scholarly journals Rigid Sets and Coherent Sets in Realistic Ocean Flows

2022 ◽  
Author(s):  
Florian Feppon ◽  
Pierre Lermusiaux
Keyword(s):  
Large Scale ◽  
Ocean Current ◽  
Island Region ◽  
New Methods ◽  
Ocean Flows ◽  
Flow Map ◽  
Matrix Free ◽  
The Western Pacific ◽  
Volume Preserving ◽  
Simulated Flow

Abstract. This paper focuses on the extractions of Lagrangian Coherent Sets from realistic velocity fields obtained from ocean data and simulations, each of which can be highly resolved and non volume-preserving. We introduce two novel methods for computing two formulations of such sets. First, we propose a new “diffeomorphism-based” criterion to extract “rigid sets”, defined as sets over which the flow map acts approximately as a rigid transformation. Second, we develop a matrix-free methodology that provides a simple and efficient framework to compute “coherent sets” with operator methods. Both new methods and their resulting rigid sets and coherent sets are illustrated and compared using three numerically simulated flow examples, including a high-resolution realistic, submesoscale to large-scale dynamic ocean current field in the Palau Island region of the western Pacific Ocean.

scholarly journals Steady Large-Scale Ocean Flows in Spherical Coordinates

Oceanography ◽  
2018 ◽  
Vol 31 (3) ◽  
pp. 42-50 ◽  
Author(s):  
Adrian Constantin ◽  
◽  
Robin Johnson
Keyword(s):  
Large Scale ◽  
Spherical Coordinates ◽  
Ocean Flows

scholarly journals The Dynamic and Thermodynamic Structures Associated with a Series of Heavy Precipitation Events over China during January 2008

2010 ◽  
Vol 25 (4) ◽  
pp. 1124-1141 ◽  
Author(s):  
Xiaohui Shi ◽  
Xiangde Xu ◽  
Chungu Lu
Keyword(s):  
Large Scale ◽  
East Coast ◽  
Heavy Precipitation ◽  
Chinese History ◽  
Physical Processes ◽  
Ice Storms ◽  
Upper Level ◽  
Upper Level Jet ◽  
The Western Pacific ◽  
Precipitation Events

Abstract In the winter of 2008, China experienced once-in-50-yr (or once in 100 yr for some regions) snow and ice storms. These storms brought huge socio economical impacts upon the Chinese people and government. Although the storms had been predicted, their severity and persistence were largely underestimated. In this study, these cases were revisited and comprehensive analyses of the storms’ dynamic and thermodynamic structures were conducted. These snowstorms were also compared with U.S. east coast snowstorms. The results from this study will provide insights on how to improve forecasts for these kinds of snowstorms. The analyses demonstrated that the storms exhibited classic patterns of large-scale circulation common to these types of snowstorms. However, several physical processes were found to be unique and thought to have played crucial roles in intensifying and prolonging China’s great snowstorms of 2008. These include a subtropical high over the western Pacific, an upper-level jet stream, and temperature and moisture inversions. The combined effects of these dynamic and thermodynamic structures are responsible for the development of the storms into one of the most disastrous events in Chinese history.

New methods of metaphor identification in various types of discourse (Review of publications)

2021 ◽  
Vol 1 (6) ◽  
pp. 19-31
Author(s):  
Peter M. Shitikov ◽  
◽  
Svetlana V. Vershinina
Keyword(s):  
Corpus Linguistics ◽  
Large Scale ◽  
Historical Background ◽  
Great Success ◽  
Research Groups ◽  
Identification Procedure ◽  
New Methods ◽  
Starting Point ◽  
Different Types ◽  
Theoretical Foundations

This article presents a review of the latest procedures for identifying metaphor in multilingual texts and different types of discourse. The choice of methods for identifying and decoding metaphorical expressions is the starting point of any research in the field of metaphorology. With the development of corpus linguistics methods, the volume of analyzed material has grown thousands of times. So, the identification of linguistic expressions in discourse that realize conceptual metaphors has become one of the most challenging issues of modern metaphorology. The paper describes theoretical foundations and historical background for the solution of this issue. It is shown that it is impossible to verify this or that method without a large-scale approbation; in this connection, the developments of research groups (PALASIGMET, PRAGGLEJAZ) proved to be the most perspective. The MIP (metaphor identification procedure) was finalized in the metaphor laboratory of the Free University of Amsterdam with the name MIPVU. This methodology was a great success all over the world, however, in Russia only a few articles of introductory character have appeared. This article summarizes the experience of applying the procedures of metaphor identification in different languages and types of discourse.

