Article
Meteorology & Atmospheric Sciences
Lili Lei, Yangjinxi Ge, Zhe-Min Tan, Yi Zhang, Kekuan Chu, Xin Qiu, Qifeng Qian
Summary: This study evaluates the ensemble Kalman filter (EnKF) combined with the Advanced Research Weather Research and Forecasting model (WRF) for western North Pacific typhoons in 2016. The results show that the WRF/EnKF system provides better ensemble forecasts and higher predictability for typhoon intensity compared to NCEP and ECMWF ensemble forecasts.
ADVANCES IN ATMOSPHERIC SCIENCES
(2022)
Article
Mechanics
Zhiwen Deng, Chuangxin He, Yingzheng Liu
Summary: This paper focuses on the optimal sensor placement strategy based on a deep neural network for turbulent flow recovery within the data assimilation framework of the ensemble Kalman filter. The results demonstrate the effectiveness and robustness of the proposed strategy, showing that RANS models with EnKF augmentation were substantially improved over their original counterparts. The study concludes that the DNN-based OSP with the selection of the five most sensitive sensors can efficiently reduce the number of sensors while achieving similar or better assimilated performance.
Article
Mathematics, Applied
Alexander Wikner, Jaideep Pathak, Brian R. Hunt, Istvan Szunyogh, Michelle Girvan, Edward Ott
Summary: This study discusses the forecasting of chaotic dynamical systems using noisy partial measurements data, with a focus on combining machine learning with knowledge-based models to improve predictions. By assimilating synthetic data and training machine learning models with partial measurements, it shows potential to correct imperfections in knowledge-based models and improve forecasting accuracy.
Article
Engineering, Marine
Shaokun Deng, Zheqi Shen, Shengli Chen, Renxi Wang
Summary: The initial ensemble has an impact on the performance of ensemble-based assimilation techniques. The differences in the initial ensemble affect the convergence rate of assimilation, but all experiments eventually reach convergence. Sea surface height and sea surface salinity are more sensitive to the initial ensemble. The white-noise perturbation scheme has the largest effect, and the influence of different initial ensembles on sea surface height is concentrated in the region of the Antarctic Circumpolar Current.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2022)
Article
Meteorology & Atmospheric Sciences
Qian Zou, Quanjia Zhong, Jiangyu Mao, Ruiqiang Ding, Deyu Lu, Jianping Li, Xuan Li
Summary: Based on a simple coupled Lorenz model, this study investigates how to assess an appropriate initial perturbation scheme for ensemble forecasting in a multiscale system. Four initial perturbation approaches are used, and the results show that the ensemble averages perform better than the control forecast after short lead times in a fast subsystem and after a relatively long period of time in a slow subsystem. Adding perturbations to fast variables or slow variables can contribute to an improvement in the forecasting skill for these variables. The nonlinear local Lyapunov vectors (NLLVs) show higher forecasting skill compared to bred vectors (BVs) or random perturbations (RPs).
ADVANCES IN ATMOSPHERIC SCIENCES
(2023)
Article
Meteorology & Atmospheric Sciences
Eviatar Bach, Michael Ghil
Summary: Data assimilation aims to optimally combine partial and noisy model forecasts and observations. Multi-model data assimilation generalizes the variational or Bayesian formulation of the Kalman filter and is proven to be the minimum variance linear unbiased estimator. In this study, a multi-model ensemble Kalman filter (MM-EnKF) based on this framework is formulated and implemented. The MM-EnKF can combine multiple model ensembles for both data assimilation and forecasting in a flow-dependent manner by providing adaptive model error estimation and matrix-valued weights for the separate models and observations. Numerical experiments using the Lorenz96 model show that the MM-EnKF results in significant error reductions compared to the best model and an unweighted multi-model ensemble in terms of probabilistic and deterministic metrics.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2023)
Article
Meteorology & Atmospheric Sciences
Yangjinxi Ge, Lili Lei, Jeffrey S. Whitaker, Zhe-Min Tan
Summary: Intermittent data assimilation methods can result in inconsistent and unbalanced analyses, but incremental analysis updates (IAU) have proven effective in combating these issues. Different implementations of IAU, with varying increment frequencies, are systematically evaluated for regional simulations, with 3DIAU generally producing smaller errors and retaining more observation information.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Oceanography
Yoshitaka Matsuzaki, Tetsunori Inoue
Summary: In this study, regional data assimilation for a coastal estuary was carried out using the ensemble Kalman filter, real observation data, and a simulation model. The method's applicability and robustness were examined, and the relationship between boundary conditions and data assimilation results of water temperature and salinity were analyzed. The study also proposed a method of creating an ensemble by perturbing three boundary conditions, and found that applying these perturbations did not result in filter divergence.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Article
