ORCID Profile
0000-0002-3149-4096
Current Organisation
Luxembourg Institute of Science and Technology
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Publisher: Authorea, Inc.
Date: 18-09-2023
Publisher: MDPI AG
Date: 26-10-2018
DOI: 10.20944/PREPRINTS201810.0625.V1
Abstract: Operational weather and also flood forecasting has been performed successfully for decades and is of great socioeconomic importance. Up to now, forecast products focus on atmospheric variables, such as precipitation, air temperature and, in hydrology, on river discharge. Considering the full terrestrial system from groundwater across the land surface into the atmosphere, a number of important hydrologic variables are missing especially with regard to the shallow and deeper subsurface (e.g. groundwater), which are gaining considerable attention in the context of global change. In this study, we propose a terrestrial monitoring/forecasting system using the Terrestrial Systems Modeling Platform (TSMP) that predicts all essential states and fluxes of the terrestrial hydrologic and energy cycles from groundwater into the atmosphere. Closure of the terrestrial cycles provides a physically consistent picture of the terrestrial system in TSMP. TSMP has been implemented over a regional domain over North Rhine-Westphalia and a continental domain over European in a real-time forecast/monitoring workflow. Applying a real-time forecasting/monitoring workflow over both domains, experimental forecasts are being produced with different lead times since the beginning of 2016. Real-time forecast/monitoring products encompass all compartments of the terrestrial system including additional hydrologic variables, such as plant available soil water, groundwater table depth, and groundwater recharge and storage.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-2186
Abstract: & & & #8216 Aerodynamic resistance& #8217 (hereafter r& sub& a& /sub& ) is a preeminent variable in the modelling of evapotranspiration (ET), and its accurate quantification plays a critical role in determining the performance and consistency of thermal remote sensing-based surface energy balance (SEB) models for estimating ET at local to regional scales. Atmospheric stability links r& sub& a& /sub& with land surface temperature (LST) and the representation of their interactions in the SEB models determines the accuracy of ET estimates.& & & & The present study investigates the influence of r& sub& a& /sub& and its relation to LST uncertainties on the performance of three structurally different SEB models by combining nine OzFlux eddy covariance datasets from 2011 to 2019 from sites of different aridity in Australia with MODIS Terra and Aqua LST and leaf area index (LAI) products. Simulations of the latent heat flux (LE, energy equivalent of ET in W/m& sup& & /sup& ) from the SPARSE (Soil Plant Atmosphere and Remote Sensing Evapotranspiration), SEBS (Surface Energy Balance System) and STIC (Surface Temperature Initiated Closure) models forced with MODIS LST, LAI, and in-situ meteorological datasets were evaluated using observed flux data across water-limited (semi-arid and arid) and radiation-limited (mesic) ecosystems.& & & & Our results revealed that the three models tend to overestimate instantaneous LE in the water-limited shrubland, woodland and grassland ecosystems by up to 60% on average, which was caused by an underestimation of the sensible heat flux (H). LE overestimation was associated with discrepancies in r& sub& a& /sub& retrievals under conditions of high atmospheric instability, during which errors in LST (expressed as the difference between MODIS LST and in-situ LST) apparently played a minor role. On the other hand, a positive bias in LST coincides with low r& sub& a& /sub& and causes slight underestimation of LE at the water-limited sites. The impact of r& sub& a& /sub& on the LE residual error was found to be of the same magnitude as the influence of errors in LST in the semi-arid ecosystems as indicated by variable importance in projection (VIP) coefficients from partial least squares regression above unity. In contrast, our results for mesic forest ecosystems indicated minor dependency on r& sub& a& /sub& for modelling LE (VIP& .4), which was due to a higher roughness length and lower LST resulting in dominance of mechanically generated turbulence, thereby diminishing the importance of atmospheric stability in the determination of r& sub& a& /sub& .& &
Publisher: MDPI AG
Date: 16-11-2018
DOI: 10.20944/PREPRINTS201810.0625.V2
Abstract: Operational weather and also flood forecasting has been performed successfully for decades and is of great socioeconomic importance. Up to now, forecast products focus on atmospheric variables, such as precipitation, air temperature and, in hydrology, on river discharge. Considering the full terrestrial system from groundwater across the land surface into the atmosphere, a number of important hydrologic variables are missing especially with regard to the shallow and deeper subsurface (e.g. groundwater), which are gaining considerable attention in the context of global change. In this study, we propose a terrestrial monitoring/forecasting system using the Terrestrial Systems Modeling Platform (TSMP) that predicts all essential states and fluxes of the terrestrial hydrologic and energy cycles from groundwater into the atmosphere. Closure of the terrestrial cycles provides a physically consistent picture of the terrestrial system in TSMP. TSMP has been implemented over a regional domain over North Rhine-Westphalia and a continental domain over European in a real-time forecast/monitoring workflow. Applying a real-time forecasting/monitoring workflow over both domains, experimental forecasts are being produced with different lead times since the beginning of 2016. Real-time forecast/monitoring products encompass all compartments of the terrestrial system including additional hydrologic variables, such as plant available soil water, groundwater table depth, and groundwater recharge and storage.
