Gerbrand Koren

• Doctor of Philosophy
• Professor (Assistant) at Utrecht University

This paper reviews the current state of high‐resolution remotely sensed soil moisture (SM) and evapotranspiration (ET) products and modeling, and the coupling relationship between SM and ET. SM downscaling approaches for satellite passive microwave products leverage advances in artificial intelligence and high‐resolution remote sensing using visibl...

Chemical reanalysis products have been produced by integrating various satellite observational data to provide comprehensive information on atmospheric composition. Five global chemical reanalysis datasets were used to evaluate the relative impacts of assimilating satellite ozone and its precursor measurements on surface and free-tropospheric ozone...

Over the past few decades, ozone risk assessments for vegetation have been developed based on stomatal O3 flux since this metric is more biologically meaningful than the traditional concentration-based approaches. However, uncertainty remains in the ability to simulate stomatal O3 fluxes accurately. Here, we investigate stomatal O3 fluxes simulated...

Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a poor representation of such coupling processes; drifts in a model's circulation related to model biases, resol...

A new proliferation of optical instruments that can be attached to towers over or within ecosystems, or ‘proximal’ remote sensing, enables a comprehensive characterization of terrestrial ecosystem structure, function, and fluxes of energy, water, and carbon. Proximal remote sensing can bridge the gap between individual plants, site‐level eddy‐covar...

In 2023, the biogeographic Amazon experienced temperature anomalies of 1.5°C above the 1991-2020 average from September to November. These conditions were driven by high sea surface temperature in the Atlantic and Pacific oceans, together with reduced moisture advection from the Atlantic, causing large vapor pressure and water deficits in the secon...

This literature review synthesizes the role of soil moisture in regulating carbon sequestration and greenhouse gas emissions (CS-GHG). Soil moisture directly affects photosynthesis, respiration, microbial activity, and soil organic matter dynamics, with optimal levels enhancing carbon storage while extremes, such as drought and flooding, disrupt th...

We evaluate regional and interannual variations in tropospheric ozone in five chemical reanalyses, consisting of the Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA), the second-generation Tropospheric Chemistry Reanalysis (TCR-2), the GEOS-Chem reanalysis, the Community Multiscale Air Quality (CMAQ) regional analysis, and the Chinese a...

Machine learning (ML) is transforming atmospheric chemistry, offering powerful tools to address challenges in tropospheric ozone research, a critical area for climate resilience and public health. As in adjacent fields, ML approaches complement existing research by learning patterns from ever-increasing volumes of atmospheric and environmental data...

The 2022 Hunga volcanic eruption injected a significant amount of water vapor and a moderate amount of sulfur dioxide into the stratosphere causing observable responses in the climate system. We have developed a model-observation comparison project to investigate the evolution of volcanic water and aerosols, and their impacts on atmospheric dynamic...

High precision measurements of the triple oxygen isotope composition of CO2 (∆′17O) can be used to estimate biosphere-atmosphere exchange of CO2, the residence time of tropospheric CO2 and stratosphere-troposphere exchange. In this study, we report measurements of the ∆′17O(CO2) from air samples collected during two aircraft based programs, CARIBIC...

The ability to access physiologically driven signals, such as surface temperature, photochemical reflectance index (PRI), and sun-induced chlorophyll fluorescence (SIF), through remote sensing (RS) are exciting developments for vegetation studies. Accessing this ecophysiological information requires considering processes operating at scales from th...

Stable isotope ratios of hydrogen (δ2H) and oxygen (δ18O) are crucial for studying ecohydrological dynamics in forests. However, most studies are confined to single sites, resulting in a lack of large-scale isotope data for understanding tree water uptake. Here, we provide a first systematic isotope dataset of soil and stem xylem water collected du...

Owing to its specialised methodology, palaeoecology is often regarded as a separate field from ecology, even though it is essential for understanding long-term ecological processes that have shaped the ecosystems that ecologists study and manage. Despite advances in ecological modelling, sample dating, and proxy-based reconstructions facilitating d...

The field of extreme event attribution (EEA) has rapidly developed over the last two decades. Various methods have been developed and implemented, physical modelling capabilities have generally improved, the field of impact attribution has emerged, and assessments serve as a popular communication tool for conveying how climate change is influencing...

