Article
Environmental Sciences
Jiongming Pang, Xuemei Wang
Summary: Accurate estimation of background error covariance (BEC) is essential for successful data assimilation (DA), especially in aerosol three-dimensional variational (3DVAR) DA. A modified module was developed to adjust the BEC of individual aerosol species, showing that horizontal length scales play a more crucial role than standard deviations in the impacts of BEC on PM(10 )24-hour forecast. The study highlights the importance of modifying aerosol BEC in 3DVAR for better aerosol forecast and analysis, especially during polluted periods.
SCIENCE OF THE TOTAL ENVIRONMENT
(2021)
Article
Meteorology & Atmospheric Sciences
Anthony T. Weaver, Marcin Chrust, Benjamin Menetrier, Andrea Piacentini
Summary: Modeling and cycling the background-error covariance matrix is an active area of research in data assimilation, especially when using filters to model background-error correlations. Updating the normalization factors on each assimilation cycle can be costly, but methods like randomization can provide accurate estimates. By approximating the normalization matrix as a separable product of two matrices, one for the horizontal and one for the vertical components, accurate estimates can be obtained with a large random sample.
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
(2021)
Article
Environmental Sciences
Hao Hu, Fuzhong Weng
Summary: The study shows that microwave spaceborne passive sounding instruments can effectively reduce retrieval errors for temperature and humidity in tropical cyclones. Using ARMS as an observation operator achieves higher retrieval accuracy due to comprehensive handling of scattering from various hydrometeors under cloudy conditions.
Article
Meteorology & Atmospheric Sciences
Tao Sun, Yaodeng Chen, Deming Meng, Haiqin Chen
Summary: This study proposed a Quasi-Softmax transform method to transform hydrometeors into more Gaussian variables, meeting the Gaussian unbiased assumptions of data assimilation systems. Results show that the Quasi-Softmax method, compared to other methods, not only retains the vertical distribution of hydrometeor mixing ratios but also approaches a Gaussian distribution.
ADVANCES IN ATMOSPHERIC SCIENCES
(2021)
Article
Environmental Sciences
Jian Zhu, Shanshan Wang, Xu Dao, Duanyang Liu, Jie Wang, Sanbao Zhang, Ruibin Xue, Guigang Tang, Bin Zhou
Summary: Ground-based MAX-DOAS instruments were used to observe aerosol in urban and suburban areas of Shanghai, showing time delay and altitude distribution differences between different sites, possibly due to varying influences of aerosol transport and boundary layer dynamics. There was mutual aerosol transport between urban and suburban areas, affecting aerosol optical properties in these regions.
SCIENCE OF THE TOTAL ENVIRONMENT
(2022)
Article
Agronomy
Yibo Sun, Bilige Sude, Bing Geng, Junyong Ma, Xingwen Lin, Zhenzhen Hao, Wenjie Jing, Qiting Chen, Zhanjun Quan
Summary: The study utilized UAV-based eddy-covariance system to observe the regional evaporative fraction (EF) over Yancheng coastal wetland, demonstrating reliable EF observations, and revealed the EF of different land cover classes through data disaggregation.
AGRICULTURAL AND FOREST METEOROLOGY
(2021)
Article
Environmental Sciences
Istvan Major, Mihaly Molnar, Istvan Futo, Virag Gergely, Sandor Ban, Attila Machon, Imre Salma, Tamas Varga
Summary: This study aimed to estimate and refine the potential sources of carbon in atmospheric PM2.5 aerosol at three sampling sites in Hungary. The results showed that carbon concentrations varied significantly between seasons, with modern carbon sources contributing significantly to total carbon throughout the year.
Article
Meteorology & Atmospheric Sciences
Yaodeng Chen, Kuiming Fang, Min Chen, Hongli Wang
Summary: This study estimated diurnal variation BECs using three month forecast error samples from RMAPS-ST, and conducted single observation tests and one-month cycling experiments. The results showed that diurnal variation BECs could improve the assimilation and forecasting performance of RMAPS-ST.
ATMOSPHERIC RESEARCH
(2021)
Article
Energy & Fuels
Zhonghua Yun, Wenhu Qin, Weipeng Shi
Summary: A method to improve the estimation performance of State of Charge (SoC) is proposed in this paper by introducing the concept of Variable Bayesian iteration into nonlinear filters, resulting in the Variable Bayesian unscented Kalman filter and the Variable Bayesian square-root cubature filter. Experimental results show that this method can effectively improve the estimation performance of SoC.
JOURNAL OF ENERGY STORAGE
(2022)
Article
Computer Science, Interdisciplinary Applications
Sibo Cheng, Didier Lucor, Jean-Philippe Argaud
Summary: Accurate estimation of error covariances is crucial for efficient observation compression approaches in data assimilation. A new combination of covariance tuning algorithm and existing PCA-type data compression approaches is proposed to reduce computational cost in real-time updating. The method is validated on a shallow water twin experiment and applied to a challenging industrial hydrological model.