Publisher: Copernicus GmbH
Date: 29-10-2014
Abstract: Abstract. Continental-scale hyper-resolution simulations constitute a grand challenge in characterizing nonlinear feedbacks of states and fluxes of the coupled water, energy, and biogeochemical cycles of terrestrial systems. Tackling this challenge requires advanced coupling and supercomputing technologies for earth system models that are discussed in this study, utilizing the ex le of the implementation of the newly developed Terrestrial Systems Modeling Platform (TerrSysMP v1.0) on JUQUEEN (IBM Blue Gene/Q) of the Jülich Supercomputing Centre, Germany. The applied coupling strategies rely on the Multiple Program Multiple Data (MPMD) paradigm using the OASIS suite of external couplers, and require memory and load balancing considerations in the exchange of the coupling fields between different component models and the allocation of computational resources, respectively. Using the advanced profiling and tracing tool Scalasca to determine an optimum load balancing leads to a 19% speedup. In massively parallel supercomputer environments, the coupler OASIS-MCT is recommended, which resolves memory limitations that may be significant in case of very large computational domains and exchange fields as they occur in these specific test cases and in many applications in terrestrial research. However, model I/O and initialization in the petascale range still require major attention, as they constitute true big data challenges in light of future exascale computing resources. Based on a factor-two speedup due to compiler optimizations, a refactored coupling interface using OASIS-MCT and an optimum load balancing, the problem size in a weak scaling study can be increased by a factor of 64 from 512 to 32 768 processes while maintaining parallel efficiencies above 80% for the component models.
Publisher: Copernicus GmbH
Date: 28-01-2022
DOI: 10.5194/BG-2021-311
Abstract: Abstract. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by soil moisture availability, and regulated by plant physiological properties. During summer periods, soil moisture availability at sites with thin soils can be limited, forcing the plants to access moisture stored in the weathered bedrock. Land surface models (LSMs) have considerably evolved in the description of the physical processes related to vegetation water use but the effects of bedrock position and water uptake from fractured bedrock has not received much attention. In this study, the Community Land Model version 5.0 (CLM 5) is implemented at four forested sites with relatively shallow bedrock and located across an environmental gradient in Europe. Three different bedrock configurations (i.e., default, deeper, and fractured) are applied to evaluate if the omission of water uptake from weathered bedrock could explain some model deficiencies with respect to the simulation of seasonal transpiration patterns. Sap flow measurements are used to benchmark the response of these three bedrock configurations. It was found that the simulated transpiration response of the default model configuration is strongly limited by soil moisture availability at sites with extended dry seasons. Under these climate conditions, the implementation of an alternative (i.e., deeper and fractured) bedrock configuration resulted in a better agreement between modeled and measured transpiration. At the site with a continental climate, the default model configuration accurately reproduced the magnitude and temporal patterns of the measured transpiration. The implementation of the alternative bedrock configurations at this site provided more realistic water potentials in plant tissues but negatively affects the modeled transpiration during the summer period. Finally, all three bedrock configurations did not show differences in terms of water potentials, fluxes, and performances on the more northern and colder site exhibiting a transition between oceanic and continental climate. Model performances at this site are low, with a clear overestimation of transpiration compared to sap flow data. The results of this study call for increased efforts into better representing lithological controls on plant water uptake in LSMs.
Publisher: American Geophysical Union (AGU)
Date: 08-08-2022
DOI: 10.1029/2021GL097568
Abstract: Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State‐of‐the‐art one‐source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non‐parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio‐temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research.
