Article
Meteorology & Atmospheric Sciences
Jindong Jiang, Jiuxin Shi, Fei Huang
Summary: By analyzing the interannual variability of the subduction rate of Indian Ocean Subtropical Mode Water (IOSTMW), it was found that there are significant fluctuations in the southwestern part of the southern Indian Ocean subtropical circulation, with a quasi-biennial period dominating the variations. The depth of the wintertime mixed layer plays a key role in the subduction rate changes, while vertical pumping has a relatively small contribution.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Jessica S. Kenigson, M. -L. Timmermans
Summary: The Beaufort high and its accompanying anticyclonic winds play a crucial role in driving the Beaufort Gyre in the Arctic Ocean, affecting freshwater accumulation and release. The study suggests a correlation between Nordic seas cyclones and the intensity of the Beaufort high, with increased cyclone activity potentially linked to a weaker Beaufort high in a warming Arctic. The findings also highlight a regime shift towards increased cyclone activity and weakening Beaufort high over the past decades, which can have implications for Arctic dynamics and freshwater resources.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Qiang Wang, Stefano Pierini
Summary: The eddy kinetic energy (EKE) in the Kuroshio Extension (KE) region may be affected by the Kuroshio large meander (KLM) region and the North Pacific Gyre Oscillation (NPGO). Previous studies have shown that the KLM EKE only affects the EKE in the upstream area of KE, while the NPGO has a remarkable effect on the EKE in both upstream and downstream areas. Changes in KLM EKE impact the advection of eddies and the position of the Kuroshio over the Izu Ridge, causing different EKE levels. The NPGO affects KE EKE through the westward propagation of sea surface height anomalies forced by wind stress anomalies associated with the North Pacific Oscillation.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Yue Wu, David P. Stevens, Ian A. Renfrew, Xiaoming Zhai
Summary: The study investigates the ocean response to wintertime sea ice retreat in the Nordic seas using the HiGEM climate model. It finds that under global warming, the impact of ocean response differs from that caused by sea ice retreat, leading to changes in water column mixing, temperature, and salinity.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Yu Zhang, Shiyun Yu, Dillon J. Amaya, Yu Kosaka, Sarah M. Larson, Xudong Wang, Jun-Chao Yang, Malte F. Stuecker, Shang-Ping Xie, Arthur J. Miller, Xiaopei Lin
Summary: Investigating the North PMM and South PMM through a mechanically decoupled climate model simulation revealed new insights into their associated atmospheric forcing and response processes.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Seung H. Baek, Jason E. Smerdon, Benjamin I. Cook, A. Park Williams
Summary: This study examines the droughts across Washington, Oregon, and California and finds that internal atmospheric variability is the main driver, accounting for 84% of the severity. Cold phases of the Pacific Ocean play a secondary role, contributing only 16% to drought severity. Additionally, spatiotemporal analyses of precipitation and soil moisture confirm these findings.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Yuhao Cai, Xiang Han, Haikun Zhao, Philip J. Klotzbach, Liguang Wu, Graciela B. Raga, Chao Wang
Summary: This study reveals an enhanced relationship between snow depth in the eastern Tibetan Plateau in January-March and the frequency of rapidly intensifying tropical cyclones over the western North Pacific during the following peak TC season. The correlation between these two factors is significant in recent years, but was insignificant in the past. The relationship is influenced by the presence of an anomalous anticyclone and the associated wind anomalies and cooler sea surface temperatures in the subtropical eastern North Pacific.
JOURNAL OF CLIMATE
(2022)
Article
Oceanography
Paul A. Hwang
Summary: This paper presents the analysis of low-pass mean square slope (LPMSS) data obtained by space-borne microwave altimeters and reflectometers. The study reveals a power function relationship between the spectral components and the ratio between wind friction velocity and wave phase speed, suggesting that wave breaking is not only an energy sink but also a source of surface roughness generation.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2022)
Article
Meteorology & Atmospheric Sciences
Benjamin O. Johnson, Homas L. Delworth
Summary: This study uses a global climate model to investigate the role of the Gulf of California in the North American monsoon. The results show that the Gulf of California significantly impacts circulation and increases moisture fluxes, leading to higher precipitation in the monsoon region. This highlights the importance of considering the Gulf of California in climate simulations and future projections.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
T. O. N. G. Lu, Z. H. I. W. E. I. Zhu, Y. I. N. G. Yang, J. I. N. G. Ma, G. A. N. G. Huang
Summary: This study investigates the formation mechanism of the summer Western North Pacific Anomalous Anticyclone (WNPAC) that is independent of El Niño-Southern Oscillation (ENSO). It is found that besides the significant relationship with ENSO, the WNPAC index remains almost unchanged after removing the impact of ENSO, suggesting the possibility of other origins of the WNPAC. A two-step mechanism from the Atlantic to the Pacific is proposed for the formation of ENSO-independent summer WNPAC.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Ayumu Miyamoto, Hisashi Nakamura, Takafumi Miyasaka, Yu Kosaka
Summary: The study reveals that low-level clouds play a crucial role in reinforcing the summertime Mascarene high by affecting sea surface temperature, forming a tight positive feedback system with the subtropical high.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Ying Yang, Zhiwei Zhu, Xinyong Shen, Leishan Jiang, Tim Li
Summary: The study finds that sea surface temperature anomalies in both the tropical Atlantic and extratropical North Atlantic are related to the interannual variation of East Asian summer monsoon rainfall. These anomalies induce atmospheric teleconnections, leading to circulation anomalies over East Asia and subsequently modulating the monsoon rainfall. The results highlight the important role of Atlantic sea surface temperature anomalies in driving East Asian summer monsoon rainfall.
