Jon Blower | University of Reading (original) (raw)
Papers by Jon Blower
Bulletin of Volcanology, 2001
A model has been developed to investigate the sensitivity of magma permeability, k, to various pa... more A model has been developed to investigate the sensitivity of magma permeability, k, to various parameters. Power-law relationships between k and porosity J are revealed, in agreement with previous experimental and theoretical studies. These relationships take the form % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfKttLearuavTnhis1MBaeXatLxBI9gBae % rbd9wDYLwzYbWexLMBbXgBcf2CPn2qVrwzqf2zLnharyavP1wzZbIt % LDhis9wBH5garqqtubsr4rNCHbGeaGqiVCI8FfYJH8sipiYdHaVhbb % f9v8qqaqFr0xc9pk0xbba9q8WqFfeaY-biLkVcLq-JHqpepeea0-as % 0Fb9pgeaYRXxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaabau % aaaOqaaiqbdUgaRzaajaGaeyypa0Jaem4AaSMaei4la8IaemOCai3a % aWbaaSqabeaacqaIYaGmaaGccqGH9aqpcqWGHbqycqGGOaakcqaHgp % GzcqGHsislcqaHgpGzdaWgaaWcbaGaem4yamMaemOCaihabeaakiab % cMcaPmaaCaaaleqabaGaemOyaigaaaaa!4CE4! \hat k
Procedia Computer Science, 2011
Climate-G is a large scale distributed testbed devoted to climate change research. It is an unfun... more Climate-G is a large scale distributed testbed devoted to climate change research. It is an unfunded effort started in 2008 and involving a wide community both in Europe and US. The testbed is an interdisciplinary effort involving partners from several institutions and joining expertise in the field of climate change and computational science. Its main goal is to allow scientists carrying out geographical and cross-institutional data discovery, access, analysis, visualization and sharing of climate data. It represents an attempt to address, in a real environment, challenging data and metadata management issues. This paper presents a complete overview about the Climate-G testbed highlighting the most important results that have been achieved since the beginning of this project.
Earth and Planetary Science Letters, 2001
The coupling of viscosity and diffusivity during explosive volcanic degassing is investigated usi... more The coupling of viscosity and diffusivity during explosive volcanic degassing is investigated using a numerical model of bubble growth in rhyolitic melts. The model allows melt viscosity and water diffusivity to vary spatially and temporally with water content. We find that the system is highly sensitive to the distribution of volatiles around the bubble, primarily as a consequence of the
Journal of Volcanology and Geothermal Research, 2003
We review observations of bubble size distributions (BSDs) generated during explosive volcanic er... more We review observations of bubble size distributions (BSDs) generated during explosive volcanic eruptions and laboratory explosions, as inferred from vesicle size distributions found in the end products. Unimodal, polymodal, exponential and power law BSDs are common, even in the absence of coalescence, and both power law and exponential distributions have been generated in the same eruption. To date theoretical models
We review observations of bubble size distributions (BSDs) generated during explosive volcanic er... more We review observations of bubble size distributions (BSDs) generated during explosive volcanic eruptions and laboratory explosions, as inferred from vesicle size distributions found in the end products. Unimodal, polymodal, exponential and power law BSDs are common, even in the absence of coalescence, and both power law and exponential distributions have been generated in the same eruption. To date theoretical models
Both power law and exponential vesicle size distributions (VSDs) have been observed in many diere... more Both power law and exponential vesicle size distributions (VSDs) have been observed in many dierent typesofvolcanicrocks. Wepresentresultsofcomputersim- ulations and laboratory analogue experiments which repro- duce these ndings and show that the distributions can be interpreted as the product of continuous bubble nucleation resulting from non-equilibrium degassing. This ongoing nu- cleationcausesthebubblestoevolvethroughanexponential size distribution into a power law size distribution as nucle-
Geophysical Research Letters, 2001
Both power law and exponential vesicle size distributions (VSDs) have been observed in many diffe... more Both power law and exponential vesicle size distributions (VSDs) have been observed in many different types of volcanic rocks. We present results of computer simulations and laboratory analogue experiments which reproduce these findings and show that the distributions can be interpreted as the product of continuous bubble nucleation resulting from non-equilibrium degassing. This ongoing nucleation causes the bubbles to evolve through an exponential size distribution into a power law size distribution as nucleation and growth progress. These findings may explain the apparent contradiction between present models of bubble growth in magmas, which predict that degassing in explosive eruptions is a non-equilibrium process, and models of conduit flow, which assume perfect equilibrium degassing. The process of continuous nucleation is the mechanism whereby the volcanic system maintains near-equilibrium in the case of rapid depressurization and slow volatile diffusion.
