Rats anticipate location of food-guarding robots when foraging

Specific cells in rats’ brains mark distant places to avoid after negative experiences, and rats think of these locations even after they leave

PLOS

 

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A rat peeking around a corner is concerned about the robot at the end of the hall.

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Credit: Redish Lab, University of Minnesota (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)

Researchers find that rats create neurological maps of places to avoid after experiencing a threat and think about these locations when exhibiting worry-related behaviors. These findings—which A. David Redish of the University of Minnesota, US, and colleagues presented in the open-access journal PLOS Biology on January 14th—may provide insight into the neuroscience of common psychological conditions like anxiety.

There are many theories as to why people experience anxiety. One is that anxiety is associated with a psychological phenomenon called “approach-avoidance conflict,” where an individual desires something but is weighing that against an associated negative outcome.

To examine the neurological underpinnings of this phenomenon, researchers studied rats navigating an L-shape track. The rats would enter at one end, with food available at the opposite end of the track, but partially hidden around the corner would be a robot with claws on the front and a stinger-like tail, somewhat resembling a cross between a pincer beetle and a scorpion.

As the rats approached the food, the robot would sometimes charge forward and gnash its claws and wriggle its tail to simulate an attack. After these attacks, the rats began performing avoidant behaviors, like hesitating or fleeing back to safety, which the researchers propose are associated with worry about the robot.

Some of the rats in the experiment were implanted with probes to monitor the hippocampus, part of the brain thought to be involved in learning and memory. The researchers specifically focused on the activity of neurons called “place cells,” which activate when an animal visits a specific location. By scrutinizing their activity, the researchers could map which place cells were associated with the location of the food or of the robot.

When the rats hesitated while approaching the food, the researchers found increased activity in the place cells associated with the location of the robot and of the food. This may represent the approach-avoidance conflict between wanting the food and worry about the robot. However, when the rats turned around part-way down the track, the active place cells were mainly associated with the location of the robot.

Usually, place cells are only active when the cells’ associated location is the animal’s location or just ahead of the animal. However, as the rats turned around and fled back to the safe end of the track, their place cells associated with the distant robot remained active.

Anxiety is related to the ability to imagine situations, something the hippocampus and place cells are known to be involved in. The activity of place cells associated with negative events—especially when at a distance from their associated locations—may help scientists better understand the neuroscience of anxiety.

Underlining this association, the researchers observed far fewer worry-related behaviors among the rats when given the anti-anxiety drug diazepam, commonly known as Valium. This medication also altered the activity of the hippocampus, reducing the neural patterns associated with these anxiety-like behaviors.

The authors add, “Worrying about the future requires mental representations of imagined negative future outcomes. Rats facing a predator-like robot guarding a food source developed new mental representations of the robot’s location, resulting in rats transiently thinking about where the robot is prior to foraging for food.”

 

In your coverage, please use this URL to provide access to the freely available paper in PLOS Biology: http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002954

Citation: Calvin OL, Erickson MT, Walters CJ, Redish AD (2025) Dorsal hippocampus represents locations to avoid as well as locations to approach during approach-avoidance conflict. PLoS Biol 23(1): e3002954. https://doi.org/10.1371/journal.pbio.3002954

Author Countries: United States

Funding: This work was funded by grants from the US National Institute of Health: R01-MH080318 (ADR), R01-MH112688 (ADR), a T32 fellowship to OLC (T32-DA037183), a T32 fellowship to CJW (T32-DA007234), summer project funding from St. Olaf College to MTE, and funding from the University of Minnesota Medical School. The funders had no role in study design, data collection, and analysis, decision to publish, or preparation of the manuscript.

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Journal

PLOS Biology

DOI

10.1371/journal.pbio.3002954 

Method of Research

Experimental study

Subject of Research

Animals

COI Statement

Competing interests: The authors have declared that no competing interests exist.

 

 

Beach guardians: How hidden microbes protect coastal waters in a changing climate

Stanford University

A hidden world teeming with life lies below beach sands. New Stanford-led research sheds light on how microbial communities in coastal groundwater respond to infiltrating seawater. The study, published Dec. 22 in Environmental Microbiology, reveals the diversity of microbial life inhabiting these critical ecosystems and what might happen if they are inundated by rising seas.

