Tim Hoar - Academia.edu (original) (raw)
Papers by Tim Hoar
Progress in Oceanography
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ABSTRACT
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Background/Question/Methods The National Ecological Observatory Network (NEON) is a continental-s... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a continental-scale facility that will collect ecological data, including eddy covariance flux observations, from 60 sites in the continental US, Alaska, Hawaii, and Puerto Rico over 30 years. We are vigorously quantifying uncertainty in all NEON data products and are investigating the propagation of uncertainty from basic observations when generating high-level data products, such as continental-scale, gridded maps of carbon and energy fluxes. One approach we are using to integrate many observational data streams into high-level data products is to use model-data fusion. In this approach a process model is used to provide an analytical framework for data interpretation, synthesis, interpolation and extrapolation. In theory, uncertainty from many sources can be accounted for including: (i) observational data, due to incomplete and noisy observations and biases; (ii) process model structure; (iii) proce...
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Background/Question/Methods As we enter a new “data rich” period for ecological science new possi... more Background/Question/Methods As we enter a new “data rich” period for ecological science new possibilities become available which allow for better forecasting of many ecosystem processes. We are utilizing data from the continental-scale NEON platform and other monitoring networks (FLUXNET, ICOS, LTER etc.), in conjunction with ever-increasing computing power, land surface model sophistication and new statistical and optimization methodologies to address a pressing societal need for improved quantification and reduction of uncertainty of projections of carbon and energy fluxes across the US. We have developed a data assimilation system coupling the Community Land Model (CLM) with the Data Assimilation Research Testbed (DART), an advanced facility for ensemble data assimilation (DA). Using this new tool we are able to constrain the model with data to give predictions that best approximate the observations. Using this approach, in theory we able to account for multiple sources of uncert...
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Snow is a critical component of the global energy and water balances, in particular at middle to ... more Snow is a critical component of the global energy and water balances, in particular at middle to high latitudes, because of snow’s high albedo, low thermal conductivity, and water holding capacity. Data assimilation has been an important tool to obtain the distribution of snow depth and snow water equivalent (SWE), which are critical for climate and water resource applications. In previous studies, passive microwave (PM) radiance assimilation (RA) has shown promise for improving SWE estimations at point, local, and basin scales. In this study, we aim to address the feasibility of RA to improve SWE estimates at the continental scale. We use the Community Land Model version 4 (CLM4) for snow dynamics and the Dense Media Radiative Transfer–Multi Layers model (DMRT-ML) for snowpack brightness temperature (TB) estimations. Atmospheric and vegetation radiative transfer models (RTMs) are also incorporated to consider the effects of atmosphere and vegetation on TB at the top of the atmosphe...
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The Data Assimilation Research Testbed (DART) is a mature community software facility providing r... more The Data Assimilation Research Testbed (DART) is a mature community software facility providing researchers access to state-of-the-art ensemble data assimilation tools. The freely-available DART distribution includes fully functional low-order and high-order models, support for commonly available observations, hooks to easily add both new models and observation types, diagnostic programs to interpret the results, and a full tutorial suitable for self-study
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Tellus A, 1998
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Journal of Geophysical Research: Atmospheres, 2014
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Journal of Climate, 2013
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Dynamics of Atmospheres and Oceans, 2013
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AGU Fall Meeting Abstracts, Dec 1, 2008
The ECCO system is a new generation of ocean assimilation systems based on the Massachusetts Inst... more The ECCO system is a new generation of ocean assimilation systems based on the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint. The system has been used to produce the first global 1o ocean state estimates (Köhl et al., 2006 and Wunsch and Heimbach, 2008). It is now also used for regional and coastal MITgcm applications (Hoteit et al., 2005; Gebbie et al., 2006; Hoteit et al., 2008). To improve the predictive capabilities of the ECCO system, the Data Assimilation Research Testbed ( ...
