Wednesday, July 15, 2020

Weather company using tiny satellites inks deals with NASA, top European agencies to improve forecasts

Delta Air Lines passenger planes are parked during the coronavirus pandemic at Birmingham-Shuttlesworth International Airport in Birmingham, Ala., on March 25.
(Elijah Nouvelage/Reuters)
From WP by Andrew Freedman

Private-sector satellite companies are increasingly seen as players in weather forecasting

When the novel coronavirus pandemic grounded a large portion of air traffic worldwide in March and April, Peter Platzer saw an opportunity.
The Luxembourg-based CEO of the satellite firm Spire Global offered up his company’s weather data free to some of the top weather forecasting centers around the world.

With thousands of flights grounded, weather forecasters were sounding alarm bells about lost data that could harm forecast accuracy.
Sensors aboard commercial aircraft gather data that augments information from the weather balloon network at observation sites around the world.

Depriving computer models of the aircraft data threatened to erode forecast accuracy for all the major models in use, from the vaunted European model to the main U.S. model, known as the Global Forecast System, or GFS.

Spire, which has 88 tiny satellites, each the size of a loaf of bread, in low Earth orbit, gathers what’s known as radio occultation data, which can be used to develop profiles of moisture and other properties of the atmosphere.
To help plug any aircraft-related holes in data gathering, the company offered its data free to the European Center for Medium-Range Weather Forecasts and the United Kingdom Met Office.

So far, it would seem those agencies are pleased by the proof of concept, although it’s not clear the data has been a game-changer for them.
In a statement, John Eyre, a fellow at the Met Office, said radio occultation data helps improve weather forecast accuracy in general.

“We have used RO data from other satellites for many years, and we know their value for improving our weather forecasts.
The offer of data from Spire is very welcome.
It will make a valuable contribution to mitigating the loss of other weather observations during the COVID-19 period,” Eyre said, referencing the disease caused by the coronavirus.

Spire’s satellites, which it has named LEMURs, for low-Earth multiuse receivers, also collect maritime and aircraft tracking information, providing the company with another source of revenue.

Radio occultation can be thought of as akin to a space-based scan of the atmosphere, and it allows meteorologists to gain observations of atmospheric temperature and moisture using a satellite receiver that measures signals sent by GPS and other navigation satellite systems.

The signal between the two satellites gets refracted, and information about the temperature and water vapor content of the atmosphere can be gleaned from the magnitude of this refraction.

NASA deal marks a key step for Spire, and for similar companies

A plume of dust from the Sahara Desert approaches the United States from the Caribbean in an image from the NOAA GOES-East satellite on June 24.

Now the company, which has raised $150 million in five funding rounds, has taken another step that puts it ahead of some competitors in the race to supplement weather data gathered by far larger and more expensive government-procured satellites.
The company inked a one-year, $7 million deal with NASA to provide it with radio occultation data, which will be available to agency scientists for use in their Earth-observing missions.

The contract is part of a NASA pilot program to evaluate how Earth science data from commercial small-satellite systems could supplement observations from the agency’s satellite fleet.
Spire, which has offices in six locations (including Luxembourg; Boulder, Colo.; and Singapore) was awarded a contract for test data in September 2018, along with Planet and Maxar.

Platzer said the combination of deals with the U.K.’s weather agency, the European center and now NASA signal “a growing-up moment for the small-satellite industry contributing to weather prediction in a very meaningful way.”
Platzer said in an interview that just a few years ago, his company’s tiny satellites were dismissed as “a toy.”

The test data, and now the contract through NASA’s Commercial Smallsat Data Acquisition Program, is ultimately aimed at improving the information available to the agency and potentially forming a different model where, instead of building large, multibillion-dollar satellites, the agency contracts with companies to use fleets of lower-cost satellites that can provide similar or superior information.

A NOAA decision looms

NOAA's GOES-East satellite captures Hurricane Harvey as the storm makes landfall on Aug.
25, 2017, on the mid-Texas coast.
(NASA/NOAA GOES Project/Getty Images)

Like NASA, the National Oceanic and Atmospheric Administration has evaluated Spire’s radio occultation data using an initial private-sector project.
Platzer said that the agency’s feedback was that it would like to see more data volume from Spire’s network and that the company has since focused on generating more information from each small satellite it launches.

On Friday, NOAA released its evaluation of the initial private-sector project, known as the commercial weather data pilot.
The agency concluded that, based on trial data from Spire and its main competitor, GeoOptics, the commercial weather sector “is able to provide radio occultation data that can support NOAA’s operational products and services.” Data from these companies showed a potential to improve weather forecast accuracy, particularly for near-term forecasts.

Before the end of the current fiscal year, NOAA is scheduled to announce a draft statement of work and request for public comment for its first acquisition of commercial space-based radio occultation data for operational use.
The NOAA budget contains $5 million for this data purchase in fiscal 2020, with the president’s budget requesting $15 million in 2021.

This is a tiny fraction of the $1 billion-plus that NOAA spends on its weather satellites each year, but it represents the agency dipping its toes into the rapidly growing private-sector space industry.

Spire offered NOAA the ability to tap into its occultation data free during the coronavirus-related air travel slowdown, but the agency was unable to move as quickly as its European counterparts, Platzer said.
He said this may be because of the structural difference between NOAA and the European center; the latter is singularly focused on producing medium-range forecasts, whereas NOAA manages fish stocks and operates weather satellites and the sprawling National Weather Service, among other functions.

“That is a structural difference, a structural burden that the NOAA administrator has,” Platzer said.

One dilemma that NOAA faces with moving forward on purchasing weather data from a private company such as Spire is that the agency will still be on the hook for providing accurate weather forecasts regardless of what happens with the contract.
So if Spire’s satellites were to fail or the company’s data turned out to be unreliable, then NOAA would still be responsible for finding a way to avoid losing accuracy.

“Ultimately, NOAA must have confidence in the commercial sector to be able to use their capabilities to serve our mission, which we must meet with or without commercial data contributions,” NOAA spokesman John Leslie said in a statement.
“NOAA looks forward to working closely with the private sector to meet its mission.”

Shali Mohleji, a NOAA policy adviser in the Obama administration, said contracting with private firms comes with pros and cons for NOAA.

“I think that the responsibility to provide regular and reliable forecasts remains with NOAA, so the risk of losing data remains a risk to the agency,” she said in an email.
“The new arrangement doesn’t actually ‘offload’ this risk, it just converts it to a critical supply chain risk, and one that is likely to be harder for NOAA to monitor and mitigate.”

Spire’s main rival for the upcoming NOAA data contract is GeoOptics, which launched its first satellite in January 2018.
It is headed by former NOAA administrator Conrad C.
Lautenbacher and was also awarded a contract under NOAA’s pilot program to evaluate the accuracy and uses of private-sector occultation information for weather forecasting.

In April, GeoOptics announced the launch of a processing system for its radio occultation data, which it says helps improve its accuracy and the speed at which it reaches users.

Spire and GeoOptics aren’t the only providers of occultation data.
A publicly funded program between the United States and Taiwan known as Cosmic-2 gathers such data as well.
Spire and GeoOptics maintain that even more occultation profiles would be beneficial for forecasting and other uses.