In the decade since OceanObs `99, great advances have been made in the field of ocean data dissem... more In the decade since OceanObs `99, great advances have been made in the field of ocean data dissemination. The use of Internet technologies in particular has transformed the landscape: users can now find, evaluate and access data rapidly and securely using only a web browser. This paper describes the current state of the art in dissemination methods for ocean data, focussing particularly on ocean observations from in situ and remote sensing platforms. We discuss current efforts in increasing the consistency of delivered data and in increasing the potential for automated integration of diverse datasets. An important recent development is the adoption of open standards from the Geographic Information Systems community; we discuss the current impact of these new technologies and their future potential. We conclude that new approaches will indeed be necessary to exchange data more effectively and forge links between communities, but these approaches must be evaluated critically through p...
The flow of exsolved gases through the volcanic system exerts a fundamental control on the nature... more The flow of exsolved gases through the volcanic system exerts a fundamental control on the nature of a volcano's activity. Gas flow determines the internal pressure of magmatic bubbles and so strongly influences bubble growth kinetics and the process of magma fragmentation, both of which exert a first-order control on the magnitude and intensity of energy release during an eruption. Gas flows through connected networks of bubbles and cracks which may change dynamically. The complex and highly-variable nature of the network geometries has hitherto prevented the development of a general, quantitative description of the permeability of volcanic materials. We present a combined experimental--numerical investigation of the permeability of these networks comprising: 1) direct numerical simulation of gas flow through permeable networks using the lattice-Boltzmann method (LBM) and the finite element method (FEM); 2) direct imaging of fluid flow through permeable real and analogue volcan...
The University of Reading has in developed techniques for fast visualisation of gridded data, suc... more The University of Reading has in developed techniques for fast visualisation of gridded data, such that they can be used in a WMS (web-map server) system. The aim is to provide data visualisation which is quick enough to be used interactively (e.g. on a website) even with very large underlying datasets. The two main tools which have come out of this effort are ncWMS (a WMS server for displaying NetCDF data) and its accompanying web client, Godiva2. This software is very widely used by oceanographic (and other) institutions and this presentation describes some of the most recent advances, together with plans for the future. For the MyOcean View Service, the University of Reading has extended ncWMS to allow it to display in situ measurement data. This accesses a supporting system, Oceanotron, created by Ifremer, which performs spatial indexing to retrieve observations from a database. By incorporating Oceanotron into the widely-used ncWMS software, map images of such point data can be...
Since 2009, MyOcean (http://www.myocean.eu) is providing an operational service, for forecasts, a... more Since 2009, MyOcean (http://www.myocean.eu) is providing an operational service, for forecasts, analysis and expertise on ocean currents, temperature, salinity, sea level, primary ecosystems and ice coverage. The production of observation and forecasting data is done by 42 Production Units (PU). Product download and visualisation are hosted by 25 Dissemination Units (DU). All these products and associated services are gathered in a single catalogue hiding the intricate distributed organization of PUs and DUs. Besides applying INSPIRE directive and OGC recommendations, MyOcean overcomes technical choices and challenges. This presentation focuses on 3 specific issues met by MyOcean and relevant for many Spatial Data Infrastructures: user's transaction accounting, large volume download and stream line the catalogue maintenance. Transaction Accounting: Set up powerful means to get detailed knowledge of system usage in order to subsequently improve the products (ocean observations, a...
