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Turbulent transport extraction in time and frequency and the estimation of eddy fluxes at high resolution / Nikola Besic in Atmospheric measurement techniques, vol 18 n°13 ([01/09/2025])  

Public [article]  inAtmospheric measurement techniques > vol 18 n°13 [01/09/2025] . - 24 p. Titre : Turbulent transport extraction in time and frequency and the estimation of eddy fluxes at high resolution Type de document : Article/Communication Auteurs : Nikola Besic , Auteur Année de publication : 2025 Article en page(s) : 24 p. Langues : Anglais (eng) Descripteur : [Termes IGN] atmosphère terrestre [Termes IGN] turbulence Résumé : We introduce a novel framework for estimating eddy fluxes using cross-scalogram smoothing, addressing key limitations of the standard eddy-covariance method. The standard approach suffers from fixed averaging times (typically 30 min) and limited frequency resolution, which can lead to biases and an inability to capture fast dynamics. Our method, based on wavelet transforms, allows for high-resolution analysis of fluxes in both time and frequency domains. It adaptively localises turbulent scales using a metric derived from the vertical component of the Reynolds stress tensor, enabling more accurate flux estimation under varying turbulence conditions. The proposed metric is similar to the u* and σw tests, but it is adapted to the time–frequency setting. By decoupling the filtering of perturbative scales from flux calculations, our approach allows for flexible averaging times. This adaptability makes it particularly suitable for studying rapid ecosystem responses to environmental changes, such as those occurring on timescales shorter than 1 h. We show application of the framework at the beech forest site Hesse (code FR-Hes) and demonstrate its relation with standard eddy-covariance calculations. The proposed method allows for varying the averaging time without impacting the filtering of the perturbative scales. It thus allows for producing estimates of CO2, latent heat, and sensible heat fluxes with faster dynamics (e.g. with 1, 10, and 30 min averaging time). We present statistics of the 10 min averaged fluxes and show that they align well with estimates of the 30 min standard eddy-covariance method. The improved localisation of turbulent scales results in higher estimates of carbon uptake during summer (+2 ± 1 µmolm-2s-1) and a more accurate assessment of nighttime respiration compared to standard eddy-covariance estimates. The methodology is implemented in the Julia package TurbulenceFlux.jl, making it readily accessible for practical applications. Numéro de notice : A2025-0005 Affiliation des auteurs : LIF+Ext (2020- ) Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.5194/amt-18-3193-2025 Accessibilité : Non accessible via le SUDOC En ligne : https://hal.inrae.fr/hal-05265598 Format de la ressource électronique : HAL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=104304 [article]

Remote-sensing-based forest canopy height mapping: some models are useful, but might they provide us with even more insights when combined? / Nikola Besic in Geoscientific Model Development, vol 18 n° 2 (January 2025)  

Public [article]  inGeoscientific Model Development > vol 18 n° 2 (January 2025) . - 24 p. Titre : Remote-sensing-based forest canopy height mapping: some models are useful, but might they provide us with even more insights when combined? Type de document : Article/Communication Auteurs : Nikola Besic , Auteur ; Cédric Vega , Auteur ; Jean-Daniel Bontemps , Auteur ; Raphaël Hertzog, Auteur ; Jean-Pierre Renaud , Auteur Année de publication : 2025 Article en page(s) : 24 p. Langues : Anglais (eng) Descripteur : [Termes IGN] atmosphère terrestre [Termes IGN] cartographie automatique [Termes IGN] océan Résumé : The development of high-resolution mapping models for forest attributes based on remote sensing data combined with machine or deep learning techniques has become a prominent topic in the field of forest observation and monitoring. This has resulted in the availability of multiple, sometimes conflicting, sources of information, but, at face value, it also makes it possible to learn about forest attribute uncertainty through the joint interpretation of multiple models. This article seeks to endorse the latter by utilizing the Bayesian model averaging approach to diagnose and interpret the differences between predictions from different models. The predictions in our case are forest canopy height estimations for metropolitan France arising from five different models. An independent reference dataset, containing four different definitions of forest height (dominant, mean, maximum, and Lorey's) was established based on around 5500 plots of the French National Forest Inventory (NFI), distributed across the entire area of interest. In this study, we evaluate models with respect to their probabilities of correctly predicting measurements or estimations obtained from NFI plots, highlighting the spatial variability in respective model probabilities across the study area. We observed sig-nificant variability in these probabilities depending on the forest height definition used, implying that the different models inadvertently predict different types of canopy height. We also present the respective inter-model and intra-model variance estimations, enabling us to grasp where the employed models have comparable contributions but contrasting predictions. We show that topography has an important impact on the models spread. Moreover, we observed that the forest stand vertical structure, the dominant tree species, and the type of forest ownership systematically emerge as statistically significant factors influencing the model divergences. Finally, we observed that the fitted higher-order mixtures, which enabled the presented analyses, do not necessarily reduce bias or prevent the saturation of the predicted heights observed in the individual models. Numéro de notice : A2025-0008 Affiliation des auteurs : LIF+Ext (2020- ) Thématique : FORET Nature : Article DOI : 10.5194/gmd-18-337-2025 Accessibilité : Non accessible via le SUDOC En ligne : https://hal.science/hal-04918197 Format de la ressource électronique : HAL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=104310 [article]