JOURNAL OF COMPUTATIONAL SCIENCE
(2021)
Article
Multidisciplinary Sciences
Massimo Tessarotto, Claudio Cremaschini
Summary: This article considers the implications of the principles of general and manifest covariance, along with the objectivity principle, in establishing a DeDonder-Weyl-type Hamiltonian variational formulation for classical general relativity. By analyzing the Einstein-Hilbert variational principle, it is shown that only synchronous variational principles allow for the construction of fully 4-tensor Lagrangian and Hamiltonian theories of this kind. Additionally, the potential validity of an extended Hamiltonian formulation that includes the Ricci tensor as Lagrangian variables is investigated, and it is shown to occur when the classical cosmological constant is non-zero.
Article
Computer Science, Artificial Intelligence
Sibo Cheng, Mingming Qiu
Summary: In this study, a data-driven approach based on LSTM recurrent neural networks is proposed to improve the accuracy and efficiency of observation covariance specification in data assimilation for dynamical systems. This novel method does not rely on prior error distribution knowledge or assumptions, leading to significant advantages in observation covariance specification, assimilation accuracy, and computational efficiency.
NEURAL COMPUTING & APPLICATIONS
(2022)
Article
Mathematics, Applied
Remi Gribonval, Mila Nikolova
Summary: The paper discusses two major routes in addressing inverse problems in signal and image processing, Bayesian modeling and optimization problems, and explores their relations and common characteristics. It also disproves some widely spread misconceptions and generalizes results beyond Gaussian denoising.
APPLIED AND COMPUTATIONAL HARMONIC ANALYSIS
(2021)
Article
Astronomy & Astrophysics
Victoriya V. Forsythe, Irfan Azeem, Ryan Blay, Geoff Crowley, Federico Gasperini, Joe Hughes, Roman A. Makarevich, Wanli Wu
Summary: This paper evaluates the newly developed covariance model for ionospheric data assimilation technique, showing that the vertical part of the covariance model plays the most important role in improving algorithm accuracy. The new covariance model enhances the fidelity of the IDA4D algorithm, making it more suitable for regional assimilation.
Article
Meteorology & Atmospheric Sciences
Guannan Hu, Sarah L. Dance
Summary: Recent studies have shown that using spatially correlated observation error covariance information in data assimilation systems improves numerical weather prediction skill. The fast multipole method (FMM) with singular value decomposition (SVD-FMM) reduces computational complexity and accurately computes matrix-vector products in various scenarios.
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
(2021)
Article
Optics
Michael Kahnert
Article
Optics
Franz Kanngiesser, Michael Kahnert
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2018)
Article
Meteorology & Atmospheric Sciences
Michael Kahnert
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
(2018)
Article
Optics
Franz Kanngiesser, Michael Kahnert
Article
Optics
Michael Kahnert, Ronald Scheirer
Review
Optics
Michael Kahnert, Franz Kanngiesser
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2020)
Article
Optics
Michael Kahnert, Franz Kanngiesser, Emma Jarvinen, Martin Schnaiter
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
(2020)
Article
Optics
Michael Kahnert, Tom Rother
Article
Meteorology & Atmospheric Sciences
Franz Kanngiesser, Michael Kahnert
Summary: In this study, different model geometries were investigated to simulate the optical properties of marine aerosol particles. It was found that cuboidal superellipsoids provided consistent predictions with observations, while octahedral superellipsoids strongly overestimated certain optical ratios. Gaussian random surface perturbations resulted in a positive shift in the depolarization ratio, while convex polyhedra showed more random scattering behavior compared to regular cubes. Additionally, uncertainties in the refractive index had comparable effects on depolarization and extinction-to-backscatter ratios as geometric perturbations.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Optics
Michael Kahnert, Franz Kanngiesser
Summary: This study introduces a novel core-grey-shell dimer model to accurately reproduce the radiometric and polarimetric properties of black carbon aerosols. Depolarization is mainly influenced by the relative size of the monomers, while optical cross sections depend on the core-shell partitioning of black carbon. The optimal parameters for these characteristics remain stable across different particle sizes and soot volume fractions, as demonstrated through comparison with a more realistic coated aggregate model.
Article
Optics
Franz Kanngiesser, Michael Kahnert
Summary: The optical properties of marine aerosol are found to be related to water content, and simple models can reproduce these properties, with overall nonsphericity and inhomogeneity identified as key morphological parameters.
Article
Environmental Sciences
Manu Anna Thomas, Abhay Devasthale, Michael Kahnert
Summary: Marine aerosols, especially sea salt, play a significant role in the climate system, but their net impact depends on the local meteorological conditions. This study investigated the sensitivity of marine aerosol properties over the Southern Ocean to meteorological parameters using aerosol profiling and meteorological data. The results showed a clear relationship between aerosol properties and relative humidity, wind speed, and sea surface temperature. These findings can help improve the parameterizations of sea salt aerosols in climate models.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)
Article
Meteorology & Atmospheric Sciences
Robin Ekelund, Patrick Eriksson, Michael Kahnert
ATMOSPHERIC MEASUREMENT TECHNIQUES
(2020)
Article
Environmental Sciences
Paivi Haapanala, Petri Raisanen, Greg M. McFarquhar, Jussi Tiira, Andreas Macke, Michael Kahnert, John DeVore, Timo Nousiainen
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2017)
Article
Environmental Sciences
Michael Kahnert, Emma Andersson
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2017)