Nonlinear Processes in Geophysics最新文献_第9页

Weather pattern dynamics over western Europe under climate change: predictability, information entropy and production 气候变化下西欧的天气模式动态:可预测性、信息熵和产生

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2023-01-09 DOI: 10.5194/npg-30-1-2023

S. Vannitsem

{"title":"Weather pattern dynamics over western Europe under climate change: predictability, information entropy and production","authors":"S. Vannitsem","doi":"10.5194/npg-30-1-2023","DOIUrl":"https://doi.org/10.5194/npg-30-1-2023","url":null,"abstract":"Abstract. The impact of climate change on weather pattern dynamics over the North Atlantic is explored through the lens of the information theory of forced dissipative dynamical systems. The predictability problem is first tackled by investigating the evolution of block entropies on observational time series of weather patterns produced by the Met Office, which reveals that predictability is increasing as a function of time in the observations during the 19th century and beginning of the 20th century, while the trend is reversed at the end of the 20th century and beginning of the 21st century. This feature is also investigated in the 15-member ensemble of the UK Met Office CMIP5 model for the 20th and 21st centuries under two climate change scenarios, revealing a wide range of possible evolutions depending on the realization considered, with an overall decrease in predictability in the 21st century for both scenarios. Lower bounds of the information entropy production are also extracted, providing information on the degree of time asymmetry and irreversibility of the dynamics. The analysis of the UK Met Office model runs suggests that the information entropy production will increase by the end of the 21st century, by a factor of 10 % in the Representative Carbon Pathway RCP2.6 scenario and a factor of 30 %–40 % in the RCP8.5 one, as compared to the beginning of the 20th century. This allows one to make the conjecture that the degree of irreversibility is increasing, and hence heat production and dissipation will also increase under climate change, corroborating earlier findings based on the analysis of the thermodynamic entropy production.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44708779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Guidance on how to improve vertical covariance localization based on a 1000-member ensemble 关于如何改进基于1000人集合的垂直协方差定位的指导

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2023-01-09 DOI: 10.5194/npg-30-13-2023

Tobias Necker, David Hinger, P. Griewank, T. Miyoshi, M. Weissmann

{"title":"Guidance on how to improve vertical covariance localization based on a 1000-member ensemble","authors":"Tobias Necker, David Hinger, P. Griewank, T. Miyoshi, M. Weissmann","doi":"10.5194/npg-30-13-2023","DOIUrl":"https://doi.org/10.5194/npg-30-13-2023","url":null,"abstract":"Abstract. The success of ensemble data assimilation systems substantially depends on localization, which is required to mitigate sampling errors caused by modeling background error covariances with undersized ensembles. However, finding an optimal localization is highly challenging, as covariances, sampling errors, and appropriate localization depend on various factors. Our study investigates vertical localization based on a unique convection-permitting 1000-member ensemble simulation; 1000-member ensemble correlations serve as truth for examining vertical correlations and their sampling error. We discuss requirements for vertical localization by deriving an empirical optimal localization (EOL) that minimizes the sampling error in 40-member subsample correlations with respect to the 1000-member reference. Our analysis covers temperature, specific humidity, and wind correlations on various pressure levels. Results suggest that vertical localization should depend on several aspects, such as the respective variable, vertical level, or correlation type (self- or cross-correlations). Comparing the empirical optimal localization with common distance-dependent localization approaches highlights that finding suitable localization functions bears substantial room for improvement. Furthermore, we examine approaches for achieving positive semi-definiteness for covariance localization that hardly affect the sampling error reduction. Finally, we discuss the gain of combining different localization approaches with an adaptive statistical sampling error correction.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44031858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Physically constrained covariance inflation from location uncertainty 由位置不确定性引起的物理约束协方差膨胀

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-11-08 DOI: 10.5194/npg-30-237-2023

Yicun Zhen, V. Resseguier, B. Chapron

引用次数: 1

An approach for projecting the timing of abrupt winter Arctic sea ice loss 一种预测冬季北极海冰突然消失时间的方法

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-10-28 DOI: 10.5194/npg-30-299-2023

Camille Hankel, E. Tziperman

引用次数: 0

Applying dynamical systems techniques to real ocean drifters 动力学系统技术在实际海洋漂流者中的应用

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-10-07 DOI: 10.5194/npg-29-345-2022

