Locusts & Monkeys

Soil moisture data from the SMOS satellite and the MODIS instrument acquired between July and October 2016 were used by isardSAT and CIRAD to create this map showing areas with favourable locust swarming conditions (in red) during the November 2016 outbreak. Data courtesy of ESA. Copyright : CIRAD, SMELLS consortium.

Spatial resolution is a key characteristic in remote sensing, as we’ve previously discussed. Often the view is that you need an object to be significantly larger than the resolution to be able to see it on an image. However, this is not always the case as often satellites can identify indicators of objects that are much smaller.

We’ve previously written about satellites identifying phytoplankton in algal blooms, and recently two interesting reports have described how satellites are being used to determine the presence of locusts and monkeys!

Locusts

Desert locusts are a type of grasshopper, and whilst individually they are harmless as a swarm they can cause huge damage to populations in their paths. Between 2003 and 2005 a swarm in West Africa affected eight million people, with reported losses of 100% for cereals, 90% for legumes and 85% for pasture.

Swarms occur when certain conditions are present; namely a drought, followed by rain and vegetation growth. ESA and the UN Food and Agriculture Organization (FAO) have being working together to determine if data from the Soil Moisture and Ocean Salinity (SMOS) satellite can be used to forecast these conditions. SMOS carries a Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) instrument – a 2D interferometric L-band radiometer with 69 antenna receivers distributed on a Y-shaped deployable antenna array. It observes the ‘brightness temperature’ of the Earth, which indicates the radiation emitted from planet’s surface. It has a temporal resolution of three days and a spatial resolution of around 50 km.

By combining the SMOS soil moisture observations with data from NASA’s MODIS instrument, the team were able to downscale SMOS to 1km spatial resolution and then use this data to create maps. This approach then predicted favourable locust swarming conditions approximately 70 days ahead of the November 2016 outbreak in Mauritania, giving the potential for an early warning system.

This is interesting for us as we’re currently using soil moisture data in a project to provide an early warning system for droughts and floods.

Monkeys

Earlier this month the paper, ‘Connecting Earth Observation to High-Throughput Biodiversity Data’, was published in the journal Nature Ecology and Evolution. It describes the work of scientists from the Universities of Leicester and East Anglia who have used satellite data to help identify monkey populations that have declined through hunting.

The team have used a variety of technologies and techniques to pull together indicators of monkey distribution, including:

  • Earth observation data to map roads and human settlements.
  • Automated recordings of animal sounds to determine what species are in the area.
  • Mosquitos have been caught and analysed to determine what they have been feeding on.

Combining these various datasets provides a huge amount of information, and can be used to identify areas where monkey populations are vulnerable.

These projects demonstrate an interesting capability of satellites, which is not always recognised and understood. By using satellites to monitor certain aspects of the planet, the data can be used to infer things happening on a much smaller scale than individual pixels.

World Oceans Day

Phytoplankton Bloom off South West England. Acquired by MODIS on 12th June 2003. Data courtesy of NASA.

June 8th is World Oceans Day. This is an annual global celebration of the oceans, their importance and how they can be protected for the future.

The idea of a World Ocean Day was originally proposed by the Canadian Government at the Earth Summit in Rio in 1992. In December 2008 a resolution was passed by United Nations General Assembly which officially declared that June 8th would be World Oceans Day. The annual celebration is co-ordinated by the Ocean Project organisation, and is growing from strength to strength with over 100 countries having participated last year.

There is a different theme each year and for 2017 it’s “Our Oceans, Our Future”, with a focus on preventing plastic pollution of the ocean and cleaning marine litter.

Why The Oceans Are Important?

  • The oceans cover over 71% of the planet and account for 96% of the water on Earth.
  • Half of all the oxygen in the atmosphere is released by phytoplankton through photosynthesis. Phytoplankton blooms are of huge interest to us at Pixalytics as despite their miniscule size, in large enough quantities, phytoplankton can be seen from space.
  • They help regulate climate by absorbing around 25% of the CO2 human activities release into the atmosphere.
  • Between 50% and 80% of all life on the planet is found in the oceans.
  • Less than 10% of the oceans have been explored by humans. More people have stood on the moon than the deepest point of the oceans – the Mariana Trench in the Pacific Ocean at around 11 km deep.
  • Fish accounted for about 17% of the global population’s intake of animal protein in 2013.

