Group for Earth Observation

No 57 - March 2018

The north of Scotland has suffered one of its most severe winters for years with huge accumulations of snow fallingon the mountain ranges. In this image from NASA’s Terra satellite, acquired on February 21, 2018, most of Scotland
is cloud-free, highlighting the snow cover on both the Northwest Highlands and the Cairngorms/

Francis BellWelcome to the new format and presentation of our
GEO Quarterly and my report. We have said before
the production and posting of our printed Quarterly
is very expensive, compounded by diminishing copy
contributions, thus making it difficult for the editor
to produce a worthwhile Quarterly without having
to research material himself. Hence the decision
has been made to use a more flexible approach via
the website, which incurs few costs.
The printing and posting of our printed Quarterlycame to about £3,000 for each edition. Now relieved
from this financial commitment, the decision wasmade to abolish the membership subscription:that is, after completing the joining protocol new
membership is free and existing members may
continue with their membership without annual
renewals. New members are most welcome. The
hope is that we can all continue to exchange
our experiences of satellite reception to mutual
benefit. The details and time scales for membershiprenewals still have to be established by our GEO
Management Team.
In the background of free membership there is an
expectation that our membership numbers will
increase, and that communication will increasingly
be via the Internet/Email rather than just personal
contact. It has been pointed out to me more thanonce—quite independently—that if we wish to
regularly communicate with people on our personal
list these individuals must specifically opt into thesystem of GEO emails rather than receiving themas unsolicited communications. Apparently this will
become law in mid 2018.
GEO’s management is currently looking into these
protocols and will advise members when the newrules become clearer. My personal expectation isthat we will be asking our members to specificallyconfirm that they wish to receive appropriate
communications from us: however, the protocols
for this have still to be established for our group.
MSG3 or MSG4?
Recently, during last February, I experienced a few
days of frustration with my EUMETCast receiving
systems. Quite suddenly and unexpectedly thesystem stopped receiving regular Earth images,
even though all the meter readings indicated thateverything was working. Rather eccentrically, theonly images I did occasionally receive were relayed
from the NOAA GOES-W satellite, but there was2

nothing showing Europe or Africa. I checkedand double checked both dishes, receives andcables. Except for an intermittent fault in a coax
connector, which I corrected, everything was inorder. But still no images!
Agh! My ‘Road to Damascus’! Somehow, I
remembered a similar experience about three years
ago when EUMETCast switched its regular service
from one satellite to another. Perhaps this had
happened again without me knowing. To checkthis using my SatSignal software, I clicked on theadvanced system setup menu and changed thesatellite from MSG3 to MSG4. Magic: within aminute I was once more receiving the images I was
hoping for and everything seemed to be working
perfectly.
The lesson here for me, and I guess others, is to be
more attentive to notices from EUMETSAT relating
to current satellite operations, hence avoiding thismistake for a third time. If this transmission switch
happens again, which I expect it will, I will try to
issue some form of notice, so our GEO members
will then have a double chance of recognising achange in EUMETCast transmissions.
Symposium 2018
I have only received a very small number of
responses to my enquiries relating to thosemembers who would be interested in having
a group meeting in 2018. As a result of thisapparent lack of interest, nothing is planned forthis year, but I most sincerely hope that we canvisit EUMETSAT HQ in Darmstadt next year. In
the past these visits have been well supported by
GEO members and we have always experienced
great hospitality, informative presentations andcentre tours: however, such a repeat visit next year
does depend on the cooperation of a very busy
EUMETSAT.
Rallies
GEO will definitely have a stand at the South
London Radio and Computer Rally, to be held at
Kempton Park on April 15, 2018. This is usually abusy rally which I judge to be worthwhile for boththose running stands and the many visitors. Visit
their website for more information.
www.radiofairs.co.uk
Other meetings
It is possible that we will also attend the Newbury
Radio Rally on Sunday June 24, 2018, which is a

www.geo-web.org.uk

popular outdoor event held on the Newbury race
course. Visit their website for more information.

cover a frequency range of about 500 kHz to 2 GHzwith various modulations and bandwidths. Theiruse is very flexible and suitable for satellite APT
reception and perhaps also HRPT, but I have noexperience here. If you want to buy a dongle sendan email to:www.nadars.org.uk
Another possible idea is to ask for a stand at the
RSGB’s three day annual meeting in the autumn
but this idea still has to be researched. It could
be attractive, sharing a busy event with many
amateur radio people attending. I understandthat AMSAT-UK had a presence at the equivalentmeeting last year.
Sales
The GEO Shop no longer stocks Software DefinedRadio (SDR ) dongles. As an alternative I have a
few available together with a connecting cable for a
price of £20, which includes postage. These dongles

francis@francisbell.com
Footnote
If any reader is currently experimenting with
HRPT reception using an SDR dongle, we would
be most interested to hear from you. It would
be good to learn of even rudimentary success:sufficient to hint that such reception could bepossible. Any contributions in this field will bewelcome by myself, the Editor, and members of the
GEO Subscribers YAHOO Group.