I. Rypina, Timothy R. Getscher, L. Pratt, Tamay Ozgokmen

{"title":"Applying dynamical systems techniques to real ocean drifters","authors":"I. Rypina, Timothy R. Getscher, L. Pratt, Tamay Ozgokmen","doi":"10.5194/npg-29-345-2022","DOIUrl":"https://doi.org/10.5194/npg-29-345-2022","url":null,"abstract":"Abstract. This paper presents the first comprehensive comparison of several different\u0000dynamical-systems-based measures of stirring and Lagrangian coherence,\u0000computed from real ocean drifters. Seven commonly used methods (finite-time\u0000Lyapunov exponent (FTLE), trajectory path length, trajectory correlation dimension,\u0000trajectory encounter volume, Lagrangian-averaged vorticity deviation,\u0000dilation, and spectral clustering) were applied to 144 surface drifters in\u0000the Gulf of Mexico in order to map out the dominant Lagrangian coherent\u0000structures. Among the detected structures were regions of hyperbolic nature\u0000resembling stable manifolds from classical examples, divergent and\u0000convergent zones, and groups of drifters that moved more coherently and\u0000stayed closer together than the rest of the drifters. Many methods\u0000highlighted the same structures, but there were differences too. Overall, five\u0000out of seven methods provided useful information about the geometry of transport within the domain spanned by the drifters, whereas the path length and correlation dimension methods were less useful than others.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43345946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Using a hybrid optimal interpolation–ensemble Kalman filter for the Canadian Precipitation Analysis 使用混合最优插值-集合卡尔曼滤波器进行加拿大降水分析

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-10-06 DOI: 10.5194/npg-29-329-2022

D. Khedhaouiria, S. Bélair, V. Fortin, G. Roy, F. Lespinas

{"title":"Using a hybrid optimal interpolation–ensemble Kalman filter for the Canadian Precipitation Analysis","authors":"D. Khedhaouiria, S. Bélair, V. Fortin, G. Roy, F. Lespinas","doi":"10.5194/npg-29-329-2022","DOIUrl":"https://doi.org/10.5194/npg-29-329-2022","url":null,"abstract":"Abstract. Several data assimilation (DA) approaches exist to generate consistent and continuous precipitation fields valuable for hydrometeorological applications and land data assimilation. Usually, DA is based on either static or dynamic approaches. Static methods rely on deterministic forecasts to estimate background error covariance matrices, whereas dynamic approaches use ensemble forecasts. Associating the two methods is known as hybrid DA, and it has proven beneficial for different applications as it combines the advantages of both approaches. The present study intends to explore hybrid DA for the 6 h Canadian Precipitation Analysis (CaPA). Based on optimal interpolation (OI), CaPA blends forecasts and observations from surface stations and ground-based radar datasets to provide precipitation fields over the North American domain. The application of hybrid DA to CaPA consisted of finding the optimal linear combination between (i) an OI based on the Regional Deterministic Prediction System (RDPS) and (ii) an ensemble Kalman filter (EnKF) based on the 20-member Regional Ensemble Prediction System (REPS). The results confirmed the known effectiveness of the hybrid approach when low-density observation networks are assimilated. Indeed, the experiments conducted for the summer without radar datasets and for the winter (characterized by very few observations in CaPA) showed that attributing a relatively high weight to the EnKF (50 % and 70 % for summer and winter, respectively) resulted in better analysis skill and a reduction in false alarms compared with the OI method. A deterioration in the moderate- to high-intensity precipitation bias was, however, observed during summer. Reducing the weight attributed to the EnKF to 30 % alleviated the bias deterioration while improving skill compared with the OI-based CaPA.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42501908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Applying prior correlations for ensemble-based spatial localization 基于集合的空间定位应用先验相关

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-09-01 DOI: 10.5194/npg-29-317-2022

Chu-Chun Chang, E. Kalnay

{"title":"Applying prior correlations for ensemble-based spatial localization","authors":"Chu-Chun Chang, E. Kalnay","doi":"10.5194/npg-29-317-2022","DOIUrl":"https://doi.org/10.5194/npg-29-317-2022","url":null,"abstract":"Abstract. Localization is an essential technique for ensemble-based\u0000data assimilations (DAs) to reduce sampling errors due to limited ensembles. Unlike traditional distance-dependent localization, the correlation cutoff method (Yoshida and Kalnay, 2018; Yoshida, 2019) tends to localize the observation impacts based on their background error correlations. This method was initially proposed as a variable localization strategy for coupled systems, but it can also can be utilized extensively as a spatial localization. This study introduced and examined the feasibility of the correlation cutoff method as an alternative spatial localization with the local ensemble transform Kalman filter (LETKF) preliminary on the Lorenz (1996) model. We compared the accuracy of the distance-dependent and correlation-dependent localizations and extensively explored the potential of the hybrid localization strategies. Our results suggest that the correlation cutoff method can deliver comparable analysis to the traditional localization more efficiently and with a faster DA spin-up. These benefits would become even more pronounced under a more complicated model, especially when the ensemble and observation sizes are reduced.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70695249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Effects of rotation and topography on internal solitary waves governed by the rotating Gardner equation 旋转和地形对旋转Gardner方程控制的内部孤立波的影响