Currently, there are many web portals available which focus on visualizing environmental data, bu... more Currently, there are many web portals available which focus on visualizing environmental data, but for comparing datasets and carrying out analyses users turn to desktop applications such as Matlab and IDL. These are powerful, but require users to download large datasets and manually get to grips with low-level data formats and metadata conventions. Until this time there have been a number of factors inhibiting the transfer of basic data analysis and comparison from desktop applications to web portals. These include the size of the datasets involved, their diversity of format and location, and security constraints. MashMyData is a UK NERC (Natural Environment Research Council) funded "Technology Proof of Concept" programme which aims to address these needs by creating a system to allow environmental scientists to compare and combine diverse datasets over the web without the need to understand the low-level technical details of the data's format or physical location. Us...
We present the Styx Grid Service (SGS), a remote service type that allows data to be streamed dir... more We present the Styx Grid Service (SGS), a remote service type that allows data to be streamed directly between service instances. The Styx Grid Service is built upon the Styx protocol, an established protocol for building distributed systems. Through the use of persistent connections, clients can monitor progress, status and other service data without requiring inbound ports to be open
There is remarkable agreement in expectations today for vastly improved ocean data management a d... more There is remarkable agreement in expectations today for vastly improved ocean data management a decade from now --capabilities that will help to bring significant benefits to ocean research and to society. Advancing data management to such a degree, however, will require cultural and policy changes that are slow to effect. The technological foundations upon which data management systems are built are certain to continue advancing rapidly in parallel. These considerations argue for adopting attitudes of pragmatism and realism when planning data management strategies. In this paper we adopt those attitudes as we outline opportunities for progress in ocean data management. We begin with a synopsis of expectations for integrated ocean data management a decade from now. We discuss factors that should be considered by those evaluating candidate "standards". We highlight challenges and opportunities in a number of technical areas, including "Web 2.0" applications, data ...
Improving Knowledge Discovery in Science, Engineering, and Business, 2013
ABSTRACT The question of data quality is a prominent topic of current research in Earth observati... more ABSTRACT The question of data quality is a prominent topic of current research in Earth observation. However, different users have different views and visions on data quality. There exists a set of standards and specifications in relation to data quality for Earth observation (e.g. ISO standards, W3C standards, QA4EO), and how to choose appropriate one for quality information representation also present a challenge. In order to address the need, we carried out interviews with environmental scientists to elicit their views on matters such as how they choose data for their studies, and what encourages them to trust the accuracy and validity of the data. Interviews were structured around a carefully-designed questionnaire. Face-to-face and telephone interviews were performed in order to gain maximum value from the consultation process. An array of views and visions on Earth observation data have been gathered, which will provide valuable input to the community and other data providers. Informed by the interview findings, we critically review the existing standards and specifications and propose a new, integrated quality information model for Earth observation. This builds upon existing models, notably the ISO standards suite, filling gaps that we have identified in order to encompass other important aspects of data quality. This work has been performed in the context of the EU FP7 GeoViQua project, which aims to augment the Global Earth Observation System of Systems (GEOSS) with information about the quality of data holdings, and to provide visualization capabilities for users to view data together with associated quality information.
We describe ncWMS, an implementation of the Open Geospatial Consortium's Web Map Service (WMS) sp... more We describe ncWMS, an implementation of the Open Geospatial Consortium's Web Map Service (WMS) specification for multidimensional gridded environmental data. ncWMS can read data in a large number of common scientific data formats e notably the NetCDF format with the Climate and Forecast conventions e then efficiently generate map imagery in thousands of different coordinate reference systems. It is designed to require minimal configuration from the system administrator and, when used in conjunction with a suitable client tool, provides end users with an interactive means for visualizing data without the need to download large files or interpret complex metadata. It is also used as a "bridging" tool providing interoperability between the environmental science community and users of geographic information systems. ncWMS implements a number of extensions to the WMS standard in order to fulfil some common scientific requirements, including the ability to generate plots representing timeseries and vertical sections. We discuss these extensions and their impact upon present and future interoperability. We discuss the conceptual mapping between the WMS data model and the data models used by gridded data formats, highlighting areas in which the mapping is incomplete or ambiguous. We discuss the architecture of the system and particular technical innovations of note, including the algorithms used for fast data reading and image generation. ncWMS has been widely adopted within the environmental data community and we discuss some of the ways in which the software is integrated within data infrastructures and portals.