Publisher: Wiley
Date: 02-11-2022
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7199
Abstract: & & The drought resilience of forest ecosystems depends on the water use strategies and the degree of vulnerability to hydraulic failure of in idual tree species. The coordination between hydraulic and allocation traits along with stomatal control determines the tree water-use strategy, ranging from acquisitive to conservative tree species. This work explores the role of different plant hydraulic traits (& #936 & sub& P50& /sub& , & em& c& /em& & sub& k& /sub& , and & em& k& /em& & sub& max& /sub& in the Community Land Model 5.0) on the simulated plant water use dynamics. We selected two broadleaved tree species (& em& Quercus ilex& /em& L. and & em& Fagus sylvatica& /em& L.) at four SAPFLUXNET experimental sites having contrasting climate conditions. From the range of plant hydraulic traits reported for each species in the Xylem Functional Traits (XFT) database and other literature, the most vulnerable and most resistant parameter combination was chosen as extreme cases. Four sets of experiments were carried out that include modification of the shape of the plant vulnerability curve changing only & #936 & sub& P50& /sub& and & em& c& /em& & sub& k& /sub& (CS-experiment), changing only & em& k& /em& & sub& max& /sub& (k-experiment), changing the three parameters of the vulnerability equation (FC-experiment), and changing gradually & em& k& /em& & sub& max& /sub& (KS-experiment) to test the model sensitivity to & em& k& /em& & sub& max& /sub& . The stand transpiration obtained from SAPFLUXNET was used as a benchmark for the model comparisons. The CS-experiment revealed that a vulnerable configuration increases the modeled transpiration during conditions with le water supply, and causes severe water stress and reduced transpiration during dry periods as compared to a resistant configuration. This indicates that transpiration is hydraulically limited even at le water supply in the model so that the more negative & #936 & sub& P50& /sub& enables increased transpiration. Although a more negative & #936 & sub& P50& /sub& allows the vegetation to access more soil water than would be the case for vulnerable configurations, the difference in actual plant available water is small at this dry end of the water retention curve, and hence the dry period water stress is mainly determined by early-season transpiration. The K- and KS- experiments illustrate the role of & em& k& /em& & sub& max& /sub& to effectively scale up/down the transpiration response. Finally, the FC-experiments revealed the potential of plant hydraulic traits to mimic either conservative or acquisitive water-use strategies, allowing the vegetation to manage more efficiently the soil water resources. This work underlines the importance of selecting a suitable plant hydraulic parametrization contemplating the ersity of plant water use strategies.& &
Publisher: Copernicus GmbH
Date: 03-06-2014
Abstract: Abstract. Continental-scale hyper-resolution simulations constitute a grand challenge in characterizing non-linear feedbacks of states and fluxes of the coupled water, energy, and biogeochemical cycles of terrestrial systems. Tackling this challenge requires advanced coupling and supercomputing technologies for earth system models that are discussed in this study, utilizing the ex le of the implementation of the newly developed Terrestrial Systems Modeling Platform (TerrSysMP) on JUQUEEN (IBM Blue Gene/Q) of the Jülich Supercomputing Centre, Germany. The applied coupling strategies rely on the Multiple Program Multiple Data (MPMD) paradigm and require memory and load balancing considerations in the exchange of the coupling fields between different component models and allocation of computational resources, respectively. These considerations can be reached with advanced profiling and tracing tools leading to the efficient use of massively parallel computing environments, which is then mainly determined by the parallel performance of in idual component models. However, the problem of model I/O and initialization in the peta-scale range requires major attention, because this constitutes a true big data challenge in the perspective of future exa-scale capabilities, which is unsolved.
Publisher: Copernicus GmbH
Date: 20-07-2022
Abstract: Abstract. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by soil moisture availability, and regulated by plant physiological properties. During summer periods, soil moisture availability at sites with thin soils can be limited, forcing the plants to access moisture stored in the weathered bedrock. Land surface models (LSMs) have considerably evolved in the description of the physical processes related to vegetation water use, but the effects of bedrock position and water uptake from fractured bedrock have not received much attention. In this study, the Community Land Model version 5.0 (CLM 5) is implemented at four forested sites with relatively shallow bedrock and located across an environmental gradient in Europe. Three different bedrock configurations (i.e., default, deeper, and fractured) are applied to evaluate if the omission of water uptake from weathered bedrock could explain some model deficiencies with respect to the simulation of seasonal transpiration patterns. Sap flow measurements are used to benchmark the response of these three bedrock configurations. It was found that the simulated transpiration response of the default model configuration is strongly limited by soil moisture availability at sites with extended dry seasons. Under these climate conditions, the implementation of an alternative (i.e., deeper and fractured) bedrock configuration resulted in a better agreement between modeled and measured transpiration. At the site with a continental climate, the default model configuration accurately reproduced the magnitude and temporal patterns of the measured transpiration. The implementation of the alternative bedrock configurations at this site provided more realistic water potentials in plant tissues but negatively affected the modeled transpiration during the summer period. Finally, all three bedrock configurations did not show differences in terms of water potentials, fluxes, and performances on the more northern and colder site exhibiting a transition between oceanic and continental climate. Model performances at this site are low, with a clear overestimation of transpiration compared to sap flow data. The results of this study call for increased efforts into better representing lithological controls on plant water uptake in LSMs.