Astronomy & Astrophysics
Angelica M. Castillo Tibocha, Jana de Wiljes, Yuri Y. Shprits, Nikita A. Aseev
Summary: This study applies ensemble Kalman filter for data assimilation in the radiation belts, developing two new methods and validating their accuracy. The use of split-operator technique allows inclusion of more physical processes in simulations and improves computational efficiency.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2021)
Article
Meteorology & Atmospheric Sciences
Troy Arcomano, Istvan Szunyogh, Alexander Wikner, Jaideep Pathak, Brian R. Hunt, Edward Ott
Summary: This paper describes the implementation of a combined hybrid-parallel prediction approach on a low-resolution atmospheric global circulation model. The hybrid model, which combines a physics-based numerical model with a machine learning component, produces more accurate forecasts for various atmospheric variables compared to the host model. Furthermore, the hybrid model exhibits smaller systematic errors and more realistic temporal variability in simulating the climate.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Oceanography
Neill Mackay, Andrew Watson
Summary: In the Southern Ocean south of the Polar Front, utilizing summertime observations to reconstruct wintertime pCO2surf greatly improved coverage and enhanced accuracy of flux estimates. The addition of pseudo observations initially increased outgassing, which gradually decreased over time.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2021)
Article
Meteorology & Atmospheric Sciences
Zhili Wang, Lei Lin, Yangyang Xu, Huizheng Che, Xiaoye Zhang, Hua Zhang, Wenjie Dong, Chense Wang, Ke Gui, Bing Xie
Summary: The study reveals that CMIP6 models fail to accurately capture the observed trends of aerosol optical depth over Asia, mainly due to problematic anthropogenic aerosol emissions adopted by the models. Differences in simulated regional aerosol radiative forcing and temperature responses over Asia are evident when using different emissions inventories. Additionally, some widely adopted CMIP6 pathways underestimate the recent decline in anthropogenic aerosol emissions over China.
NPJ CLIMATE AND ATMOSPHERIC SCIENCE
(2021)
Article
Engineering, Electrical & Electronic
M. A. Gonzalez-Cagigal, J. A. Rosendo-Macias, A. Gomez-Exposito
Summary: This research presents a state estimation approach using Kalman filtering to identify the phase to which single-phase customers are connected in three-phase distribution grids. The study compares different nonlinear formulations of the Kalman filter and shows that the ensemble Kalman filter provides better estimation results as the system size increases. The accuracy, robustness, and limitations of the estimator are also tested with consideration of measurement errors.
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
(2021)
Article
Meteorology & Atmospheric Sciences
Hans W. W. Chen, Fuqing Zhang, Thomas Lauvaux, Marko Scholze, Kenneth J. J. Davis, Richard B. B. Alley
Summary: This study introduces the TRACE Regional Atmosphere-Carbon Ensemble (TRACE) system, which uses an ensemble-based approach to assimilate large volumes of observations for constraining CO2 flux parameters. The system shows high accuracy and feasibility in a series of simulation experiments, making it a promising method for advancing CO2 inversion techniques.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2023)
Article
Environmental Sciences
Lei Kong, Xiao Tang, Jiang Zhu, Zifa Wang, Yele Sun, Pingqing Fu, Meng Gao, Huangjian Wu, Miaomiao Lu, Qian Wu, Shuyuan Huang, Wenxuan Sui, Jie Li, Xiaole Pan, Lin Wu, Hajime Akimoto, Gregory R. Carmichael
Summary: The lockdown measures during the COVID-19 pandemic in China had limited impact on air pollution, and traffic control alone cannot effectively address O-3 and PM2.5 pollution.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2023)
Article
Geosciences, Multidisciplinary
Elisabeth Tschumi, Sebastian Lienert, Karin van Der Wiel, Fortunat Joos, Jakob Zscheischler
Summary: This study presents six climate scenarios with varying drought-heat signatures to investigate their impacts on vegetation and the terrestrial carbon cycle. These scenarios show moderate differences in global mean climate without any long-term trends. The research findings may be useful for understanding the differential impacts of droughts and heatwaves in various other areas.
GEOSCIENCE DATA JOURNAL
(2022)
Article
Environmental Sciences
Tobias Frischknecht, Altug Ekici, Fortunat Joos
Summary: Large amounts of C-14 isotopes were released into the atmosphere during atomic bomb tests in the 1950s and 1960s, affecting the carbon cycle. Land component simulations showed a mismatch with observed C-14 uptake, suggesting biases in forest productivity or carbon allocation. Ocean component simulations matched observations, but indicated slow deep ocean ventilation, causing biases in biogeochemical tracers and global warming projections. This study highlights the importance of C-14 observations for improving representations of carbon fluxes and transport timescales in Earth system models.