Why This Year’s Theme Is Important?

The pollution of the oceans by plastic is something which affects us all. From bags and containers washed up on beaches to the plastic filled garbage gyres that circulate within the Atlantic, Pacific and Indian Oceans, human activity is polluting the oceans with plastic and waste. The United Nations believe that as many as 51 trillion particles of microplastic are in the oceans, which is a huge environmental problem.

Everyone will have seen images of dolphins, turtles or birds either eating or being trapped by plastic waste. However, recently Dr Richard Kirby – a friend of Pixalytics – was able to film plastic microfibre being eaten by plankton. As plankton are, in turn, eaten by many marine creatures, this is one example of how waste plastic is entering the food chain. The video can seen here on a BBC report.

Dr Kirby also runs the Secchi Disk project which is a citizen science project to study phytoplankton across the globe and receives data from every ocean.

Get Involved With World Oceans Day

The world oceans are critical to the health of the planet and us! They help regulate climate, generate most of the oxygen we breathe and provide a variety of food and sources of medicines. So everyone should want to help protect and conserve these natural environments. They are a number of ways you can get involved:

  • Participate: There are events planned all across the world. You can have a look here and see if any are close to you.
  • Look: The Ocean Project website has a fantastic set of resources available.
  • Think: Can you reduce your use, or reliance on plastic?
  • Promote: Talk about World Oceans Day, Oceans and their importance.

Monitoring ocean acidification from space

Enhanced pseudo-true colour composite of the United Kingdom showing coccolithophore blooms in light blue. Image acquired by MODIS-Aqua on 24th May 2016. Data courtesy of NASA.

Enhanced pseudo-true colour composite of the United Kingdom showing coccolithophore blooms in light blue. Image acquired by MODIS-Aqua on 24th May 2016. Data courtesy of NASA.

What is ocean acidification?
Since the industrial revolution the oceans have absorbed approximately 50% of the CO2 produced by human activities (The Royal Society, 2005). Scientists previously saw this oceanic absorption as advantageous, however ocean observations in recent decades have shown it has caused a profound change in the ocean chemistry – resulting in ocean acidification (OA); as CO2 dissolves into the oceans it forms carbonic acid, lowering the pH and moving the oceans into a more acidic state. According to the National Oceanic Atmospheric Administration (NOAA) ocean pH has already decreased by about 30% and some studies suggest that if no changes are made, by 2100, ocean pH will decrease by 150%.

Impacts of OA
It’s anticipated OA will impact many marine species. For example, it’s expected it will have a harmful effect on some calcifying species such as corals, oysters, crustaceans, and calcareous plankton e.g. coccolithophores.

OA can significantly reduce the ability of reef-building corals to produce their skeletons and can cause the dissolution of oyster’s and crustacean’s protective shells, making them more susceptible to predation and death. This in turn would affect the entire food web, the wider environment and would have many socio-economic impacts.

Calcifying phytoplankton, such as coccolithophores, are thought to be especially vulnerable to OA. They are the most abundant type of calcifying phytoplankton in the ocean, and are important for the global biogeochemical cycling of carbon and are the base of many marine food webs. It’s projected that OA may disrupt the formation and/or dissolution of coccolithophores, calcium carbonate (CaCO3) shells, impacting future populations. Thus, changes in their abundance due to OA could have far-reaching effects.

Unlike other phytoplankton, coccolithophores are highly effective light scatterers relative to their surroundings due to their production of highly reflective calcium carbonate plates. This allows them to be easily seen on satellite imagery. The figure at the top of this page shows multiple coccolithophore blooms, in light blue, off the coast of the United Kingdom on 24th March 2016.