GEO MANAGEMENT TEAM
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 Editor
Les Hamilton,
8 Deeside Place,
Aberdeen AB15 7PW, Scotland UK.
email: geoeditor@geo-web.org.uk
Technical Consultant (Hardware)David Simmons
email: tech@geo-web.org.uk
Webmaster and Website Matters
Alan Banks,e-mail: webmaster@geo-web.org.uk

GEO Shop Manager

Les Hamilton

W

elcome to the ﬁrst issue of the new, rebranded
GEO Quarterly. For reasons explained by Francis
Bell on page 2, it is no longer possibly, ﬁnancially, toproduce printed magazines. It is also not feasible forme to continue single-handedly generating some 30
or so pages of relevant content every quarter: so ourelectronic publication will now be called GEO Newsletter.

B

ut we do still wish to keep in touch with our readers,even if may sometimes only be to the extent of an
8 or 10 page document from time to time. It’s frequency
will depend on material submitted, but we would hope tobe able to continue publishing the GEO Newsletter every
quarter, as previously.

To place the recent winter in perspective, I havereprinted a 2002 article from the late Cedric Roberts,
which detailed the far worse scenario experienced forthree long months in early 1947.

As ever, we value contributions of images and articles
from readers, however small these may be, and theseshould continue to be sent to me atgeoeditor@geo-web.org.uk(or to any other Management Team Member).

Nigel Evans (Assistant: David Simmons),

Contents

email: shop@geo-web.org.uk

Management Committee Members
Rob Denton
David Anderson
Clive Finnis
Carol FinnisPeter GreenGEO Report
Quarterly Question
Plumes over Kamchatka
Meteor M2-1 Failure
Current Satellite Data
GEO Visits Harwell Rally
Atlantic Ship Tracks
The Winter of 1947

Francis Bell
Francis Bell
NASA Earth Observatory
Les Hamilton
Francis BellLes Hamilton
Cedric Roberts

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Francis Bell
Quarterly Question 56
My thanks to those members who responded to
Quarterly Question 56, which related to a photographtaken by UK astronaut Tim Peake while he was on
the International Space Station (ISS) about two years
ago. I understand that the photograph was taken witha hand-held camera rather than an image created bya dedicated onboard instrument, hence the slightly
oblique view of the Earth shown in the photograph. The
photograph showed the city of Istanbul in the centre of
the image with the Sea of Marmara to the south and the

Bosporus seaway connection to the Black Sea towards
the top with at least two bridges visible spanning thiswaterway. Hence the answer to the question, asking forthe name of the city, was ‘Istanbul’.
Additionally, my thanks to the member who corrected me
about the famous mosque in Istanbul which I referred
to as the ‘Golden Mosque’. It is in fact called the ‘Blue
Mosque’. I must have named this mosque in anticipationof my next foreign expedition to India where a visit to theGolden Temple at Amritsar is anticipated.

Figure 1 - This is an Earth image recorded by Sentinel-2 highlighting an active volcano with red lava streams running from its
summit. The Quarterly Question is to name this volcano. See the adjacent text for more information.
Image: modified Copernicus Sentinel data (2017), processed by ESA

Quarterly Question 57
This question come in two parts, and was prompted by
Earth images I regularly receive from ESA. The datewhen Figure 1 was recorded is overlaid on it, together
with an indication of scale. The image was recordedby the Copernicus Sentinel-2 satellite on January 30,
2018 using the visible light, and shows a volcanic

4eruption with flowing red lava. Because of the anticipatedconsequences of this eruption ESA quickly issued an
appropriate alert warning of the event on February 1.
Question No 1 is quite straightforward. Name theerupting volcano shown on the ESA image (Figure 1) andthis additional question: “With which ‘Ring’ is this volcano
associated?”www.geo-web.org.uk

Without additional information it
would be very difficult to locate andname this volcano because thescale is quite small and there is little
coastal outline to act as a guide,
hence some addition information
may be necessary.
The volcano is located on one of
the main islands of the Philippines,
the same island that also hosts thecountry’s capital city Manila. The
caption associated with Figure 2 will
be of great help because it names
a city from which a conventional
photograph of the same volcano wastaken, although at that time it was
not erupting.
During my personal travels I havevisited a number of countries
with volcanoes, and I’m always
impressed that, throughout muchof the world, not far below my feetat high pressure, lies molten rocktrying to force its way to the surface.
The dynamics and convection ofthis material changes our planet’s
magnetic field on a daily basis andin the longer term influences climatechange in which ice ages come andgo.

Figure 2 - This is a conventional photograph of the subject volcano taken about 8 km
from the volcano’s peak. The photographer was located on the edge of Legazpi City,in the Philippines (visible at bottom right of the ESA image).
Copyright Wikipedia.