JOURNAL OF CLIMATE
(2023)
Article
Oceanography
J. S. Kenigson, M-L Timmermans
Summary: This study reveals a co-variation of freshwater content in the Nordic seas with the position of the Subarctic Front on decadal time scales. When the Subpolar Gyre is strong, it increases the contribution of subpolar relative to subtropical source water to the Atlantic inflow, and vice versa. Arctic Ocean fluxes primarily influence the hydrography of the Nordic seas via indirect means.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2021)
Article
Meteorology & Atmospheric Sciences
Chul-Su Shin, Paul A. Dirmeyer, Bohua Huang
Summary: This study presents a joint approach combining correlation and NMI to examine land and ocean surface forcing of U.S. drought at varying lead times. The proposed method can discriminate linear and nonlinear relationships more intuitively and identify non-linear relationships, particularly in cases where there are clusters and blank areas in the joint probability distributions between source and target variables. Therefore, this joint approach is a potentially powerful tool to reveal complex and heretofore undetected relationships.
JOURNAL OF CLIMATE
(2023)
Article
Oceanography
Kathryn L. Gunn, K. McMonigal, Lisa M. Beal, Shane Elipot
Summary: The global freshwater cycle is intensifying, especially in Indian Ocean rim countries. However, due to the lack of observations and model biases, it is still uncertain how the Indian Ocean's freshwater cycle has responded to climate change and its variability at different time scales. This study estimates the magnitude and variability of the Indian Ocean's freshwater budget using monthly oceanic data from 2016 to 2018. The findings suggest that the Indian Ocean has remained net evaporative since the 1980s and shows seasonal and monthly variability.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2022)
Article
Geochemistry & Geophysics
Vladimir Kudryavtsev, Shengren Fan, Biao Zhang, Bertrand Chapron, Johnny A. Johannessen, Artem Moiseev
Summary: This article proposes a Doppler velocity (DV) model based on dual co-polarized (co-pol) decomposition of radar returns from an ocean surface. The model provides a quantitative description of resonant and nonpolarized scattering and their dependence on various factors. It quantifies the contributions of different velocity components and hydrodynamic modulations to the resulting DV, using measured/empirical functions. The model is validated with simulations and empirical data.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Meteorology & Atmospheric Sciences
Maria Yurovskaya, Vladimir Kudryavtsev, Bertrand Chapron
Summary: Today's advanced operational wave models provide accurate solutions, but predicting surface waves under extreme weather conditions remains challenging. To address this issue, Kudryavtsev et al. proposed a simplified framework using self-similar functions to rapidly assess evolving wave fields under typical tropical cyclone conditions. Their methodology, based on a small number of parameters, demonstrates robustness and efficiency in estimating surface wave characteristics within the intense cyclone core region.
Article
Mathematics, Applied
Said Ouala, Steven L. Brunton, Bertrand Chapron, Ananda Pascual, Fabrice Collard, Lucile Gaultier, Ronan Fablet
Summary: The complexity of real-world geophysical systems is often due to the presence of hidden variables that affect observed measurements. This is especially true for ocean-atmosphere dynamics, where unknown internal dynamics can influence surface observations. In this study, we explore the use of physics-constrained learning and neural ordinary differential equation representations to capture the dynamics of partially-observed and highly nonlinear systems. The proposed architecture, which incorporates linear-quadratic dynamics and a global boundedness constraint, shows promising results in different geophysical case studies.
PHYSICA D-NONLINEAR PHENOMENA
(2023)
Article
Environmental Sciences
Yury Yu. Yurovsky, Vladimir N. N. Kudryavtsev, Semyon A. A. Grodsky, Bertrand Chapron
Summary: Field-tower-based observations were conducted to estimate the Doppler velocity of deep water plunging breaking waves. Computer vision methods were used to analyze about 1000 breaking wave events observed by a synchronized video camera and dual-polarization Doppler continuous-wave Ka-band radar. It was found that the Doppler velocity showed a correlation with the whitecap optical velocity, but was systematically smaller, with the difference depending on the incidence angle and azimuth. The observed Doppler velocity was consistent with previously reported data.