17O) measurements of atmospheric CO2 have the potential to be a tracer for gross primary production and stratosphere–troposphere mixing. A positive Δ(17O) originates from intrusions of stratospheric CO2, whereas values close to -0.21‰ result from the equilibration of CO2 and water, which predominantly happens inside plants. The stratospheric source...

Although Artificial Intelligence (AI) projects are common and desired by many institutions and research teams, there are still relatively few success stories of AI in practical use for the Earth science community. Many AI practitioners in Earth science are trapped in the prototyping stage and their results have not yet been adopted by users. Many s...

The negative effects of tropospheric ozone (O3) on vegetation can lead to reduced photosynthesis, accelerated leaf senescence, and other negative outcomes which affect crop yields and biodiversity. This study presents a flux-based assessment of the global impact of O3 on bread wheat (Triticum aestivum) for the 21st century, under various climate sc...

Open biomass burning has major impacts globally and regionally on atmospheric composition. Fire emissions include particulate matter, tropospheric ozone precursors, greenhouse gases, as well as persistent organic pollutants, mercury 55 and other metals. Fire frequency, intensity, duration, and location are changing as the climate warms, and modelli...

Chemical reanalysis products have been produced by integrating various satellite observational data to provide comprehensive information on atmospheric composition. Five global chemical reanalysis datasets were used to evaluate the relative impacts of assimilating satellite ozone and its precursor measurements on surface and free tropospheric ozone...

The field of extreme event attribution (EEA) has rapidly developed over the last two decades. Various methods have been developed and implemented, physical modelling capabilities have generally improved, the field of impact attribution has emerged, and assessments serve as a popular communication tool for conveying how climate change is influencing...

In tropical South America there has been substantial progress on atmospheric monitoring capacity, but the region still has a limited number of continental atmospheric stations relative to its large area, hindering net carbon flux estimates using atmospheric inversions. In this study, we use dry air CO2 mole fractions measured at the Amazon Tall Tow...

This article presents a case study, in which ChatGPT has been integrated into the writing assignment of a course in a Dutch university whereby the students co-wrote an essay with the AI-powered chatbot, ChatGPT 3.5. We examined 1) how the students used it, 2) their experienced challenges and benefits, 3) their view of its responsible use, and 4) th...

Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a poor representation of such coupling processes; drifts in a model’s circulation related to model biases, resol...

Determining the sources of water inside plants using its isotopic composition is a long‐standing research challenge in ecohydrology. A better understanding of water sources can help improve models and ultimately contribute to more accurate forecasts of water availability, food production, carbon sequestration or ecosystem status. Over the years, se...

Models have become a key component of scientific hypothesis testing and climate and sustainability planning, as enabled by increased data availability and computing power. As a result, understanding how the perceived ‘complexity’ of a model corresponds to its accuracy and predictive power has become a prevalent research topic. However, a wide varie...

Reliable and robust monitoring tools are crucial to assess the effectiveness of land mitigation techniques (LMTs) in enhancing carbon uptake, enabling informed decision making by policymakers. This study, addressing one of the scientific goals of the EU Horizon 2020 Land Use Based Mitigation for Resilient Climate Pathways (LANDMARC) project, examin...

Language matters in shaping perceptions and guiding behaviour. The term stakeholder is widely used, yet little attention is paid to the possibility that its use may inadvertently perpetuate colonial narratives and reinforce systemic inequities. In this article, we critically examine the limitations of the stakeholder concept and its ambiguity, norm...

Vegetation productivity is a critical indicator of global ecosystem health and is impacted by human activities and climate change. A wide range of optical sensing platforms, from ground-based to airborne and satellite, provide spatially continuous information on terrestrial vegetation status and functioning. As optical Earth observation (EO) data a...

17O )measurements of atmospheric CO2 have the potential to be a tracer for gross primary production and stratosphere-troposphere mixing. A positive Δ(17O) originates from intrusions of stratospheric CO2, whereas values close to zero result from equilibration of CO2 and water, predominantly happening inside plants. The stratospheric source of CO2 ca...