Platzer said Cosmic-2 is limited to the equatorial regions and generates 5,000 to 8,000 radio occultation profiles a day, whereas Spire’s network can generate more than 10,000 profiles a day and cover the whole globe.

Questions about data quality and value

A meteorologist prepares to launch a National Weather Service balloon.
(Benjamin C Tankersley/The Washington Post)

Outside experts unaffiliated with Spire said that while it is important that agencies such as NASA and NOAA engage with the rapidly growing private-sector satellite industry, it’s not clear how big the upsides will be.
“We don’t quite know what the additional value of Spire or GeoOptics [data] will be yet,” said Frederick Carr, a professor emeritus at the University of Oklahoma.

Mary M. Glackin, who serves as president of the American Meteorological Society but spoke in her capacity as a former executive at IBM’s the Weather Company, said Spire is noteworthy because it is also developing its own weather prediction model, which would allow it to get a clear internal idea of how its satellites are performing.

She said that with any private weather company, it is important to question the value of the data.
Companies tend to think their data is worth more than it really is, she said.
For example, if an increase in the number of radio occultation profiles allows the Weather Company, which operates the popular website, to improve its three-day forecast by 2 percent, “how much more money can you really make on that?” she said.
“It’s not at this point enabling whole new business lines or anything like that.”

Links :

Tuesday, July 14, 2020

Brazil (DHN) layer update in the GeoGarage platform

98 nautical raster charts updated & 20 new charts addedsee GeoGarage news

The history and evolution of satellite remote sensing ocean color science

This webinar explores the history and evolution of satellite-borne ocean color sensors.
You will learn about the impact of past and present sensors, and how future platforms will contribute toward a growing NASA oceanography data archive.
An overview of how to discover and access ocean color data, services and tools that are available at NASA's Ocean Biology Distributed Active Archive Center (OB.DAAC) is also provided.
To discover and access NASA ocean color data, services and tools

Monday, July 13, 2020

Giant A-68 iceberg three years on

A huge iceberg called A-68 calved from the Antarctic Peninsula’s Larsen C ice shelf on 12 July 2017. Three years on, it is in open waters near the South Orkney Islands in the South Atlantic Ocean – about 1050 km from its birthplace.
The berg has already lost two chunks of ice, which were big enough to be given names: A-68B and A68C.
Copernicus Sentinel-1 captured this image of the parent berg, A-68A, on 5 July 2020.

From ESA

The colossus iceberg that split from Antarctica’s Larsen C ice shelf on 12 July 2017 is now in the open waters of the South Atlantic near the South Orkney Islands, about 1050 km from its birthplace.

South Orkney Islands on the GeoGarage platform (DHN nautical chart)

Having lost two chunks of ice, this record berg is a little less huge than it once was – and now that it is in rougher waters, it may break up further.

When it calved, A-68 was about twice the size of Luxemburg and one of the largest icebergs on record, changing the outline of the Antarctic Peninsula forever.
Despite its size, however, it is remarkably thin, just a couple of hundred metres thick.

Over the last three years, satellite missions such as Copernicus Sentinel-1 have been used to track the berg as it drifted in the Southern Ocean.
For the first two years, it remained close to its parent ice sheet, impeded by sea ice.

However, it lost a chunk of ice almost immediately after being calved, resulting in it being renamed A-68A, and its offspring became A-68B.
More recently, in April 2020, A-68A lost another chunk: A-68C.

 The drift of A68 iceberg, Antarctica continues.
Images acquired by #Sentinel3 between December 2019 - March2020

Rather unromantically, Antarctic icebergs are named from the Antarctic quadrant in which they were originally sighted, then a sequential number, then, if the iceberg breaks, a sequential letter.

Although A-68A is a relatively thin iceberg, it has held together reasonably well, but satellites will be key to monitoring how it changes in open waters.

Captured by the Copernicus Sentinel-1 radar mission, the image above shows the berg on 5 July 2020, a few days before its third birthday.
Satellites carrying radar continue to deliver images regardless of the dark and bad weather, which is indispensable when monitoring the remote polar regions which are shrouded in darkness during the winter months.

The map shows the different positions of A-68A during its three-year journey.
The map not only highlights how long it remained close to the Larsen C ice sheet, but how, over the last year or so, its pace of drift has increased considerably.

The map also includes historic iceberg tracks, based on data from a number of satellites including ESA’s ERS-1 and ERS-2, and shows that A-68A is following this well-trodden path.

The wider-view image below from the Copernicus Sentinel-3 mission shows A-68A’s position in February 2020.

Links :

Sunday, July 12, 2020

Germany (BSH) layer update in the GeoGarage platform

86 nautical raster charts updated

New Zealand (Linz) update in the GeoGarage platform

3 nautical raster charts updated

Piracy & time travel

Access this data as an ArcGIS Feed :  ArcGIS Living Atlas of the World

From ESRI by John Nelson,

This StoryMap walks through the visual analysis of 30 years of nautical piracy through various cross-sections of the calendar.

The story map presents nautical piracy in place and time, which offers up all sorts of questions.
Questions I don’t know the answer to; but maps don’t necessarily have to answer questions.
Maps prompt new and more specific questions.
Here are a couple extracts from the StoryMap.

First, a linear look at the past three decades…

Thirty years of nautical piracy through slices of the calendar

And here is a seasonal cross-section of this era…

The National Geospatial Intelligence Agency has collected and maintained a record self-reported incidents from the victims of nautical piracy for decades.

In any human-centric collection of data, however unsavory, a time span like this can reveal underlying patterns and trends that echo or illuminate local and global socioeconomic factors.
I'll leave that interpretation to the experts.

I will, however, endeavor to provide visual resources that prompt the sort of questions and commentary that shed light on a living and breathing phenomenon.
The combination of geographic information with time is a powerful coupling...
Where and when are the most intuitive precepts of our everyday job of sorting and make sense of the world around us.
Data that captures these two categories represents an enormous potential to understand the underlying phenomenon it describes.
Data, after all, is just a tiny model of reality.
Each element describes some specific facet of an impossibly complex and interrelated system.
When stepping back and seeing a host of independent elements, a faint picture of reality begins to be painted.
A host of tiny bits converge to reveal some echo of a phenomenon.
Cool, right?
Then you can start asking questions of it...
The best part of data exploration is sliding on those magic sunglasses that reveal structure from within the masses. The query.

Show me this, show me that.
And when time is involved, all sorts of trends and patterns are likely to emerge.
Time just makes sense.
But time isn't just linear...
We live in a world of repeating nested patterns.
Our planet rotates around its axis while it revolves around our sun.
We slice up bits of these patterns and name them things like months and weeks and days.
When sampling these recurring cross-sections from a broad time span, maybe there are patterns that emerge?
We can become time travelers, floating above the word, with rewind, fast-forward, and calendar buttons.
Let's put on some time-travel goggles and take a look at nautical piracy.

Here are nearly eight thousand incidents of piracy reported since 1990.
A quick look shows a handful of especially dense locations...
 The Gulf of Guinea, located in the topical waters of the Atlantic Ocean along the central western coast of equatorial Africa, is home to many active offshore petroleum extraction systems, and the urban ports of Ghana, Togo, Benin, Nigeria, Cameroon.
Through the years, piracy has been tightly clustered around these ports.