A consistent regional vertical ionospheric model and application in PPP-RTK under sparse networks / Sijie Lyu in Navigation : journal of the Institute of navigation, vol 70 n° 3 (Fall 2023)  

Public [article]  inNavigation : journal of the Institute of navigation > vol 70 n° 3 (Fall 2023) . - n° 568 Titre : A consistent regional vertical ionospheric model and application in PPP-RTK under sparse networks Type de document : Article/Communication Auteurs : Sijie Lyu, Auteur ; Yan Xiang, Auteur ; Tiantian Tang, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : n° 568 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] carte ionosphérique mondiale [Termes IGN] correction ionosphérique [Termes IGN] modèle ionosphérique [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] teneur totale en électrons [Termes IGN] teneur verticale totale en électrons Numéro de notice : A2023-201 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.33012/navi.568 Date de publication en ligne : 23/09/2022 En ligne : https://doi.org/10.33012/navi.568 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103096 [article]

Ambiguity resolution method using BDS/INS model / F. Wu in Survey review, vol 55 n° 390 (May 2023)  

Public [article]  inSurvey review > vol 55 n° 390 (May 2023) . - pp 274 - 284 Titre : Ambiguity resolution method using BDS/INS model Type de document : Article/Communication Auteurs : F. Wu, Auteur ; J. Zhao, Auteur ; J. Xue, Auteur ; et al., Auteur Année de publication : 2023 Article en page(s) : pp 274 - 284 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] BDS-INS [Termes IGN] correction atmosphérique [Termes IGN] ligne de base [Termes IGN] modèle atmosphérique [Termes IGN] navigation inertielle [Termes IGN] positionnement par BeiDou [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Due to the highly dynamic changes of the environment, the frequent loss of signal will seriously reduce the accuracy of realtime dynamic positioning. Meanwhile, the ambiguity resolution for medium/long baseline is more affected by atmospheric delay. To solve this problem, an Inertial Navigation System (INS) assisted Beidou Navigation System (BDS) medium/long baseline partial ambiguity resolution (PAR) method is designed. Firstly, constructing the BDS/INS tight integrated system that uses INS provided initial information to ambiguity resolution when the signal outages. Secondly, the atmospheric delay constraint is introduced to improve the precision of float ambiguity. Finally, the PAR based on the elevation angle information is applied to enhance fixed speed and accuracy. The vehicle experiments show that the proposed algorithm can quickly fix the ambiguity of medium/long baseline when the satellite signal outages for a short time, and improve the positioning accuracy of medium/long baseline in the dynamic environment. Numéro de notice : A2023-192 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2022.2089822 Date de publication en ligne : 28/06/2022 En ligne : https://doi.org/10.1080/00396265.2022.2089822 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103067 [article]

Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations / Xulei Jin in Journal of geodesy, vol 97 n° 3 (March 2023)  

