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Determination of thermal stratification and turbulence of the atmospheric surface layer over various types of terrain by optical scintillometry / Alexandra Weiss (2002)
Titre : Determination of thermal stratification and turbulence of the atmospheric surface layer over various types of terrain by optical scintillometry Type de document : Thèse/HDR Auteurs : Alexandra Weiss, Auteur Editeur : Zurich : Institut für Geodäsie und Photogrammetrie IGP - ETH Année de publication : 2002 Collection : IGP Mitteilungen, ISSN 0252-9335 num. 075 Importance : 152 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-906467-36-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Atmosphère
[Termes IGN] atmosphère terrestre
[Termes IGN] capteur optique
[Termes IGN] rayonnement électromagnétique
[Termes IGN] rayonnement solaire
[Termes IGN] réfraction atmosphérique
[Termes IGN] scintillation
[Termes IGN] turbulenceRésumé : (Auteur) Thermal stratification and turbulence in the atmospheric surface layer cause refraction and scintillation of an optical beam. On the one hand, such atmospherically induced effects are undesirable in many applications which are based on optical wave propagation through the atmospheric boundary layer. Such examples are found in many applications of terrestrial optical surveying. On the other hand, such atmospherically induced effects can be used to derive various meteorological parameters. Based on these consideration the present work deals with the determination of thermal stratification and turbulence of the atmospheric surface layer over different types of terrain by optical scintillometry.
First, in this study a method is introduced and experimentally verified to derive correction values for precise terrestrial geodetic measurements. For highly precise optical direction and distance measurements, such corrections require lineaveraged temperature or refractive index gradients. Secondly, this study investigates how precisely lineaveraged turbulence parameters can be derived in the atmospheric surface layer by scintillometry and whether their derivation deepens our understanding of the structure of the atmospheric surface layer, especially over nonhomogeneous terrain. Here, the main focus lies in the investigation of the accuracy of the turbulent sensible heat and momentum fluxes, and the dissipation rate of turbulent kinetic energy, which are of grave importance for many meteorological applications. This work is based on various field experiments conducted with a socalled displacedbeam scintillometer under different atmospheric conditions. The experimental sites varied from homogeneous and flat terrain to flat, nonhomogeneous terrain up to slanted, nonhomogeneous terrain in an alpine valley. For validation of the method, additional meteorological measurement techniques are used and are considered in the data analysis, such as eddycorrelation measurements with sonic anemometerthermometers and Krypton hygrometers, and temperature profile measurements with Pt 1000 sensors.
The derivation of the thermal stratification from the scintillation method is especially dependent on the accuracy of the derived turbulent sensible heat flux. In the scope of this study, satisfactory accuracy of the derived turbulent sensible heat fluxes is obtained, even for nonhomogeneous terrain. It is shown that the presented method is applicable for deriving, lineaveraged refraction correction values over various types of terrain and for different atmospheric conditions with a good temporal resolution. This result is confirmed by comparisons with local temperature profile measurements. The linfitations of this method are discussed on the basis of the experimental datasets. For instance, under neutral conditions, with weak thermal turbulence, the derivation of accurate values of the turbulent momentum flux can be problematic with this method. However, in this work it is shown that the scintillation method gives accurate values under many atmospheric conditions including the turbulent momentum flux and for several other turbulence parameters. On the basis of the field experiments, new insights into the turbulence structure of the surface layer can be achieved by scintillometry, even over nonhomogeneous terrain. In this context the turbulent structure in an alpine valley is analysed and described under various boundary layer features.Numéro de notice : 15052 Affiliation des auteurs : non IGN Nature : Thèse étrangère En ligne : http://dx.doi.org/10.3929/ethz-a-004283039 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=55054 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 15052-01 47.50 Livre Centre de documentation En réserve M-103 Disponible
Titre : Fast precise GPS positioning in the presence of ionospheric delays Type de document : Thèse/HDR Auteurs : Dennis Odijk, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2002 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 52 Importance : 242 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-90-6132-278-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] ambiguïté entière
[Termes IGN] correction ionosphérique
[Termes IGN] correction troposphérique
[Termes IGN] données GPS
[Termes IGN] interpolation
[Termes IGN] krigeage
[Termes IGN] mesurage de phase
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle de Gauss-Markov
[Termes IGN] modèle ionosphérique
[Termes IGN] modèle stochastique
[Termes IGN] propagation ionosphérique
[Termes IGN] propagation troposphérique
[Termes IGN] réfraction atmosphérique
[Termes IGN] résolution d'ambiguïté
[Termes IGN] signal GPS
[Termes IGN] station virtuelle
[Termes IGN] traitement de données GNSS
[Termes IGN] traitement du signalIndex. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Résumé : (Auteur) This thesis deals about geodetic applications of the Global Positioning System (GPS), in which the position of the GPS receiver must be determined with cm precision. This requires a relative measurement setup, together with an advanced processing strategy based on observations of the carrierphase of the signal. To keep it economically interesting, this CPS technique should be based on relatively short time spans in which the satellite observations are collected. The key to precise positioning using short time spans is to take advantage of the integer property of the ambiguities of the phase observations in the processing.
