SimSphere
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Recent papers in SimSphere
Abstract This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar... more
Abstract
This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar Radiation (Rg), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3m (Tair 1.3m) and Air Temperature at 50m (Tair 50m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation.
The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement
between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, Tair 1.3m and Tair 50m parameters (RMSD= 39.47, 55.06Wm2, 3.23, 3.77 C respectively). A systematic underestimation of Rg and Rnet (RMSD=67.83, 58.69Wm2, MBE= 67.83, 58.69Wm2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations.
To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.
This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar Radiation (Rg), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3m (Tair 1.3m) and Air Temperature at 50m (Tair 50m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation.
The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement
between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, Tair 1.3m and Tair 50m parameters (RMSD= 39.47, 55.06Wm2, 3.23, 3.77 C respectively). A systematic underestimation of Rg and Rnet (RMSD=67.83, 58.69Wm2, MBE= 67.83, 58.69Wm2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations.
To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.
This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar Radiation... more
This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models’ ability in predicting Shortwave Incoming Solar Radiation (Rg
), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3 m (T 5 air 1.3 m) and Air Temperature at 50 m (Tair 50 m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation.
The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement
between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, Tair 1.3 m and Tair 50 m parameters (RMSD = 39.47, 55.06 Wm−2 , 3.23, 3.77 ◦C respectively). A systematic underestimation of Rg and Rnet (RMSD = 67.83, 58.69 W m−2, MBE = 67.83, 58.69 W m−2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations. To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important
and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.
), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3 m (T 5 air 1.3 m) and Air Temperature at 50 m (Tair 50 m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation.
The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement
between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, Tair 1.3 m and Tair 50 m parameters (RMSD = 39.47, 55.06 Wm−2 , 3.23, 3.77 ◦C respectively). A systematic underestimation of Rg and Rnet (RMSD = 67.83, 58.69 W m−2, MBE = 67.83, 58.69 W m−2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations. To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important
and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.
Abstract In this present study the ability of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model in estimating key parameters characterising land surface interactions was evaluated. Specifically, SimSphere’s performance in... more
Abstract
In this present study the ability of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model in estimating key parameters characterising land surface interactions was evaluated. Specifically, SimSphere’s performance in predicting Net Radiation (Rnet), Latent Heat (LE), 5 Sensible Heat (H) and Air Temperature (Tair) at 1.3 and 50m was examined. Model simulations were validated by ground-based measurements of
the corresponding parameters for a total of 70 days of the year 2011 from 7 CarboEurope network sites. These included a variety of biomes, environmental and climatic conditions in the models evaluation.Overall, model performance can largely be described as satisfactory for most of the experimental sites and evaluated parameters. For all model parameters compared,
predicted H fluxes consistently obtained the highest agreement to the in-situ data in all ecosystems, with an average RMSD of 55.36Wm2. LE fluxes and Rnet also agreed well with the in-situ data with RSMDs of 62.75 and 64.65Wm2 respectively. A good
15 agreement between modelled and measured LE and H fluxes was found, especially for smoothed daily flux trends. For both Tair 1.3m and Tair 50m a mean RMSD of 4.14 and 3.54 C was reported respectively. This work presents the first all-inclusive evaluation of SimSphere, particularly so in
a European setting. Results of this study contribute decisively towards obtaining a better understanding of the model’s structure and its correspondence to the real world system. Findings also further establish the model’s capability as a useful teaching and research tool in modelling Earth’s land surface interactions. This is of considerable importance in the light of the rapidly expanding use of the model worldwide, including
ongoing research by various Space Agencies examining its synergistic use with Earth Observation data towards the development of operational products at a global scale.
In this present study the ability of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model in estimating key parameters characterising land surface interactions was evaluated. Specifically, SimSphere’s performance in predicting Net Radiation (Rnet), Latent Heat (LE), 5 Sensible Heat (H) and Air Temperature (Tair) at 1.3 and 50m was examined. Model simulations were validated by ground-based measurements of
the corresponding parameters for a total of 70 days of the year 2011 from 7 CarboEurope network sites. These included a variety of biomes, environmental and climatic conditions in the models evaluation.Overall, model performance can largely be described as satisfactory for most of the experimental sites and evaluated parameters. For all model parameters compared,
predicted H fluxes consistently obtained the highest agreement to the in-situ data in all ecosystems, with an average RMSD of 55.36Wm2. LE fluxes and Rnet also agreed well with the in-situ data with RSMDs of 62.75 and 64.65Wm2 respectively. A good
15 agreement between modelled and measured LE and H fluxes was found, especially for smoothed daily flux trends. For both Tair 1.3m and Tair 50m a mean RMSD of 4.14 and 3.54 C was reported respectively. This work presents the first all-inclusive evaluation of SimSphere, particularly so in
a European setting. Results of this study contribute decisively towards obtaining a better understanding of the model’s structure and its correspondence to the real world system. Findings also further establish the model’s capability as a useful teaching and research tool in modelling Earth’s land surface interactions. This is of considerable importance in the light of the rapidly expanding use of the model worldwide, including
ongoing research by various Space Agencies examining its synergistic use with Earth Observation data towards the development of operational products at a global scale.