“Beaches can act as a filter between land and sea, processing groundwater and associated chemicals before they reach the ocean,” said study co-first author Jessica Bullington, a Ph.D. student in Earth system science in the Stanford Doerr School of Sustainability. “Understanding how these ecosystems function is key to safeguarding their services in the face of sea level rise.”

The research team conducted the intensive study at Stinson Beach, north of San Francisco. Stinson Beach is representative of a “high-energy” beach, which has only a handful of previous papers on the microbiome worldwide. 

Microbial guardians

Microbial communities living in groundwater within beach sand play a crucial role in maintaining coastal water quality. These microbes help break down chemicals, including excess nutrients like nitrogen, which can come from natural sources, such as decomposing plant matter, or human sources, like agricultural runoff and wastewater.

To better understand the dynamics of this microbial filtering system, the research team headed to Stinson Beach. Over two weeks, during both a wet and dry season, they collected samples from the beach’s subterranean estuary around the clock to capture changing tides. Then, the researchers analyzed the microbial DNA using advanced gene sequencing techniques. This approach – the first of its kind at such a fine time scale – provided unprecedented insight into the microbial community’s composition and stability.

The researchers found that the microbial communities remained relatively stable over changing tidal conditions and seasons. However, a wave overtopping event – when seawater surged into the aquifer due to high-energy waves – caused significant changes in the microbial makeup. Such disturbances are expected to become more frequent with rising sea levels and storm surges, making it harder for the microbes to do their water purification work.

“These microbes live in complex communities, many with specialized roles that include processing nutrients and even producing or consuming greenhouse gases,” said co-senior author Christopher Francis, a professor of Earth system science and of oceans in the Stanford Doerr School of Sustainability. “The microbial community’s resilience under typical conditions is encouraging, but disturbances like wave overtopping highlight their vulnerability to climate change,” said co-first author Katie Langenfeld, a postdoctoral scholar in civil and environmental engineering at Stanford at the time of the research and current postdoctoral fellow at the University of Michigan.

Implications for coastal resilience

The study’s findings establish a critical baseline for understanding how subterranean estuaries function and respond to environmental changes. As sea levels rise, beach sands will be forced inland or erode, altering groundwater hydrology, chemistry, and microbial composition.

The research adds a crucial piece to the puzzle of coastal resilience. By highlighting the interplay between microbial dynamics and physical processes like wave action, the study brings into question impending changes to coastal groundwater. Policymakers and coastal planners should consider the role of these hidden ecosystems when designing strategies to manage sea level rise, according to the researchers.  

“We rely on these microbial communities for essential biogeochemical cycling at the land-sea interface,” said co-senior author Alexandria Boehm, the Richard and Rhoda Goldman Professor of Environmental Studies in the Stanford Doerr School of Sustainability and the Stanford School of Engineering. “If their capacity diminishes due to climate impacts, we could see cascading effects on coastal water quality and marine life.”

Acknowledgements

This work was supported by the National Science Foundation, the Stanford University McGee and Levorsen Research Grant, and ARCO Stanford University Graduate Fellowship.

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Journal

Environmental Microbiology

DOI

10.1111/1462-2920.70009 

 NO NEED TO DRILL BABY, DRILL

Floating solar panels could support US energy goals

New study shows federally controlled reservoirs could host enough energy to power approximately 100 million US homes a year

DOE/National Renewable Energy Laboratory

Federal reservoirs could help meet the country’s solar energy needs, according to a new study published in Solar Energy.

For the study, Evan Rosenlieb and Marie Rivers, geospatial scientists at the U.S. Department of Energy National Renewable Energy Laboratory (NREL), as well as Aaron Levine, a senior legal and regulatory analyst at NREL, quantified for the first time exactly how much energy could be generated from floating solar panel projects installed on federally owned or regulated reservoirs. (Developers can find specific details for each reservoir on the website AquaPV.)

And the potential is surprisingly large: Reservoirs could host enough floating solar panels to generate up to 1,476 terawatt hours, or enough energy to power approximately 100 million homes a year.

