Keith Oleson | National Center for Atmospheric Research (NCAR) (original) (raw)

Papers by Keith Oleson

Research paper thumbnail of Offline evaluation of the Community Land Model-Urban for Toulouse (France) and Melbourne (Australia)

ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surfa... more ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surface modification on urban climates. It provides a mechanism for trialling different scenarios for urban heat island mitigation. Only recently, urban land surfaces have been included in global and regional climate models. Often they represent a trade-off between the complexity of the biophysical processes of the urban canopy layer and the computational demands in order to be workable on regional climate time scales. This study employs the Community Land Model (CLM) which was recently extended with a single layer urban canopy scheme (CLM-U). And although it is primarily developed as a tool for regional climate scales, we intent to extend its reach and use it for local (neighborhood) scales in a changing climate context. Hence, an off-line validation is performed using meteorological observations for Toulouse (France) and multiple medium density urban areas in Melbourne (Australia). Model results are evaluated against observations of the surface energy balance from flux towers, including evapotranspiration, and show that the model is able to correctly address (urban) energy partitioning including high urban heat storage, and low evapotranspiration rates. Furthermore an investigation was undertaken to explore first of all the capacity of the model to incorporate Water Sensitive Urban Design (WSUD) features, mimicking vegetated and non-vegetated infiltration systems, open water bodies and other green infrastructure. In a second step, the effectiveness of WSUD integration scenarios are also compared with other common mitigation strategies such as increasing albedo and controlling urban morphology.

Research paper thumbnail of Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban

International Journal of Climatology, 2013

A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contras... more A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contrasting urban environments of Toulouse (France) and Melbourne (Australia). For the latter, three measurement sites are available characterized by a varying amount of vegetation, which supports a detailed assessment of the representation of urban vegetation in CLMU. For Toulouse, observed roof, wall and road surface temperatures allow for a detailed evaluation of the anthropogenic heat parameterization. Overall, CLMU performs well in simulating the canyon and urban surface temperatures, anthropogenic heat flux and urban energy balance, with an overall better performance for the dense old city centre of Toulouse in comparison to the more vegetated sites in Melbourne. Results for the latter sites reveal that the pervious road fraction provides a reasonable approximation of vegetation in the urban canyon while the tile approach often results in an underestimation of latent heat fluxes. A detailed analysis of the radiative, turbulent and anthropogenic heat fluxes as well as surface temperatures for Toulouse point to a complex interaction between urban surfaces and canyon properties. Decoupling the roof from the urban canyon to the atmosphere aloft is shown to be important. Our findings suggest that more evaluation is necessary for contrasting urban geometries in order to obtain a better understanding of the interaction between the roof surface on the one hand and canyon air and air aloft on the other hand. The results simultaneously reveal a trade-off in errors between surface temperatures, radiative and turbulent fluxes and anthropogenic heat which again stresses the importance of the intended model application. Also, our results suggest that model complexity should, perhaps, relate to the site complexity. These results provide a robust basis for the construction of additional sensitivity experiments, tailored towards the intended application for urban climate mitigation studies.

Research paper thumbnail of The representation of space and stochasticity in one-dimensional and deterministic global vegetation models

ABSTRACT Implementation of plant community dynamics into global land surface models is in a phase... more ABSTRACT Implementation of plant community dynamics into global land surface models is in a phase of rapid development. Multiple individual-, cohort- and canopy- based approaches are being deployed and, as a result, many common challenges in the representation of ecological principles in a predictive, global framework are being identifying and confronted. In this talk we introduce the implementation of the Ecosystem Demography framework into the Community Land Model (CLM) and test the response of the model to a set of residual ecological uncertainties that must be represented during the simulation of coexisting plant communities. In particular, we focus on the intensity of competition for light resources, the density dependence of seedling recruitment, and the impact of sub-grid heterogeneity on below-ground competition. All of these processes alter the tendency of the model to generate high-diversity ecosystems, with subsequent impacts on the resilience to climate. Appropriate benchmarks of community resilience to climate change are sparse, but slowly emerging, and we analyse how the alternative simulations of plant community structure alter the ability of the model to predict regional-scale observations of ecosystem vulnerability to drought stress.