More distributed, offshore, incidents have occurred around the Niger River delta, home to Port Harcourt.
Shipping lanes passing through the Gulf of Aden, particularly the narrow Bab al-Mandab Strait separating Yemen on the Arabian Peninsula and the countries of Eritrea, Djibouti, and Somalia on the African continent, have seen high instances of piracy.

Piracy is also tightly clustered within the narrow waters of the Singapore Strait, which weaves through the territories of Singapore, Malaysia, and Indonesia.
Taking a look at the three previous decades, we see a stark increase in the 2000s in nearly all regions.
Within our three areas of interest, only Singapore shows appreciable activity in the 1990s.
The waters off the southeastern coast of China, and the South China Sea in genral, have bucked this trend, where piracy was frequent in the 1990s but quite rare in the decades thereafter.
Similarly, reports of piracy around the island of Sri Lanka, off the southeast coast of India, appears to have nearly ceased in the past decade.

Let's take a look at each decade individually, starting with the 1990s...
The 1990s were comparatively quiet.
Incidents globally, and within our areas of interest, are rare and somewhat randomly sprinkled throughout the decade.
The anomalously high rate of incidents in the South China Sea, situated between China to the north, Vietnam to the west, and the Philippines to the west, comes into finer temporal focus here, reveal 1993 to be a banner year for reports of piracy in those waters.

The 2000s are a much different story...
Perhaps most starkly obvious is the punctuated emergence of piracy in the Gulf of Aden in the year 2008—first along the northern shipping lane that passes between Yemen and Somalia, then in the southern shipping lane the following year.
To the south of this Gulf of Aden area of interest, incidents of piracy along the southeastern coast of Somalia, specifically the waters around Mogadishu, show a nascent emergence a few years earlier, in 2005.
These early instances tended to be closer to shore but each following year shows an inclination to venture much further out to sea such that by 2009 the waters east of continental Africa and north of Madagascar were as a vast and active piracy zone.

This increase in reach continued into the following decade...
Through 2010 and 2011, incidents of piracy continue robustly into the high seas east of Africa and deep into the Arabian Sea.
As sharply as these incidents appeared late in the previous decade, they appear to recede beginning in 2012, retracting back to coastal waters and nearly evaporating by 2015.
Similarly, though to a lesser extent, piracy also retracted from the deeper shipping channels extending from Singapore to fewer, more local, incidents.
While global piracy witnessed a precipitous decline during the mid part of the decade, the Gulf of Guinea experienced an expansion in both numbers and distance.
This linear look at piracy provides lots of trends and non-random patterns—so much fodder for an analyst to follow up on, and for those new to this topic to formulate better, more specific questions.

There are clear chronological expansions and contractions, but what about a seasonal look across these thirty years?
Can the month of the year have an influence on where piracy occurs?
Let's take a less linear, more calendar-based, look at the potential seasonality of piracy...
Here is a look at each month of the year, as a cross-section through the decades.
While linear trends of piracy reveal underlying economic forces driving the market of piracy, a seasonal look may reveal cyclical annual patterns.
Twelve frames can be a taxing to track, visually.
If your eyes detect a seasonal wave of activity then I commend your short-term memory's acuity and your generous persistence of vision.

But perhaps a sequence where these months are grouped into their seasons can be easier to visualize. Let's switch our time goggles to a courser resolution.
I'll be referring to seasons from a Northern Hemispherical perspective, but the graphics will retain month names, for clarity...
If there were no seasonality to these decades of piracy, then each seasonal cross-sections would appear equally random.
While less distinct than linear time views, there are, however, some apparent non-random patterns emerging here.
The vast cloud of piracy deep into the waters of the Indian Ocean east of Africa clearly favor Spring and Fall.
A stark two-wave annual pattern of piracy emerges in these transition seasons and breaks back to shore for Winter and Summer.
Piracy in the Gulf of Guinea appears to follow an annual cycle as well.
Summertime is a quieter season with fewer, and more coastal, incidents.
Fall builds up activity into deeper waters and peaks in range and distribution in Wintertime, and finally recedes back to the coast in Springtime.
The Singapore area of interest also shows a mild seasonal fluctuation.
Most notable, perhaps, is the anomalous Wintertime disappearance of piracy around the small Riau Archipelago to the northeast of Singapore, an area rife with piracy in other seasons.
One last observation on seasonality.
The Mediterranean area, which is home to relatively few incidents of piracy, shows a very slight uptick in activity in Summer months.

Are seasonal trends driven intrinsically by the annual cycles of the pirates that carry them out?
Or are they driven by external forces like the business cycles of their target vessels or the seasonal patterns of monsoon seasons that might suppress a pirate's inclination to venture far from shore? Because a large proportion of piracy occurs in the mid latitudes, I expected a somewhat random seasonal pattern.
These fluctuations caught me a bit by surprise and have served to queue up a list of climatic, social, and economic questions.

We all bring preconceived notions to maps, both in their making and their viewing.
Good maps help to wash those away with sometimes surprising clues.
It's important, still, to recognize the biases that we bring to a visualization, and the phenomenon it represents.
Maps don't always have to explain something; sometimes their brightest contribution is to shine a light on new and better questions.

Let's form a tighter time loop and try to identify patterns in the day of the week that incidents of piracy occur.
Is piracy, like any other profession, dependent on the prevailing cultural cycle of the work week—both for those engaging in piracy, and the crews of the vessels they target?
Let's see if we can identify any patterns for this recurring resolution of time...
Piracy is a wholly human endeavor, and humans tend to follow a weekly schedule.
While incidents of piracy show no overall peak or trough throughout the days of the week (the proportion of incidents per day-of-week in almost perfectly flat), there do appear to be some mild fluctuations in the geographic dispersion of these incidents.
Piracy in the Gulf of Guinea tends to cluster closer to the Niger River delta on Wednesdays and Saturdays, while intermediate days show incidents more distributed throughout the gulf.
The northern shipping lane that passes through the Gulf of Aden appears to be targeted more so on Sundays than other days of the week.
These patterns are rather weak, admittedly.

Perhaps the long duration of international shipping journeys spreads the opportunity rather evenly throughout the week so that no particular day presents a target rich environment?
There's an adage in science that goes something like "the absence of data is data."
And, in this case, the absence of strong weekday patterns is also interesting.
Not quite as interesting as a concrete pattern, but still informative and fuel for additional questions. Time, coupled with geography, provides a rich opportunity for the visual exploration of any topic.
As a geographer, the strength of where is foremost in my mind, and it's capacity to surprise and inform in a continued adventure.
But to see a geographic phenomenon de-laminated across time scales, both linear and categorical, is endlessly fascinating and ripe for insights.

