual data.

To save an image, use the Camera Icon in the top toolbar—it’s thesecond one along from the left, next to the Power (program exit)
button. Images are saved in the program’s directory unless you
choose otherwise. It is well worth visiting the EUMETCastViewer
home page at
http://hvanruys.github.io/

44

Concluding Remarks

It is to be hoped that readers more experienced in using
EUMETCastView will feel encouraged to prepare further articles
detailing with this software in greater depth.

www.geo-web.org.uk

Figure 11 - The Suomi-NPP satellite imaged this scene in its day-night band on January 30, 2017. Not only are the illuminations of major cities
prominent but you can even see evidence of shipping and North Sea oil activity.
Image © EUMETSAT 2017www.geo-web.org.uk

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March 2017

John Tellick
Following the long period of high pressure overwestern Europe and the southern half of the UK
throughout much of January, which blocked theadvance of Atlantic depressions, the first few daysof February saw a whole collection of Atlanticlows heading in our direction. A strong jet stream,
blowing over the north Atlantic at around 300 kph
at this time, helped to spawn these storms anddirect them eastwards towards Europe.
The first storm mid-week, centred west of Ireland,
was deflected by the fading high pressure to theeast and caused rain and gales in Ireland and thewestern part of the UK before tracking off to thenorthwest for a couple of days.
The following storm was far more intense andearly warnings were issued to southern partsof the UK and the English Channel for possibly
damaging winds, all dependent on the storms
eventual track: it could go a bit further north or
south.

Figure 1 - The north Atlantic Jet Stream on February 1
Image: earth.nullschool.net

The storm, thankfully, tracked quite a bit further
south, and the Atlantic coast of France, Portugal
and parts of Spain bore the brunt of the winds
which caused considerable structural damage:trees and electricity pylons came down, leavingsome 250,000 French residents without electricity
on February 3rd and 4th. Météo France reported
wind speeds of up to 148 kilometres per hour on
the coast and warned that in some places they
could reach 160 kph. The Mediterranean islandof Corsica registered a 155 kph gust across its
northern cape, while Santander in northern Spain
also felt the storm with winds up to 104 kph.
On February 1, the European Space Agency’s
Sentinel 3 satellite measured significant wave
heights of about 16 metres off the coast of France,
which is extraordinary, even for the typicallystormy winter season in the North Atlantic basin.
Individual waves were likely higher than that.

Figure 2 - The storm approaches France on February 3
Image © EUMETSAT 2017

As the storms in western France became stronger,
weather agency Météo France urged residents not
to travel and to remain indoors, further addingthat they should keep off roofs and be vigilant
about the risks of falling trees. Because of theviolence of the winds and the ensuing flood
risks, the western Departments of Charente,
Charente-Maritime, and Gironde were all placedon red alert. In addition, there were warningsof ‘very strong waves’ on the northern coasts ofBrittany and Normandy, where storm surges were
producing wave peaks of up to twelve metres,bringing the risk of ‘marine submersion’.
No sooner had this storm passed but anothertracked across France on February 5th narrowly
missing southern England – again.

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Figure 3 - The storm centred over France on February 5
Image © EUMETSAT 2017www.geo-web.org.uk

It’s mid-evening on November 20, 2016 and winter is already biting hard over Scotland. This infrared LRPT image
comes from the 20.02 UT pass of Russia’s Meteor N2 satellite, showing the entire country fully in the grip of a hard
frost. By daybreak the following morning, the temperature had dropped to minus 8°C or lower almost everywhere.

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Mike Stevens submitted this remarkable Sentinel 3A image that he acquired on January 3, this year.
Image © EUMETSAT 201748www.geo-web.org.uk

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European Space Agency

Lake Oroville and the Oroville Dam were imaged by the Copernicus Sentinel-2A satellite on December 21, 2016 (left) and January 30, 2017.
Copyright contains modified Copernicus Sentinel data (2016–17), processed by ESA

Almost 200 000 people were evacuated from their homes in earlyFebruary after channels draining the Oroville Dam in northern
California were damaged because of unusually heavy rain.
Images captured by the Copernicus Sentinel‑2A satellite on
December 21, 2016 and again on January 30, 2017 show theremarkable difference in the height of the dam water. Far more of
the shoreline is exposed in the earlier image, for example. There
are a couple of islands visible to the north of the dam in the firstimage which were almost entirely submerged following the rains.
The comparison also shows that the water was much lighterin colour in December and much darker in January owing tosediment washed into the dam. The ‘spillway’ appears dry in thefirst image but water can be seen clearly gushing down it in thelater image. This is the first time that water had ever run down
the spillway. In turn, damage to this spillway caused by excessive
water led to fears about safety and the area being evacuated.
With a height of 235 metres, Oroville is the highest dam andsecond largest reservoir in the USA. It provides an importantwater supply and is used to generate hydroelectricity. Until the
recent rains it had been a defining image of the state’s drought.