Current OA monitoring methods
Presently, the monitoring of OA and its effects are predominantly carried out by in situ observations from ships and moorings using buoys and wave gliders for example. Although vital, in situ data is notoriously spatially sparse as it is difficult to take measurements in certain areas of the world, especially in hostile regions (e.g. Polar Oceans). On their own they do not provide a comprehensive and cost-effective way to monitor OA globally. Consequently, this has driven the development of satellite-based sensors.

How can OA be monitored from space?
Although it is difficult to directly monitor changes in ocean pH using remote sensing, satellites can measure sea surface temperature and salinity (SST & SSS) and surface chlorophyll-a, from which ocean pH can be estimated using empirical relationships derived from in situ data. Although surface measurements may not be representative of deeper biological processes, surface observations are important for OA because the change in pH occurs at the surface first.

In 2015 researchers at the University of Exeter, UK became the first scientists to use remote sensing to develop a worldwide map of the ocean’s acidity using satellite imagery from the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite that was launched in 2009 and NASA’s Aquarius satellite that was launched in 2011; both are still currently in operation. Thermal mounted sensors on the satellites measure the SST while the microwave sensors measure SSS; there are also microwave SST sensors, but they have a coarse spatial resolution.

Future Opportunities – The Copernicus Program
The European Union’s Copernicus Programme is in the process of launching a series of satellites, known as Sentinel satellites, which will improve understanding of large scale global dynamics and climate change. Of all the Sentinel satellite types, Sentinels 2 and 3 are most appropriate for assessment of the marine carbonate system. The Sentinel-3 satellite was launched in February this year andwill be mainly focussing on ocean measurements, including SST, ocean colour and chlorophyll-a.

Overall, OA is a relatively new field of research, with most of the studies being conducted over the last decade. It’s certain that remote sensing will have an exciting and important role to play in the future monitoring of this issue and its effects on the marine environment.

Blog written by Charlie Leaman, BSc, University of Bath during work placement at Pixalytics.

Sentinel-2A dips its toe into the water

Detailed image of algal bloom in the Baltic Sea acquired by Sentinel-2A on 7 August 2015. Data courtesy of Copernicus Sentinel data (2015)/ESA.

Detailed image of algal bloom in the Baltic Sea acquired by Sentinel-2A on 7 August 2015. Data courtesy of Copernicus Sentinel data (2015)/ESA.

With spectacular images of an algal bloom in the Baltic Sea, ESA’s Sentinel-2A has announced its arrival to the ocean colour community. As we highlighted an earlier blog, Sentinel-2A was launched in June predominately as a land monitoring mission. However, given it offers higher resolution data than other current marine focussed missions; it was always expected to dip it’s toe into ocean colour. And what a toe it has dipped!

The images show a huge bloom of cyanobacteria in the Baltic Sea, with the blue-green swirls of eddies and currents. The image at the top of the blog shows the detail of the surface floating bloom caught in the currents, and there is a ship making its way through the bloom with its wake producing a straight black line as deeper waters are brought to the surface.

Algal bloom in the Baltic Sea acquired by Sentinel-2A on 7 August 2015. Data courtesy of Copernicus Sentinel data (2015)/ESA.

Algal bloom in the Baltic Sea acquired by Sentinel-2A on 7 August 2015. Data courtesy of Copernicus Sentinel data (2015)/ESA.

To the right is a wider view of the bloom within the Baltic Sea. The images were acquired on the 7th August using the Multispectral Imager, which has 13 spectral bands and the visible, which were used here, have a spatial resolution of 10 m.

The Baltic Sea has long suffered from poor water quality and in 1974 it became the first entire sea to be subject to measures to prevent pollution, with the signing of the Helsinki Convention on the Protection of the Marine Environment of the Baltic Sea Area. Originally signed by the Baltic coastal countries, a revised version was signed by the majority of European countries in 1992. This convention came into force into force on the 17th January 2000 and is overseen by the Helsinki Commission – Baltic Marine Environment Protection Commission – also known as HELCOM. The convention aims to protect the Baltic Sea area from harmful substances from land based sources, ships, incineration, dumping and from the exploitation of the seabed.

