Tim Hoar - Academia.edu (original) (raw)

Papers by Tim Hoar

Research paper thumbnail of Regional and basin scale applications of ensemble adjustment Kalman filter and 4D-Var ocean data assimilation systems

Progress in Oceanography

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Research paper thumbnail of Estimating continental scaling of ecological driver-response feedbacks through model-data fusion

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Research paper thumbnail of POPDART: An Ensemble Data Assimilation System for the Ocean Component of CESM

ABSTRACT

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Research paper thumbnail of The impacts of uncertainty in observations on a data assimilation system for ecological forecasting

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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Research paper thumbnail of Quantifying uncertainty in projections of continental fluxes of carbon and energy using the NEON platform

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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Research paper thumbnail of Passive microwave radiance data assimilation for estimating snow water equivalent over North America

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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Research paper thumbnail of Assimilation of near-surface cosmic-ray neutrons improves summertime soil moisture profile estimates at three distinct biomes in the USA

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Research paper thumbnail of DART: A Community Facility for Ensemble Data Assimilation

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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Research paper thumbnail of Fast, eastward-moving disturbances in the surface winds of the equatorial Pacific

Tellus A, 1998

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Research paper thumbnail of Assimilation of MODIS snow cover through the Data Assimilation Research Testbed and the Community Land Model version 4

Journal of Geophysical Research: Atmospheres, 2014

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Research paper thumbnail of An Ensemble Adjustment Kalman Filter for the CCSM4 Ocean Component

Journal of Climate, 2013

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Research paper thumbnail of A MITgcm/DART ensemble analysis and prediction system with application to the Gulf of Mexico

Dynamics of Atmospheres and Oceans, 2013

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Research paper thumbnail of A MITgcm/DART Ocean Analysis and Prediction System with Application to the Gulf of Mexico

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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Research paper thumbnail of The Data Assimilation Research Testbed: A Community Facility

Bulletin of the American Meteorological Society, 2009

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Research paper thumbnail of Regional and basin scale applications of ensemble adjustment Kalman filter and 4D-Var ocean data assimilation systems

Progress in Oceanography

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Research paper thumbnail of Estimating continental scaling of ecological driver-response feedbacks through model-data fusion

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Research paper thumbnail of POPDART: An Ensemble Data Assimilation System for the Ocean Component of CESM

ABSTRACT

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Research paper thumbnail of The impacts of uncertainty in observations on a data assimilation system for ecological forecasting

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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Research paper thumbnail of Quantifying uncertainty in projections of continental fluxes of carbon and energy using the NEON platform

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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Research paper thumbnail of Passive microwave radiance data assimilation for estimating snow water equivalent over North America

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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Research paper thumbnail of Assimilation of near-surface cosmic-ray neutrons improves summertime soil moisture profile estimates at three distinct biomes in the USA

Bookmarks Related papers MentionsView impact

Research paper thumbnail of DART: A Community Facility for Ensemble Data Assimilation

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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Research paper thumbnail of Fast, eastward-moving disturbances in the surface winds of the equatorial Pacific

Tellus A, 1998

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Research paper thumbnail of Assimilation of MODIS snow cover through the Data Assimilation Research Testbed and the Community Land Model version 4

Journal of Geophysical Research: Atmospheres, 2014

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Research paper thumbnail of An Ensemble Adjustment Kalman Filter for the CCSM4 Ocean Component

Journal of Climate, 2013

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Research paper thumbnail of A MITgcm/DART ensemble analysis and prediction system with application to the Gulf of Mexico

Dynamics of Atmospheres and Oceans, 2013

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Research paper thumbnail of A MITgcm/DART Ocean Analysis and Prediction System with Application to the Gulf of Mexico

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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Research paper thumbnail of The Data Assimilation Research Testbed: A Community Facility

Bulletin of the American Meteorological Society, 2009

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