“That’s a technical potential,” Rosenlieb said, meaning the maximum amount of energy that could be generated if each reservoir held as many floating solar panels as possible. “We know we’re not going to be able to develop all of this. But even if you could develop 10% of what we identified, that would go a long way.”

Levine and Rosenlieb have yet to consider how human and wildlife activities might impact floating solar energy development on specific reservoirs. But they plan to address this limitation in future work.

This study provides far more accurate data on floating solar power’s potential in the United States. And that accuracy could help developers more easily plan projects on U.S. reservoirs and help researchers better assess how these technologies fit into the country’s broader energy goals.

Floating solar panels, also known as floating PV, come with many benefits: Not only do these buoyed power plants generate electricity, but they do so without competing for limited land. They also shade and cool bodies of water, which helps prevent evaporation and conserves valuable water supplies.

“But we haven’t seen any large-scale installations, like at a large reservoir,” Levine said. “In the United States, we don't have a single project over 10 megawatts.”

Previous studies have tried to quantify how much energy the country could generate from floating solar panels. But Levine and Rosenlieb are the first to consider which water sources have the right conditions to support these kinds of power plants.

In some reservoirs, for example, shipping traffic causes wakes that could damage the mooring lines or impact the float infrastructure. Others get too cold, are too shallow, or have sloping bottoms that are too steep to secure solar panels in place.

And yet, some hydropower reservoirs could be ideal locations for floating solar power plants. A hybrid energy system that relies on both solar energy and hydropower could provide more reliable and resilient energy to the power grid. If, for example, a drought depletes a hydropower facility’s reservoir, solar panels could generate energy while the facility pauses to allow the water to replenish.

And, to build new pumped storage hydropower projects—which pump water from one reservoir to another at a higher elevation to store and generate energy as needed—some developers create entirely new bodies of water. These new reservoirs are disconnected from naturally flowing rivers, and no human or animal depends on them for recreation, habitat, or food (at least not yet).

In the future, the researchers plan to review which locations are close to transmission lines or electricity demand, how much development might cost at specific sites, whether a site should be avoided to protect the local environment, and how developers can navigate state and federal regulations. The team would also like to evaluate even more potential locations, including other, smaller reservoirs, estuaries, and even ocean sites.

The research was funded by the Solar Energy Technologies Office and the Water Power Technologies Office in DOE’s Office of Energy Efficiency and Renewable Energy (EERE).

Access the study to learn more about the immense potential for floating solar plants in the United States, or visit AquaPV to dig into the data on specific reservoirs.

NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by the Alliance for Sustainable Energy LLC.

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Journal

Solar Energy

DOI

10.1016/j.solener.2024.113177 

Method of Research

Meta-analysis

Subject of Research

Not applicable

Article Title

Floating photovoltaic technical potential: A novel geospatial approach on federally controlled reservoirs in the United States

Article Publication Date

3-Feb-2025

 GET WOKE!

Waking up is not stressful, study finds

University of Bristol

Waking up does not activate an increase in the release of the stress hormone cortisol. Cortisol does, however, increase in the hours prior to wakening as part of the body’s preparation for the next day, new research led by the University of Bristol has found.  The study is published today [15 January] in the Proceedings of the Royal Society B.

For many years it has been generally accepted that waking up results in a stimulus to release hormone cortisol  - a phenomenon called the “cortisol awakening response” (CAR). This response has been used to investigate many clinical conditions including PTSD, depression, obesity, and chronic fatigue syndrome (ME/CFS).

A major limitation of studies using CAR is that protocols typically only assess samples obtained after waking up, and not in the period prior to this, since measurements are taken in saliva. Consequently, the studies are not able to prove a change in the rate of cortisol secretion over the awakening period.

To resolve the critical question of whether the rate of cortisol secretion actually increases after wakening, the Bristol research team used an automated sampling system to measure tissue cortisol levels both before and after wakening in 201 healthy male and female participants aged between 18 to 68 years old.

The researchers found awakening did NOT result in an increase in cortisol release, with no evidence for a change in the rate of cortisol increase in the hour after waking when compared with the hour prior to waking. This suggests that any change in cortisol levels immediately after waking are much more likely to be the tail end of the daily rhythm of cortisol - which starts increasing in the early hours of the morning, and reach a peak shortly after habitual wake time.