Public [article]  inJournal of geodesy > vol 97 n° 3 (March 2023) . - n° 27 Titre : Near real-time global ionospheric total electron content modeling and nowcasting based on GNSS observations Type de document : Article/Communication Auteurs : Xulei Jin, Auteur ; Shuli Song, Auteur Année de publication : 2023 Article en page(s) : n° 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] carte ionosphérique mondiale [Termes IGN] données Jason [Termes IGN] modèle ionosphérique [Termes IGN] temps réel [Termes IGN] teneur totale en électrons [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) For the purposes of routinely providing reliable and low-latency Global Ionosphere Maps (GIMs), a method of estimating hourly updated near real-time GIM with a time latency of about 1–2 h based on a 24-h data sliding window of Global Navigation Satellite System (GNSS) near real-time observations and real-time data streams was presented. On the basis of the implementation of near real-time GIM estimation, an hourly updated GIM nowcasting method was further proposed to improve the accurate of short-term total electron content (TEC) prediction. We estimated the Shanghai Astronomical Observatory near real-time GIM (SHUG) and nowcasting GIM (SHPG) in the solar relatively active year (2014) and quiet year (2021), and employed GIMs provided by the International GNSS Service, the Global Positioning System (GPS) differential slant TECs (dSTECs) extracted from global independent GNSS stations, and the vertical TECs (VTECs) inverted from satellite altimetry as the references to validate the estimated results. The GPS dSTECs evaluation results show that SHUG behaves fairly consistent with the rapid GIMs, with a discrepancy of less than 1 TEC unit (TECu) overall. The standard deviations (STDs) of SHUG with respect to Jason-2/-3 VTECs are no more than 10% over the majority of rapid GIMs due to the instability of observations. The performance of 1-h nowcasting SHPG is significantlybetter than the Center for Orbit Determination in Europe (CODE) 1-day predicted GIM (C1PG). GPS dSTEC validation results indicate that 1-h nowcasting SHPG is 1 to 2 TECu more reliable than C1PG in eventful ionospheric electron activity regions, and it outperforms the C1PG by 10% overall versus Jason-2/-3 VTECs. The hourly updated SHUG and SHPG have relatively high reliability and low time latency, and thus can provide excellent service for (near) real-time users and offer more accurate TEC background information than daily predicted GIM for real-time GIM estimation. Numéro de notice : A2023-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-023-01715-3 Date de publication en ligne : 20/03/2023 En ligne : https://doi.org/10.1007/s00190-023-01715-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102950 [article]

Undifferenced and uncombined GNSS time and frequency transfer with integer ambiguity resolution / Xiaolong Mi in Journal of geodesy, vol 97 n° 2 (February 2023)  

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Parameterisation of the GNSS troposphere tomography domain with optimisation of the nodes’ distribution / Estera Trzcina in Journal of geodesy, vol 97 n° 1 (January 2023)  

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Precipitation frequency in Med-CORDEX and EURO-CORDEX ensembles from 0.44° to convection-permitting resolution: impact of model resolution and convection representation / Minh Ha-Truong in Climate Dynamics, vol 60 n° inconnu (2023)  

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Spatiotemporal accuracy evaluation and errors analysis of global VTEC maps using a simulation technique / Jian Lin in GPS solutions, vol 27 n° 1 (January 2023)  

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Multi-frequency simulation of ionospheric scintillation using a phase-screen model / Fernando D. Nunes in Navigation : journal of the Institute of navigation, vol 69 n° 4 (Fall 2022)  

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Navigation and Ionosphere Characterization Using High-Frequency Signals: A Performance Analysis / Yoav Baumgarten in Navigation : journal of the Institute of navigation, vol 69 n° 4 (Fall 2022)  

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Testing of new ionospheric models along the meridian 110° E over the Northern Hemisphere / Olga Maltseva in Geodesy and Geodynamics, vol 13 n° 6 (November 2022)  

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Estimation of ionospheric total electron content using GNSS observations derived from a smartphone / Li Xu in GPS solutions, vol 26 n° 4 (October 2022)  

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Global forecasting of ionospheric vertical total electron contents via ConvLSTM with spectrum analysis / Jinpei Chen in GPS solutions, vol 26 n° 3 (July 2022)  

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Validation of regional and global ionosphere maps from GNSS measurements versus IRI2016 during different magnetic activity / Ahmed Sedeek in Journal of applied geodesy, vol 16 n° 3 (July 2022)  

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