Since 2019, Central South America (CSA) has been reeling under drought conditions, with the last 4 months of 2022 receiving only 44% of the average total precipitation. Simultaneously to the drought, a series of record-breaking heat waves has affected the region. The rainfall deficit during October-November-December (OND) is highly correlated with...

Due to a specialised methodology, palaeoecology is often regarded as a separate field from ecology even though it is essential to understand long-term ecological processes that have shaped ecosystems that ecologists study and manage. Even though advances in ecological modelling, sample dating, and proxy-based reconstructions have enabled direct com...

This paper summarizes the open community conventions developed by the Ecological Forecasting Initiative (EFI) for the common formatting and archiving of ecological forecasts and the metadata associated with these forecasts. Such open standards are intended to promote interoperability and facilitate forecast communication, distribution, validation,...

The year 2022 saw record breaking temperatures in Europe during both summer and fall. Similar to the recent 2018 drought, close to 30% (3.0 million km²) of the European continent was under severe summer drought. In 2022, the drought was located in central and southeastern Europe, contrasting the Northern-centered 2018 drought. We show, using multip...

Current and upcoming Sun-Induced chlorophyll Fluorescence (SIF) satellite products (e.g., GOME, TROPOMI, OCO, FLEX) have medium-to-coarse spatial resolutions (i.e., 0.3–80 km) and integrate radiances from different sources into a single ground surface unit (i.e., pixel). However, intrapixel heterogeneity, i.e., different soil and vegetation fractio...

Models that simulate water flow and quality, particularly related to nitrate ions, are commonly used on a catchment-scale. However, tracking nitrate ions is a challenging task due to the intricate processes that affect them, such as phase exchanges, transformations, and interactions with various environmental media. In general, models capable of ca...

Reliable and robust monitoring tools are crucial to assess the effectiveness of land mitigation techniques (LMTs) in enhancing carbon uptake, enabling informed decision-making by policymakers. This study, addressing one of the scientific goals of the EU H2020 LANDMARC project, examines the feasibility of using satellite solar-induced fluorescence (...

Crop phenology data offer crucial information for crop yield estimation, agricultural management, and assessment of agroecosystems. Such information becomes more important in the context of increasing year-to-year climatic variability. The dataset provides in-situ crop phenology data (first leaves emergence and harvest date) of major European crops...

A large area including the central-northern part of Argentina, southern Bolivia, central Chile, and most of Paraguay and Uruguay, experienced record-breaking temperatures during two consecutive heatwaves in late November and early December 2022. During the second heatwave, nine locations in northern Argentina registered their highest maximum temper...

How to enhance paleoscientific research, collaboration and application in the Global South? The INQUA-funded multiyear pSESYNTH project envisions the first multi-disciplinary Holocene paleo database through a collaborative vision for past human–environmental systems in the Global South, and their future sustainability.

The aim of this guidance note is to provide recommendations on best statistical practices and to ensure consistent communication of statistical analysis and associated uncertainty across TOAR publications. The scope includes approaches for reporting trends, a discussion of strengths and weaknesses of commonly used techniques, and calibrated languag...

The year 2022 saw record breaking temperatures in Europe during both summer and fall. Close to 30% of the European continent was under severe summer drought with a similarly large area affected (3.0 million km ² ) as during the recent 2018 drought, but now located in central and southeastern Europe. Multiple sets of observations suggest a reduction...

The southeastern Amazon has recently been shown to be a net carbon source, which is partly caused by drying conditions. Drying depends on a number of factors, one of which is the land cover at the locations where the moisture has originated as evaporation. Here we assess for the first time the origins of the moisture that precipitates in the Amazon...

In July 2021, parts of Germany and Belgium were hit by severe floods. In ‘The central role of forests in the 2021 European floods’, published in Environmental Research Letters (2022 Environ. Res. Lett. 17 064053), Insua-Costa et al reported that ‘moisture from North American forests was a more important source [of the rainfall contributing to the e...

Mesophyll conductance to CO2 from the intercellular airspace to the CO2-H2O exchange site has been estimated using δ18O measurements (gm18). However, the gm18 estimates are affected by the uncertainties in the δ18O of leaf water where CO2-H2O exchange takes place and the degree of equilibration between CO2 and H2O. We show that measurements of Δ17O...