scholarly journals Characterizing ERA-Interim and ERA5 surface wind biases using ASCAT

Ocean Science ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 831-852 ◽  
Author(s):  
Maria Belmonte Rivas ◽  
Ad Stoffelen
Keyword(s):  
Large Scale ◽  
Surface Wind ◽  
Atmospheric Stability ◽  
Ocean Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Wind Stress Curl ◽  
Meridional Winds ◽  
Mesoscale Convective ◽  
Transient Wind

Abstract. This paper analyzes the differences between ERA-Interim and ERA5 surface winds fields relative to Advanced Scatterometer (ASCAT) ocean vector wind observations, after adjustment for the effects of atmospheric stability and density, using stress-equivalent winds (U10S) and air–sea relative motion using ocean current velocities. In terms of instantaneous root mean square (rms) wind speed agreement, ERA5 winds show a 20 % improvement relative to ERA-Interim and a performance similar to that of currently operational ECMWF forecasts. ERA5 also performs better than ERA-Interim in terms of mean and transient wind errors, wind divergence and wind stress curl biases. Yet, both ERA products show systematic errors in the partition of the wind kinetic energy into zonal and meridional, mean and transient components. ERA winds are characterized by excessive mean zonal winds (westerlies) with too-weak mean poleward flows in the midlatitudes and too-weak mean meridional winds (trades) in the tropics. ERA stress curl is too cyclonic in midlatitudes and high latitudes, with implications for Ekman upwelling estimates, and lacks detail in the representation of sea surface temperature (SST) gradient effects (along the equatorial cold tongues and Western Boundary Current (WBC) jets) and mesoscale convective airflows (along the Intertropical Convergence Zone and the warm flanks for the WBC jets). It is conjectured that large-scale mean wind biases in ERA are related to their lack of high-frequency (transient wind) variability, which should be promoting residual meridional circulations in the Ferrel and Hadley cells.

A low-rank approximation for large-scale 3D controlled-source electromagnetic Gauss-Newton inversion

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. E211-E225 ◽  
Author(s):  
Manuel Amaya ◽  
Jan Petter Morten ◽  
Linus Boman
Keyword(s):  
Large Scale ◽  
Low Rank ◽  
Low Rank Approximation ◽  
Controlled Source ◽  
Newton Equation ◽  
Rank Approximation ◽  
Memory Complexity ◽  
Simultaneous Source ◽  
The Impact ◽  
Matrix Free

We have developed an approximation to the Hessian for inversion of 3D controlled source electromagnetic data. Our approach can considerably reduce the numerical complexity in terms of the number of forward solutions as well as the size and complexity of the calculations required to compute the update direction from the Gauss-Newton equation. The approach makes use of “supershots,” in which several source positions are combined for simultaneous-source simulations. The resulting Hessian can be described as a low-rank approximation to the Gauss-Newton Hessian. The structure of the approximate Hessian facilitates a matrix-free direct solver for the Gauss-Newton equation, and the reduced memory complexity allows the use of a large number of unknowns. We studied the crosstalk introduced in the approximation, and we determined how the dissipative nature of marine electromagnetic field propagation reduces the impact of this noise. Inversion results from recent field data demonstrated the numerical and practical feasibility of the approach.

scholarly journals Observed Evolution of Northward-Propagating Intraseasonal Variation over the Western Pacific: A Case Study in Boreal Early Summer

2013 ◽  
Vol 141 (2) ◽  
pp. 690-706 ◽  
Author(s):  
Masaki Katsumata ◽  
Hiroyuki Yamada ◽  
Hisayuki Kubota ◽  
Qoosaku Moteki ◽  
Ryuichi Shirooka
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Boreal Summer ◽  
Intraseasonal Variation ◽  
Middle Troposphere ◽  
Inactive Period ◽  
The Western Pacific

Abstract This report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation (BSISV) in the tropical western Pacific Ocean. The convectively active region of the BSISV proceeded northward over the sounding and radar network. Over the array, the situation changed from a convectively inactive period to an active period. Inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period. The sounding-derived heat and moisture budget analyses indicated that both the convective- and large-scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently. This study is the first to identify such a “preconditioning” process for the BSISV in the western Pacific using detailed in situ observational data. During the preconditioning, an increase in CAPE was observed, as in previous studies of the MJO. An increase of moisture in the boundary layer was responsible for the increase of CAPE. The large-scale horizontal convergence in the boundary layer may be a key factor to moisten the boundary layer through the convective-scale processes, as well as through the large-scale processes to moisten the lower and middle troposphere.

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