Figure 3 - This old volcanic peak, one of many in the area, was photographed by Francis Bell in 2011 while travelling
between Indonesian islands separating the Flores Sea and the Savu Sea. It is believed to be one of the volcanoes ofEast Nusa, Tenggar in the ‘East Flores Regency’ of Indonesia. The many volcanic peaks in this area are connected to
the Quarterly Question because they form part of the ‘Ring’ associated with the volcano in the Philippines.
Photograph copyright free.

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Figure 4 - This is a satellite image showing Manila the capital of the Philippines with two volcanoes visible to the upper left. The
scale of the image is approximately 100 km across and vertical.
Image: Modified Copernicus Sentinel data (2016), processed by ESA

My visits to active volcanoes include Vesuvius andEtna in Italy, Tiede in Tenerife and Fuji in Japan.
However, I think I have been most impressed with thesight of volcanoes when travelling between some of
the islands of Indonesia. In 2011 I was aboard a ship
which cruised between some of these islands, andon some occasions there was an impressive 360°
view with many conical shaped volcanoes lining thehorizon. One of my photographs is shown in Figure 3.
Question No 2 was prompted by an image that
I found during my researches relating to the first
Quarterly Question. In my text to the first question
I correctly stated that the erupting volcano is on
the main island of the Philippines, which hosts thecountry’s capital of Manila.
This second image (figure 4) is a Sentinel-1A multispectral wavelength radar image, and clearly shows
the Philippine’s capital Manila slightly above centre.
Manila is the most densely populated city in theworld and lies on the eastern shore of Manila Bay in
the South China Sea. To the east of the city lies thelargest lake in the Philippines, Laguna de Baý.

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But interestingly, to the upper left of the image can beseen two distinctive conical shaped volcanoes.
The second Question is therefore to name these two
volcanoes.

A Reminder of the Questions
Question No 1
“What is the name of the active volcano shown in
the ESA Sentinel-2 image (figure 1) and what is its
relationship with a ‘ring’?
Question No 2
“What are the names of the two volcanoes in figure 4”.
Answers by email to Francis Bell please, atfrancis@geo-web.org.uk
by June 1, 2018.

www.geo-web.org.uk

Plumes Over the Kamchatka Peninsula
A NASA Earth Observatory Report

Sitting along the northwest rim of the
Pacific Ring of Fire, Kamchatka is oneof the most volcanically active parcelsof land in the world. At least 300
volcanoes dot the peninsula, and at
least 29 of them are active.
Two of those volcanoes were busily
puffing away in early January 2018.
The Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s
Terra satellite caught a glimpse ofplumes rising from Shiveluch and
Klyuchevskaya on January 9. The
plume from Shiveluch stretched forat least 100 kilometres. Note the longshadows, which are caused by highpeaks and thick clouds and the low,
oblique angle of the Sun in the wintersky.

Plumes rising from Shiveluch and Klyuchevskaya on January 9, 2011.

On January 10, the Operational Land
Imager (OLI) on Landsat 8 got clear,close-up views of the area around
Klyuchevskaya.
Shiveluch is one of the largest
and most active volcanoes on the
Kamchatka Peninsula, with at least
60 eruptions in the past 10,000
years. The current eruption has beenongoing since 1999. On January
10, 2018, the Kamchatka Volcanic
Eruption Response Team reported
that volcanic explosions had lofted
ash 10 to 11 kilometres into theatmosphere. The aviation threat level
was briefly raised to code red, but
was lowered to orange by the end of
the day. Volcanic emissions can posea hazard to aeroplane engines, which
can stall or fail when choked withsmoke and ash.
By comparison, Klyuchevskaya wasrelatively docile on January 10,
emitting a small plume of gas, steam,and ash. The volcano is the tallest
and most active on the peninsula,and the latest eruption has beenongoing since August 2015. Morethan 100 eruptions have occurred
at Klyuchevskaya in the past 3,000
years, with 12 eruptions since 2000.

On January 10, the Operational Land Imager (OLI) on Landsat 8 acquired thisclear, close-up view of the area around Klyuchevskaya.

NASA Earth Observatory images by Joshua Stevens and Jeff Schmaltz, using Landsat data from the U.S.
Geological Survey and MODIS data from LANCE/EOSDIS Rapid Response. Story by Michael Carlowicz.

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Russia’s Meteor M2-1 Launch Failure
Les Hamilton
On November 28, 2017, a Russian governmentoperated Soyuz-2 booster launched the 45 million dollar
Meteor-M No. 2-1 meteorological satellite from thenation’s new far-east Vostochny spaceport in the Amur
Oblast. All the initial stages of the rocket flight progressedsmoothly until, 9 minutes 23 seconds into the launch,
the Fregat upper stage initiated sequence to insert the
spacecraft into orbit. Alas, that proved to be the last thatwas heard from the mission.