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Bulletin of the American Meteorological Society, 2009
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Progress in Oceanography
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ABSTRACT
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Background/Question/Methods The National Ecological Observatory Network (NEON) is a continental-s... more Background/Question/Methods The National Ecological Observatory Network (NEON) is a continental-scale facility that will collect ecological data, including eddy covariance flux observations, from 60 sites in the continental US, Alaska, Hawaii, and Puerto Rico over 30 years. We are vigorously quantifying uncertainty in all NEON data products and are investigating the propagation of uncertainty from basic observations when generating high-level data products, such as continental-scale, gridded maps of carbon and energy fluxes. One approach we are using to integrate many observational data streams into high-level data products is to use model-data fusion. In this approach a process model is used to provide an analytical framework for data interpretation, synthesis, interpolation and extrapolation. In theory, uncertainty from many sources can be accounted for including: (i) observational data, due to incomplete and noisy observations and biases; (ii) process model structure; (iii) proce...
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Background/Question/Methods As we enter a new “data rich” period for ecological science new possi... more Background/Question/Methods As we enter a new “data rich” period for ecological science new possibilities become available which allow for better forecasting of many ecosystem processes. We are utilizing data from the continental-scale NEON platform and other monitoring networks (FLUXNET, ICOS, LTER etc.), in conjunction with ever-increasing computing power, land surface model sophistication and new statistical and optimization methodologies to address a pressing societal need for improved quantification and reduction of uncertainty of projections of carbon and energy fluxes across the US. We have developed a data assimilation system coupling the Community Land Model (CLM) with the Data Assimilation Research Testbed (DART), an advanced facility for ensemble data assimilation (DA). Using this new tool we are able to constrain the model with data to give predictions that best approximate the observations. Using this approach, in theory we able to account for multiple sources of uncert...
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Snow is a critical component of the global energy and water balances, in particular at middle to ... more Snow is a critical component of the global energy and water balances, in particular at middle to high latitudes, because of snow’s high albedo, low thermal conductivity, and water holding capacity. Data assimilation has been an important tool to obtain the distribution of snow depth and snow water equivalent (SWE), which are critical for climate and water resource applications. In previous studies, passive microwave (PM) radiance assimilation (RA) has shown promise for improving SWE estimations at point, local, and basin scales. In this study, we aim to address the feasibility of RA to improve SWE estimates at the continental scale. We use the Community Land Model version 4 (CLM4) for snow dynamics and the Dense Media Radiative Transfer–Multi Layers model (DMRT-ML) for snowpack brightness temperature (TB) estimations. Atmospheric and vegetation radiative transfer models (RTMs) are also incorporated to consider the effects of atmosphere and vegetation on TB at the top of the atmosphe...
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Bookmarks Related papers MentionsView impact
The Data Assimilation Research Testbed (DART) is a mature community software facility providing r... more The Data Assimilation Research Testbed (DART) is a mature community software facility providing researchers access to state-of-the-art ensemble data assimilation tools. The freely-available DART distribution includes fully functional low-order and high-order models, support for commonly available observations, hooks to easily add both new models and observation types, diagnostic programs to interpret the results, and a full tutorial suitable for self-study
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Tellus A, 1998
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Journal of Geophysical Research: Atmospheres, 2014
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Journal of Climate, 2013
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Dynamics of Atmospheres and Oceans, 2013
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AGU Fall Meeting Abstracts, Dec 1, 2008
The ECCO system is a new generation of ocean assimilation systems based on the Massachusetts Inst... more The ECCO system is a new generation of ocean assimilation systems based on the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint. The system has been used to produce the first global 1o ocean state estimates (Köhl et al., 2006 and Wunsch and Heimbach, 2008). It is now also used for regional and coastal MITgcm applications (Hoteit et al., 2005; Gebbie et al., 2006; Hoteit et al., 2008). To improve the predictive capabilities of the ECCO system, the Data Assimilation Research Testbed ( ...
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Bulletin of the American Meteorological Society, 2009
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