Research paper thumbnail of Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5

Geoscientific Model Development

We implement and analyze 13 different metrics (4 moist thermodynamic quantities and 9 heat stress... more We implement and analyze 13 different metrics (4 moist thermodynamic quantities and 9 heat stress metrics) in the Community Land Model (CLM4.5), the land surface component of the Community Earth System Model (CESM). We call these routines the HumanIndexMod. We limit the algorithms of the HumanIndexMod to meteorological inputs of temperature, moisture, and pressure for their calculation. All metrics assume no direct sunlight exposure. The goal of this project is to implement a common framework for calculating operationally used heat stress metrics, in climate models, offline output, and locally sourced weather data sets, with the intent that the HumanIndexMod may be used with the broadest of applications. The thermodynamic quantities use the latest, most accurate and efficient algorithms available, which in turn are used as inputs to the heat stress metrics. There are three advantages of adding these metrics to CLM4.5: (1) improved moist thermodynamic quantities; (2) quantifying heat...

Research paper thumbnail of Urban modeling over Houston in support of SIMMER

Abstract Extreme heat is a leading cause of weather-related human mortality in the United States.... more Abstract Extreme heat is a leading cause of weather-related human mortality in the United States. As global warming patterns continue, researchers anticipate increases in the severity, frequency and duration of extreme heat events, especially in the southern and western US Many cities in these regions may have amplified vulnerability due to their rapidly evolving socioeconomic fabric (for example, growing elderly populations). This raises a series of questions about the increased health risks of urban residents to extreme heat, ...

Research paper thumbnail of Contributions of coastal megacities to environmental changes at regional and global scales

Research paper thumbnail of Modeling the integrated ecology, biogeochemistry, and hydrology of the global terrestrial biosphere in the Community Land Model (CLM4) (Invited)

Agu Fall Meeting Abstracts, Dec 1, 2010

Terrestrial ecosystems influence climate through physical, chemical, and biological processes tha... more Terrestrial ecosystems influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. Much of our understanding of how terrestrial ecosystems affect climate comes from numerical models of Earth’s climate and their representation of the terrestrial biosphere. These models initially simulated only hydrometeorological processes at the land surface. They have since evolved to simulate the coupled ecology, biogeochemistry, and hydrology of terrestrial ecosystems so that the biosphere and atmosphere form a coupled system. As such, the simulated hydrologic cycle is an emergent property of the ecology and biogeochemistry represented in the model. Here, we use the Community Land Model (CLM4), the land component of the Community Earth System Model, to examine interactions among hydrology, ecology, and biogeochemistry with respect to energy, water, and carbon fluxes. Specifically, carbon uptake during gross primary production (GPP) is linked to water loss during evapotranspiration (ET). Model functional errors in the parameterization of canopy radiative transfer, leaf photosynthesis and stomatal conductance, and canopy scaling lead to substantial errors in simulated GPP and ET. Improvements to these parameterizations gained from theoretical considerations and empirical studies reduce biases in GPP, with concomitant improvement in ET. Most of the bias reduction comes from the revised photosynthesis-stomatal conductance formulation; improved canopy radiation has lesser effect; and changes to canopy scaling have minor effect. A key model parameter is the maximum rate of leaf carboxylation, which is highly uncertain for large-scale climate models and for which various disparate estimates have been published. The effect of model parameter errors on GPP and ET is of comparable magnitude to that of model functional errors and offset bias reductions from improved model parameterizations. Our results imply that this key leaf-level physiological parameter cannot be defined independent of model-specific parameterizations. Our analyses suggest that we still have much to learn about the biochemistry of photosynthesis, the biophysics of evapotranspiration, their interdependencies, and how to represent these processes in models of the terrestrial biosphere for climate simulation.