Meteor M2-1 undergoing leakproof testing prior to mating with
the Fregat launcher
Image: Roscosmos
Meteor M2-1 satellite
Image: Roscosmos

Following extensive investigations into the loss of Meteor
and the mission’s associated payload of 18 smaller
research and commercial satellites for the US, Japan,
Canada, Germany and other nations, Russian authorities
conceded that the high-profile failure occurred because
scientists had programmed the Fregat with incorrect
coordinates for Vostochny.
Ever since the 1950’s, the Russians had been launching
their satellites from the Baikonur Cosmodrome in thesouth of Kazakhstan. Following the collapse of theSoviet Union, Russia has been leasing the facility from
Kazakhstan. Now preferring to launch satellites fromhome territory, Russia has been constructing its own,
brand new five billion dollar cosmodrome at Vostochny inthe southeast of the country since 2011.
Initially, a spokesman for Russian space agency
Roscosmos stated that: “the first scheduled
communication session with the Fregat has failed toestablish contact with the satellite due to its absencefrom the designated orbit”.
After some days it was established that the failure was
not due to any malfunction of the booster itself but rather
to human error. Apparently, the software aboard theFregat had been programmed, not with the coordinatesof Vostochny, but with those of Baikonur. Consequently,
the on-board computers, sensing incorrectly that the
Fregat was in the ‘wrong’ inclination to launch its
payload, applied what it considered to be the appropriate‘correction’. The attitude of the payload was thus
adjusted, and ended up being deposited somewhere in
the North Atlantic Ocean.

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The Soyuz launcher bearing Meteor-M2-1 on the launchpad
Image: Roscosmos

The launch of the successor to Meteor M2, the next
satellite in the series, will now be Meteor M2-2, whichis scheduled for a launch late this year. Let’s keep ourfingers crossed that lessons have been learned, and thatthe next launch will be successful.

www.geo-web.org.uk

GOES-16: Moon over Planet Earth
Image Credit: NOAA, NASA

Launched on November 19, 2017 from Cape Canaveral Air Force Station, the satellite now known as GOES-16
observes planet Earth from a geostationary orbit 22,300 miles above the equator. Its Advanced Baseline Imager
captured this contrasting view of Earth and a gibbous Moon on January 15. The stark and airless Moon is not reallythe focus of GOES-16, though. Capable of providing a high resolution full disk image of Earth every 15 minutes, in
16 spectral channels, the new generation satellite's instrumentation is geared to provide sharper, more detailed viewsof Earth's dynamic weather systems and enable more accurate weather forecasting. Like previous GOES weather
satellites, GOES-16 will use the moon over our fair planet as a calibration target.

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www.geo-web.org.uk

Francis BellGEO attended its first radio and electronics rally of the year at Didcot, Oxfordshire on February 11. If
you are not familiar with the location of Didcot, it is situated about three miles from the village of Harwell
which is noted for the world of high technology and nuclear physics not to mention a new office of theEuropean Space Agency (ESA). Based in this village is the amateur radio group Harwell Amateur Radio
Society (HARS) and it was this organisation which ran the rally in Didcot Leisure Centre.
GEO have attended this rally inprevious years, but I judge thisyear’s event to have been thebusiest ever with 140 display
stands covering amateur radio,
computing and other hightechnology interests. Our GEO
stand had on display recorded
satellite images, plus recent
animations from geostationary
satellites together with a selectionof high resolution images relayedby ESA as well as literatureand personal advice relating toweather satellite reception at
home.
There was particular interest
during the day relating to thelive reception of NOAA andRussian polar orbiting satellites
on 137 MHz FM using a Software
Defined Radio (SDR) dongle:
in fact so much interest thatthe few SDR dongles we had
available were soon sold. After
that, enthusiasts were directed
to our GEO shop to buy theirdongle.
Between the opening time of
10.00 a.m. and 2.00 p.m. wePart of the main hall at the HARS showing some of
the 140 stands plus some of the visitors.

were very busy with visitors to our stand. Some people were very
knowledgeable about their own specialist areas: for example, a test
pilot for new aircraft or computer systems—but with others lessknowledgeable but enjoying the potential experience of live personal
reception of satellite images—which is what many GEO members do
best! During the day we enrolled six new members to our GEO group.
Future planned rallies include a definite booking for a stand at
the South London Radio and Computer Rally at Kempton Park on
April 15, 2018, together with other possible events during the year
but which still have to be confirmed. If any reader belongs to a radio
group or is involved with planning a rally/show, depending on details
perhaps GEO could contribute in some way to such an event.
My personal thanks go to David Simmons for attending this rally withme. David’s knowledge and experience with SDR was particularly
valued by many of the visitors to our stand.

A view of our GEO stand at the HARS rally.