Importantly, the study also observed substantial interindividual variability in absolute concentration and rate of change, and differences in dynamics that may be attributed to length and timing of sleep. Based on these findings, the researchers suggest caution is needed when interpreting cortisol measurements solely obtained in the hour after waking.

The findings demonstrate that the major cause of any changes in cortisol around the time of awakening are predominantly related to the endogenous circadian rhythm of cortisol. Furthermore, the results also suggest that if cortisol has any relationship to awakening, it is with factors that contribute to the initiation of awakening rather than being a response to it.

Circadian rhythms, the natural 24-hour cycles of physiological and behavioural patterns, are extremely important adaptations to living on our planet with its daily light:dark and temperature oscillations, and disturbances of these rhythms contribute to many psychological, metabolic, cardiovascular and immunological health conditions. Understanding the role of cortisol rhythms in many of these conditions will be very important for researchers understanding of these disorders and their potential treatment.

Stafford Lightman, Professor of Medicine a Bristol Medical School: Translational Health Sciences (THS), and one of the lead authors of the study, said: “Our study opens up a whole new framework for understanding the relationship of overnight increases in cortisol with  sleep, and how this may be disrupted in sleep disorders, depression and many other conditions.”

Dr Thomas Upton, Clinical Research Fellow and co-lead author in the Bristol Medical School: (THS), explained: “By measuring both before and after waking, this study provides much needed and crucial insight into the dynamics of cortisol with respect to sleep and endogenous rhythms. For me, a key message is that much caution should be exercised if attempting to interpret post-wake cortisol values where information about the pre-waking state is not known.”

Marcus Munafò, Professor of Biological Psychology and Associate Pro Vice-Chancellor - Research Culture at the University of Bristol, added: “As well as providing important insights into the biology of our sleep-wake cycles, this work illustrates how findings that have become received wisdom within the research community may be wrong.

“Making sure our work is robust and reproducible – including rigorously testing previous findings – is a central part of the research culture we try to foster at the University of Bristol.”

The research team suggest that future studies on mechanisms of arousal from sleep both overnight and during the morning should carefully consider dynamic changes in the activity of the hypothalamic pituitary axis - the system in the body that regulates the stress response and the release of cortisol – in addition to sleep and behaviour.

The study was funded by an EU Horizon 2020 grant ‘Ultradian’ (grant no. 633515) and a Biotechnology and Biological Sciences Research Council (BBSRC) follow-on fund (BB/M019268/1).

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Journal

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2024.1844 

Method of Research

Observational study

Subject of Research

People

Article Title

Awakening not associated with an increased rate of cortisol secretion

Article Publication Date

15-Jan-2025

 

Protein shapes can help untangle life’s ancient history

A new way of merging genomic and structural data can help dive deep into evolutionary relationships

Center for Genomic Regulation

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Artistic concept of protein structures solving saturation

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Credit: Queralt Tolosa/Centro de Regulación Genómica

The three-dimensional shape of a protein can be used to resolve deep, ancient evolutionary relationships in the tree of life, according to a study in Nature Communications.  

It is the first time researchers use data from protein shapes and combine it with data from genomic sequences to improve the reliability of evolutionary trees, a critical resource used by the scientific community for understanding the history of life, monitor the spread of pathogens or create new treatments for disease. 

Crucially, the approach works even with the predicted structures of proteins that have never been experimentally determined. It has implications for the massive amount of structural data being generated by tools like AlphaFold 2 and help open new windows into the ancient history of life on Earth. 

There are 210 thousand experimentally determined protein structures but 250 million known protein sequences. Initiatives like the EarthBioGenome project could generate billions more protein sequences in the next few years. The abundance of data opens the door to applying the approach on an unprecedented scale. 

For many decades, biologists have been reconstructing evolution by tracing how species and genes diverge from common ancestors. These phylogenetic or evolutionary trees are traditionally built by comparing DNA or protein sequences and counting the similarities and differences to infer relationships.  