Publisher: Wiley
Date: 04-04-2022
Publisher: Copernicus GmbH
Date: 28-06-2022
DOI: 10.5194/EMS2022-643
Abstract: & & The structural uncertainty of a climate model is defined as the range of outcomes that can be obtained through different representations of physical processes of the climate system, the selection of different unconstrained parameter values and different choices for the numerical solution of underlying fundamental equations. Exploring the range of these outcomes with the goal of determining a model configuration that produces results in closer agreement with observational data is defined as model calibration or tuning.& & & & In this study, the preliminary results of the Coordinated Parameter Testing 2 (COPAT2) initiative of the CLM-Community are presented. In COPAT2, volunteer members of the community join forces together, with the objective of testing and providing recommended configurations for the new and final version of COSMO-CLM (6.0), as well as for the newly released regional climate model ICON-CLM, for climate modeling applications over the European CORDEX domain.& & & & & A series of sensitivity tests is performed in which various configurations of the models are explored. The aspects that are tested have been carefully selected, based on expert judgment. In the case of COSMO-CLM 6.0, the primary focus is on newly introduced and recently updated parameterizations and physical schemes. For ICON-CLM, these& tests are the first ever conducted with the climate version of the model and are based on the operational configuration and on information of experiments performed for the development of the NWP mode of ICON.& & & & The simulations are conducted at a horizontal resolution of approximately 12 km over Europe, using ERA5 reanalysis data as boundary conditions. In a first step, a series of relatively short tests is conducted over a 7-year period, from 1979 to 1985. Successively, depending on the sensitivity of the model to the applied changes in its configuration, a sub-set of simulations is extended over a total period of 12 years. The results are systematically analyzed with an evaluation suite that has been further developed and extended for COPAT2. The standardized analysis and condensation of results in very few indices summarizing the models performance allow for an easy and fast comparison of the quality of the different simulations.& & & & & & Beside introducing preliminary results of the conducted sensitivity tests, an overview of the calibration strategy followed in COPAT2 will be presented, including information on the selected metrics, employed observational data sets and further details inherent to the ranking of the different experiments.& & & & & & & br& & br& & &
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-4268
Abstract: & & The concept of canopy-scale resistances was developed to investigate and evaluate the transfer of momentum, heat and mass from the leaf surface to the canopy air space and to the atmosphere. Therefore, reliable estimates of resistances are of fundamental importance for studying the ecosystem scale fluxes and land-atmosphere interaction. The canopy-scale resistance has two components: the leaf boundary layer resistance and canopy-air-to-atmosphere resistance. In big-leaf conceptualizations, canopy-scale resistances are represented in a single term called aerodynamic resistance, which refers to the resistance between an idealized & #8216 big-leaf& #8217 and the atmosphere for the transfer of momentum, heat and mass. A decent amount of literature exists on the estimation of aerodynamic resistances for various ecosystems based on the roughness length parametrizations and atmospheric stability correction. Most of these parametrizations do not include the leaf boundary layer explicitly and therefore rely on a conceptual 'aerodynamic temperature' at some distance above the leaf surface. This gap h ers reliable modelling of canopy gas exchange (transpiration and CO2 assimilation) as these processes happen directly at the leaf surface and strongly rely on accurately capturing the leaf surface temperature. To bridge this gap, an additional resistance based on a & #8216 kB& sup& -1& /sup& ' parametrization is commonly added to the classical aerodynamic resistance.& & & & & & & & & The objective of the present study is to estimate the total resistance to heat transfer from the heat exchanging surfaces to the measurement height and to find the most appropriate mathematical formulation for this resistance. We used radiometric and eddy covariance (EC) measurements from a wide range of land cover types and estimated the total resistance to heat transport using measured fluxes and radiometric surface temperatures by inverting the flux-profile equation. We also performed a comprehensive comparison of total resistance estimates with commonly used stability and roughness-based resistance formulations, including & #8216 KB& sup& -1& /sup& ' parametrizations and the momentum flux resistance inverted from EC measurements. We found that total resistances were consistently greater than the roughness length-based resistance parametrizations at most of the study sites. We further found that the difference between the total and aerodynamic resistance can be largely explained by dominant leaf sizes at the in idual sites.