Despite the international agreements, the ecosystems of the Baltic Sea are still threatened by overfishing, marine and chemical pollution. However, the twin threats that cause the area to suffer from algal blooms are warm temperatures and excessive levels of nutrients, such as phosphorus and nitrogen. This not only contributes towards the algal blooms, but the Baltic Sea is also home to seven of the world’s ten largest marine dead zones due to the low levels of oxygen in the water, which prevent marine life from thriving.

These images certainly whet the appetite of marine remote sensors, who also have Sentinel-3 to look forward to later this year. That mission will focus on sea-surface topography, sea surface temperature and ocean colour, and is due to the launched in the last few months of 2015. It’s an exciting time to be monitoring and researching the world’s oceans!

Month on the World’s Oceans

San Francisco USA, Pseudo-true colour image. Landsat 8 data courtesy USGS/NASA/ESA

San Francisco USA, Pseudo-true colour image. Landsat 8 data courtesy USGS/NASA/ESA

June’s been a really busy month for me on the world’s oceans. I’ve not actually been out on the water, but flying over it having attended both the World Ocean Summit and the International Ocean Colour Science (IOCS) meeting. Both of these events focussed on the oceans, although they had very different participants and perspectives. In addition, the 8th June was also World Oceans Day and had the theme ‘Healthy Oceans, Healthy Planet’.

The World Ocean Summit, organised by The Economist, took place at the start of June in Cascais, Portugal. It focused on the development of the blue economy, with most of the participants from governments or non-profit non-governmental organizations. There were a number of talks highlighting the potential innovation opportunities the world’s ocean might offer, and the policy and worldwide governance framework needed. Throughout the summit, there was a repeatedly voiced concern over the state of the world’s oceans, and the serious peril and decline it’s in. Whilst many large organisations are now looking to exploit the oceans, many local communities have been doing this for years and they are seeing changes and challenges. The oceans are an integral part of Earth’s ecosystem, and without them we could not survive on this planet. The resources are potentially huge, but tapping into these requires a co-ordinated bottom up approach. Otherwise we risk damaging the ocean and our own existence.

My second major event was IOCS last week in San Francisco, and as the name suggests the meeting focused on mapping and understanding the ocean through the use of ocean colour remote sensing i.e., detecting and quantifying what causes changes in the colour. The participants were mostly scientists, students and space agencies, who were discussing current work and future plans. There was obvious excitement over the launch of Sentinel-2 (which incidentally occurred successfully very early yesterday morning) and Sentinel-3, which will carry the OLCI ocean colour sensor, due to be launched towards the end of this year. Cloud cover remains a limiting factor in many locations, as clouds get in the way when optically sensing of the ocean and so the more data collected the better insight we’ll gain into the complexities of the biological processes.

There were lots of new areas of focus discussed at the meeting. I was particularly interested in exporting of carbon to the deep ocean and the calculation of uncertainties i.e., how well have we estimated the values that have been derived.

I was also fascinated by the development in our understanding of rapidly changing ecosystems, such as the Arabian Sea and high latitude polar oceans, which are strongly affected by the effects of climate changing; for example, the reduction of the snow cover over the Himalayan-Tibetan Plateau region changes the strength of the Asian monsoon season, which in turn impacts the phytoplankton that bloom in the Arabian Sea. This has caused a particular species of plankton to bloom (Noctiluca, also known as sea sparkle because it can glow when disturbed at night), which are eaten by jellyfish but can negatively affect fisheries as they’re too big for zooplankton to eat.

I’d love to say after a busy month it’s good be home, but I’ve not quite got there yet! I went straight from San Francisco to Switzerland, where this week I’m attending the 2015 Dragon Symposium that’s focused on an Earth observation scientific exchange programme between the European Space Agency and China.