However, researchers face a significant hurdle – a problem known as saturation. Over vast timescales, genomic sequences can change so much that they no longer resemble their ancestral forms, erasing signals of shared heritage. 

“The issue of saturation dominates phylogeny and represents the main obstacle for the reconstruction of ancient relationships,” says Dr. Cedric Notredame, researcher at the Centre for Genomic Regulation (CRG) and lead author of the study. “It’s like the erosion of an ancient text. The letters become indistinct, and the message is lost.” 

To overcome this challenge, the research team turned to the physical structures of proteins. Proteins fold into complex shapes that determine a cell’s function. These shapes are more conserved over evolutionary time than the sequences themselves, meaning they change more slowly and retain ancestral features for longer. 

The shape of a protein is dictated by its amino acid sequence. While sequences may mutate, the overall structure often remains similar to preserve function. The researchers hypothesised they could gauge how much the structures diverge over time by measuring the distance between pairs of amino acids within a protein, also known as intra-molecular distances (IMDs). 

The study compiled a massive dataset of proteins with known structures, covering a wide range of species. They calculated the IMDs for each protein and used these measurements to construct phylogenetic trees.  

They found that trees built from structural data closely matched those derived from genetic sequences, but with a crucial advantage: the structural trees were less affected by saturation. This means they retained reliable signals even when genetic sequences had diverged significantly. 

Recognising that both sequences and structures offer valuable insights, the team developed a combined approach which not only improved the reliability of the tree branches but also helped distinguish between correct and incorrect relationships.  

"It's akin to having two witnesses describe an event from different angles," explains Dr. Leila Mansouri, coauthor of the study. "Each provides unique details, but together they give a fuller, more accurate account." 

One practical example where the combined approach could make a significant impact is in understanding the relationships among kinases in the human genome. Kinases are proteins involved in many different important cellular functions. 

"The genome of most mammals, including humans, contains about 500 protein kinases that regulate most aspects of our biology," says Dr. Notredame. "These kinases are major targets for cancer therapy, for example drugs like imatinib for humans or toceranib for dogs." 

Human kinases have arisen through duplications occurring over the last billion years. "Within the human genome, the most distantly related kinases are about a billion years apart," says Dr. Notredame. "They duplicated in the common ancestor of the common ancestor of our common ancestor." 

This vast timescale involved makes it incredibly difficult to build accurate gene trees that show how all these kinases are related. "Yet, as imperfect as it may be, the kinase evolutionary tree is widely used to understand how it interacts with other drugs. Improving this tree, or improving trees of other important protein families, would be an important advance for human health,” adds Dr. Notredame. 

The potential applications of the work go beyond cancer. Using the approach to create more accurate evolutionary trees could also improve our understanding of how diseases evolve more generally, aiding in the development of vaccines and treatments. They can also help shed light on the origins of complex traits, guide the discovery of new enzymes for biotechnology, and even help trace the spread of species in response to climate change. 

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Journal

Nature Communications

DOI

10.1038/s41467-024-55264-0 

Method of Research

Experimental study

Article Publication Date

15-Jan-2025

 

Bioinspired weather-responsive adaptive shading

Universitaet Stuttgart

 

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The adaptive, self-adjusting shading system “Solar Gate” supports the climate control of buildings.

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Credit: ©ICD/IntCDC Universität Stuttgart

Pine cones as a model: Researchers at the universities of Stuttgart and Freiburg have developed a new, energy-autonomous facade system that adapts passively to the weather. The journal Nature Communications has published the research results.

"Most attempts at weather responsiveness in architectural facades rely heavily on elaborate technical devices. Our research explores how we can harness the responsiveness of the material itself through advanced computational design and additive manufacturing," says Professor Achim Menges, head of the Institute for Computational Design and Construction (ICD) and spokesperson for the Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) at the University of Stuttgart. "We are achieving a shading system that opens and closes autonomously in response to changes in the weather, without the need for operational energy or any mechatronic elements. The bio-material structure itself is the machine."