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Atlantic Ship Tracks
Les Hamilton
The European Space Agency (ESA) recently releaseda fascinating image showing ship tracks over the
Atlantic Ocean to the west of the United Kingdom.
The subject of Ship Tracks was covered in an article
in the June 2005 issue of GEO Quarterly, which it
seems timely to reproduce below.
The Formation of CloudTo understand how ship trails arise, it is necessary
first to detail how ‘normal’ cloud forms in Earth’s
atmosphere. Ship trails are, after all, just one
particular form of cloud, albeit man-induced.
Earth’s atmosphere contains water vapour but
this does not automatically condense into liquid
droplets to form clouds, even when the temperature
is well below freezing. Cloud formation depends
on the presence of aerosols—suspensions of tiny,
microscopic solid and liquid particles dispersed
throughout the atmosphere.
Cloud-forming aerosols originate, in the main, fromnatural sources like sea salt, volcanic ash, desert
dust and biomass burning but also, increasingly,
through the burning of fossil fuels by man.
Aerosol particles often contain substances that
dissolve easily in water (such as sea salt, sulphur
dioxide etc.) and it is these that provide the cloud
condensation nuclei (CCN) around which watermolecules condense. If the air were devoid of aerosol
particles, cloud, mist and fog would never form at
all and the sky would be forever clear and cloudless!

Figure 1 - Ship trails west of Ireland
Copyright contains modified Copernicus Sentinel data (2018),
processed by ESA, CC BY-SA 3.0 IGO

When do Ship Trails Form?
Ship trails generally form in the still, moist air
commonly associated with anticyclonic conditions,when the sea is overlain with a stable layer of air at
a similar temperature to that of the water itself. This
layer may on occasions already contain thin cloudor mist but it is in effect supersaturated and lacks
sufficient CCNs to generate full scale cloud.
When ships pass through this region, fine aerosol
particles from their exhausts float up through the
moist layer of air where they become additional
CCNs (figure 2). This means that water vapour inthe air now contains many more nuclei upon whichto condense and these produce new cloud droplets
where few may have existed before. The outcome isthat the cloud becomes more reflective to sunlight.

Figure 2 - Formation of Cloud Condensation Nuclei (CCN)
A layer of moist air, relatively depleted in condensation nuclei,
is trapped beneath a high pressure inversion. The ship’s
exhaust fumes can rise to the upper reaches of the trappedairmass but no farther, greatly increasing the concentration ofcondensation nuclei present. The increased numbers of tiny
water droplets produced in the air-mass makes it more reflective,
giving rise to the phenomenon of ‘ship trails’ in satellite images.

1212

As a ship crosses the ocean its exhaust issues acontinual stream of CCNs in its wake. Consequently,
its path shows up as a trail of shallow stratus
clouds—a ‘ship trail’. This cloud streamer often
stretches for hundreds of kilometres and can extend
tens of kilometres in width.
Generally speaking, the faster a ship travels, thenarrower, longer, and less diffuse its ship trail willbe. Slower ships leave shorter, wider, and more

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diffuse trails. It is worth noting that ship trails often
reflect the direction and speed of local winds as much as
the direction and speed of the ship itself.
Ship trails normally persist for many hours andsometimes remain visible for days on end provided
that the air mass surrounding them remains relatively
undisturbed.
Ship trails show up well in satellite images, even thosefrom low-resolution APT transmissions. The trails show
up most strongly in reflected radiation (NOAA channels
1, 2 and 3) where they appear as bright lines that canbe distinguished clearly from any surrounding clouds.
The same trails are usually all but invisible in theradiated infrared from NOAA channels 4 and 5 because
the temperature of the sea and surrounding air are very
similar.
What Conditions Favour Ship trails?
Persistent ship trails often form beneath a low-level
temperature inversion where humidity is high and lowlevel stratus or stratocumulus cloud may already exist.
Such conditions are most likely to occur during conditionsof high pressure, when the lower atmosphere canbecome especially calm due to a layer of warmer air lying
approximately 500 meters above the sea surface. Thiseffectively places a ‘cap’ over the cooler moist air below,
trapping pollutants and water vapour alike. In general,
ships vent their exhausts into still, relatively clean marine
air that suffers minimal convective turbulence and which
is near-saturated and generally depleted in CCNs. Under
these conditions exhaust fumes are able to rise only as far
as the top of the cool air-mass where particulates greatly
increase the number of CCNs present (figure 2). The result
is the formation of many tiny water droplets, too small
to produce precipitation, but which form relatively lowelevation clouds that resemble larger versions of aeroplane
contrails. Unlike contrails, ship trails last for many hours.

Temperature Inversions
Under normal conditions, airtemperature decreases with altitude.
That’s why high mountains retain snow
even during summer. A temperature
inversion is a situation where thistemperature decrease is interrupted by
the presence of a layer of warmer air at
higher altitude.
An inversion is an extremely stablelayer of the atmosphere which acts
rather like a lid. Rising currents of
air within the lower cool air mass lose
their buoyancy when they reach thewarmer, less dense inversion layer:
they cannot rise any higher and areforced to spread laterally. Any pollutant
particles released into the lower layer
become trapped there because normal
convective mixing of the atmosphere isprevented.
Phenomena associated with temperature
inversions are valley fog (where
surrounding mountain peaks may bebathed in sunshine) and red sunsets(caused by the build-up of pollution
particles).