Use of simulation process models often combined with Earth Observation (EO) data, has played a key role in extending our abilities to study land surface interaction processes and enhancing our understanding of how different components of... more
Use of simulation process models often combined with Earth Observation (EO) data, has played a key role in extending our abilities to study land surface interaction processes and enhancing our understanding of how different components of the Earth system interplay. Use of these synergistic techniques aims to improve the estimates of key parameters characterising land surface interactions by combining the horizontal coverage and spectral resolution of remote sensing data with the vertical coverage and fine temporal continuity of simulation process models.
This study performs a Global Sensitivity Analysis (GSA) on the SimSphere land surface model aiming to further extend our understanding of the model structure and establish its coherence. It builds on previous works conducted on the model to which a sophisticated and cutting edge GSA meta-modelling method adopting Bayesian theory is implemented. Our first objective is to examine the effect of assuming uniform probability distribution function (PDFs) for the model inputs/outputs on the sensitivity of key quantities simulated by SimSphere. A further objective is to explore the sensitivity of new, previously unexplored variables simulated by the model, namely of the Daily Evaporative, Non-Evaporative Fractions and Radiometric Temperature.
The GSA conducted assuming uniform PDFs showed comparable results to previous studies in terms of identifying the most sensitive model inputs to each of the outputs considered. Yet, in absolute terms, the statistical parameters measuring the sensitivity of the model inputs were notably different. SA on the newly examined model outputs showed largely explainable results and allowed identification of the most responsive model inputs and interactions. In general, our results provided further evidence supporting the model coherence and correspondence to the behaviour of a natural system. The implications of the main findings are discussed in the framework of the model use either as a stand-alone tool or synergistically with EO data, particularly so towards the operational development of such products.
This study performs a Global Sensitivity Analysis (GSA) on the SimSphere land surface model aiming to further extend our understanding of the model structure and establish its coherence. It builds on previous works conducted on the model to which a sophisticated and cutting edge GSA meta-modelling method adopting Bayesian theory is implemented. Our first objective is to examine the effect of assuming uniform probability distribution function (PDFs) for the model inputs/outputs on the sensitivity of key quantities simulated by SimSphere. A further objective is to explore the sensitivity of new, previously unexplored variables simulated by the model, namely of the Daily Evaporative, Non-Evaporative Fractions and Radiometric Temperature.
The GSA conducted assuming uniform PDFs showed comparable results to previous studies in terms of identifying the most sensitive model inputs to each of the outputs considered. Yet, in absolute terms, the statistical parameters measuring the sensitivity of the model inputs were notably different. SA on the newly examined model outputs showed largely explainable results and allowed identification of the most responsive model inputs and interactions. In general, our results provided further evidence supporting the model coherence and correspondence to the behaviour of a natural system. The implications of the main findings are discussed in the framework of the model use either as a stand-alone tool or synergistically with EO data, particularly so towards the operational development of such products.
In this present study the ability of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model in estimating key parameters characterising land surface interactions was evaluated. Specifically, SimSphere’s performance in predicting... more
In this present study the ability of the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model in estimating key parameters characterising land surface interactions was evaluated. Specifically, SimSphere’s performance in predicting Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H) and Air Temperature (Tair 5 ) at 1.3 and 50 m was examined. Model simulations were validated by ground-based measurements of
the corresponding parameters for a total of 70 days of the year 2011 from 7 CarboEurope network sites. These included a variety of biomes, environmental and climatic conditions in the models evaluation. Overall, model performance can largely be described as satisfactory for most of the experimental sites and evaluated parameters. For all model parameters compared,
predicted H fluxes consistently obtained the highest agreement to the in-situ data in all ecosystems, with an average RMSD of 55.36 W m−2 . LE fluxes and Rnet also agreed well with the in-situ data with RSMDs of 62.75 and 64.65 W m−2 respectively. A good agreement between modelled and measured LE and H fluxes was found, especially for smoothed daily flux trends. For both Tair 1.3 m and Tair 50 m a mean RMSD of 4.14 and
3.54 ◦C was reported respectively. This work presents the first all-inclusive evaluation of SimSphere, particularly so in a European setting. Results of this study contribute decisively towards obtaining a better understanding of the model’s structure and its correspondence to the real world system. Findings also further establish the model’s capability as a useful teaching and research tool in modelling Earth’s land surface interactions. This is of considerable importance in the light of the rapidly expanding use of the model worldwide, including
ongoing research by various Space Agencies examining its synergistic use with Earth Observation data towards the development of operational products at a global scale.