Ocean Colour Partnership Blooms

Landsat 8 Natural Colour image of Algal Blooms in Lake Erie acquired on 01 August 2014. Image Courtesy of NASA/USGS.

Landsat 8 Natural Colour image of Algal Blooms in Lake Erie acquired on 01 August 2014. Image Courtesy of NASA/USGS.

Last week NASA, NOAA, USGS and the US Environmental Protection Agency announced a $3.6 million partnership to use satellite data as an early warning system for harmful freshwater algae blooms.

An algae bloom refers to a high concentration of micro algae, known as phytoplankton, in a body of water. Blooms can grow quickly in nutrient rich waters and potentially have toxic effects. Shellfish filter large quantities of water and can concentrate the algae in their tissues, allowing it to enter the marine food chain and potentially causing a risk to human consumption. Blooms can also contaminate drinking water. For example, last August over 40,000 people were banned from drinking water in Toledo, Ohio, after an algal bloom in Lake Erie.

The partnership will use the satellite remote sensing technique of ocean colour as the basis for the early warning system.  Ocean colour isn’t a new technique, it has been recorded as early as the 1600s when Henry Hudson noted in his ship’s log that a sea pestered with ice had a black-blue colour.

Phytoplankton within algae blooms are microscopic, some only 1,000th of a millimetre in size, and so it’s not possible to see individual organisms from space. Phytoplankton contain a photosynthetic pigment visible with the human eye, and in sufficient quantities this material can be measured from space. As the phytoplankton concentration increases the reflectance in the blue waveband decreases, whilst the reflectance in the green waveband increases slightly. Therefore, a ratio of blue to green reflectance can be used to derive quantitative estimates of the concentration of phytoplankton.

The US agency partnership is the first step in a five-year project to create a reliable and standard method for identifying blooms in US freshwater lakes and reservoirs for the specific phytoplankton species, cyanobacteria. To detect blooms it will be necessary to study local environments to understand the factors that influence the initiation and evolution of a bloom.

It won’t be easy to create this methodology as inland waters, unlike open oceans, have a variety of other organic and inorganic materials suspended in the water through land surface run-off, which will also have a reflectance signal. Hence, it will be necessary to ensure that other types of suspended particulate matter are excluded from the prediction methodology.

It’s an exciting development in our specialist area of ocean colour. We wish them luck and we’ll be looking forward to their research findings in the coming years.

Goodbye HICO, Hello PACE – Ocean Colour’s Satellite Symmetry

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

HICO™ Data, image of Hong Kong from the Oregon State University HICO Sample Image Gallery, provided by the Naval Research Laboratory

Ocean colour is the acorn from which Pixalytics eventually grew, and so we were delighted to see last week’s NASA announcement that one of their next generation ocean colour satellites is now more secure with a scheduled launched for 2022.

Unsurprisingly the term ocean colour refers to the study of the colour of the ocean, although in reality it’s a name that includes a suite of different products, with the central one for the open oceans being the concentration of phytoplankton. Ocean colour is determined by the how much of the sun’s energy the ocean scatters and absorbs, which in turn is dependent on the water itself alongside substances within the water that include phytoplankton and suspended sediments together with dissolves substances and chemicals. Phytoplankton can be used a barometer of the health of the oceans; in that phytoplankton are found where nutrient levels are high and oceans with low nutrients have little phytoplankton. Sam’s PhD involved the measurement of suspended sediment coming out of the Humber estuary back in 1995, and it’s remained an active field of her research for the last 20 years.

Satellite ocean colour remote sensing began with the launch of NASA’s Coastal Zone Colour Scanner (CZCS) on the 24th October 1978. It had six spectral bands, four of which were devoted to ocean colour, and a spatial resolution of around 800m. Despite only having an anticipated lifespan of one year, it operated until the 22nd June 1986 and has been used as a key dataset ever since. Sadly, CZCS’s demise marked the start of a decade gap in NASA’s ocean colour data archive.