Aircraft Contrails
Enthusiasts spotting these cloud trails on their satellite
images for the first time often mistake them for aeroplane
contrails.

What causes an Inversion?
Temperature inversions are produced ina variety of ways. A familiar but usuallyshort-lived example occurs in secluded
mountain valleys where overnight
radiative cooling of the ground produces
low-level air that is colder than the air
above. If the cooling is sufficient, valley
fog may form although the mountainpeaks, surrounded in the warmer
inversion layer, remain clear. This
inversion ends when the morning sun
warms the lower levels once more.

Contrails (condensation trails) produced by jet aircraft
normally form at altitudes of eight kilometres and more,
where the temperature is around -40°C. Under these
conditions, water vapour in the exhaust can change
directly into ice crystals (without forming liquid water atall), a process that does not require nuclei such as dust
particles.

The type of inversion that results inship tracks is of longer duration, and isfound within a region of high pressure.
High pressure is caused by descending
air and as the air descends it becomescompressed and experiences adiabatic
warming.

Aeroplane contrails can be observed in satellite images,
but show up most strongly in NOAA infrared channels
4 and 5—the very ones where ship trails are least likely
to be visible. Contrails are much colder than the terrain
beneath them and this temperature differential shows
up sharply in these radiant infrared channels. Of course,
contrails (and their shadows) also show up by reflectedradiation, but are so narrow (a few hundred metres only)that they rarely appear in APT images. They can, however,be readily identified in many HRPT images.

This increases its buoyancy, eventuallyarresting its descent and isolating acooler, denser layer of air below it. Thisis known as a ‘subsidence inversion’. As
high pressure systems often combine
temperature inversion conditions withlow wind speeds, they can persist for along time, and provide ideal conditions
for the formation of ship trails.

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Perfect LRPT from Meteor M2
On January 30 this year, Enrico Gobbetti was pleasantly
surprised to discover that Meteor M2 had transmitted
two LRPT images without the customary breaks intransmission every six minutes or so. The image below isfrom the 07:44 UT pass that morning.

The Winter of 1947 inHalesowen, West Midlands
Cedric Roberts F.R.Met.S. M.B.E.

Most readers who experienced the severe weatherof late February and early March, brought by the‘Beast from the East’, can be forgiven for thinking
this is the worst ever winter to hit the British Isles.
Not so! A mere flea-bite compared with the severityof the weather in early 1947, as recounted for the
RIG Journal in 2002 by the late Cedric Roberts.
His article, describing three months of continuously
horrendous weather, is reproduced below.
This article relates to the three months from January
through March 1947, a period of 90 days, which
represented one of the most severe spells of weather
encountered in England for very many years, possibly
since the 17th century! Not only was there searing cold,
but also exceptionally heavy falls of snow totalling morethan two metres, awesome indeed for the U.K.
January 1947
January 1947 began fairly mild and wet, the first fivedays experiencing 17 mm of rain, but cooler air from thecontinent brought a heavy fall of snow early on the 6th,
and 9 cm lay on the ground by dawn on the 7th. Duringthat day the snow turned to sleet then rain, and by themorning of the 9th most of the lying snow had become
very patchy. The weather then turned much milder undermainly westerly winds, with rain on most days until the
17th when it became fine and sunny.
But cooler conditions returned on the 18th, although it
was not until the 20th that night frosts again set in. By
the 22nd much colder northeasterly winds were bringing
frequent snow showers, leading to a full snow cover of
2.5 cm on the 23rd. Further heavy snow showers on the
25th and 26th brought the level snow cover to 13.5 cm.
Heavy snowfall continued during the following two days
as winds gusting to 28 knots caused widespread drifting

Alas, this situation did not last long and members inNorth America reported that the image breaks were
present as usual in their images later that day.
Enrico queried what happened with the Russianauthorities and was informed that the image breaks
result when an internal buffer aboard Meteor overflows.
This is most likely when the Earth below the satellite isfree of continuous clouds and snow cover, making theimage data more diverse and saturated. Apparently, onJanuary 30, because the scene was largely cloudy anddid not exhibit a great contrast range, the captured image
could be sufficiently compressed to prevent the internalbuffer from overflowing.

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Figure 1 - Walking to work along paths between the snowdrifts.

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up to depths of 2 metres in many rural areas while
persistent frost kept daytime maxima at or below 0°C for
the remainder of the month.
The gusting southeasterly winds piled up ever deeper
drifts, and many minor roads became almost impassable.
Overnight temperatures tumbled to -10°C in the air and-13.3°C on the snow, and by the end of January, levelsnow lay 14 cm deep with drifts of up to 2.5 metresin isolated and open areas. Table 1 summarises theprincipal features of the month’s weather. Thus ended
the start of what was to be a memorable and extremely
trying spell of severe winter weather.