GLOBAL BIOGEOCHEMICAL CYCLES
(2022)
Article
Environmental Sciences
Ashley Dinauer, Charlotte Laufkoetter, Scott C. Doney, Fortunat Joos
Summary: A new and cost-efficient model is proposed in this paper to simulate the penetration of sinking particulate organic carbon (POC) into the ocean interior. The model considers various factors such as particle size, density, dissolved oxygen, and seawater temperature, to explicitly represent the gravitational settling and removal/transformation processes. The model shows good agreement with observed POC flux attenuation in the North Atlantic and North Pacific, and reveals that high latitudes exhibit higher transfer efficiencies compared to low latitudes due to the abundance of large-sized, rapidly sinking particles and slower rate of remineralization.
GLOBAL BIOGEOCHEMICAL CYCLES
(2022)
Article
Environmental Sciences
Jens Terhaar, Thomas L. Froelicher, Fortunat Joos
Summary: Future ocean acidification depends on continuous ocean uptake of CO2, which is influenced by climate policies. Traditional climate models have low uncertainties in projected acidification but high uncertainties in global warming. Converging climate simulations to given temperature levels reveals that uncertainties in acidification are much larger than reported, and are dominated by the reduction of non-CO2 greenhouse gases and TCRE.
ENVIRONMENTAL RESEARCH LETTERS
(2023)
Article
Environmental Sciences
Jens Terhaar, Thomas L. Frolicher, Mathias T. Aschwanden, Pierre Friedlingstein, Fortunat Joos
Summary: This study proposes an adaptive approach based on past observations to quantify global emissions reductions and achieve temperature targets, demonstrating its robustness against uncertainties.
NATURE CLIMATE CHANGE
(2022)
Article
Environmental Sciences
Shangrong Lin, Zhongmin Hu, Yingping Wang, Xiuzhi Chen, Bin He, Zhaoliang Song, Shaobo Sun, Chaoyang Wu, Yi Zheng, Xiaosheng Xia, Liyang Liu, Jing Tang, Qing Sun, Fortunat Joos, Wenping Yuan
Summary: This study found that current TEMs substantially underestimate the interannual variability (IAV) of GPP, especially in nonforest ecosystem types. One possible cause is that the models underestimate the changes of canopy physiology responding to climate change. The differences between the simulated and observed interannual variations of leaf area index (LAI) also contribute to the underestimation of IAV.
GLOBAL BIOGEOCHEMICAL CYCLES
(2023)
Article
Biodiversity Conservation
Kuang-Yu Chang, William J. Riley, Nathan Collier, Gavin McNicol, Etienne Fluet-Chouinard, Sara H. Knox, Kyle B. Delwiche, Robert B. Jackson, Benjamin Poulter, Marielle Saunois, Naveen Chandra, Nicola Gedney, Misa Ishizawa, Akihiko Ito, Fortunat Joos, Thomas Kleinen, Federico Maggi, Joe McNorton, Joe R. Melton, Paul Miller, Yosuke Niwa, Chiara Pasut, Prabir K. Patra, Changhui Peng, Sushi Peng, Arjo Segers, Hanqin Tian, Aki Tsuruta, Yuanzhi Yao, Yi Yin, Wenxin Zhang, Zhen Zhang, Qing Zhu, Qiuan Zhu, Qianlai Zhuang
Summary: The recent rise in atmospheric methane concentrations has negative effects on climate change and mitigation efforts. Estimates of global wetland methane emissions vary widely among different approaches, but using better-performing models can reduce the spread of these estimates. However, discrepancies in the estimates increase when using the top 20% models. It is important to expand benchmark sites to account for environmental variability and encourage the development of wetland methane models to focus on site-specific and ecosystem-specific variabilities.
GLOBAL CHANGE BIOLOGY
(2023)
Article
Geosciences, Multidisciplinary
Frerk Poppelmeier, Aurich Jeltsch-Thommes, Joerg Lippold, Fortunat Joos, Thomas F. Stocker
Summary: According to a reassessment of proxy records and model simulations, the Atlantic meridional overturning circulation was shallow and weak during the Last Glacial Maximum, and it took time for water masses to adjust to circulation shifts during the Last Deglaciation. However, uncertainties still exist in understanding the Atlantic circulation and its response to external perturbations.