Research paper thumbnail of Technical Description of an Urban Parameterization for the Community Land Model (CLMU)

The Technical Notes series provides an outlet for a variety of NCAR Manuscripts that contribute i... more The Technical Notes series provides an outlet for a variety of NCAR Manuscripts that contribute in specialized ways to the body of scientific knowledge but that are not suitable for journal, monograph, or book publication. Reports in this series are issued by the NCAR scientific divisions. Designation symbols for the series include:

Research paper thumbnail of Seasonal surface urban energy balance and wintertime stability simulated using three land-surface models in the high-latitude city Helsinki

Quarterly Journal of the Royal Meteorological Society, 2015

The performance of three urban land surface models, run in offline mode, with their default exter... more The performance of three urban land surface models, run in offline mode, with their default external parameters, is evaluated for two distinctly different sites in Helsinki:

Research paper thumbnail of Unmixing multiple land-cover type reflectances from coarse spatial resolution satellite data

Remote Sensing of Environment, 1995

We present a technique for extracting subpixel cover type reflectances from the mixed pixels of a... more We present a technique for extracting subpixel cover type reflectances from the mixed pixels of a coarse spatial resolution image. A Gaussian filter is used to spatially degrade a set of fine spatial resolution images [based on, e.g., Landsat Thematic Mapper (TM)], each of which represent the spatial structure and extent of a land-cover type. From the degraded image data, a set of weights representing the proportions of cover types within the mixed pixels of a coarse spatial/fine temporal resolution image [e.g., NOAA Advanced Very High Resolution Radiometer (AVHRR)] is produced. These weights and the A VHRR spectral band reflectances are used in multiple linear regression analyses to extract mean cover type reflectances. A simulation study was conducted to define the operational limitations of this technique. Cover type reflectances are accurately estimated if the cover types are spatially well represented within the area of interest, are spectrally distinct, and have small within-class spectral variability. The accuracy of retrieved reflectances is most sensitive to errors in the coarse spatial resolution data and least sensitive to errors in the weights'. By applying this technique to multiple images, temporal profiles of subpixel cover type reflectance may be obtained. This particular application is demonstrated by using TM and A VHRR data from the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) to create normalized difference vegetation index (NDVI) temporal profiles of the dominant land-cover types.

Research paper thumbnail of The Sensitivity of a Land Surface Parameterization Scheme to the Choice of Remotely Sensed Land-Cover Datasets

Monthly Weather Review, 1997

The characteristics of satellite-derived land-cover data for climate models vary depending on sen... more The characteristics of satellite-derived land-cover data for climate models vary depending on sensor properties and processing options. To better understand the first-order effects of differences in land-cover data on a land surface parameterization scheme (VBATS), stand-alone model runs were performed for two adjacent 2.8Њ ϫ 2.8Њ GCM grid cells in Wyoming using land cover from two satellite-derived maps (AVHRR, TM) and a global land-cover dataset commonly used in GCMs.

Research paper thumbnail of Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4

Journal of Geophysical Research: Biogeosciences, 2012

Research paper thumbnail of Evaluating land surface parameters in the Biosphere-Atmosphere Transfer Scheme using remotely sensed data sets

Journal of Geophysical Research, 2000

ABSTRACT

Research paper thumbnail of Initial results from Phase 2 of the international urban energy balance model comparison

International Journal of Climatology, 2011

Many urban land surface schemes have been developed, incorporating different assumptions about th... more Many urban land surface schemes have been developed, incorporating different assumptions about the features of, and processes occurring at, the surface. Here, the first results from Phase 2 of an international comparison are presented. Evaluation is based on analysis of the last 12 months of a 15 month dataset. In general, the schemes have best overall capability to model net all-wave radiation. The models that perform well for one flux do not necessarily perform well for other fluxes. Generally there is better performance for net all wave radiation than sensible heat flux. The degree of complexity included in the models is outlined, and impacts on model performance are discussed in terms of the data made available to modellers at four successive stages.

Research paper thumbnail of Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban

International Journal of Climatology, 2013

A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contras... more A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contrasting urban environments of Toulouse (France) and Melbourne (Australia). For the latter, three measurement sites are available characterized by a varying amount of vegetation, which supports a detailed assessment of the representation of urban vegetation in CLMU. For Toulouse, observed roof, wall and road surface temperatures allow for a detailed evaluation of the anthropogenic heat parameterization. Overall, CLMU performs well in simulating the canyon and urban surface temperatures, anthropogenic heat flux and urban energy balance, with an overall better performance for the dense old city centre of Toulouse in comparison to the more vegetated sites in Melbourne. Results for the latter sites reveal that the pervious road fraction provides a reasonable approximation of vegetation in the urban canyon while the tile approach often results in an underestimation of latent heat fluxes. A detailed analysis of the radiative, turbulent and anthropogenic heat fluxes as well as surface temperatures for Toulouse point to a complex interaction between urban surfaces and canyon properties. Decoupling the roof from the urban canyon to the atmosphere aloft is shown to be important. Our findings suggest that more evaluation is necessary for contrasting urban geometries in order to obtain a better understanding of the interaction between the roof surface on the one hand and canyon air and air aloft on the other hand. The results simultaneously reveal a trade-off in errors between surface temperatures, radiative and turbulent fluxes and anthropogenic heat which again stresses the importance of the intended model application. Also, our results suggest that model complexity should, perhaps, relate to the site complexity. These results provide a robust basis for the construction of additional sensitivity experiments, tailored towards the intended application for urban climate mitigation studies.

Research paper thumbnail of Interactions between urbanization, heat stress, and climate change

Climatic Change, 2013

Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

Research paper thumbnail of Offline evaluation of the Community Land Model-Urban for Toulouse (France) and Melbourne (Australia)

ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surfa... more ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surface modification on urban climates. It provides a mechanism for trialling different scenarios for urban heat island mitigation. Only recently, urban land surfaces have been included in global and regional climate models. Often they represent a trade-off between the complexity of the biophysical processes of the urban canopy layer and the computational demands in order to be workable on regional climate time scales. This study employs the Community Land Model (CLM) which was recently extended with a single layer urban canopy scheme (CLM-U). And although it is primarily developed as a tool for regional climate scales, we intent to extend its reach and use it for local (neighborhood) scales in a changing climate context. Hence, an off-line validation is performed using meteorological observations for Toulouse (France) and multiple medium density urban areas in Melbourne (Australia). Model results are evaluated against observations of the surface energy balance from flux towers, including evapotranspiration, and show that the model is able to correctly address (urban) energy partitioning including high urban heat storage, and low evapotranspiration rates. Furthermore an investigation was undertaken to explore first of all the capacity of the model to incorporate Water Sensitive Urban Design (WSUD) features, mimicking vegetated and non-vegetated infiltration systems, open water bodies and other green infrastructure. In a second step, the effectiveness of WSUD integration scenarios are also compared with other common mitigation strategies such as increasing albedo and controlling urban morphology.

Research paper thumbnail of Modeling feedbacks and interactions between the land, climate, and human systems in the Community Land Model (CLM4): Successes and further research needs

AGU Fall Meeting Abstracts, Dec 1, 2010

The breadth with which models of Earth's land surface for climate simulation now represent t... more The breadth with which models of Earth's land surface for climate simulation now represent the physics, chemistry, and biology of terrestrial ecosystems (both managed and unmanaged), the responsiveness of ecosystems to and their influence on atmospheric processes, and the pervasive influence of human activity on the biosphere (including also urbanization) has contributed to the evolution of climate models to models of the Earth system. Prominent themes of research are biogeochemical cycles, anthropogenic land ...

Research paper thumbnail of Modeling the integrated ecology, biogeochemistry, and hydrology of the global terrestrial biosphere in the Community Land Model (CLM4)

AGU Fall Meeting Abstracts, Dec 1, 2010

Terrestrial ecosystems influence climate through physical, chemical, and biological processes tha... more Terrestrial ecosystems influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. Much of our understanding of how terrestrial ecosystems affect climate comes from numerical models of Earth's climate and their representation of the terrestrial biosphere. These models initially simulated only hydrometeorological processes at the land surface. They have since evolved to simulate the coupled ecology, biogeochemistry, and ...

Research paper thumbnail of CLM3. 5 documentation

National Center for Atmospheric Research, Boulder, 34pp, Apr 1, 2007

The circulation of water through the Earth system is of critical importance to life on Earth. The... more The circulation of water through the Earth system is of critical importance to life on Earth. The hydrological cycle is also intimately linked to the energy cycle and to biogeochemical processes including the carbon cycle. Simulating the various processes that interact to form the hydrological cycle is a daunting task for climate models. In particular, over land, interactions between precipitation and the vegetation/soil system determine the partitioning of water into various storage reservoirs and the subsequent release of water vapor to the ...