Measuring Snow-Depth
Due to the very strong and gusting winds that blew
for practically the whole month, it became necessary
to make very careful estimates of snow-depth, due tothe widespread and deep drifting which had occurred.
Several measurements were taken across the plot,
melt water was measured and converted, while a board
was placed on a clear patch to estimate fresh falls. In
addition, estimates were made on the farmland adjacentto the site to give a further idea of falls in ‘open’ areas.
All depths of snow relate to the plot or its immediate
environs. Conditions in open country could, and did, varyconsiderably and this is commented upon in the text.
February 1947
February was ushered in with brisk southeasterly winds
and sub-zero temperatures, though no fresh snow fellon the first. However, further heavy snowfall began ataround 4 a.m. on the 2nd and continuing fresh falls ofsnow and snow grains during the subsequent five days
brought the ‘level’ snow to a depth of 19 cm with drifts
over 4 metres in places. Winds remained in an easterly
quarter throughout and gusted to 40 knots, causing
severe wind-chill and blowing snow back into drifts assoon as attempts were made at clearance. By now
most local roads were blocked and their clearance was
becoming futile.

Table 1 - Summary of the salient statistics for the period
January to March 1947.

Figure 2 - A bus almost buried by drifting snow.

During that first week temperatures rose no higher than
1.1°C and fell at night to -4.4°C in the air and -6.7°C
over the snowfield, with winds regularly gusting aroundthe 30 knot mark and peaking at 40 knots. With thecontinued falls of snow, permanent frost and continuously
overcast skies, Britain was akin to the Antarctic. Fromearly on the 4th, there ensued a period of sub-zerotemperatures lasting the best part of 100 hours andit was not until the 9th that daytime maxima reached
1°C; and this rise lasted barely 48 hours. To add to thedepression felt by many struggling in to work or school(neither factories, schools nor shops closed), the skies
remained totally overcast by day and night until the 15th,
apart from a one hour break on the 6th when we had our
first glimpse of the sun for the month.
From February 11, persistent frost occurred, totallingin excess of 320 hours of sub-zero conditions with thedaytime temperature reaching no higher than -3.9°C on
the 17th. In addition, three days, the 3rd, 7th and 10th saw
freezing fog at 9 a.m., with thick fog at other times ona further six occasions (smokeless zones had not yet
arrived). Throughout this spell winds had been gusting
regularly to levels between 20 and 30 knots, bringing
severe windchill, widespread drifting and reduced
visibility due to blowing snow. By the 23rd level snow hadreached 23 cm though drifting, which was widespreadand severe, resulted in all roads (and railways) which
passed through cuttings being totally filled and blocked.
In several places drifts were deep enough to coverhedges and reach the window-sills on the upper floors ofhouses. The only way from the front door to the ‘road’ inmany cases was to dig a tunnel beneath the snow, akinto that from an igloo. By this date we had experienced
snow or sleet on 15 days and sunshine on just two.

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heated, with the bedrooms like iceboxes. I remember
ink freezing on a table under my bedroom window, andgetting into bed was like slipping between a couple ofsheets of ice.
And so, to draw the threads for February together,snow lay on 28 days to a maximum ‘level’ depth in
the enclosure of 27 cm and locally drifting to almost
4 metres. Air frost occurred every night bar one (whenit struggled up to zero). There was precipitation on 21
days, while 22 days were sunless, during a month when
the total sunshine totalled just a shade over 15 hours.
Wind-chill regularly reached -13°C and sometimes -15°C.
The nation was ‘shell-shocked’, but March was to bringeven worse privations.
March 1947
Although February 1947 produced some dramatic andextreme conditions, March was to throw even more
severe weather at us, including blizzard conditions,glazed ice, a gale, severe wind-chill and widespreadflooding.
Figure 3 - Tunnelling through the snow

February 24 was the first really sunny day of the monthwith 7.1 hours, but the clear skies sent the temperatureplummeting, resulting in an overnight air frost of -8.9°C,
while the snow surface temperatures plunged to -20.0°C.
Despite this respite, snow or sleet continued to fall,and only four days during the second half of the monthescaped solid precipitation. At no time during the month
did night time minima rise above zero, and the mean
daily temperatures were positive on only three days
overall.
By the end of February the countryside was in chaos,
as were many towns and cities. Fuel was in very
short supply since the railways were strike-ridden
and impassable, as were almost all roads (we did nothave any motorways then). In truth, everywhere waspractically at a standstill. People had to walk to work or
school, an easier task in the immediate post-war years
as almost everyone lived very near to their place of work;the ‘commuter-age’ was fortunately still decades in the
future.