The above procedure has been applied in a successful way for the last decade to applications in which the distance between the receivers is restricted to about 10 km (the socalled rapidstatic and realtime kinematic GPS techniques over short distances). Above this distance, it is known that certain errors in the GPS observations start to significantly bias the computed receiver position when they are not taken care of. The aim of this research therefore is to develop a processing procedure, taking into account the errors in GPS observations due to propagation of the signals through the ionosphere, the atmospheric layer above about 80 kill. Although other errors (due to troposphere and satellite orbit) are of relevance as well, the research is restricted to an improved modelling of the ionospheric error. since it is by far the largest error. For the other errors standard modelling techniques are applied in this research. Using the procedure, it should be possible to determine the desired receiver positions with cmprecision using a short tinle span. The research is restricted to GPS receivers with a mutual distance of a few hundred km (mediumdistance baselines), located in midlatitude regions.
To facilitate a modelling of the ionospheric error, using the theor ' y of atmospheric refraction it is possible to decompose this error into a firstorder effect, which contains the gross of the error, plus some higherorder effects and a term due to bending of the signal path. Under worstcase conditions. the firstorder term may range up to about 80 m (on the GPS L2 frequency), whereas the accumulated effect of higherorder and bending terms can be tip to 4 cm (for L2). For the future L5 frequency (from 2008) these effects are even larger. Fortunately, because of the relative setup and the assumed medium distances, it is proved for this research it is allowed to neglect the higherorder and bending errors.
In the procedure a stochastic modelling of the firstorder ionospheric errors (referred to as ionospheric delays) is chosen. This means that the ionospheric delays are not modelled as completely unknown parameters, but that stochastic prior information is incorporated by means of ionospheric pseudoobservations. This model is referred to as the ionosphereweighted model: The weight of the ionospheric information can be tuned by the a priori standard deviation of the pseudoobservations. When this standard deviation is chosen zero, the ionosphereweighted model reduces to the ionospherefixed model, which is the usual processing model for shortdistance baselines (for which the ionospheric delays may be neglected). On the other hand, with an infinitely large ionospheric standard deviation, the model will be equivalent to the ionospherefloat model, in which the ionospheric delays are assumed as completely unknown parameters. This latter model is closely related to the ionospherefree combination, for which it is known that it cannot be used to achieve fast positioning results. It is shown that the ionosphereweighted model is only suitable for fast ambiguity resolution (and consequently positioning), when the ionospheric standard deviation is small. This requires very precise a priori ionospheric information.
The developed procedure consists of three steps. It is required that a user collects CPS observations in the vicinity of a network of permanent GPS stations. In the first step, the observations at the network stations are processed simultaneously using the ionosphereweighted model. Since in this research the goal is precise positioning within the shortest time span possible, i.e. instantaneous or singleepoch positioning, it is required that the network data is also processed instantaneously. To make instantaneous resolution of the network ambiguities possible, the sample values of the ionospheric pseudoobservations are temporal predictions based on estimates of previous epochs. Test computations using a network with a station spacing of more than 100 km demonstrated that in this way high network ambiguity success rates (close to 100%) can be obtained. In the second step, precise ambiguityfixed network ionospheric delays are spatially interpolated at the approximate location of the user's receiver. In the procedure for this purpose the concept of virtual reference station (VRS) observations is used. In this concept the network estimates (ionospheric delays and other parameters) are transformed to VRS observations. which should correspond to the data a real receiver would have collected at the user's location. The processing of the user's observations relative to this VRS is the third step of the procedure. Because of the presence of possible residual ionospheric delays also in this step the ionosphereweighted model is applied. The difference with the application in the network processing is that the sample values of the pseudoobservations are now taken zero. and the ionospheric standard deviation is computed as a function of the distance to the closest real network station. Using this, test computations demonstrated that instantaneous ambiguity success rates of 90% are feasible. When the ionospherefixed model would be applied, the success rates would not be higher than about 60%.Numéro de notice : 13101 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : sans En ligne : https://www.ncgeo.nl/downloads/52Odijk.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54884 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 13101-01 30.61 Livre Centre de documentation Géodésie Disponible Mesoscale meteorological modeling / R.A. Pielke (2002)
Titre : Mesoscale meteorological modeling Type de document : Monographie Auteurs : R.A. Pielke, Auteur Mention d'édition : 2 Editeur : Londres, New York : Academic Press Année de publication : 2002 Collection : International geophysics series num. 78 Importance : 676 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-0-12-554766-6 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Atmosphère