Bulletin of Volcanology, 2001
A model has been developed to investigate the sensitivity of magma permeability, k, to various pa... more A model has been developed to investigate the sensitivity of magma permeability, k, to various parameters. Power-law relationships between k and porosity J are revealed, in agreement with previous experimental and theoretical studies. These relationships take the form % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfKttLearuavTnhis1MBaeXatLxBI9gBae % rbd9wDYLwzYbWexLMBbXgBcf2CPn2qVrwzqf2zLnharyavP1wzZbIt % LDhis9wBH5garqqtubsr4rNCHbGeaGqiVCI8FfYJH8sipiYdHaVhbb % f9v8qqaqFr0xc9pk0xbba9q8WqFfeaY-biLkVcLq-JHqpepeea0-as % 0Fb9pgeaYRXxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaabau % aaaOqaaiqbdUgaRzaajaGaeyypa0Jaem4AaSMaei4la8IaemOCai3a % aWbaaSqabeaacqaIYaGmaaGccqGH9aqpcqWGHbqycqGGOaakcqaHgp % GzcqGHsislcqaHgpGzdaWgaaWcbaGaem4yamMaemOCaihabeaakiab % cMcaPmaaCaaaleqabaGaemOyaigaaaaa!4CE4! \hat k
Procedia Computer Science, 2011
Climate-G is a large scale distributed testbed devoted to climate change research. It is an unfun... more Climate-G is a large scale distributed testbed devoted to climate change research. It is an unfunded effort started in 2008 and involving a wide community both in Europe and US. The testbed is an interdisciplinary effort involving partners from several institutions and joining expertise in the field of climate change and computational science. Its main goal is to allow scientists carrying out geographical and cross-institutional data discovery, access, analysis, visualization and sharing of climate data. It represents an attempt to address, in a real environment, challenging data and metadata management issues. This paper presents a complete overview about the Climate-G testbed highlighting the most important results that have been achieved since the beginning of this project.
Earth and Planetary Science Letters, 2001
The coupling of viscosity and diffusivity during explosive volcanic degassing is investigated usi... more The coupling of viscosity and diffusivity during explosive volcanic degassing is investigated using a numerical model of bubble growth in rhyolitic melts. The model allows melt viscosity and water diffusivity to vary spatially and temporally with water content. We find that the system is highly sensitive to the distribution of volatiles around the bubble, primarily as a consequence of the
Journal of Volcanology and Geothermal Research, 2003
We review observations of bubble size distributions (BSDs) generated during explosive volcanic er... more We review observations of bubble size distributions (BSDs) generated during explosive volcanic eruptions and laboratory explosions, as inferred from vesicle size distributions found in the end products. Unimodal, polymodal, exponential and power law BSDs are common, even in the absence of coalescence, and both power law and exponential distributions have been generated in the same eruption. To date theoretical models
We review observations of bubble size distributions (BSDs) generated during explosive volcanic er... more We review observations of bubble size distributions (BSDs) generated during explosive volcanic eruptions and laboratory explosions, as inferred from vesicle size distributions found in the end products. Unimodal, polymodal, exponential and power law BSDs are common, even in the absence of coalescence, and both power law and exponential distributions have been generated in the same eruption. To date theoretical models
Both power law and exponential vesicle size distributions (VSDs) have been observed in many diere... more Both power law and exponential vesicle size distributions (VSDs) have been observed in many dierent typesofvolcanicrocks. Wepresentresultsofcomputersim- ulations and laboratory analogue experiments which repro- duce these ndings and show that the distributions can be interpreted as the product of continuous bubble nucleation resulting from non-equilibrium degassing. This ongoing nu- cleationcausesthebubblestoevolvethroughanexponential size distribution into a power law size distribution as nucle-
Geophysical Research Letters, 2001
Both power law and exponential vesicle size distributions (VSDs) have been observed in many diffe... more Both power law and exponential vesicle size distributions (VSDs) have been observed in many different types of volcanic rocks. We present results of computer simulations and laboratory analogue experiments which reproduce these findings and show that the distributions can be interpreted as the product of continuous bubble nucleation resulting from non-equilibrium degassing. This ongoing nucleation causes the bubbles to evolve through an exponential size distribution into a power law size distribution as nucleation and growth progress. These findings may explain the apparent contradiction between present models of bubble growth in magmas, which predict that degassing in explosive eruptions is a non-equilibrium process, and models of conduit flow, which assume perfect equilibrium degassing. The process of continuous nucleation is the mechanism whereby the volcanic system maintains near-equilibrium in the case of rapid depressurization and slow volatile diffusion.