Research paper thumbnail of Offline evaluation of the Community Land Model-Urban for Toulouse (France) and Melbourne (Australia)

ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surfa... more ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surface modification on urban climates. It provides a mechanism for trialling different scenarios for urban heat island mitigation. Only recently, urban land surfaces have been included in global and regional climate models. Often they represent a trade-off between the complexity of the biophysical processes of the urban canopy layer and the computational demands in order to be workable on regional climate time scales. This study employs the Community Land Model (CLM) which was recently extended with a single layer urban canopy scheme (CLM-U). And although it is primarily developed as a tool for regional climate scales, we intent to extend its reach and use it for local (neighborhood) scales in a changing climate context. Hence, an off-line validation is performed using meteorological observations for Toulouse (France) and multiple medium density urban areas in Melbourne (Australia). Model results are evaluated against observations of the surface energy balance from flux towers, including evapotranspiration, and show that the model is able to correctly address (urban) energy partitioning including high urban heat storage, and low evapotranspiration rates. Furthermore an investigation was undertaken to explore first of all the capacity of the model to incorporate Water Sensitive Urban Design (WSUD) features, mimicking vegetated and non-vegetated infiltration systems, open water bodies and other green infrastructure. In a second step, the effectiveness of WSUD integration scenarios are also compared with other common mitigation strategies such as increasing albedo and controlling urban morphology.

Research paper thumbnail of Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban

International Journal of Climatology, 2013

A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contras... more A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contrasting urban environments of Toulouse (France) and Melbourne (Australia). For the latter, three measurement sites are available characterized by a varying amount of vegetation, which supports a detailed assessment of the representation of urban vegetation in CLMU. For Toulouse, observed roof, wall and road surface temperatures allow for a detailed evaluation of the anthropogenic heat parameterization. Overall, CLMU performs well in simulating the canyon and urban surface temperatures, anthropogenic heat flux and urban energy balance, with an overall better performance for the dense old city centre of Toulouse in comparison to the more vegetated sites in Melbourne. Results for the latter sites reveal that the pervious road fraction provides a reasonable approximation of vegetation in the urban canyon while the tile approach often results in an underestimation of latent heat fluxes. A detailed analysis of the radiative, turbulent and anthropogenic heat fluxes as well as surface temperatures for Toulouse point to a complex interaction between urban surfaces and canyon properties. Decoupling the roof from the urban canyon to the atmosphere aloft is shown to be important. Our findings suggest that more evaluation is necessary for contrasting urban geometries in order to obtain a better understanding of the interaction between the roof surface on the one hand and canyon air and air aloft on the other hand. The results simultaneously reveal a trade-off in errors between surface temperatures, radiative and turbulent fluxes and anthropogenic heat which again stresses the importance of the intended model application. Also, our results suggest that model complexity should, perhaps, relate to the site complexity. These results provide a robust basis for the construction of additional sensitivity experiments, tailored towards the intended application for urban climate mitigation studies.

Research paper thumbnail of The representation of space and stochasticity in one-dimensional and deterministic global vegetation models

ABSTRACT Implementation of plant community dynamics into global land surface models is in a phase... more ABSTRACT Implementation of plant community dynamics into global land surface models is in a phase of rapid development. Multiple individual-, cohort- and canopy- based approaches are being deployed and, as a result, many common challenges in the representation of ecological principles in a predictive, global framework are being identifying and confronted. In this talk we introduce the implementation of the Ecosystem Demography framework into the Community Land Model (CLM) and test the response of the model to a set of residual ecological uncertainties that must be represented during the simulation of coexisting plant communities. In particular, we focus on the intensity of competition for light resources, the density dependence of seedling recruitment, and the impact of sub-grid heterogeneity on below-ground competition. All of these processes alter the tendency of the model to generate high-diversity ecosystems, with subsequent impacts on the resilience to climate. Appropriate benchmarks of community resilience to climate change are sparse, but slowly emerging, and we analyse how the alternative simulations of plant community structure alter the ability of the model to predict regional-scale observations of ecosystem vulnerability to drought stress.

