Saturday, May 15, 2021
ClubSwan 125 - The fastest monohull ever conceived
Friday, May 14, 2021
Ship tracks show how aerosols affect clouds fast and slow
From Imperial College London by Hayley Dunning
Satellite images show how quickly clouds respond to aerosols emitted by ships, helping inform climate modelling.
Knowing how aerosols – particles released by the burning of fossil fuels – change clouds is important for creating accurate climate models. In particular, aerosols can change the reflectivity of clouds, which can influence the amount of energy from the Sun that the atmosphere reflects back into space.
More reflective clouds would decrease the energy that reaches the Earth’s surface, and therefore reduce the impact of global heating.
This means that we can more accurately check the behaviour of clouds in weather and climate models, leading to better models and more accurate future climate projections.Dr Edward Gryspeerdt
Knowing the speed at which clouds change in response to aerosol is important to understand their effect on the climate.
Aerosols released from ships form distinct lines within cloud formations, known as ‘ship tracks’. Over the open ocean, the clouds are unlikely to be affected by factors other than the aerosols, making ship tracks the ideal ‘natural experiment’ for determining the aerosols’ impact.
The team looked at satellite images of ship tracks and used wind information and ship logs to determine how long ago each ship passed by certain points.
The study, published today in Atmospheric Chemistry and Physics, is the first to study ship tracks over time.
Climate changes
They found that while the number of water droplets in ship track clouds increased within an hour, as they formed around the aerosols, some changes occurred more than 20 hours later.
Satellite image showing the impact of ships on droplet number.Lead researcher Dr Edward Gryspeerdt, from the Department of Physics at Imperial, said: “Short-term changes have been relatively well studied, but how the response changes over longer timescales is less well known, and has largely been studied with computer models alone.
“This is important for the climate as we often rely on short-term changes to build our understanding of how aerosol pollution affects clouds, but our results show the water status of clouds could be underestimated if the full impact of aerosols over time isn’t taken into account.
“This means that we can more accurately check the behaviour of clouds in weather and climate models, leading to better models and more accurate future climate projections.”
While the study was the first to measure the speed of cloud changes in static images the team would like to study images from satellites that can see changes in real time.
Too clean for clouds?
The study also helped answer another question: can the atmosphere ever be ‘too clean’ to form clouds? In other words, are there places where all the other conditions are perfect for clouds but there are too few aerosols for them to form?
The team found places where before the ship passed, there were no clouds, but the passing of the ship caused a new cloud to form.
- ScienceNews : Ship exhaust studies overestimate cooling from pollution-altered clouds
- GeoGarage blog : Ship tracks reveal pollution's effects on clouds / Ship tracks off North America /Sentinel tracks ships' dirty emissions from orbit / Image of the week : signs of ships in the clouds / Finding Hidden Ship Tracks / Ship Tracks off the Kamchatka Peninsula
- NASA : Summer ship tracks in the Pacific / Ship Tracks, Aleutian Islands
Thursday, May 13, 2021
Mapping and monitoring the wreck of La Surveillante
Ongoing collaboration between INFOMAR and the National Monuments Service continues to produce exciting results on Ireland’s underwater cultural heritage.
The wreck was originally surveyed in 2007 by the Marine Institute’s Celtic Voyager as part of the initial INFOMAR survey of Bantry Bay.
Dynamic Environment
NMS site plan of 'La Surveillante' generated during the detailed survey of the wreck undertaken by Dr Colin Breen in 1999-2000. When compared alongside INFOMAR’s La Surveillante 2020 imagery, both are impressively similar, suggesting the wreck site is relatively stable. (© National Monuments Service & INFOMAR)Built as a warship, the three-masted frigate La Surveillante was fully copper-sheathed and carried 32 iron guns.
Comparison of Datasets
Re-survey imagery of the wreck of 'La Surveillante' by the RV Keary as part of the 2020 INFOMAR Programme.
Left: The GSI inshore mapping fleet at sea during INFOMAR survey operations (© Geological Survey Ireland 2020) Right: The Marine Institute's Celtic Voyager at sea during INFOMAR survey operations. (© Marine Institute 2020)La Surveillante is one of the most intact 18th-century wrecks in Irish waters, the remains surviving from the orlop deck down to its copper-sheathed keelson; as such, it is of critical importance for our understanding of frigate construction and ships from that period as well as being a tangible link to one of the major maritime events of that time in our history.
References
Brady, K, McKeon, C., Lyttleton, J & Lawler, I. 2012. Warships, U-Boats and Liners: A Guide to
Shipwrecks Mapped in Irish Waters, (Government of Ireland Publications).
Breen, C. 2001. Integrated Marine Investigations on the Historic Shipwreck La Surveillante. Centre
for Maritime Archaeology Monograph Series No. 1 (University of Ulster Publication).
Wednesday, May 12, 2021
China makes ‘world’s largest satellite image database’ to train AI better
A satellite imaging database containing detailed information of more than a million locations has been launched in China to help reduce errors made by
artificial intelligences when identifying objects from space, the Chinese Academy of Sciences said on Wednesday.
The fine-grained object recognition in the high-resolution remote sensing imagery (FAIR1M) database is tens or even hundreds of times larger than similar data sets used in other countries, it said.
Professor Fu Kun, a lead scientist on the FAIR1M project with the academy’s Aerospace Information Research Institute in Beijing, said the relatively small size of databases for artificial intelligence (AI) training in satellite image recognition had affected accuracy in real-life applications.
Militaries have used spy satellites to study objects of interest since the 1960s.
Some researchers in China have used the technology to track the speed of city expansion in
Xinjiang, wild animal movements on the Tibetan Plateau and worldwide construction of infrastructure under the Belt and Road Initiative.
A satellite imaging database containing detailed information of more than a million locations has been launched in China to help reduce errors made by
Militaries have used spy satellites to study objects of interest since the 1960s. Assessment was initially done manually by trained professionals, before computers helped to speed up the process.
In recent years, rapid development of AI technology has enabled civilians to obtain valuable information from commercial satellite images.
Counting the number of cargo trucks on the roads of a city or even a country, for instance, could provide insight into economic activity, transport and infrastructure.
Some researchers in China have used the technology to track the speed of city expansion in
Xinjiang, wild animal movements on the Tibetan Plateau and worldwide construction of infrastructure under the Belt and Road Initiative.
Existing AI algorithms have sometimes struggled to recognise objects in images taken from orbit, however. Most civilian tools were trained using photographs taken in daily life, but an image of the Eiffel Tower taken by a tourist, for instance, would have little similarity to a shot taken from 300km (186 miles) above.
“Building a large database is quite challenging,” said Xia Guisong, professor of remote sensing at Wuhan University, who was not involved in the FAIR1M project. “Objects need to be verified and properly labelled by hand.”
FAIR1M is not the only large-scale satellite image object database for AI in China.
“We focused on objects viewed by satellites from different angles; they focused more on details in high resolution,” he said.
Military target recognition technology is believed to perform better than civilian counterparts, but the latter is catching up thanks to quickly evolving AI technology and improved training data.
“The algorithms that we develop work at fundamental levels,” Xia said, meaning they can be used in military or civilian settings.
Development of AI image recognition technology in China previously depended mostly on databases from other countries.
“The database is a platform. On this platform any research team from any country can develop different algorithms to beat one another, according to certain rules,” Xia said.
More than 80 per cent of the images in the FAIR1M database came from the Chinese satellites, and the rest from Google Earth, according to Fu’s team.
The competition would “drive the development and application of China’s high-definition satellite image data and technology in international society”, it said.