As a direct consequence of extreme monsoon rainfall throughout the summer 2022 season Pakistan experienced the worst flooding in its history. We employ a probabilistic event attribution methodology as well as a detailed assessment of the dynamics to understand the role of climate change in this event. Many of the available state-of-the-art climate...

As a direct consequence of extreme monsoon rainfall throughout the summer 2022 season Pakistan experienced the worst flooding in its history. We employ a probabilistic event attribution methodology as well as a detailed assessment of the dynamics to understand the role of climate change in this event. Many of the available state-of-the-art climate...

We present the CarbonTracker Europe High-Resolution (CTE-HR) system that estimates carbon dioxide (CO2) exchange over Europe at high resolution (0.1 × 0.2∘) and in near real time (about 2 months' latency). It includes a dynamic anthropogenic emission model, which uses easily available statistics on economic activity, energy use, and weather to gene...

Main findings • The flooding occurred as a consequence of above average rainfall throughout the 2022 rainy season exacerbated by shorter spikes of very heavy rain leading to flash floods as well as riverine floods. We therefore consider seasonal average rainfall over Lake Chad and 7-day maximum rainfall along the lower Niger Basin as the basis for...

Despite the consensus on the overall downward trend in Amazon forest loss in the previous decade, estimates of yearly carbon emissions from deforestation still vary widely. Estimated carbon emissions are currently often based on data from local logging activity reports, changes in remotely sensed biomass, and remote detection of fire hotspots and b...

Main findings: A large part of the population of Central Sahel strongly depends on the annual rains and is thus chronically vulnerable to deviations from a normal season (e.g., delay in the onset of the rainy season, dry period within the rainy season, early end, etc); Rainfall during the wet season (June to September) in Central Sahel is highly va...

Presenting the "Spatial Scaling Challenge" (SSC) launched by the Cost Action CA17143 SENSECO - WG1 Scaling Gap. This is an open exercise aimed at defining the best scaling practices and knowledge gaps from the community experience. Participants are asked to retrieve Cab, LAI, Vcmax, and NPQ from simulated field and airborne imagery (R, SIF and LST)...

Ecological forecasting provides a powerful set of methods for predicting short‐ and long‐term change in living systems. Forecasts are now widely produced, enabling proactive management for many applied ecological problems. However, despite numerous calls for an increased emphasis on prediction in ecology, the potential for forecasting to accelerate...

Quantum yield of fluorescence (φF) is key to interpret remote measurements of sun-induced fluorescence (SIF), and whether the SIF signal is governed by photochemical quenching (PQ) or non-photochemical quenching (NPQ). Disentangling PQ from NPQ allows using SIF estimates in various applications in aquatic optics. However, obtaining φF is challengin...

Plain Language Summary Climate science research can be described by three key foundational activities: developing scientific theories and hypotheses, testing hypotheses using data and theory to generate scientific outcomes, and finally communication of scientific outcomes to inform climate actions, that is, adaptation and mitigation. The progress o...

We present the CarbonTracker Europe High-Resolution system that estimates carbon dioxide (CO2) exchange over Europe at high-resolution (0.1 x 0.2°) and in near real-time (about 2 months latency). It includes a dynamic fossil fuel emission model, which uses easily available statistics on economic activity, energy-use, and weather to generate fossil...

Despite consensus on the overall downward trend in Amazon forest loss in the previous decade, estimates of yearly carbon emissions from deforestation still vary widely. Estimated carbon emissions are currently often based on data from local logging activity reports, changes in remotely sensed biomass as well as remote detection of fire hotspots, an...

This article is composed of two independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1029/2021eo153180) in Global Environmental Change and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (Section...

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles in the American Geophysical Union Biogeosciences section, and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (a) Global collaboration, technology tra...

This collaborative article discusses the opportunities and challenges of adopting integrated, coordinated, open, and networked (ICON) principles in atmospheric sciences. From the global nature of the atmosphere, there has always been a need for atmospheric science to be an ICON science. With the help of evolving technology, it is possible to go fur...