In the decade since OceanObs `99, great advances have been made in the field of ocean data dissem... more In the decade since OceanObs `99, great advances have been made in the field of ocean data dissemination. The use of Internet technologies in particular has transformed the landscape: users can now find, evaluate and access data rapidly and securely using only a web browser. This paper describes the current state of the art in dissemination methods for ocean data, focussing particularly on ocean observations from in situ and remote sensing platforms. We discuss current efforts in increasing the consistency of delivered data and in increasing the potential for automated integration of diverse datasets. An important recent development is the adoption of open standards from the Geographic Information Systems community; we discuss the current impact of these new technologies and their future potential. We conclude that new approaches will indeed be necessary to exchange data more effectively and forge links between communities, but these approaches must be evaluated critically through p...
The flow of exsolved gases through the volcanic system exerts a fundamental control on the nature... more The flow of exsolved gases through the volcanic system exerts a fundamental control on the nature of a volcano's activity. Gas flow determines the internal pressure of magmatic bubbles and so strongly influences bubble growth kinetics and the process of magma fragmentation, both of which exert a first-order control on the magnitude and intensity of energy release during an eruption. Gas flows through connected networks of bubbles and cracks which may change dynamically. The complex and highly-variable nature of the network geometries has hitherto prevented the development of a general, quantitative description of the permeability of volcanic materials. We present a combined experimental--numerical investigation of the permeability of these networks comprising: 1) direct numerical simulation of gas flow through permeable networks using the lattice-Boltzmann method (LBM) and the finite element method (FEM); 2) direct imaging of fluid flow through permeable real and analogue volcan...
The University of Reading has in developed techniques for fast visualisation of gridded data, suc... more The University of Reading has in developed techniques for fast visualisation of gridded data, such that they can be used in a WMS (web-map server) system. The aim is to provide data visualisation which is quick enough to be used interactively (e.g. on a website) even with very large underlying datasets. The two main tools which have come out of this effort are ncWMS (a WMS server for displaying NetCDF data) and its accompanying web client, Godiva2. This software is very widely used by oceanographic (and other) institutions and this presentation describes some of the most recent advances, together with plans for the future. For the MyOcean View Service, the University of Reading has extended ncWMS to allow it to display in situ measurement data. This accesses a supporting system, Oceanotron, created by Ifremer, which performs spatial indexing to retrieve observations from a database. By incorporating Oceanotron into the widely-used ncWMS software, map images of such point data can be...
Since 2009, MyOcean (http://www.myocean.eu) is providing an operational service, for forecasts, a... more Since 2009, MyOcean (http://www.myocean.eu) is providing an operational service, for forecasts, analysis and expertise on ocean currents, temperature, salinity, sea level, primary ecosystems and ice coverage. The production of observation and forecasting data is done by 42 Production Units (PU). Product download and visualisation are hosted by 25 Dissemination Units (DU). All these products and associated services are gathered in a single catalogue hiding the intricate distributed organization of PUs and DUs. Besides applying INSPIRE directive and OGC recommendations, MyOcean overcomes technical choices and challenges. This presentation focuses on 3 specific issues met by MyOcean and relevant for many Spatial Data Infrastructures: user's transaction accounting, large volume download and stream line the catalogue maintenance. Transaction Accounting: Set up powerful means to get detailed knowledge of system usage in order to subsequently improve the products (ocean observations, a...