Although there were some intermediate ocean colour missions, it was the launch of the Sea-viewing Wide Field-of-view (SeaWiFS) satellite that brought the next significant archive of ocean colour data. SeaWiFS had 8 spectral bands optimized for ocean colour and operated at a 1 km spatial resolution. One of Sam’s first jobs was developing a SeaWiFS data processor, and the satellite collected data until the end of its mission in December 2010.

Currently, global ocean colour data primarily comes from either NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on-board the twin Aqua and Terra satellites, or the Visible Infrared Imaging Radiometer Suite (VIIRS) which is on a joint NOAA / NASA satellite called Suomi NPP. MODIS has 36 spectral bands and spatial resolution ranging from 250 to 1000 m; whilst VIIRS has twenty two spectral bands and a resolution of 375 to 750 m.

Until recently, there was also the ONR / NRL / NASA Hyperspectral Imager for the Coastal Ocean (HICO) mission on-board the International Space Station. It collected selected coastal region data with a spectral resolution range of 380 to 960nm and 90m spatial resolution. It was designed to collect only one scene per orbit and has acquired over 10,000 such scenes since its launch. However, unfortunately it suffered during a solar storm in September 2014. Its retirement was officially announced a few days ago with the confirmation that it wasn’t possible to repair the damage.

In the same week we wave goodbye to HICO, NASA announced the 2022 launch of the Pre-Aerosol and ocean Ecosystem (PACE) mission in a form of ocean colour symmetry. PACE is part of the next generation of ocean colour satellites, and it’s intended to have an ocean ecosystem spectrometer/radiometer called built by NASA’s Goddard Space Flight Centre and will measure spectral wavebands from ultraviolet to near infrared. It will also have an aerosol/cloud polarimeter to help improve our understanding of the flow, and role, of aerosols in the environment.

PACE will be preceded by several other missions with an ocean colour focus including the European Sentinel-3 mission within the next year; it will have an Ocean and Land Colour Instrument with 21 spectral bands and 300 m spatial resolution, and will be building on Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument. Sentinel-3 will also carry a Sea and Land Surface Temperature Radiometer and a polarimeter for mapping aerosols and clouds. It should help to significantly improve the quality of the ocean colour data by supporting the improvement of atmospheric correction.

Knowledge the global phytoplankton biomass is critical to understanding the health of the oceans, which in turn impacts on the planet’s carbon cycle and in turn affects the evolution of our planet’s climate. A continuous ocean colour time series data is critical to this, and so we are already looking forward to the data from Sentinel-3 and PACE.

British Science Won’t Be Eclipsed

Hawthorn leaves opening in Plymouth on 18th March 2015

Hawthorn leaves opening in Plymouth on 18th March 2015

We’re celebrating science in this blog, as it’s British Science Week in the UK! Despite its name British Science Week is actually a ten day programme celebrating science, technology, engineering, and maths (STEM). The week is co-ordinated by the British Science Association, a charity founded in 1831.

The British Science Association, like ourselves at Pixalytics, firmly believe that science should be at heart of society and culture and have the desire to inform, educate, and inspire people to get interested and involved in science. They promote their aims by supporting a variety of conferences, festivals, awards, training and encouraging young people to get involved in STEM subjects.

British Science week is one of their major annual festivals, and has hundreds of events running up and down the country. The website has a search facility, so you can see what events are running locally. Down here in Plymouth, the events include Ocean Science at The National Marine Aquarium, tomorrow at Museum & Art Gallery learn about the science behind the headlines and on Saturday, also at the Museum, an animal themed day including some real mini-beasts from Dartmoor Zoo – the place that inspired the 2011 film ‘We Bought A Zoo’, which starred Matt Damon and Scarlett Johnansson.

If you can’t get to any of the events in your local area, British Science Week is also promoting two citizen’s science projects:

  • Nature’s Calendar run by the Woodland Trust, asking everyone to look out for up to six common natural events to see how fast spring is arriving this year. They want to be informed of your first sightings of the orange tipped butterfly, the 7-spot ladybird, frog spawn, oak leaves, Hawthorn leaves, and Hawthorn flowers. This will continue a dataset which began in 1736, and we thought the Landsat archive was doing well.
  • Worm Watch Lab – A project to help scientists better understand how our brain works by observing the egg laying behaviour of nematode worms. You watch a 30 second video, and click a key if you see a worm lay an egg. We’ve watched a few and are yet to see the egg laying moment, but all the video watching is developing a lot of datasets for the scientists.