Article
Environmental Sciences
Elisabeth Tschumi, Sebastian Lienert, Ana Bastos, Philippe Ciais, Konstantin Gregor, Fortunat Joos, Juergen Knauer, Philip Papastefanou, Anja Rammig, Karin van der Wiel, Karina Williams, Yidi Xu, Soenke Zaehle, Jakob Zscheischler
Summary: The frequency of heatwaves and droughts vary greatly in different climate models. Understanding the response of vegetation models to different climate conditions during these extreme events is important. Previous work has developed six different climate scenarios to study the effects of single and compound extremes on vegetation and carbon dynamics. Using these scenarios, six global vegetation models were tested, and the results showed significant variation in their responses. The findings highlight the need to improve the representation of compound events in climate models to reduce uncertainties in future carbon cycle projections.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2023)
Article
Geosciences, Multidisciplinary
A. Jeltsch-Thoemmes, F. Joos
Summary: The causes of CO2 variations over the past million years are still not well understood. Imbalances between rock weathering input and the removal of elements from the atmosphere-ocean-biosphere system likely play a role in these changes. Our study shows that carbon-climate responses reach equilibrium within tens of thousands of years, but several hundred thousand years are required for carbon isotope ratio equilibrium. Changes in dissolved CO2 affect carbon isotope fractionation and burial flux, highlighting the significant impact of weathering-burial imbalances.
PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
(2023)
Article
Geosciences, Multidisciplinary
Fortunat Joos, Angelique Hameau, Thomas L. Frolicher, David B. Stephenson
Summary: This study analyzes historical climate simulations to determine the cause of the positive trend in the seasonal amplitude of surface ocean pCO(2) and finds evidence of anthropogenic forcing. The results indicate that the trends in mid-latitudes are attributable to human activities, while no trends are detected in the tropics and the Southern Ocean.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
A. Ito, T. Li, Z. Qin, J. R. Melton, H. Tian, T. Kleinen, W. Zhang, Z. Zhang, F. Joos, P. Ciais, P. O. Hopcroft, D. J. Beerling, X. Liu, Q. Zhuang, Q. Zhu, C. Peng, K. -Y Chang, E. Fluet-Chouinard, G. McNicol, P. Patra, B. Poulter, S. Sitch, W. Riley
Summary: The cold-season methane emissions in wetland models are poorly constrained. We evaluated 16 models participating in the Global Carbon Project model intercomparison and found that they underestimated the cold-season methane emissions, especially during the months with subzero air temperatures. However, due to winter warming, the contribution of cold-season emissions is expected to increase. There is a need for model refinement, as the variability among models suggests different parameterizations of processes.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Geosciences, Multidisciplinary
Sian Kou-Giesbrecht, Vivek K. Arora, Christian Seiler, Almut Arneth, Stefanie Falk, Atul K. Jain, Fortunat Joos, Daniel Kennedy, Jurgen Knauer, Stephen Sitch, Michael O'Sullivan, Naiqing Pan, Qing Sun, Hanqin Tian, Nicolas Vuichard, Sonke Zaehle
Summary: Terrestrial carbon (C) sequestration is limited by nitrogen (N), an empirically established constraint that could intensify under CO2 fertilization and future global change. The ability of terrestrial biosphere models to reproduce observations of nitrogen (N) cycling and its regulation of terrestrial C sequestration has been largely unexplored. Our evaluation of an ensemble of terrestrial biosphere models reveals significant variability in the simulation of N cycling, indicating that the processes regulating terrestrial C sequestration operate differently across models and are uncoupled from the simulation of C cycling. The overestimation of C storage per unit N suggests biases in projections of the future terrestrial C sink under CO2 fertilization and future global change.
EARTH SYSTEM DYNAMICS
(2023)
Article
Ecology
Jens Terhaar, Thomas L. Frolicher, Fortunat Joos
Summary: The ocean plays a significant role in slowing down global warming by absorbing CO2 emissions. However, estimates of ocean anthropogenic carbon uptake vary. In this study, the researchers found that the ocean carbon sink can be constrained by specific physical and biogeochemical parameters. By using these constraints with observations, they provided a new estimate of the global ocean anthropogenic carbon sink, which is larger than previously estimated. This constraint also reduces uncertainties in past, present, and future ocean carbon sink estimates, enhancing our understanding of the global carbon cycle and guiding climate and ocean policies.
Article
Ecology
Elisabeth Tschumi, Sebastian Lienert, Karin van der Wiel, Fortunat Joos, Jakob Zscheischler
Summary: This study examines the effects of different drought-heat climate scenarios on vegetation distribution and land carbon dynamics. The findings show that climate without extreme events increases tree coverage and ecosystem productivity, while more heatwaves lead to increased tree coverage in higher latitudes. Drought and particularly hot-dry scenarios reduce tree coverage and ecosystem productivity. The study highlights the importance of correctly simulating compound extremes for future impact assessment.