Research paper thumbnail of Implementation and comparison of a suite of heat stress metrics within the Community Land Model version 4.5

Geoscientific Model Development

We implement and analyze 13 different metrics (4 moist thermodynamic quantities and 9 heat stress... more We implement and analyze 13 different metrics (4 moist thermodynamic quantities and 9 heat stress metrics) in the Community Land Model (CLM4.5), the land surface component of the Community Earth System Model (CESM). We call these routines the HumanIndexMod. We limit the algorithms of the HumanIndexMod to meteorological inputs of temperature, moisture, and pressure for their calculation. All metrics assume no direct sunlight exposure. The goal of this project is to implement a common framework for calculating operationally used heat stress metrics, in climate models, offline output, and locally sourced weather data sets, with the intent that the HumanIndexMod may be used with the broadest of applications. The thermodynamic quantities use the latest, most accurate and efficient algorithms available, which in turn are used as inputs to the heat stress metrics. There are three advantages of adding these metrics to CLM4.5: (1) improved moist thermodynamic quantities; (2) quantifying heat...

Research paper thumbnail of Urban modeling over Houston in support of SIMMER

Abstract Extreme heat is a leading cause of weather-related human mortality in the United States.... more Abstract Extreme heat is a leading cause of weather-related human mortality in the United States. As global warming patterns continue, researchers anticipate increases in the severity, frequency and duration of extreme heat events, especially in the southern and western US Many cities in these regions may have amplified vulnerability due to their rapidly evolving socioeconomic fabric (for example, growing elderly populations). This raises a series of questions about the increased health risks of urban residents to extreme heat, ...

Research paper thumbnail of Contributions of coastal megacities to environmental changes at regional and global scales

Research paper thumbnail of Modeling the integrated ecology, biogeochemistry, and hydrology of the global terrestrial biosphere in the Community Land Model (CLM4) (Invited)

Agu Fall Meeting Abstracts, Dec 1, 2010

Terrestrial ecosystems influence climate through physical, chemical, and biological processes tha... more Terrestrial ecosystems influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. Much of our understanding of how terrestrial ecosystems affect climate comes from numerical models of Earth’s climate and their representation of the terrestrial biosphere. These models initially simulated only hydrometeorological processes at the land surface. They have since evolved to simulate the coupled ecology, biogeochemistry, and hydrology of terrestrial ecosystems so that the biosphere and atmosphere form a coupled system. As such, the simulated hydrologic cycle is an emergent property of the ecology and biogeochemistry represented in the model. Here, we use the Community Land Model (CLM4), the land component of the Community Earth System Model, to examine interactions among hydrology, ecology, and biogeochemistry with respect to energy, water, and carbon fluxes. Specifically, carbon uptake during gross primary production (GPP) is linked to water loss during evapotranspiration (ET). Model functional errors in the parameterization of canopy radiative transfer, leaf photosynthesis and stomatal conductance, and canopy scaling lead to substantial errors in simulated GPP and ET. Improvements to these parameterizations gained from theoretical considerations and empirical studies reduce biases in GPP, with concomitant improvement in ET. Most of the bias reduction comes from the revised photosynthesis-stomatal conductance formulation; improved canopy radiation has lesser effect; and changes to canopy scaling have minor effect. A key model parameter is the maximum rate of leaf carboxylation, which is highly uncertain for large-scale climate models and for which various disparate estimates have been published. The effect of model parameter errors on GPP and ET is of comparable magnitude to that of model functional errors and offset bias reductions from improved model parameterizations. Our results imply that this key leaf-level physiological parameter cannot be defined independent of model-specific parameterizations. Our analyses suggest that we still have much to learn about the biochemistry of photosynthesis, the biophysics of evapotranspiration, their interdependencies, and how to represent these processes in models of the terrestrial biosphere for climate simulation.

Research paper thumbnail of Technical Description of an Urban Parameterization for the Community Land Model (CLMU)

The Technical Notes series provides an outlet for a variety of NCAR Manuscripts that contribute i... more The Technical Notes series provides an outlet for a variety of NCAR Manuscripts that contribute in specialized ways to the body of scientific knowledge but that are not suitable for journal, monograph, or book publication. Reports in this series are issued by the NCAR scientific divisions. Designation symbols for the series include:

Research paper thumbnail of Seasonal surface urban energy balance and wintertime stability simulated using three land-surface models in the high-latitude city Helsinki