Using bioinspired design, natural materials, and widely accessible technologies, researchers at the universities of Stuttgart and Freiburg have developed the "Solar Gate" facade system – the first weather-responsive, adaptive shading system that operates without electrical energy. The scientists used the movement mechanisms of pine cones as a model for the "Solar Gate", which opens and closes in response to changes in humidity and temperature without consuming any metabolic energy. The team succeeded in replicating the anisotropic (direction-dependent) structure of cellulose in plant tissues using standard 3D-printers. The research results have been published in the journal Nature Communications.

Biobased hygromorphic materials and bioinspired 4D-printing

Cellulose is a natural, abundant, and renewable material that swells and shrinks with variations in humidity. This property, known as hygromorphism, is frequently observed in nature, for example in the opening and closing of the scales of pine cones or the inflorescences of the silver thistle. The research team leveraged this hygromorphic property by custom-engineering biobased cellulose fibers and 4D-printing them into a bilayered structure inspired by the scales of the pine cone.

Material systems produced by this additive manufacturing technique called 4D-printing can autonomously change their shape in response to external stimuli. For the "Solar Gate," the researchers developed a computational fabrication method to control the extrusion of cellulosic materials using a standard 3D-printer, making it possible to harness the self-shaping and reversible behavior of the 4D-printed material system. In high humidity, the cellulosic materials absorb moisture and expand, causing the printed elements to curl and open. Conversely, in low humidity, the cellulosic materials release moisture and contract, causing the printed elements to flatten and close.

“Inspired by the hygroscopic movements of the scales of pine cones and the bracts of silver thistle, Solar Gate has succeeded in translating not only the high functionality and robustness of biological models into a bioinspired shading system but also the aesthetics of plant movements. This can be seen as the ‘royal road of bionics’, as everything that fascinates us about the biological concept generators has also been realized in the bio-inspired architectural product,” says Professor Thomas Speck, head of the Plant Biomechanics Group Freiburg and spokesperson for the Cluster of Excellence Living, Adaptive and Energy-autonomous Materials Systems (livMatS) at the University of Freiburg.

Architectural integration of self-shaping elements

The research team tested the functionality and durability of the bioinspired adaptive shading system under real weather conditions for over a year. The "Solar Gate" was then installed on the livMatS Biomimetic Shell, a building demonstrator of the Cluster of Excellence IntCDC and the Cluster of Excellence livMatS, which serves as a research building of the University of Freiburg. The shading system has been installed on its south-facing skylight, which assists in the indoor climate regulation of the building. During winter, the 4D-printed shading elements open to allow sunlight in for natural heating. In summer, they close to minimize solar radiation. Powered solely by daily and seasonal weather cycles, this adaptive process operates without any electrical energy supply.

The "Solar Gate" thus represents an energy-autonomous and resource-efficient alternative to conventional shading systems. As buildings account for a significant proportion of global carbon emissions due to the typically high energy needed to maintain indoor comfort, reducing the energy required for heating, cooling and ventilation is of high importance. The "Solar Gate" highlights the potential of accessible, cost-effective technologies such as additive manufacturing and shows how cellulose, as an abundant, renewable material, can contribute to sustainable architectural solutions.

Project partners
The “Solar Gate” has been collaboratively developed by the Institute of Computational Design and Construction (ICD), Institute for Plastics Technology (IKT), and the Cluster of Excellence Integrative Computational Design and Construction for Architecture (IntCDC) at the University of Stuttgart, together with the Plant Biomechanics Group, Department for Microsystems Engineering (IMTEK), and the Cluster of Excellence Living, Adaptive and Energy-autonomous Materials Systems (livMatS) at the University of Freiburg.

Publication
Cheng, T., Tahouni, Y., Sahin, E.S., Ulrich, K., Lajewski, S., Bonten, C., Wood, D., Rühe, J., Speck, T., Menges, A.: 2024, Weather-responsive adaptive shading through biobased and bioinspired hygromorphic 4D-printing. Nature Communications, vol. 15, no. 1. (DOI: 10.1038/s41467-024-54808-8)

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Journal

Nature Communications

DOI

10.1038/s41467-024-54808-8 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Weather-responsive adaptive shading through biobased and bioinspired hygromorphic 4D-printing

 

From drops to data: Advancing global precipitation estimates with the LETKF algorithm

Researchers propose a new data assimilation algorithm to improve precipitation predictions worldwide

Chiba University

 

image: 

(a) The elevation (m) and examples of (b) the rain gauge observation inputs and the global precipitation estimates of (c) the National Oceanic and Atmospheric Administration Climate Prediction Center (NOAA CPC), and (d) our study.