Links :

Saturday, July 11, 2020

Screw the box

Stig Pryds is a Danish record holding freediver.
He was diagnosed with psoriatic arthritis in 2008, which disabled him so much that he lost his business.
After 5 years of intense pain and increasing dependency on drugs, he decided to quit all drugs cold turkey, and find alternative ways to deal with his disease.
He began practising yoga daily, changed his diet, and started practising freediving.
This caused drastic changes: within months he could walk without a cane, and he could play with his two young daughters again.
It also taught him how good he actually was at freediving; within a year he started setting Danish records.
He started traveling the world going to freediving competitions, where the warm weather and sun also improved his condition.
He used his increased exposure from the Danish records to tell the story of his recovery and inspire people to live a healthy lifestyle.
He started teaching others how to deal with auto-immune disorders.
The downside of his new fame was that the insurance company, who paid his monthly disability check, noticed that he was doing things a healthy person does.
Despite the argument that he's only healthy because he can do these travels and trainings, the insurance company threatened to sue him for lying -he'd have to pay back all the disability checks plus a fee.
With the help from his doctors Stig managed to convince them his disease is real, just that he manages it well, but the insurance company decided to stop paying him his disability.
The stress this whole procedure caused was enormous and Stig relapsed into severe pain.
We shot this video in January, the hardest month for Stig, where he had to figure out how to proceed. We talked about how life can keep dealing you blow after blow, and how you know that you'll be ok anyway.
But it still sucks that you have to deal with the blows, and have to go through that uncertainty of what comes next.
Stig has decided to focus on his new breathing program, in which he teaches people how to breathe properly to deal with stress and disease, together with yoga and diet.
He might not be able to compete much this year, but he's getting back up and doing his best to be of use to others.

Links :

Friday, July 10, 2020

Satellites rack unusual Saharan dust plume

From ESA

Every summer, the wind carries large amounts of desert dust particles from the hot and dry Sahara Desert in northern Africa across the Atlantic Ocean.
Data from the Copernicus Sentinel satellites and ESA’s Aeolus satellite show the extent of this year’s summer dust plume, dubbed ‘Godzilla,’ on its journey across the Atlantic.

This Saharan dust storm is also known as the Saharan Air Layer, which typically forms between late spring and early autumn, peaking in late June to mid-August.
Large amounts of dust particles from the African desert are swept up into the dry air by strong winds near the ground, as well as thunder storms.
The dust can then float for days, or weeks, depending on how dry, fast and turbulent the air masses become.
Winds in the higher troposphere then sweep the dust across the Atlantic Ocean towards the Caribbean and the United States.

Although this meteorological phenomenon occurs every year, the June 2020 plume is said to be unusual owing to its size and the distance travelled.
According to NOAA’s Atlantic Oceanographic and Meteorological Laboratory, the dust plume was around 60—70% dustier than an average outbreak – making it the dustiest event since records began around 20 years ago.

The Copernicus Sentinel-5P mission is dedicated to monitoring air pollution by measuring a multitude of trace gases as well as aerosols.
This animation shows the spread of aerosols from the Saharan dust plume moving westward across the Atlantic Ocean from 1 June to 26 June 2020.
This plume has reached the Caribbean, South America and the United States.

The animation above shows the spread of aerosols from the Saharan dust plumes moving westward across the Atlantic Ocean from 1 June to 26 June 2020.
Normally, Saharan dust plumes disperse in the atmosphere and sink into the Atlantic before reaching the Americas.
However this year, the dense concentration of dust travelled approximately 8000 km and can be seen arriving near the Caribbean and the southern United States.

The composite image below shows combined observations from the Aeolus satellite and the Copernicus Sentinel-5P satellite on 19 June 2020.
The underlying Sentinel-5P aerosol index in florescent yellow and green, which indicates the extent of the elevated Saharan dust plume over the Atlantic, has been overlaid with Aeolus’ aerosol and cloud information.

Aeolus data provides valuable information regarding the altitude and vertical extent of the aerosol layer, compared to downward-looking imagers, as it can determine the height at which the dust layer is travelling.
Aeolus data in this image indicates that most of the dust was 3—6 km above the ground.

These data are extremely important for air-quality models used by, for example, the Copernicus Atmosphere Monitoring Service, to predict how far the dust layer will travel and how it develops and therefore the effects it will have locally.

Different satellites carry individual instruments that provide us with a wealth of complementary information.
While the Copernicus Sentinel-5P satellite maps a multitude of air pollutants around the globe, Aeolus is the first satellite mission to acquire profiles of Earth’s wind on a global scale.
As shown here, Aeolus also delivers information about the vertical distribution of aerosol and cloud layers.
This combination of satellite data allow scientists to improve their understanding of the Saharan Air Layer, and allows forecasters to provide better air quality predictions.

The images below, captured by the Copernicus Sentinel-2 and Sentinel-3 missions, show the dust particles over Cabo Verde, Boa Vista, Cuba and Sao Filipe.

While the dust poses a threat for our health, causing hazy skies and triggering air quality alerts, the travelling Saharan dust plays an important role in our ecosystem.
The dust is a major source of nutrients which are essential for phytoplankton – microscopic marine plants that drift on or near the surface of the ocean.
Some of the minerals from the dust falls into the ocean, triggering blooms of phytoplankton to form on the ocean surface, which in turn provides food on which other marine life depends.

The dust is also essential for life in the Amazon.
It replenishes nutrients in rainforest soils – nutrients that would otherwise be depleted by frequent rainfall in this tropical region.

The dry and dusty air layers have also been shown to suppress the development of hurricanes and storms in the Atlantic.
Tropical storms need warm ocean waters and warm humid air in order to form.
If a storm were to develop, it would collide with the dusty and dry layers of air of the Saharan dust cloud, preventing it from growing further.

Links :

Thursday, July 9, 2020

France & misc. (SHOM) layer update in the GeoGarage platform

157 charts have been updated & 1 chart replaced

Why we need sharks: the true nature of the ocean's 'monstrous villains'

There are more than a thousand known species of shark.
Mysterious and often misunderstood, the shark family is magically diverse – from glowing sharks to walking sharks to the whale shark, the ocean's largest fish.
But these magnificent animals very rarely threaten humans: so why did dolphins get Flipper while sharks got Jaws?
Sharks are increasingly considered, like whales, to play a crucial role in ocean ecosystems, keeping entire food chains in balance – and have done so for millions of years. But these apex predators are now in grave danger.
The threats they face include finning ( in which their fins are sliced off before they are thrown back into the water), warming seas, and being killed as bycatch in huge fishing operations.
To celebrate our emerging understanding of sharks’ true nature and investigate the many underreported ways in which humans rely on them, the Guardian is devoting a week to rethinking humanity's relationship with the shark – because if they are to survive, these predators cannot be prey for much longer.
Illustration: Good Wives and Warriors

From The Guardian by Helen Scales

Why we need sharks: the true nature of the ocean's 'monstrous villains' There are more than a thousand known species of shark.

Why did dolphins get Flipper while sharks got Jaws?
These majestic, diverse animals bring balance to the ocean ecosystem – and they’re in grave danger

Each day, as the sun sets over the coral-fringed Raja Ampat Islands in Indonesia, an underwater predator stirs.
As predators go, it’s not especially big or ferocious – an arm’s length from head to tail, with a snuffling, moustachioed snout.