Quarterly Journal of the Royal Meteorological Society, 2015

The performance of three urban land surface models, run in offline mode, with their default exter... more The performance of three urban land surface models, run in offline mode, with their default external parameters, is evaluated for two distinctly different sites in Helsinki:

Research paper thumbnail of Unmixing multiple land-cover type reflectances from coarse spatial resolution satellite data

Remote Sensing of Environment, 1995

We present a technique for extracting subpixel cover type reflectances from the mixed pixels of a... more We present a technique for extracting subpixel cover type reflectances from the mixed pixels of a coarse spatial resolution image. A Gaussian filter is used to spatially degrade a set of fine spatial resolution images [based on, e.g., Landsat Thematic Mapper (TM)], each of which represent the spatial structure and extent of a land-cover type. From the degraded image data, a set of weights representing the proportions of cover types within the mixed pixels of a coarse spatial/fine temporal resolution image [e.g., NOAA Advanced Very High Resolution Radiometer (AVHRR)] is produced. These weights and the A VHRR spectral band reflectances are used in multiple linear regression analyses to extract mean cover type reflectances. A simulation study was conducted to define the operational limitations of this technique. Cover type reflectances are accurately estimated if the cover types are spatially well represented within the area of interest, are spectrally distinct, and have small within-class spectral variability. The accuracy of retrieved reflectances is most sensitive to errors in the coarse spatial resolution data and least sensitive to errors in the weights'. By applying this technique to multiple images, temporal profiles of subpixel cover type reflectance may be obtained. This particular application is demonstrated by using TM and A VHRR data from the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) to create normalized difference vegetation index (NDVI) temporal profiles of the dominant land-cover types.

Research paper thumbnail of The Sensitivity of a Land Surface Parameterization Scheme to the Choice of Remotely Sensed Land-Cover Datasets

Monthly Weather Review, 1997

The characteristics of satellite-derived land-cover data for climate models vary depending on sen... more The characteristics of satellite-derived land-cover data for climate models vary depending on sensor properties and processing options. To better understand the first-order effects of differences in land-cover data on a land surface parameterization scheme (VBATS), stand-alone model runs were performed for two adjacent 2.8Њ ϫ 2.8Њ GCM grid cells in Wyoming using land cover from two satellite-derived maps (AVHRR, TM) and a global land-cover dataset commonly used in GCMs.

Research paper thumbnail of Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4

Journal of Geophysical Research: Biogeosciences, 2012

Research paper thumbnail of Evaluating land surface parameters in the Biosphere-Atmosphere Transfer Scheme using remotely sensed data sets

Journal of Geophysical Research, 2000

ABSTRACT

Research paper thumbnail of Initial results from Phase 2 of the international urban energy balance model comparison

International Journal of Climatology, 2011

Many urban land surface schemes have been developed, incorporating different assumptions about th... more Many urban land surface schemes have been developed, incorporating different assumptions about the features of, and processes occurring at, the surface. Here, the first results from Phase 2 of an international comparison are presented. Evaluation is based on analysis of the last 12 months of a 15 month dataset. In general, the schemes have best overall capability to model net all-wave radiation. The models that perform well for one flux do not necessarily perform well for other fluxes. Generally there is better performance for net all wave radiation than sensible heat flux. The degree of complexity included in the models is outlined, and impacts on model performance are discussed in terms of the data made available to modellers at four successive stages.

Research paper thumbnail of Simulating the surface energy balance over two contrasting urban environments using the Community Land Model Urban

International Journal of Climatology, 2013

A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contras... more A single-layer urban canopy model Community Land Model Urban (CLMU) is evaluated over two contrasting urban environments of Toulouse (France) and Melbourne (Australia). For the latter, three measurement sites are available characterized by a varying amount of vegetation, which supports a detailed assessment of the representation of urban vegetation in CLMU. For Toulouse, observed roof, wall and road surface temperatures allow for a detailed evaluation of the anthropogenic heat parameterization. Overall, CLMU performs well in simulating the canyon and urban surface temperatures, anthropogenic heat flux and urban energy balance, with an overall better performance for the dense old city centre of Toulouse in comparison to the more vegetated sites in Melbourne. Results for the latter sites reveal that the pervious road fraction provides a reasonable approximation of vegetation in the urban canyon while the tile approach often results in an underestimation of latent heat fluxes. A detailed analysis of the radiative, turbulent and anthropogenic heat fluxes as well as surface temperatures for Toulouse point to a complex interaction between urban surfaces and canyon properties. Decoupling the roof from the urban canyon to the atmosphere aloft is shown to be important. Our findings suggest that more evaluation is necessary for contrasting urban geometries in order to obtain a better understanding of the interaction between the roof surface on the one hand and canyon air and air aloft on the other hand. The results simultaneously reveal a trade-off in errors between surface temperatures, radiative and turbulent fluxes and anthropogenic heat which again stresses the importance of the intended model application. Also, our results suggest that model complexity should, perhaps, relate to the site complexity. These results provide a robust basis for the construction of additional sensitivity experiments, tailored towards the intended application for urban climate mitigation studies.