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GEO Quarterly No 53

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March 2017

John Tellick
For years, their existence has been debated: elusive electricaldischarges in the upper atmosphere that sport names such as
red sprites, blue jets, pixies and elves. Reported by pilots, they
are difficult to study as they occur above thunderstorms.
During his 2015 mission aboard the International Space Station,
ESA’s Danish astronaut, Andreas Mogensen, was asked to use
the most sensitive camera available
to take photographs as he ﬂew
above thunderstorms to look forthese elusive features. Denmark’s
National Space Institute has now
published the results [1], which
confirm many kilometre-wide blue
ﬂashes around 18 kilometres
altitude, including a pulsating
blue jet reaching 40 km. A video
recorded by Andreas as he ﬂew
over the Bay of Bengal at 28
800 kph on the Station shows theelectrical phenomena clearly - a firstof its kind [2]. ESA has produced
Andreas Mogensena short video in which Mogensen
Photo: ESA
describes his experiences [3].

A spectacular Blue Jet photographed from the ISS
Credit: ESA / Andreas Mortensen

Satellites had probed these events but their viewing angle is not
ideal for gathering data on the scale of the blue jets and smaller
blue discharges. In contrast, the ISS’s lower orbit is ideallyplaced to capture the sprites and jets.
Andreas aimed for cloud turrets—cloud pillars extending into
the upper atmosphere—and shot a 160 second video showing
245 blue ﬂashes from the top of a turret that drifted from the
Bay of Bengal’s thunderstorm. The image sequence below wascompiled from frames from Andreas’ video.

A cumulonimbus turret over Africa photographed by an astronaut on theInternational Space Station
Image: NASA

This sequence of photographs illustrates the progression of a Blue Jet lightning strike extending upwards from a storm cloud over the Bay of Bengal
Credit: ESA / Chanron et. al, 2017.

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atmosphere during thunderstorms—red sprites, blue jets andelves. Some of the most violent electric discharges are very
difficult to capture from the ground because of the atmosphere’s
blocking effect. From space, astronauts can judge for themselves
where to aim the camera and where to zoom in and follow
interesting regions for researchers.
The blue discharges and jets are examples of a little-understoodpart of our atmosphere. Electrical storms reach well into thestratosphere and have implications for how our atmosphere
protects us from radiation.
These experiments confirm that the ISS is a suitable base forobserving these phenomena. As a follow-up, the AtmosphereSpace Interactions Monitor [4], a climate observatory for theInternational Space Station being developed for ESA, will
be prepared for launch later this year for installation outside
Europe’s Columbus laboratory to monitor thunderstorms
continuously in order to gather more information about such‘transient luminous events’.
ESA astronaut Tim Peake took this image circling Earth 400 kilometres
up in the International Space Station.

Following his ﬂight, Andreas Mogensen concluded:

Image: ESA“It is not every day that you get to capture a new weather
phenomenon on ﬁlm, so I am very pleased with theresult—but even more so that researchers will be able toinvestigate these intriguing thunderstorms in more detailsoon.”

British astronaut Tim Peake also observed and photographedBlue Jets during his stay aboard the ISS in 2016, the image
above being one of his best examples. Tim commented:“Sometimes looking down on Earth at night can be kinda spooky.”
The image shows lightning strikes illuminating clouds overWestern Australia during a thunderstorm. The Space Station
travels at 28 800 kph, so takes only 90 minutes to complete
an orbit of Earth. Astronauts often spot thunderstorms and are
impressed by how much lightning they observe.
Although this picture was taken in Tim’s free time, the Station
is used for research into elusive phenomena in the upper

Acknowledgements
Most of the text in this article comes from the European Space
Agency website.
References
12
3
4

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071311/full

https://youtu.be/dY5F_gEexAY

https://www.youtube.com/watch?v=r50Un4LPTM4

www.asim.dk

NASA Earth Observatory
A plume of volcanic ash hangs overthe Gulf of Alaska in this natural-colour
image. The plume is not, however,the product of an active volcano: it isre-suspended ash dating back to the1912 eruption of Novarupta, according
to the Alaska Volcano Observatory. Highwinds previously stirred up ash in thearea in October 2015.
Novarupta is a young volcano that was
created as recently as 1912, and islocated on the Alaska Peninsula within
Katmai National Park and Preserve,
about 470 km southwest of Anchorage.
Formed during the largest volcanic
eruption of the 20th century, Novarupta
released thirty times the volume ofmagma as the 1980 eruption of Mount
St Helens.
The Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s
Terra satellite captured this image on
December 2, 2016.