If you are interested in Citizen Science and go to sea, why not get involved in the citizen science work we support, by taking part in the Secchi Disk Project. Phytoplankton underpin the marine food chain and is particularly sensitive to changes in sea-surface temperatures, so this project aims to better understand their current global phytoplankton abundance. You do this by lowering a Secchi disk, a plain white disk attached to a tape measure, over the side of a boat and then recording the depth below the surface where it disappears from sight. This measurement is uploaded to the website and helps develop a global dataset of seawater clarity, which turn indicates the amount of phytoplankton at the sea surface. All the details on how to get involved are on the website.

On Friday, nature is getting involved by providing a partial solar eclipse over the UK. Starting at around 8.30am the moon will take about an hour to get to the maximum effect where the partial eclipse will be visible to the majority of the country – although the level of cloud will determine exactly what you see. Plymouth will be amongst the first places in the country to see the maximum effect around 9.23am – 9.25am, however the country’s best views will be on the Isle of Lewis in Scotland with a 98% eclipse predicted. The only two landmasses who will see a total eclipse will be the Faroe Islands and the Norwegian arctic archipelago of Svalbard. The last total eclipse in the UK was on the 24th August 1999, and the next one isn’t due until 23 September 2090!

Although the eclipse is a spectacular natural event, remember not to look directly at the sun, as this can damage your eyes. To view the eclipse wear a pair of special eclipse glasses, use a pinhole camera or watch it on the television!

We fully support British Science Week, it’s a great idea and we hope it will inspire more people to get involved in science.

What do colours mean in satellite imagery?

False colour image of phytoplankton blooming off the coast of Patagonia. Acquired 2nd Dec 2014. Image Courtesy of NASA/NASA's Earth Observatory

Phytoplankton blooming off the coast of Patagonia on 2nd Dec 2014.
Image Courtesy of NASA/NASA’s Earth Observatory

Satellite images are a kaleidoscope of colours, all vying for attention. It’s important to be clear what the colours are showing, and more importantly, what they may not be showing, to interpret the image correctly. For example, a patch of white on an image might indicate snow or ice, sunglint off the ocean, fog or it could just mean it was cloudy.

On the earth’s surface different colours represent different land types:

  • Vegetation appears as shades of green from pale for grasslands to dark for forests – although some forests will progress from green to orange to brown in autumn.
  • Ocean colour is significantly influenced by phytoplankton, which can produce a range of blue and green colours. A fantastic example of this can be seen in the image at the top of the blog showing phytoplankton blooming off the cost of Patagonia.
  • Snow and ice can appear white, grey, or slightly blue.

As noted in the opening, colours can also mislead with cloud cover being the natural nemesis of optical remote sensing. However, you also have to be careful with effects such as:

  • Smoke: ranges from brown to grey to black.
  • Haze: a pale grey or a dirty white.
  • Dust: can be brown, like bare ground, but also white, red and black.
  • Shadow: Clouds or mountain shadows can look like dark surface features.

There is a good article here from NASA’s Earth Observatory giving more details on the different colours of surface land types. So far, we’ve focussed on natural colour signatures; but man-made structures also appear on imagery. Generally, urban areas tend to be silver or grey in colour; although larger objects also show up in their own right such as the bright red roof of Ferrari World in the middle of the Abu Dhabi Grand Prix Circuit – as discussed in a previous blog.