Figure 4 - Heavy drifting on the A456

Rationing meant that people were ‘adequately’ but not
well fed, and the biting cold without central heating or
sufficient fuel meant only one room in the house being

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Figure 5 - Snowdrifts blocking the A456

The month opened in relative calm, March 1 showing
little more than scattered snow showers and almost
8 hours of bright sunshine. It did, however remain bitterly
cold, with a day maximum of 2.2°C and a night minimumof -6.1°C as winds gusting to 30 knots produced severe
wind-chill somewhat ameliorating the effects of thebright sunshine. Following two further dry days withquite widespread fog, a brisk northeasterly wind on
March 4 heralded the arrival of blizzard conditions thatbrought level snow to a depth of 27 cm with drifts as
deep as 5 metres in places. Roads and railways again
succumbed as snow piled in as fast as it was cleared.
Continuing heavy snow falls the following day increasedthe ‘level’ snow depth to 42 cm, a total that continued toincrease during moderate to heavy falls from the 6th to
the 9th. Most of the country was again at a standstill andwartime ‘bulldozers’ were brought out in attempts to open
roads to isolated towns and villages. It was the second
week into March before my own village road was opened
from Halesowen, and then only by cutting a single path.
On March 12, freezing rain began to fall, coating
everything in sheets of ice and making conditions

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treacherous, putting a 5 to 6 cm layer of ice on top of
the snow surface. Additional heavy glazing occurred on
the 14th only to have a further layer of snow added after
heavy falls on the afternoon and evening of the 15th.
Under these conditions the deep layer of snow was sosolid that it was possible to walk on its surface, which inmany cases left one standing above hedgerows, fences
and road signposts.
The final air-frost of the month occurred on the 15th
and the following day saw a complete change, with thedaytime maximum rising to 8.3°C after early morning
fog. By late evening a full gale was blowing, gustingto 66 knots and for almost 11 hours, the mean windspeed remained in excess of gale force. The gale wasaccompanied (fortunately) by rain, not snow, thoughanxiety now began to mount with the prospect of flooding
if the thaw were rapid, in view of the immense volume ofsnow around.

Figure 7 - Flooding near Worcester

The inhabitants of Bewdley would have been horrified
to find that the river Severn floodwater reached the
garage forecourt near the railway bridge over the A456
Birmingham-Bewdley road. The resulting flooding along
the Severn—and most other rivers—was so severe that it
set records which in many places still stand today.
The 1947 winter was now well and truly over, and March
had added to the mass of statistics thrown up by thisspell of quite amazing weather, statistics which appear in
Table 1. The rainfall total of 151.7 mm is a March record
not exceeded to this day, with precipitation on 24 days,
11 of which experienced 5 mm or more of precipitation.
Hail occurred on 3 days with fog at 9 a.m. on eight days.
Summary
During the first three months of 1947 snow lay on the
ground for 60 days in all, with the deepest ‘level’ snow
amounting to 42 cm on the March 6. Just prior to the final
thaw, drifts extended up to, and in cases over 5 metresin road and railway cuttings and on high ground. Overthe period the heaviest single fall amounted to 17 cm
on March 12 during a final blizzard accompanied byglazed ice. The final two columns of Table 1 highlight thestatistics for this 3-month spell, with the 30-year mean
(1971-2000) included by way of comparison.

Figure 6 - Digging through snow drifts to keep the A456
Kidderminster to Birmingham road open.

Rain and fresh to strong winds persisted throughout thefollowing seven days, eating into the lying snow as achange in wind direction to a westerly quarter heralded
much higher temperatures. By March 22 these werepeaking at 11.1°C, warm days, frost-free nights andample rain removing almost all of the main volume oflying snow.
The final ten days of March were exceptionally wet
with 36.3 mm of rain. This and the water resulting fromthe melting snow caused widespread flooding along
the river valleys, a fact mentioned regularly during thefloods occurring the autumn before last (i.e. 2000).

Sub-zero temperatures occurred over 32 days, a total
in excess of 768 hours of frost, the longest continuous
spell lasting from February 11 to February 23, more than
320 hours. One gale, on March 16, blew with gusts up to
66 knots and gale force gusts were noted on 21 days inall. These figures well illustrate the problems which wereencountered, both through the severe wind-chill andby blowing snow re-filling all freshly cleared roads andrailways.
The entire severe spell had lasted 57 days, 60 if we
include the initial short spell at the start of January.
That ends this rather detailed look at the winter of 1947
seen entirely through my own eyes, with comments
made where it thought likely to enhance the data
being quoted. I do hope that this has proved of someinterest, especially to those who were not born at thetime, or were too young to ‘appreciate’ the conditions.
Figures 1,2,3,6,7 kindly supplied by the Birmingham
Evening Dispatch; Figures 4,5, by the author

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This RGB123 image segment from Meteor-M2, acquired on February 12 this year by Enrico Gobbetti, shows northern Scotland inparticular beset by heavy snow showers. The cyan colouring indicates lying snow on the ground.

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