Article
Environmental Sciences
Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard, Bertrand Chapron
Summary: In the previous study, peculiar characteristics of ocean surface wave fields generated by two rapidly propagating extra-tropical cyclones (ETCs) in the North Atlantic were described using satellite data. This study further analyzes and interprets the spatio-temporal evolution of intense ETC-generated waves using a 2D parametric wave model. The study demonstrates that the resulting waves reach extreme values in terms of significant wave height and wavelength, with values of 18 m and 500 m, respectively. The study also examines the deformation of individual ETCs and confirms the accuracy and detail provided by the parametric-2D wave-ray model in complex wind regime changes.
Article
Environmental Sciences
Maria Yurovskaya, Vladimir Kudryavtsev, Bertrand Chapron
Summary: Polar lows (PLs) are cyclonic atmospheric systems formed in polar latitudes associated with cold outbreak events, which can generate high waves that pose danger to marine and coastal infrastructures. Statistical analysis using satellite data can be performed to investigate the probability of high waves generated by PLs in the Nordic and Barents Seas. The study considers various PL parameters and their combinations to estimate the occurrence of waves exceeding specified levels. The most affected area is the near shore zone around the Scandinavian peninsula.
Article
Oceanography
Lucia Pineau-Guillou, Jean-Marc Delouis, Bertrand Chapron
Summary: This study proposes a novel statistical method, called ECHAR, to characterize the full dynamics of storm surge events. An analysis of 20 tide gauges in the North-East Atlantic reveals two distinct components of storm surges – a slow-time background Gaussian structure and a fast-time Laplace structure. The proposed method can be applied to study tropical storm surges or in any other location in the global ocean.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2023)
Article
Computer Science, Artificial Intelligence
Said Ouala, Bertrand Chapron, Fabrice Collard, Lucile Gaultier, Ronan Fablet
Summary: Bernard O Koopman proposed an alternative view of dynamical systems based on linear operator theory, showing that finite-dimensional approximations of the operator can be useful for applications such as prediction and control. This work presents a framework for identifying these approximations through the inversion of an unknown augmented linear dynamical system. It is an extended dynamical mode decomposition using a collection of latent observables and provides new means for approximating high-dimensional nonlinear systems.
MACHINE LEARNING-SCIENCE AND TECHNOLOGY
(2023)
Article
Environmental Sciences
Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard, Bertrand Chapron
Summary: This paper presents the results of a satellite data-based investigation of wind waves generated by two North Atlantic Extra-Tropical Cyclones (ETCs). It is demonstrated that the extended-fetch concept does not apply to ETCs. Instead, the concept of extended-duration wave growth is more relevant, with satellite observations confirming the validity of duration-laws for waves generated by ETCs.
Article
Geochemistry & Geophysics
Ronan Fablet, Quentin Febvre, Bertrand Chapron
Summary: The reconstruction of sea surface dynamics from satellite observations is a challenging problem due to irregular sampling. Satellite altimetry provides observation of sea surface height (SSH) which relates to sea surface currents. However, other satellite sensors provide higher-resolution observations of sea surface tracers such as sea surface temperature (SST). In this study, we propose a trainable multimodal inversion scheme for reconstructing sea surface dynamics using multisource satellite-derived observations.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Geochemistry & Geophysics
Nicolae-Catalin Ristea, Andrei Anghel, Mihai Datcu, Bertrand Chapron
Summary: A spaceborne synthetic aperture radar (SAR) is an unique asset for geophysical applications, as it provides accurate images of the ocean surface roughness day or night, in almost all weather conditions. However, automated techniques are needed to extract physical features from the huge amount of acquired data. The subaperture decomposition (SD) algorithm is used to enhance unsupervised learning retrieval on the ocean surface, improving the precision for an unsupervised transformer autoencoder network by over 20%. Furthermore, SD boosts performance when Doppler centroid images are used as input data, leading to new unsupervised physics-guided retrieval algorithms.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Geochemistry & Geophysics
Shengren Fan, Biao Zhang, Artem Moiseev, Vladimir Kudryavtsev, Johnny A. Johannessen, Bertrand Chapron
Summary: In this study, a semiempirical dual co-polarization Doppler velocity (DPDop) model is used to accurately estimate and eliminate sea-state-induced Doppler shifts in SAR measurements. The model is validated using Sentinel-1B SAR Wave (WV) mode observations, and the results show good agreement.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Geosciences, Multidisciplinary
Yicun Zhen, Valentin Resseguier, Bertrand Chapron
Summary: Motivated by the concept of location uncertainty, a scheme is proposed to perturb the location of a state variable and it is demonstrated that these perturbations can be defined by a stochastic partial differential equation (SPDE) from the original PDE. This scheme offers broader applicability and does not rely on Lagrangian mechanics or Newton's laws of force.
NONLINEAR PROCESSES IN GEOPHYSICS
(2023)