Research paper thumbnail of Interactions between urbanization, heat stress, and climate change

Climatic Change, 2013

Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

Research paper thumbnail of Offline evaluation of the Community Land Model-Urban for Toulouse (France) and Melbourne (Australia)

ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surfa... more ABSTRACT Urban climate models provide a useful tool for assessing the impacts of urban land surface modification on urban climates. It provides a mechanism for trialling different scenarios for urban heat island mitigation. Only recently, urban land surfaces have been included in global and regional climate models. Often they represent a trade-off between the complexity of the biophysical processes of the urban canopy layer and the computational demands in order to be workable on regional climate time scales. This study employs the Community Land Model (CLM) which was recently extended with a single layer urban canopy scheme (CLM-U). And although it is primarily developed as a tool for regional climate scales, we intent to extend its reach and use it for local (neighborhood) scales in a changing climate context. Hence, an off-line validation is performed using meteorological observations for Toulouse (France) and multiple medium density urban areas in Melbourne (Australia). Model results are evaluated against observations of the surface energy balance from flux towers, including evapotranspiration, and show that the model is able to correctly address (urban) energy partitioning including high urban heat storage, and low evapotranspiration rates. Furthermore an investigation was undertaken to explore first of all the capacity of the model to incorporate Water Sensitive Urban Design (WSUD) features, mimicking vegetated and non-vegetated infiltration systems, open water bodies and other green infrastructure. In a second step, the effectiveness of WSUD integration scenarios are also compared with other common mitigation strategies such as increasing albedo and controlling urban morphology.

Research paper thumbnail of Modeling feedbacks and interactions between the land, climate, and human systems in the Community Land Model (CLM4): Successes and further research needs

AGU Fall Meeting Abstracts, Dec 1, 2010

The breadth with which models of Earth's land surface for climate simulation now represent t... more The breadth with which models of Earth's land surface for climate simulation now represent the physics, chemistry, and biology of terrestrial ecosystems (both managed and unmanaged), the responsiveness of ecosystems to and their influence on atmospheric processes, and the pervasive influence of human activity on the biosphere (including also urbanization) has contributed to the evolution of climate models to models of the Earth system. Prominent themes of research are biogeochemical cycles, anthropogenic land ...

Research paper thumbnail of Modeling the integrated ecology, biogeochemistry, and hydrology of the global terrestrial biosphere in the Community Land Model (CLM4)

AGU Fall Meeting Abstracts, Dec 1, 2010

Terrestrial ecosystems influence climate through physical, chemical, and biological processes tha... more Terrestrial ecosystems influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. Much of our understanding of how terrestrial ecosystems affect climate comes from numerical models of Earth's climate and their representation of the terrestrial biosphere. These models initially simulated only hydrometeorological processes at the land surface. They have since evolved to simulate the coupled ecology, biogeochemistry, and ...

Research paper thumbnail of CLM3. 5 documentation

National Center for Atmospheric Research, Boulder, 34pp, Apr 1, 2007

The circulation of water through the Earth system is of critical importance to life on Earth. The... more The circulation of water through the Earth system is of critical importance to life on Earth. The hydrological cycle is also intimately linked to the energy cycle and to biogeochemical processes including the carbon cycle. Simulating the various processes that interact to form the hydrological cycle is a daunting task for climate models. In particular, over land, interactions between precipitation and the vegetation/soil system determine the partitioning of water into various storage reservoirs and the subsequent release of water vapor to the ...