Cristina Zenato needs only two words to describe sharks—nature’s masterpiece. A professional diver in the Bahamas, she loves sharks.
Especially the Caribbean reef sharks that flourish around Grand Bahama Island thanks in large part to her efforts to protect them.
The sharks swim right up to the woman known as the Shark Dancer and nuzzle against her while she pets them like they’re dogs or cats.
We take a dive off Grand Bahama Island with Zenato to learn how she built such a strong bond with these beautiful creatures.

What’s unique is that it doesn’t so much swim along the seabed as walk.
Using its four fins as legs, and twisting its spine like a lizard, it can emerge from the water and hold its breath for an hour, strutting across the exposed reef and clambering between tide pools to find prey.

It’s a walking shark, and far from the stereotypical view of these baleful beasts, it tells an alternative story of how sharks look and live.
Biologists recently confirmed there are nine species of walking sharks.
They are the ocean’s newest sharks – probably only 9m years old as a group, with the two youngest species splitting apart less than 2m years ago – challenging the long-held notion that sharks are ancient and unchanging.
They are not evolutionary survivors from bygone eras, but animals that continue to adapt.

The walking shark, the newest species of shark in the ocean.
Photograph: Gerry Allen/Conservation International

The walking sharks themselves are just a fraction of the immense diversity of sharks.
There are bramble sharks and gollumsharks, night sharks and shy sharks, clouded angelsharks and splendid lanternsharks; there are fat catsharks, mouse catsharks, frog, cow and weasel sharks.
In all, more than 500 elasmobranch species are alive today.
One in 10 shark species are bioluminescent: they light up in the dark.
Another is so small you could tuck it in a pocket, and it has little pockets of its own – filled, for an unknown reason, with glowing goo.
Some sharks puff up to look bigger and scarier than they really are.
Mother sharks can be pregnant for three years at a time, or have virgin births.

There are bramble sharks and gollumsharks, night sharks and shy sharks, clouded angelsharks and splendid lanternsharks

But if all you knew about sharks you learned from Hollywood, you’d think they were aquatic horrors.
Sharks have a film genre all their own: there are movies about ghost sharks and zombie sharks, sharks that squirt acid, killer sharks that swim through sand or snow, and a staggering six instalments of the Sharknado film franchise.

Even more problematic is when the more believable films depict sharks as monstrous villains: in 2016, The Shallows featured a female surfer being brutally attacked by a vengeful great white, leading a group of marine scientists to write an open letter to Columbia Pictures warning that the movie was a dangerous mischaracterisation that could keep the tide of public opinion turned against sharks.

Olympic great Michael Phelps races a 'great white shark' on Sunday as part of .
The shark was in-fact a computer simulation rather than a actual great white but its swim speed was calculated using data collected from the real thing.
Phelps finished the 100m course in 38 seconds, two second slower than the 'shark'

In reality, sharks are overfished in their millions.
They aren’t adapted to being prey, rather than predator: sharks grow slowly, spending ages as teenagers before reaching maturity; they lay few eggs and give birth to few pups, not enough to replenish dwindling populations.
Those that stay alive can spend decades, even centuries, absorbing man-made pollutants and plastics.
Individual sharks have seen their world become hotter and more acidic in their lifetime: Greenland sharks swimming around today were born when the Arctic Ocean was several degrees cooler.
The upshot of all this is bleakly predictable.
At last count, a quarter of all sharks and their flattened cousins, the rays, were found to be threatened with extinction.Q&A

What is the Guardian's Truth about Sharks series? Show

Sharks matter to humanity.
Much is lost when they vanish from the seas.
“There’s a lot we can learn from sharks,” says Jasmin Graham, shark biologist and project coordinator of MarSci-Lace at Mote Marine Laboratory in Florida, where researchers are investigating how sharks quickly heal wounds and how they evolved immunity to many diseases.
“If they’re not here, then that evolutionary history, that information, is lost.” At the 2008 Beijing Olympics, swimmer Michael Phelps won eight gold medals wearing a suit inspired by the tiny, toothlike denticles in sharks’ skin that reduce drag and boost their speed.
(The suits were later banned after studies revealed that they trap air bubbles, helping swimmers float.)

Whale sharks, the largest fish in the sea, scoop up tiny plankton as they travel.
Photograph: Nature Picture Library/Alamy

Sharks matter not just because they can be useful for humans, however, but entire ocean ecosystems.
“Lots of shark species have been shown to be keystone predators,” says Graham.
“They maintain balance in ecosystems and keep things in order, removing weaker, sicker prey and stopping any single species from exploding in numbers and taking over.” One study comparing remote islands in the Central Pacific showed that when sharks are fished out, coral reefs can become dominated by small fish and overrun by algae.
“We don’t understand until we lose the species how important it was,” says Graham.

Sharks maintain balance in ecosystems and keep things in orderJasmin Graham, shark biologist

We need to talk about sharks.
Though no sharks have yet gone the way of the dodo, plenty of species are lined up for imminent extinction.
And the loss of sharks is not just about species blinking out, but a diminishment from their former abundance.
Just like the erasing of native fauna from the continents – of bears and wolves, tigers and lions, koalas and kakapos – so the oceans are now losing their sharks.
The only difference is that their dying out mostly goes unnoticed.

In more than 20 years of diving and researching the oceans I’ve had many encounters with wild sharks, each one a moment to treasure and note in my dive logbook.
I used to feel adventurous when family and friends asked me if I was scared to dive with sharks.
(No, never.) But increasingly, as the question keeps being asked, it unsettles me – that so many people still think this way.

Tasseled wobbegong shark among coral off the coast of West Papua, Indonesia.
Photograph: Nature Picture Library/Alamy

For years, scientists and conservationists have been saying that sharks have more to fear from humans than we have from them.
Pick whichever statistic you like best of things far more likely to kill you: a toppling vending machine, a falling coconut.
Still there’s this lingering idea that sharks are dangerous, vindictive and brutal.
Fear is certainly not being deliberately stoked by the very few people who’ve been attacked by sharks, many of whom, despite losing limbs, have become outspoken advocates for shark conservation.

“As a kid, I saw Jaws, and I wasn’t particularly scared of it,” says Graham.
“I was just asking why? Why do people think that they’re so scary? How are they different from a dolphin? They’re both predators.
Why did the sharks get a bad rep and dolphins got to have Flipper?”

These majestic animals are doing much worse worldwide than they were back in 1975 when Jaws was released.
They need all the positive publicity they can get.
New stories need to be told about sharks – the big ones and small ones, the ones that walk and glow, and all the other things they can be.

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Wednesday, July 8, 2020

Coast Guard discontinues differential GPS broadcast

From Maritime Executive

On June 30, 2020 the Coast Guard switched off the last Differential Global Positioning System (DGPS) signals after more than 25 years of service.

With the improved accuracy and integrity of un-augmented GPS over the last several years, and with the introduction of the U.S.
operated satellite-based augmentation system known as Wide Area Augmentation System (WAAS), the maritime community no longer has a mission requirement for DGPS.
GPS now provides sufficient positional accuracy to meet international navigation requirements for harbor approaches and to position Federal Aids to Navigation (ATON).