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-06-15 DOI: 10.5194/npg-29-207-2022

K. Helfrich, L. Ostrovsky

引用次数: 1

Regional study of mode-2 internal solitary waves at the Pacific coast of Central America using marine seismic survey data 利用海洋地震调查资料对中美洲太平洋沿岸2型内孤立波的区域研究

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-04-04 DOI: 10.5194/npg-29-141-2022

Wenhao Fan, Haibin Song, Y. Gong, Shun-Hsing Yang, Kun Zhang

{"title":"Regional study of mode-2 internal solitary waves at the Pacific coast of Central America using marine seismic survey data","authors":"Wenhao Fan, Haibin Song, Y. Gong, Shun-Hsing Yang, Kun Zhang","doi":"10.5194/npg-29-141-2022","DOIUrl":"https://doi.org/10.5194/npg-29-141-2022","url":null,"abstract":"Abstract. In this paper, a regional study of mode-2 internal\u0000solitary waves (ISWs) at the Pacific coast of Central America is carried out using the seismic reflection method. The observed relationship between\u0000the dimensionless propagation speed and the dimensionless amplitude (DA) of\u0000the mode-2 ISW is analyzed. When DA < 1.18, the dimensionless\u0000propagation speed seems to increase with increasing DA, divided into two parts with different growth rates. When\u0000DA > 1.18, the dimensionless propagation speed increases with\u0000increasing DA at a relatively small growth rate. We\u0000suggest that the influences of seawater depth (submarine topography),\u0000pycnocline depth, and pycnocline thickness on the propagation speed of the\u0000mode-2 ISW in the study area cause the relationship between\u0000dimensionless propagation speed and DA to\u0000diversify. The observed relationship between the dimensionless wavelength\u0000and the DA of the mode-2 ISW is also analyzed. When\u0000DA < 1, the nondimensional wavelengths seem to change from 2.5 to 7\u0000for a fixed nondimensional amplitude. When DA > 1.87, the\u0000dimensionless wavelength increases with increasing DA. Additionally, the seawater depth has a great influence on the\u0000wavelength of the mode-2 ISW in the study area. Overall, the wavelength\u0000increases with increasing seawater depth. As for the vertical structure\u0000of the amplitude of the mode-2 ISW in the study area, we find that it is\u0000affected by the nonlinearity of the ISW and the pycnocline deviation\u0000(especially the downward pycnocline deviation).\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45399923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Control simulation experiment with Lorenz's butterfly attractor 洛伦兹蝴蝶吸引子控制仿真实验

IF 2.2 4区地球科学

Nonlinear Processes in Geophysics Pub Date : 2022-03-28 DOI: 10.5194/npg-29-133-2022

T. Miyoshi, Qiwen Sun

{"title":"Control simulation experiment with Lorenz's butterfly attractor","authors":"T. Miyoshi, Qiwen Sun","doi":"10.5194/npg-29-133-2022","DOIUrl":"https://doi.org/10.5194/npg-29-133-2022","url":null,"abstract":"Abstract. In numerical weather prediction (NWP), sensitivity to initial conditions brings chaotic behaviors and an intrinsic limit to\u0000predictability, but it also implies an effective control in which a small\u0000control signal grows rapidly to make a substantial difference. The Observing\u0000Systems Simulation Experiment (OSSE) is a well-known approach to study\u0000predictability, where “nature” is synthesized by an independent NWP model run. In this study, we extend the OSSE and design the control\u0000simulation experiment (CSE), where we apply a small signal to control “nature”. Idealized experiments with the Lorenz-63 three-variable system show that we can control “nature” to stay in a chosen regime without\u0000shifting to the other, i.e., in a chosen wing of Lorenz's butterfly attractor, by adding small perturbations to “nature”. Using longer-lead-time forecasts, we achieve more effective control with a\u0000perturbation size of less than only 3 % of the observation error. We anticipate our idealized CSE to be a starting point for a realistic CSE using the real-world NWP systems, toward possible future applications to reduce\u0000weather disaster risks. The CSE may be applied to other chaotic systems\u0000beyond NWP.\u0000","PeriodicalId":54714,"journal":{"name":"Nonlinear Processes in Geophysics","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41399186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2