Composite Google Earth image of the entrance to the Panama Canal: Data courtesy of DigitalGlobe

Composite Google Earth image of the entrance to the Panama Canal: Data courtesy of DigitalGlobe

We tried to repeat the identification of man-made objects for this blog using the coloured roofs of the Biomuseo building, located on the Amador Causeway – at the entrance to the Panama Canal in the Pacific Ocean. Sadly, Landsat 8 pixels are too coarse; and Google Earth has fallen prey to cloud cover preventing visibility, as shown in the image on the right. What you can see though is the buildings in Panama City and the yachts in the marinas and clustered around the four islands (Naos, Perico, Culebra and Flamenco) at the end of the Amador Causeway.

The final thing to remember when considering colours, is the format of the image itself. Some images use true-colours from the red, green and blue wavelengths, which produce colours as if you were looking at the scene directly, so trees are green, sea is blue, etc. However, other images incorporate infrared light to enhance the detection of features not easily distinguished on a true-colour image; this means colours aren’t what you would expect, for example, the ocean may appear red.

Colour is central to use of satellite imagery, but you need to know the properties of the rainbow you are looking at or you may never find the pot of satellite gold.

A Few Days In Portland: Phytoplankton, Sea Ice and Cake!

Early morning photograph of Portland, Maine

Early morning photograph of Portland, Maine

As I talked about in my last blog, this week I’m attending the Ocean Optics XXII Conference in Portland, Maine in the USA. I arrived last Thursday and spent the weekend at a two day pre-conference meeting entitled ‘Phytoplankton Composition From Space’; where we discussed techniques for mapping phytoplankton – the microscopic plants in the ocean.

The smallest phytoplankton taxa (group) are the single celled cyanobacteria known as blue-green algae, they are an ancient life form with a fossil remains of over 3.5 billion years old. They can be mapped from space using ocean colour satellites which measure a signal based on the scattering and absorption of light within the ocean. This enables Earth observation to map the total biomass, via the concentration of the main pigment that’s normally Chlorophyll, and also get a glimpse into which taxa are present.

Understanding the concentration, and diversity, of phytoplankton is valuable as they play a key role in climate processes by absorbing the greenhouse gas carbon dioxide. In addition, they are the very essence of the bottom of the food chain, as they are eaten by zooplankton, who in turn are eaten by small fish and so on. Therefore, significant changes in the concentration or diversity of phytoplankton may have ripple effects through the aquatic food chain. The film Ocean Drifters provides an overview of the role of plankton in the ocean.

The conference itself began on Monday and we’ve had a number of interesting and varied presentations, but I’ve particularly enjoyed two plenary sessions. The first was by Don Perovich, of the Thayer School of Engineering looking at the impact of sunlight on sea ice in the artic. The brightness of sea ice determines the amount of light reflected back to space. If the ice is older, and hence snow covered, then it’s bright white whilst ice that’s melting is much darker due to the pools of water and so absorbs more sunlight. Therefore, there is a positive link between melting ice causing ice to melt quicker. In the Artic, sea ice reaches a minimum in September and causes an increase in melting. There is a scientific analysis on Arctic sea ice conditions here.

The second plenary was given by Johnathan Hair from NASA Langley Research Centre, presenting a paper co-authored with his colleague Yongziang Hu and Michael Behrenfeld from Oregon State University. It focussed on using lasers for mapping vertical profiles throughout the water column from space and applications for inland waters, and how this might be used in global ocean plankton research. Regular readers of the blog will know this is topic is something that particularly interests me, and I have previously written about the subject.

Tuesday morning was eventful, as the conference venue was evacuated just as the first session was starting, due to a strong smell of gas. I took the unexpected networking opportunity, and to catch up with one of my former colleagues over a coffee. Thankfully, we were let back into the venue a couple of hours later, and everything went ahead with a bit of rescheduling. My plenary session on Crowdfunding Ocean Optics went ahead in the afternoon, and seemed to generate a good level of interest. I had lot of questions within the session, and a number of people sought me out during the rest of the day to discuss the idea and the project.

I’ve really enjoyed my time in Portland, and have found a fantastic coffee shop and bakery – Bam Bam Bakery on Commercial Street – which I highly recommend! I’m looking forward to the rest of the week.