The Global Positioning System is a U.S. government owned utility that is now ubiquitous, and provides users with free, highly accurate positioning, navigation, and timing (PNT) services.
GPS technology can be found in cell phones and watches, shipping containers, and ATMs.
It is essential for all forms of navigation, farming, surveying and construction, banking and the financial markets, and the power grid.
In its earlier iterations the information GPS provided was not accurate enough for some applications, including the Coast Guard's positioning of marine aids to navigation.
To solve this problem, in the late 1980's and early 1990's, the Coast Guard established the Maritime Differential GPS System to augment the existing GPS signal with accuracy corrections and integrity monitoring by broadcasting over Medium Frequency from terrestrial broadcast sites.
The correction brought GPS position accuracy from several meters to less than one meter.

"The process includes the installation of navigation at a precise known location, which receives the GPS signal and compares the position solution from received signal to its known location.
This result of this comparison is then generated in the form of a correction message and sent to local users via a radiobeacon broadcast.
The received correction is applied by the user's GPS equipment to reduce the system position error, thereby improving the user's absolute accuracy.
This effort was coordinated through the Special Committee (SC) 104 created by the Radio Technical Commission for Maritime Services (RTCM)," wrote Gene W. Hall Lt. Cmdr., USCG Differential GPS Navigation Service, in 1996.

The solution caught on, and the use and availability of DGPS expanded beyond Coast Guard missions.
In its heyday, DGPS operated by the Coast Guard, Department of Transportation (DOT), and the Army Corps of Engineers (USACE), broadcast corrections from 85 sites that covered the nation from coast to coast, out to 50 nautical miles offshore.
Coverage also included the Great Lakes, Hawaii, Alaska, Puerto Rico and the U.S. Virgin Islands.

DOT and USACE have already discontinued the inland DGPS component.
The Coast Guard has operated the remaining Nationwide DGPS service, consisting of one control center and 38 remote broadcast sites, through its Navigation Center in Alexandria, Va.
The phased shutdown of those 38 sites began in 2015 and concluded on June 30, 2020 by turning off the signal from the final four sites located in the Great Lakes and the St. Lawrence Seaway.

Links :

Fact sheet: ECMWF’s use of satellite observations

Composite image of Earth as seen from EUMETSAT’s Metop-B weather satellite in polar orbit at an altitude of 817 km.
(Copyright: 2016 EUMETSAT)


What is the role of satellite observations in weather forecasting?

Satellite observations make a crucial contribution to the quality of today’s weather forecasts.
Their global coverage means that they provide information on the atmosphere, the land surface, the ocean and sea ice that can’t be provided by in situ measurements.
Through a process called data assimilation, they help to produce the best possible estimate of the current state of the Earth system.
That estimate, called the analysis, is used as the initial conditions on which weather forecasts are based.
In addition, satellite data help to monitor the quality of forecasts and to identify and remedy deficiencies in the Earth system models used in weather forecasting.

What types of satellite observations are there?

Satellites carry passive instruments, which measure radiation emitted naturally, and active instruments, which send out signals and measure the backscatter.
Natural radiation contains information on, for instance, temperature, humidity, clouds and surface conditions.
It can also provide information on winds by tracing motions of humidity or cloud features in successive observations.
Active instruments use radar or lidar to probe the surface, clouds and winds.
Radio occultation observations are unique in that they involve sending signals from one satellite to another.
The bending angle of such signals crossing the troposphere or stratosphere depends on temperature and humidity.

How has the use of satellite observations at ECMWF evolved?

ECMWF’s use of satellite data has greatly increased over the last few decades.
Today such data collectively make the biggest contribution to forecast quality at ECMWF compared to other types of observations, such as weather station or aircraft data.
Satellite observations do not measure variables such as temperature or ocean wave height directly.
Instead, they measure quantities linked to these variables, such as radiances or radar echoes.
ECMWF has come to play a leading role in extracting the maximum amount of information from such observations.

How are radiances assimilated into ECMWF’s Earth system model?

Currently the vast majority of satellite data used at ECMWF come from passive instruments measuring infrared or microwave radiances.
Such radiances typically reflect conditions in a rather deep layer of the atmosphere and could be the result of any number of atmospheric states.
To be able to compare the observations with the state of the atmosphere in the forecasting model, we need to know what radiances would be observed if the model state correctly described the atmosphere.
Such simulated radiances are produced by what is known as an observation operator.
By comparing simulated radiances with observed ones, ECMWF’s 4D-Var data assimilation system can work out how the model state needs to be adjusted to pull it more closely towards the observations.

What is ‘all-sky’ satellite data assimilation?

ECMWF has pioneered the use of satellite observations of microwave radiances affected by clouds and precipitation.
Today such all-sky observations are routinely used at ECMWF and make a huge contribution to the quality of weather forecasts.
All-sky assimilation requires a good representation of raindrops, snowflakes and other hydrometeors in the model, and some knowledge of how they affect microwave radiances.
Only then can we successfully simulate the radiances a satellite instrument would measure if the state of the atmosphere corresponded to the model state.

Geostationary satellites, such as this Meteosat Second Generation satellite, are in orbit nearly 36,000 km above the Earth’s equator.

What are the main areas of research in satellite data assimilation at ECMWF?

Active areas of research include the development of techniques to fully exploit hyperspectral infrared instruments, which have many thousands of channels; all-sky assimilation for infrared radiances; the use of more of the information that satellites provide on the wider Earth system, such as surface conditions, the ocean and atmospheric composition; and the treatment of random and systematic errors in satellite observations.
In addition, the Centre works on new generations of instruments with partners such as ESA and EUMETSAT in Europe and similar agencies in Japan, the US and China.
ECMWF has, for example, begun to assimilate Doppler wind lidar observations from ESA’s ground-breaking Aeolus satellite, and it is preparing the ground for the assimilation of cloud profile observations from the EarthCARE mission planned by ESA and the Japan Aerospace Exploration Agency (JAXA).

Links :

Tuesday, July 7, 2020

The mission to raise the anchor from a shipwreck – as a monument to the generation it brought to Britain

HMT Empire Windrush arrives at the Port of Tilbury on the River Thames on 22 June, 1948.
Visible just right of centre is the anchor a team of campaigners and scientists hope to raise from the ship – which sank in 1954 – as a monument to the generation it helped establish in Britain.
Photograph by Alamy / Contraband Collection

From National Geographic by Dominic Bliss

The mission to raise the anchor from a shipwreck – as a monument to the generation it brought to Britain
Carrying migrants to Britain for a new life, the Empire Windrush gave its name to a generation – and later, a scandal.
This is the story of a ship, the people it carried, and a new plan to make a monument from its most iconic symbol.

WHEN the passenger liner HMT Empire Windrush docked at Port of Tilbury on the River Thames in June 1948 with hundreds of Caribbean immigrants aboard, it was a key moment in the establishment of multicultural Britain.
The vessel later came to symbolise the scandalous way in which the government treated many of the so-called Windrush generation – who celebrate a day of recognition on June 22.

The ship itself now lies 2,800 metres down at the bottom of the Mediterranean Sea, 23 nautical miles off the coast of Algeria.
In 1954 it caught fire while en route to the UK, and – after all but four of those aboard had been rescued – it sank.
Now a piece of it may be about to return to the surface in a bid to symbolise the winds of change the ship ushered to British shores over 70 years ago.