& & & & & & & & & Based on these results, we propose a consistent canopy resistance formulation by explicitly considering leaf sizes and leaf boundary layer resistances in combination with an adequate representation of aerodynamic canopy-atmosphere resistance. This approach will enable a consistent coupling of the aerodynamic process with physiological leaf-scale processes such as photosynthesis and stomatal control, which depend on and interact with leaf temperature, and aerodynamic stability.& & & & & & &
Publisher: American Geophysical Union (AGU)
Date: 23-11-2016
DOI: 10.1002/2016JD025426
Publisher: Springer Science and Business Media LLC
Date: 21-05-2022
DOI: 10.1038/S41598-022-12304-3
Abstract: Land surface temperature (LST) is a preeminent state variable that controls the energy and water exchange between the Earth’s surface and the atmosphere. At the landscape-scale, LST is derived from thermal infrared radiance measured using space-borne radiometers. In contrast, plot-scale LST estimation at flux tower sites is commonly based on the inversion of upwelling longwave radiation captured by tower-mounted radiometers, whereas the role of the downwelling longwave radiation component is often ignored. We found that neglecting the reflected downwelling longwave radiation leads not only to substantial bias in plot-scale LST estimation, but also have important implications for the estimation of surface emissivity on which LST is co-dependent. The present study proposes a novel method for simultaneous estimation of LST and emissivity at the plot-scale and addresses in detail the consequences of omitting down-welling longwave radiation as frequently done in the literature. Our analysis uses ten eddy covariance sites with different land cover types and found that the LST values obtained using both upwelling and downwelling longwave radiation components are 0.5–1.5 K lower than estimates using only upwelling longwave radiation. Furthermore, the proposed method helps identify inconsistencies between plot-scale radiometric and aerodynamic measurements, likely due to footprint mismatch between measurement approaches. We also found that such inconsistencies can be removed by slight corrections to the upwelling longwave component and subsequent energy balance closure, resulting in realistic estimates of surface emissivity and consistent relationships between energy fluxes and surface-air temperature differences. The correspondence between plot-scale LST and landscape-scale LST depends on site-specific characteristics, such as canopy density, sensor locations and viewing angles. Here we also quantify the uncertainty in plot-scale LST estimates due to uncertainty in tower-based measurements using the different methods. The results of this work have significant implications for the combined use of aerodynamic and radiometric measurements to understand the interactions and feedbacks between LST and surface-atmosphere exchange processes.
Publisher: Elsevier BV
Date: 10-2021
Publisher: MDPI AG
Date: 21-11-2018
DOI: 10.3390/W10111697
Abstract: Operational weather and flood forecasting has been performed successfully for decades and is of great socioeconomic importance. Up to now, forecast products focus on atmospheric variables, such as precipitation, air temperature and, in hydrology, on river discharge. Considering the full terrestrial system from groundwater across the land surface into the atmosphere, a number of important hydrologic variables are missing especially with regard to the shallow and deeper subsurface (e.g., groundwater), which are gaining considerable attention in the context of global change. In this study, we propose a terrestrial monitoring/forecasting system using the Terrestrial Systems Modeling Platform (TSMP) that predicts all essential states and fluxes of the terrestrial hydrologic and energy cycles from groundwater into the atmosphere. Closure of the terrestrial cycles provides a physically consistent picture of the terrestrial system in TSMP. TSMP has been implemented over a regional domain over North Rhine-Westphalia and a continental domain over Europe in a real-time forecast/monitoring workflow. Applying a real-time forecasting/monitoring workflow over both domains, experimental forecasts are being produced with different lead times since the beginning of 2016. Real-time forecast/monitoring products encompass all compartments of the terrestrial system including additional hydrologic variables, such as plant available soil water, groundwater table depth, and groundwater recharge and storage.
Location: Italy
No related grants have been discovered for Mauro Sulis.