Currently, there are many web portals available which focus on visualizing environmental data, bu... more Currently, there are many web portals available which focus on visualizing environmental data, but for comparing datasets and carrying out analyses users turn to desktop applications such as Matlab and IDL. These are powerful, but require users to download large datasets and manually get to grips with low-level data formats and metadata conventions. Until this time there have been a number of factors inhibiting the transfer of basic data analysis and comparison from desktop applications to web portals. These include the size of the datasets involved, their diversity of format and location, and security constraints. MashMyData is a UK NERC (Natural Environment Research Council) funded "Technology Proof of Concept" programme which aims to address these needs by creating a system to allow environmental scientists to compare and combine diverse datasets over the web without the need to understand the low-level technical details of the data's format or physical location. Us...
We present the Styx Grid Service (SGS), a remote service type that allows data to be streamed dir... more We present the Styx Grid Service (SGS), a remote service type that allows data to be streamed directly between service instances. The Styx Grid Service is built upon the Styx protocol, an established protocol for building distributed systems. Through the use of persistent connections, clients can monitor progress, status and other service data without requiring inbound ports to be open
There is remarkable agreement in expectations today for vastly improved ocean data management a d... more There is remarkable agreement in expectations today for vastly improved ocean data management a decade from now --capabilities that will help to bring significant benefits to ocean research and to society. Advancing data management to such a degree, however, will require cultural and policy changes that are slow to effect. The technological foundations upon which data management systems are built are certain to continue advancing rapidly in parallel. These considerations argue for adopting attitudes of pragmatism and realism when planning data management strategies. In this paper we adopt those attitudes as we outline opportunities for progress in ocean data management. We begin with a synopsis of expectations for integrated ocean data management a decade from now. We discuss factors that should be considered by those evaluating candidate "standards". We highlight challenges and opportunities in a number of technical areas, including "Web 2.0" applications, data ...
Improving Knowledge Discovery in Science, Engineering, and Business, 2013
ABSTRACT The question of data quality is a prominent topic of current research in Earth observati... more ABSTRACT The question of data quality is a prominent topic of current research in Earth observation. However, different users have different views and visions on data quality. There exists a set of standards and specifications in relation to data quality for Earth observation (e.g. ISO standards, W3C standards, QA4EO), and how to choose appropriate one for quality information representation also present a challenge. In order to address the need, we carried out interviews with environmental scientists to elicit their views on matters such as how they choose data for their studies, and what encourages them to trust the accuracy and validity of the data. Interviews were structured around a carefully-designed questionnaire. Face-to-face and telephone interviews were performed in order to gain maximum value from the consultation process. An array of views and visions on Earth observation data have been gathered, which will provide valuable input to the community and other data providers. Informed by the interview findings, we critically review the existing standards and specifications and propose a new, integrated quality information model for Earth observation. This builds upon existing models, notably the ISO standards suite, filling gaps that we have identified in order to encompass other important aspects of data quality. This work has been performed in the context of the EU FP7 GeoViQua project, which aims to augment the Global Earth Observation System of Systems (GEOSS) with information about the quality of data holdings, and to provide visualization capabilities for users to view data together with associated quality information.
We describe ncWMS, an implementation of the Open Geospatial Consortium's Web Map Service (WMS) sp... more We describe ncWMS, an implementation of the Open Geospatial Consortium's Web Map Service (WMS) specification for multidimensional gridded environmental data. ncWMS can read data in a large number of common scientific data formats e notably the NetCDF format with the Climate and Forecast conventions e then efficiently generate map imagery in thousands of different coordinate reference systems. It is designed to require minimal configuration from the system administrator and, when used in conjunction with a suitable client tool, provides end users with an interactive means for visualizing data without the need to download large files or interpret complex metadata. It is also used as a "bridging" tool providing interoperability between the environmental science community and users of geographic information systems. ncWMS implements a number of extensions to the WMS standard in order to fulfil some common scientific requirements, including the ability to generate plots representing timeseries and vertical sections. We discuss these extensions and their impact upon present and future interoperability. We discuss the conceptual mapping between the WMS data model and the data models used by gridded data formats, highlighting areas in which the mapping is incomplete or ambiguous. We discuss the architecture of the system and particular technical innovations of note, including the algorithms used for fast data reading and image generation. ncWMS has been widely adopted within the environmental data community and we discuss some of the ways in which the software is integrated within data infrastructures and portals.