Identification of terrestrial carbon (C) sources and sinks is critical for understanding the Earth system as well as mitigating and adapting to climate change resulting from greenhouse gas emissions. Predicting whether a given location will act as a C source or sink using terrestrial ecosystem models (TEMs) is challenging due to net flux being the...

Gerbrand Koren discusses how measurements of Δ17O in CO2 can improve estimates of photosynthesis and its response to environmental conditions.

High quality atmospheric CO2 measurements are sparse in Amazonia, but can provide critical insights into the spatial and temporal variability of sources and sinks of CO2. In this study we present the first six years (2014‐2019) of continuous, high‐precision measurements of atmospheric CO2 at the Amazon Tall Tower Observatory (ATTO, 2.1◦S, 58.9◦W)....

The clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies re...

The carbon cycle of tropical terrestrial vegetation plays a vital role in the storage and exchange of atmospheric CO2. But large uncertainties surround the impacts of land-use change emissions, climate warming, the frequency of droughts, and CO2 fertilization. This culminates in poorly quantified carbon stocks and carbon fluxes even for the major e...

Identification of terrestrial carbon (C) sources and sinks is critical for understanding the earth system and to mitigate and adapt to climate change results from greenhouse gas emissions. Predicting whether a given location will act as a C source or sink using terrestrial ecosystem models (TEMs) is challenging due to net flux being the difference...

The soil moisture status near the land surface is a key determinant of vegetation productivity. The critical soil moisture content determines the transition from an energy-limited to a water-limited evapotranspiration regime. This study quantifies the critical soil moisture content by comparison of in situ soil moisture profile measurements of the...

We analysed gross primary productivity (GPP), total ecosystem respiration (TER) and the resulting net ecosystem exchange (NEE) of carbon dioxide (CO2) by the terrestrial biosphere during the summer of 2018 through observed changes across the Integrated Carbon Observation System (ICOS) network, through biosphere and inverse modelling, and through re...

The soil moisture status near the land surface is a key determinant of vegetation productivity. The critical soil moisture content determines the transition from an energy-limited to a water-limited evapotranspiration regime. This study quantifies the critical soil moisture content by comparison of in situ soil moisture profile measurements of the...

The carbon cycle of tropical terrestrial vegetation plays a vital role in the storage and exchange of atmospheric CO2. But large uncertainties surround the impacts of land-use change emissions, climate warming, the frequency of droughts, and CO2 fertilization. This culminates in poorly quantified carbon stocks and carbon fluxes even for the major e...

Understanding the processes that affect the triple oxygen isotope composition of atmospheric CO2 during gas exchange can help constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions using three plant species. The experiments were conducted at two different ligh...

Abstract. Understanding the processes that affect the triple oxygen isotope composition of atmospheric CO₂ during gas exchange can help constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions, using three plant species. The experiments were conducted...

We investigated the sub-diurnal variability of the carbon dioxide and water vapour isotopologues by modelling a representative case measured above the Harvard Forest. To this end, we developed a model that couples the local processes governed by soil and vegetation conditions to non-local atmospheric processes such as entrainment and long-range adv...

The triple oxygen isotope signature Δ¹⁷O in atmospheric CO2, also known as its “¹⁷O excess,” has been proposed as a tracer for gross primary production (the gross uptake of CO2 by vegetation through photosynthesis). We present the first global 3‐D model simulations for Δ¹⁷O in atmospheric CO2 together with a detailed model description and sensitivi...

Rationale Determination of δ¹⁷O values directly from CO2 with traditional gas source isotope ratio mass spectrometry is not possible due to isobaric interference of ¹³C¹⁶O¹⁶O on ¹²C¹⁷O¹⁶O. The methods developed so far use either chemical conversion or isotope equilibration to determine the δ¹⁷O value of CO2. In addition, δ¹³C measurements require c...

p>The triple oxygen isotope signature Δ¹⁷O in atmospheric CO₂, also known as its “¹⁷O excess,” has been proposed as a tracer for gross primary production (the gross uptake of CO₂ by vegetation through photosynthesis). We present the first global 3-D model simulations for Δ¹⁷O in atmospheric CO<...