Empire Windrush passengers inbound from Commonwealth territories in the Caribbean included those answering calls for work, ex-servicemen and women, and children – many of whom travelled on their parents' passports.
Despite their right to remain, due to immigration law tightening and the government destroying the landing cards of passengers in 2010 many who arrived as part of the first wave were unable to prove legitimate UK citizenship in later life.
This became known as the Windrush scandal.

The story of a ship

When it comes to symbols of migration, few conveyances have been quite so mythologised as the Empire Windrush – a remarkable turn of fortune given the ship's former duties.

Built in 1930 by builders Blohm & Voss, it was originally a German liner named the M.V.
Monte Rosa.
As part of Germany's Hamburg Sud line, its first years saw it give many Germans trans-Atlantic passage to a new life in South America, escaping the economic depression in their homeland.

As National Socialism began to take root in Germany, it was recruited as a propaganda vessel to showcase the ideology of Nazism, with cruises to Scandinavia and the Mediterranean.
Then, as the Second World War began to rock Europe, its festive colours were repainted grey, and the Monte Rosa became a ship of war.

According to Paul Arnott in his book Windrush: A Ship Through Time, the vessel's trajectory turned into darker waters during the war years.
Used as a troop carrier, it brought German ground forces to Scandinavia, at one point supporting and resupplying the infamous battleship Tirpitz – Hitler's ‘beast’ – as it strafed the Norwegian coast to deter Allied attacks.

Then in October 1942, the ship that would become the Empire Windrush was one of two carrying Jews deported from Nazi-occupied Norway to Hamburg – from where they were transported to the gates of Auschwitz, and murdered.

Video: The Empire Windrush arrives at Tilbury, 1948

By the end of the war the Monte Rosa had become a hospital ship, and was seized by the Royal Navy at Kiel on the north German coast.
Sailed to the shipyards of Glasgow, it was re-fitted as a British troop transport – and given the name that would resonate through history.

The first wave

Between 1945 and 1948 the Empire Windrush was used as a Navy transport, repatriating British soldiers home from former theatres of war such as India and Greece.

Then in May 1948, it sailed to the Caribbean – calling at Trinidad, Jamaica, Tampico, Cuba and Bermuda before returning to Tilbury, in Essex on June 22.
Aboard was what would become known as the 'first wave' of Windrush migrants – some 500 mostly Jamaican and Trinidadian workers and their families who, as part of the Commonwealth, were entitled to live in Britain.
Also on board were some 66 Polish migrants who had spent much of the war in Mexico.
These too were bound for a new life in Britain under Churchill's Polish Resettlement Act, which acknowledged the contribution of Polish soldiers and intelligence to the Allied war effort.

On paper, they were both welcome and needed: a personnel gap created by the war had created a vacuum of skilled workers needed to rebuild the country's industry and economy.
But for many of the arrivals on the Empire Windrush that June – and the tens of thousands who arrived from Commonwealth territories all over the world by other means between 1948 and 1973 – the environment they arrived into wasn't the welcome they had hoped for.

Many were victims of racist attitudes and discrimination in employment, forced to accept jobs well below the entitlement of their qualifications or that occupied unsociable shifts.

As the migrants' contribution to the economy began to become evident, attitudes began to change – with some employers, including the NHS, recruiting proactively and directly from the Caribbean.
Some even paid for the migrants' fares, usually recouped through wages.
The communities born from this wave of migrants, and their influence on the arts, education and culture has in the years since been unanimously hailed as a watershed moment in the diversification of British culture.

Scandal and betrayal

The so-called Windrush scandal began to emerge in late 2017.
Under a 2012 policy employers, landlords and financial institutions had been encouraged to create what then-Home Secretary Theresa May described as a 'hostile environment' for those attempting to live in the UK illegally.

A government ruling in 1971 had entitled any Commonwealth citizen currently living in Britain indefinite leave to remain – in short granting rightful citizenship to those who had arrived and settled as part of the Windrush generation.
But the 2012 policy – an attempt to reduce annual net migration to 100,000 – potentially affected anyone who couldn't provide documentation stating right-of-residency.
This meant Windrush children who had travelled to the UK under the passports of their parents – some of whom who had lived in Britain for upwards of 50 years – were challenged to prove their immigration status was legal.

And not all of these mostly elderly people could.
The situation was worsened when it emerged the disembarkation cards of thousands of migrants from the 1950s and 1960s – potential evidence of arrival – were destroyed by the Home Office in 2010.

The consequences wrecked lives.
Citizens unable to prove legitimate citizenship found their rights eroded.
These privations included access to healthcare, legal representation, or housing.
Some who had lived in Britain legally for most of their lives lost jobs, their homes – or faced deportation back to countries they had no memory of.

Theresa May, as Prime Minister in 2018, apologised for the treatment of Windrush migrants – but many remain aggrieved by the government's betrayal of their citizenship.
A 2020 independent report into the scandal spanning 275 pages revealed the cause lay in 'profound institutional failure' – and that people of the Windrush generation ‘who had lived in the UK lawfully for decades were made to feel like criminals.’

The Evening Standard of June 21 1948 carried a story and image relating to the Empire Windrush's arrival in Britain under the headline 'Welcome Home.' Not all branches of the media were as welcoming, and many immigrants faced hardship and discrimination on arrival.
Photograph by John Frost Newspapers / Alamy

‘Added poignancy’

Now there’s a new chapter in the Windrush story.
A group of campaigners plans to locate the wreck, recover the ship’s stern anchor, and return it to the UK as “a fitting monument to multicultural Britain”.
Among them is Patrick Vernon, who was a child of the Windrush generation, maritime archaeologist Jessica Berry, and shipwreck hunter David Mearns.
Provided funding is secured, it’s the latter who will lead the search, locate the wreck and bring the anchor to the surface.

“We’ve had all the negative aspects of the Windrush scandal, and now this could become a positive one.” Mearns tells National Geographic.
“If the anchor was a centrepiece of a monument somewhere in the UK, it would be a touchstone for people to visit and literally touch, connecting themselves to that ship and the symbolism of the first wave of Windrush immigrants.”

In an era when Britons are re-examining their public monuments and statues, it would have added poignancy.
Mearns, who runs a Sussex-based shipwreck recovery service called Blue Water Recoveries, is confident he has narrowed down the position of the wreck to a search area of just 36 square nautical miles.
He has analysed the original mayday signals, and the reports from rescue vessels, and from the Royal Navy destroyer that had been towing her when she finally slipped beneath the waves.

The search for the ship

“In the grand scheme of shipwrecks, the position is very good,” Mearns says.
“Back in 1954, pre-GPS, you’re still relying on sextants, chronometers, and star and sun sightings.
36 square nautical miles is a small area.
My confidence level is high.”

With decades of experience in hunting for ships and aircraft on the ocean bed, Mearns has good reason to be confident.
A marine scientist and sonar specialist by trade, he has discovered 25 shipwrecks and boasts a 90 per cent success rate.
The more important wrecks include HMS Hood, the Royal Navy battlecruiser sunk by the German battleship Bismarck; Esmeralda, a Portuguese carrack that came to rest off the coast of Oman in 1503; and MV Lucona, a motor vessel sabotaged with a time bomb as part of an insurance fraud.