the corresponding parameters for a total of 70 days of the year 2011 from 7 CarboEurope network sites. These included a variety of biomes, environmental and climatic conditions in the models evaluation. Overall, model performance can largely be described as satisfactory for most of the experimental sites and evaluated parameters. For all model parameters compared,
predicted H fluxes consistently obtained the highest agreement to the in-situ data in all ecosystems, with an average RMSD of 55.36 W m−2 . LE fluxes and Rnet also agreed well with the in-situ data with RSMDs of 62.75 and 64.65 W m−2 respectively. A good agreement between modelled and measured LE and H fluxes was found, especially for smoothed daily flux trends. For both Tair 1.3 m and Tair 50 m a mean RMSD of 4.14 and
3.54 ◦C was reported respectively. This work presents the first all-inclusive evaluation of SimSphere, particularly so in a European setting. Results of this study contribute decisively towards obtaining a better understanding of the model’s structure and its correspondence to the real world system. Findings also further establish the model’s capability as a useful teaching and research tool in modelling Earth’s land surface interactions. This is of considerable importance in the light of the rapidly expanding use of the model worldwide, including
ongoing research by various Space Agencies examining its synergistic use with Earth Observation data towards the development of operational products at a global scale.
- by George P. Petropoulos and +2
- •
- Validation, SVAT modelling, SimSphere
Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for... more
Soil Vegetation Atmosphere Transfer (SVAT) models consist of deterministic mathematical representations of the physical processes involved between the land surface and the atmosphere and of their interactions, at time-steps acceptable for the study of land surface processes. The present article provides a comprehensive and systematic review of one such SVAT model suitable for use in mesoscale or boundary layer studies, originally developed by [1]. This model, which has evolved significantly both architecturally and functionally since its foundation, has been widely applied in over thirty interdisciplinary science investigations, and it is currently used as a learning resource for students in a number of educational institutes globally. The present review is also regarded as very timely, since a variation of a method using this specific SVAT model along with satellite observations is currently being considered in a scheme being developed for the operational retrieval of soil surface moisture by the US National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellites that are due to be launched from 2016 onwards.
Sensitivity analysis consists of an integral and important validatory check of a computer simulation model before the code is used in performing any kind of analysis operation. The present paper demonstrates the use of a relatively new... more
Sensitivity analysis consists of an integral and important validatory check of a computer simulation model before the code is used in performing any kind of analysis operation. The present paper demonstrates the use of a relatively new method and tool for conducting global sensitivity analysis (GSA) for environmental models, providing simultaneously the first GSA study of the widely used 1d soil–vegetation–atmospheric transfer (SVAT) model named SimSphere. A software platform called the Gaussian emulation machine for sensitivity analysis (GEM SA), which has been developed for performing a GSA via Bayesian theory, is applied to SimSphere model in order to identify the most responsive model inputs to the simulation of key model outputs, detect their interactions and derive absolute sensitivity measures concerning the model structure. This study is also very timely in that, use of this particular SVAT model is currently being considered to be used in a scheme being developed for the operational retrieval of the soil surface moisture content by National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellite platforms that are due to be launched in the next 12 years starting from 2016.
The employed GSA method was found capable of identifying the most responsive SimSphere inputs and also of capturing their key interactions for each of the simulated target quantities on which the GSA was conducted. The most sensitive model inputs were the topography parameters (slope, aspect) as well as the fractional vegetation cover and soil surface moisture availability. The implications of these findings for the future use of SimSphere are discussed.
The employed GSA method was found capable of identifying the most responsive SimSphere inputs and also of capturing their key interactions for each of the simulated target quantities on which the GSA was conducted. The most sensitive model inputs were the topography parameters (slope, aspect) as well as the fractional vegetation cover and soil surface moisture availability. The implications of these findings for the future use of SimSphere are discussed.