[Termes IGN] aérosol
[Termes IGN] chaleur
[Termes IGN] circulation atmosphérique
[Termes IGN] humidité de l'air
[Termes IGN] masse d'air
[Termes IGN] modèle atmosphérique
[Termes IGN] modèle physique
[Termes IGN] propagation d'erreur
[Termes IGN] transformation de coordonnéesRésumé : (Editeur) The second edition of Mesoscale Meteorological Modeling is a fully revised resource for researchers and practitioners in the growing field of meteorological modeling at the mesoscale. Pielke has enhanced the new edition by quantifying model capability (uncertainty) by a detailed evaluation of the assumptions of parameterization and error propagation. Mesoscale models are applied in a wide variety of studies, including weather prediction, regional and local climate assessments, and air pollution investigations. Note de contenu : Preface
1-Introduction
2-Basic Set of Equations
3-Simplification of the Basic Equations
4-Averaging the Conservation Relations
5-Physical and analytic modeling
6-Coordinate Transformations
7-Parameterization-Averaged Subgrid Scale Fluxes
8-Averaged Radiation Flux Divergence
9-Parameterization of Moist Thermodynamic Processes
10-Methods of Solution
11-Boundary and Initial Conditions
12-Model Evaluation
13-Examples of Mesoscale Models
Appendix A: The Solution of Equations with Periodic Boundary Conditions
Appendix B: Model SummaryNuméro de notice : 19704 Affiliation des auteurs : non IGN Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62867 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 19704-01 47.50 Livre Centre de documentation En réserve M-103 Disponible The physics of atmospheres / John Houghton (2002)
Titre : The physics of atmospheres Type de document : Monographie Auteurs : John Houghton, Auteur Mention d'édition : 3 Editeur : Cambridge [Royaume-Uni] : Cambridge University Press Année de publication : 2002 Importance : 320 p. Format : 17 x 24 cm ISBN/ISSN/EAN : 978-0-521-01122-8 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géographie physique
[Termes IGN] atmosphère de planète
[Termes IGN] atmosphère terrestre
[Termes IGN] changement climatique
[Termes IGN] circulation atmosphériqueIndex. décimale : 47.50 Atmosphère Note de contenu : 1 Some basic ideas
2 A radiative equilibrium model
3 Thermodynamics
4 More complex radiation transfer
5 The middle and upper atmospheres
6 Clouds
7 Dynamics
8 Atmospheric waves
9 Turbulence
10 The general circulation
11 Numerical modelling
12Global observation
13 Chaos and atmospheric predictability
14 Climate and climate changeNuméro de notice : 12826 Affiliation des auteurs : non IGN Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80920 Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 12826-01 47.50 Livre Centre de documentation En réserve M-103 Disponible Atmospheric modeling in GPS data analysis for high accuracy positioning / Olivier Bock in Physics and chemistry of the Earth, Part A: Solid Earth and Geodesy, vol 26 n° 6-8 (2001)
[article]
Titre : Atmospheric modeling in GPS data analysis for high accuracy positioning Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Erik Doerflinger, Auteur Année de publication : 2001 Article en page(s) : pp 373 - 383 Note générale : biblographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] données GPS
[Termes IGN] modèle atmosphérique
[Termes IGN] retard troposphérique zénithalRésumé : (auteur) In this paper we review the atmospheric modeling methods used in GPS data analysis. Due to the strong spatial inhomogeneity and temporal variability of atmospheric constituents, especially water vapor, accurate modeling of path delay in GPS signals is necessary for high-accuracy positioning (e.g., tectonics and sea-level change) and meteorological applications (climatology and weather forecasting). State-of-the-art path delay modeling consists primarily in parameter estimation. In this strategy, zenith path delays are estimated during the GPS data reduction. External correction is another common strategy, in which the wet path delay is measured by a remote sensing instrument (usually a microwave radiometer). However, the latter is not as generalized, and is rather used for specific field campaigns or local long term observations. Both strategies have led to quite similar coordinate accuracies (using daily GPS observations), at the level of 1–2 mm in the horizontal component and 5–10 mm in the vertical component. The external correction strategy is capable of achieving even higher accuracy under specific conditions. Recent models, including gradients in the parameter estimation strategy have only led to marginal improvement. A major limitation of both strategies seems to be the use of mapping functions for the hydrostatic path delay correction. With the parameter estimation strategy, this limitation applies also to wet path delay correction. The use of numerical weather prediction and analysis models, and/or spaceborne sounding instruments, is suggested for replacing mapping functions and possibly for performing directly the hydrostatic correction. New instruments, such as Raman lidars, might also be used for a more accurate external wet path delay correction in the presence of strong atmospheric inhomogeneity. Further work is still needed for achieving measurements of absolute water vapor distribution in the atmosphere for this purpose. Numéro de notice : A2001-181 Affiliation des auteurs : LOEMI+Ext (1985-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ComAvecCL&ActesPubliésIntl DOI : 10.1016/S1464-1895(01)00069-2 Date de publication en ligne : 27/06/2001 En ligne : https://doi.org/10.1016/S1464-1895(01)00069-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102953
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