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Credit: YUKA MUTO from Chiba University (https://doi.org/10.5194/hess-28-5401-2024)

With the increase in climate change, global precipitation estimates have become a necessity for predicting water-related disasters like floods and droughts, as well as for managing water resources. The most accurate data that can be used for these predictions are ground rain gauge observations, but it is often challenging due to limited locations and sparse rain gauge data. To solve this problem, Assistant Professor Yuka Muto from the Center for Environmental Remote Sensing, Japan, and Professor Shunji Kotsuki of the Institute for Advanced Academic Research, Center for Environmental Remote Sensing, as well as the Research Institute of Disaster Medicine of Chiba University, Japan, have created a state-of-the-art method using the Local Ensemble Transform Kalman Filter (LETKF) technique. This study was published in Volume 28, Issue 24 of Hydrology and Earth System Sciences on December 17, 2024.

 

LETKF is a sophisticated data assimilation algorithm that makes global precipitation fields more accurate and is used in meteorology, oceanography, and environmental science. It combines real-world observations with computer model simulations to provide accurate, real-time predictions of complex systems. When combined with different inputs, like sensors, satellites, and ground stations, it can provide more precise predictions, minimizing errors. In this study, Dr. Muto and Professor Kotsuki used the LETKF to enhance the ground data estimates through reanalysis. “We aimed to enhance the global precipitation estimates by integrating reliable ground rain gauge observations with dynamically consistent data from reanalysis precipitation,” explains Dr. Muto when talking to us about the rationale behind this study. Adding further, she says, “We observed that the LETKF algorithm not only improves the accuracy of the precipitation estimates, but it also offers computational efficiency, making it a reliable solution for large-scale applications.” 

 

To begin with, the team required two sets of inputs: the actual rain gauge observation data and the reanalysis data. For this, they utilized rain gauge observations acquired from the National Oceanic and Atmospheric Administration Climate Prediction Center (NOAA CPC). They further incorporated the reanalysis precipitation data from the European Centre for Medium-Range Weather Forecasts (ERA5), which is a fifth-generation atmospheric reanalysis dataset produced by the ERA5 using satellite inputs and numerical weather prediction models. By using a 20-year climatological dataset from the ERA5 data (for 10 years before and 10 years after a given date), the LETKF algorithm constructed a “first guess” for the precipitation field and its error covariance. Further, the rain gauge observations from NOAA CPC were integrated into these first-guess ERA5-based precipitation fields by using the LETKF. The model enabled precise interpolation, even for regions that have sparse observational coverage.

 

Explaining the efficiency of this method, Professor Kotsuki adds, “Our estimates showed better agreement with independent rain gauge observations and were more reliable even in mountainous or rain-gauge-sparse regions when compared to the existing NOAA CPC product.” The model showed significant improvements in capturing the precipitation patterns in areas including the Himalayas, the Andes, and the central region of Africa. This reliability could hold a high potential in addressing natural disasters and resource allocations.

The proposed methodology is more reliable than conventional techniques due to its ability to construct a physically consistent first-guess estimate by using reanalysis data. In this, the model preserves the critical variations in precipitation patterns while reducing the smoothing effects that are often observed in existing models. This dynamic consistency is especially beneficial for complex terrains, like mountains, where conventional methods struggle.

Reflecting on the long-term implications of the study, Dr. Muto adds, “We believe that accurate precipitation estimates can transform how we prepare for and respond to disasters. By reducing uncertainty, we can mitigate economic losses, support sustainable water management, and prevent the stagnation of economic activities caused by extreme weather events.”

In summary, this study holds the potential to drive international collaborations and also innovations in climate science to ensure that global water resources are managed well to meet the challenges of the changing climate.

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Journal

Hydrology and Earth System Sciences

DOI

10.5194/hess-28-5401-2024 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Estimating global precipitation fields by interpolating rain gauge observations using the local ensemble transform Kalman filter and reanalysis precipitation