Mearns also helped locate the final resting places of Air France Flight 447, which crashed in the Atlantic in 2009 – and the light aircraft that had been conveying Argentinean footballer Emiliano Sala across the English Channel in 2019.

David Mearns indicates the anchor on the cover of a book about the Empire Windrush.
In this most famous image of the ship – at the top of this article – the anchor is clearly visible.
Photograph by Dominic Bliss

Although the circumstances of each wreck vary enormously, the methods Mearns uses to locate them share similarities.
The bulk of his time is spent poring over maritime records, researching distress calls, eye-witness accounts from survivors and rescuers, and reports of floating debris.
He is no stranger to government records offices such as the National Archives in London and the National Archives and Records Administration in Washington, D.C.
Personal records are also enormously helpful.
While searching for HMAS Sydney and HSK Kormoran off the coast of Australia, for example, he decoded a dictionary that the captain of the latter had used while in prison to secretly document the original sea battle.
“The stuff of World War II movies like The Great Escape,” is how Mearns describes it.

Using his training in oceanography, he hunts for clues in weather reports, ocean currents, and the positions, speeds and bearings of ships at the time they are damaged.
A process called reverse drift analysis allows him to analyse the position of wreck debris or life-rafts, for example, and calculate where the ship actually sank beneath the waves.

Once he has a reasonable search area, it’s then time to mobilise a vessel and all the various equipment.
This is when his job gets complicated and very expensive.
He requires a sturdy ship, specialist team members, and acoustic searching devices such as side-scan sonars or multi-beam echo sounders.
(“We use acoustics because sound propagates through water a long distance,” he explains.) Then, once the wreck has been located, he sets loose a remotely-operated underwater vehicle on a tether (ROV) to film it or recover items.
On the ship’s deck, there must be a strong platform with cables and winches from which the sonar equipment and the ROVs can be launched and towed.

A small remotely operated vehicle (ROV) on a tether, similar to that used by Mearns in his underwater excavations.
Photograph by Brian Skerry / National Geographic Image Collection

Ocean searches last days, weeks, even months, depending on the size of the search area.
For HMS Hood, Mearns had 630 square nautical miles to cover; for HMAS Sydney it was over 1,750.
The Windrush, with just 36 square nautical miles should be a cinch by comparison.
However, Mearns is always prepared for long, sometimes queasy days at sea, staring at a sonar screen, his sleep severely rationed.

Deep sea forensics

There is a science to covering an ocean search area.
The ship normally cruises up and down in a straight line, towing the sonar device (or towfish, as it’s known) at the end of a long cable.
Since every extra day spent at sea adds to the mission cost, Mearns needs to locate wrecks as swiftly as possible.
Unlike mowing a garden lawn, for example, where you progress in orderly lanes, up and down and left to right, he first concentrates on the optimal lanes of highest probability, leaving the lanes of lowest probability until last.
It’s a statistical process based on something called Bayesian search theory, and it can mean the difference between a few days or many weeks of searching.

The vessels that Mearns operates nowadays are luxurious compared to those he endured at the start of his career, back in the 1980s.
“I’ve been on some real dogs,” he says of his early outings.
“It wasn’t uncommon to be at sea for 60 days living in a small, smelly space with five other blokes, sleeping on bunks three-high, with diesel fumes, low food quality, working 12 hours on and 12 hours off, without safety standards.”

The Empire Windrush in dock at Southampton, 1954.
The same year, the 500ft (152m) ship caught fire and sank off the coast of Algeria.
Photograph by Pa Images / Alamy

Operating complex machinery, often miles out at sea, is always a risky business.
As well as injured crew, Mearns has had to delay or abandon projects for reasons ranging from ship fires, engine failures, loss of sonar equipment and ROVs, “and in one instance literally running out of food, prompting an urgent return to port”.

But that moment of discovery, when all the research and hard work finally come to fruition, more than compensates for any hardship.
“The moment you find a wreck is exhilarating,” he says.
“You cannot help but react in a spontaneous way.
There’s a lot of adrenalin involved.
I describe it like an athlete winning a gold medal.
You spend years training for it, and it’s all encapsulated in that split-second when you cross the finish tape.
Just like seeing the sonar image of a shipwreck popping up on your screen.”

Muralising the Empire Windrush on a wall in Bristol.
The ship has come to symbolise the arrival in Britain of a new wave of cultural diversity now generations old.
The 'first wave' and subsequent arrivals up to 1971 became known as the Windrush generation.

Honouring a generation

Mearns is in his office in the Sussex town of Midhurst, riffling through a green lever-arch file containing all his research on the Empire Windrush.
On his walls are paintings and photos of the more famous wrecks he has located, as well as industry awards and Guinness World Records certificates (deepest wreck found, deepest cargo salvage, deepest live internet broadcast, oldest astrolabe and oldest shipwreck bell discovered).
On his shelves are artefacts and memorabilia he has collected over the years: a three-foot-high Roman amphora; part of a cannonball from the Portuguese carrack he located in Oman; an ancient compass housing; the hub of a ship’s wheel from a German blockader; a diving helmet.
In between all these are dozens of research files and books on maritime history and ocean science.
The room is an office-cum-library-cum-museum.

Originally from New Jersey, in the United States, Mearns came to Britain 25 years ago and took over ownership of Blue Water Recoveries in late 2008.
Having spent much of his career on lucrative salvage projects and accident investigations, he’s now in a position where he can donate his services pro bono if, as is the case with the Empire Windrush, he feels it’s a worthwhile cause.
“Passion as opposed to profit,” he says.
In his 2017 book, The Shipwreck Hunter, he describes his motivation: “When deciding what shipwrecks are worth pursuing, I specifically look for… human stories hiding within the overall drama of the shipwreck itself.”

This partly explains why he favours historical wrecks over treasure-laden wrecks.
(Sunken treasure is further complicated by UNESCO regulations and opposition from archaeologists.) Two historical ships he is very keen to search for are TSS Athenia (the passenger liner torpedoed by a German U-boat at the beginning of World War II, with 117 lives lost) and the Endurance (Ernest Shackleton’s ship which sank off the coast of Antarctica).

Mearns says he’s “99 per cent positive” he has located the final resting place of the Athenia.
Any efforts to find the Endurance, however, would be severely hampered by the constantly moving pack ice above its last known location.

Before all that, however, he is directing his attention to the Empire Windrush.
Although he’s sure of her location in the Mediterranean, and confident he can cut free and raise the anchor, he knows that funding for the estimated £1.5 to £2.5 million project will be a challenge.
“I know I can find the ship, but if we reach out to the [Windrush] community and they say the project is inappropriate, we’re not going to do it.”
David Mearns
A 'solidarity with the Windrush generation' demonstration in London, 2018.
A new report has revealed 'profound institutional failure' in the government's handling of the affair.
Photograph by Alamy

Most critical is the need for members and relatives of the Windrush generation to give their blessing.
On June 24th there will be an online consultation, open to the public.
“It’s the families who should decide. This is for their benefit, but they have to want it,” he says, aware of how sensitive the mission would be.
“I know I can find the ship, but the moral authority rests with them.
If we reach out to the [Windrush] community and they say the project is inappropriate, we’re not going to do it.”