NASA Earth Observatory images by Jeff Schmaltz,
using MODIS data from LANCE/EOSDIS Rapid Response.

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John Tellick
Mount Etna is Europe’s tallest and most active volcano,with an eruptive history reaching back more than
2,000 years. It seems to be in nearly constant activity,with intermittent short pauses. The eruptions can be
relatively quiet, with tremors accompanying gas andash plumes, but at times Etna can produce spectacular
explosive eruptions. Though generally mild in nature,these eruptions can produce glowing lava fountains thatrise high above the summit craters.
Following the reception on February 5, 2017 of a
NOAA 19 image of snow-topped Mount Etna, not that
unusual in winter, ESA later published a false-colour
Sentinel 2A image of part of Sicily captured earlier on
January 8 showing heavy snowfall.
I was surprised to find, during a quick search, that
Mount Etna regularly receives considerable wintersnowfall with the opportunity for winter sports activities
at two ski resorts: Linguaglossa (Etna North) andNicolosi (Etna South).

Mount Etna with the city of Catania in the foregroundPhoto: BenAveling / Wikimedia CommonsThe Sentinel image depicts a period of unusual coldand snowfall across parts of southern Europe. As aconsequence, the mountains of Sicily are visible inwhite across the northern part of the island. While
Italy’s northern regions experienced little snowfall
this winter, the central and southern areas haveseen abnormally cold conditions and snowfall inmountainous areas.
Mount Etna, an active volcano, is visible at upper
right of the Sentinel image. Positioned over the zone
where the African plate collides with and slips under
the Eurasian plate, Etna’s frequent eruptions are often
accompanied by large lava ﬂows, smoke and ash.
Sentinel-2 provides optical data for land and vegetation
monitoring. Its main instrument has 13 spectral bands,
and this false-colour image was processed including
the near-infrared channel—which explains why
vegetation appears as red.

NOAA 19 images Mount Etna on February 5, 2017
Image © EUMETSAT 2017

The varying shades of red and other colours acrossthe entire image indicate how sensitive the instrument
is to differences in chlorophyll content. This is used toprovide key information on plant health: brighter reds
indicate healthier vegetation.
Sentinel-2 is a two-satellite mission for Europe’s
Copernicus programme. The first satellite waslaunched in June 2015 and its Sentinel-2B twin is set
for launch from French Guiana on March 7 this year, at
01:49 GMT.
Live Mount Etna Webcams
www.skylinewebcams.com/en/webcam/
italia/sicilia/catania/vulcano-etna-sud.html
www.skylinewebcams.com/en/webcam/
italia/sicilia/catania/vulcano-etna-nord.html

52Part of Sicily with Mount Etna visible at upper right© Contains modified Copernicus Sentinel data (2017), processed by ESA

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NASA Earth Observatory

In Ethiopia’s Afar Depression, three tectonic plates are tearing
apart in spectacular fashion. As the plates separate, several
active volcanoes have emerged along the seams. One of themost active is Erta Ale, a shield volcano near the Ethiopian
border with Eritrea. It is known as the ‘smoking mountain’ and the‘gateway to hell’ in the Afar language.
Erta Ale has a long-lived lava lake that has gurgled and spatteredin its caldera for decades, but the most recent bout of activity
involves the southeast ﬂank of the gently sloping mountain.
According to reports posted by Volcano Discovery, new fissuresopened up on January 21, 2017, about 7 kilometres from thesummit caldera, spilling large quantities of lava. Meanwhile, atleast one of the lava lakes has experienced large changes in thelevel of its lava that have led to overﬂows and intense spattering.
This image was captured by the Operational Land Imager (OLI)
sensor on Landsat 8 on January 26, 2017, and is a composite
of natural colour (OLI bands 4-3-2) and shortwave infrared(OLI band 7). Shortwave infrared radiation (SWIR) is invisible
to the naked eye, but strong SWIR signals indicate increased
temperatures. Infrared hot spots representing two distinct lava
ﬂows are visible. Plumes of volcanic gases and steam can beseen drifting northward from the lava lakes.
NASA Earth Observatory image by Joshua Stevens, using Landsat data from the
US Geological Survey. Caption by Adam Voiland.

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Here’s another stunning image from Mike Stevens who is clearly enjoying his experiences with Sentinel 3A imagery. This
image, dating from February 9, showcases the Bahamas, Turks and Caicos Islands, Haiti, Cuba and Jamaica

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