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Articoli di riviste sul tema "Vegetation-Atmosphere System"
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Vella, Ryan, Matthew Forrest, Jos Lelieveld e Holger Tost. "Isoprene and monoterpene simulations using the chemistry–climate model EMAC (v2.55) with interactive vegetation from LPJ-GUESS (v4.0)". Geoscientific Model Development 16, n. 3 (3 febbraio 2023): 885–906. http://dx.doi.org/10.5194/gmd-16-885-2023.
Testo completoAbstract (sommario):
Abstract. Earth system models (ESMs) integrate previously separate models of the ocean, atmosphere and vegetation into one comprehensive modelling system enabling the investigation of interactions between different components of the Earth system. Global isoprene and monoterpene emissions from terrestrial vegetation, which represent the most important source of volatile organic compounds (VOCs) in the Earth system, need to be included in global and regional chemical transport models given their major chemical impacts on the atmosphere. Due to the feedback of vegetation activity involving interactions with weather and climate, a coupled modelling system between vegetation and atmospheric chemistry is recommended to address the fate of biogenic volatile organic compounds (BVOCs). In this work, further development in linking LPJ-GUESS, a global dynamic vegetation model, to the atmospheric-chemistry-enabled atmosphere–ocean general circulation model EMAC is presented. New parameterisations are included to calculate the foliar density and leaf area density (LAD) distribution from LPJ-GUESS information. The new vegetation parameters are combined with existing LPJ-GUESS output (i.e. leaf area index and cover fractions) and used in empirically based BVOC modules in EMAC. Estimates of terrestrial BVOC emissions from EMAC's submodels ONEMIS and MEGAN are evaluated using (1) prescribed climatological vegetation boundary conditions at the land–atmosphere interface and (2) dynamic vegetation states calculated in LPJ-GUESS (replacing the “offline” vegetation inputs). LPJ-GUESS-driven global emission estimates for isoprene and monoterpenes from the submodel ONEMIS were 546 and 102 Tg yr−1, respectively. MEGAN determines 657 and 55 Tg of isoprene and monoterpene emissions annually. The new vegetation-sensitive BVOC fluxes in EMAC are in good agreement with emissions from the semi-process-based module in LPJ-GUESS. The new coupled system is used to evaluate the temperature and vegetation sensitivity of BVOC fluxes in doubling CO2 scenarios. This work provides evidence that the new coupled model yields suitable estimates for global BVOC emissions that are responsive to vegetation dynamics. It is concluded that the proposed model set-up is useful for studying land–biosphere–atmosphere interactions in the Earth system.
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Yoshioka, H. "Vegetation Isoline Equations for an Atmosphere–Canopy–Soil System". IEEE Transactions on Geoscience and Remote Sensing 42, n. 1 (gennaio 2004): 166–75. http://dx.doi.org/10.1109/tgrs.2003.817793.
Testo completo
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Port, U., e M. Claussen. "Stability of the vegetation–atmosphere system in the early Eocene climate". Climate of the Past Discussions 11, n. 3 (5 maggio 2015): 1551–78. http://dx.doi.org/10.5194/cpd-11-1551-2015.
Testo completoAbstract (sommario):
Abstract. We explore the stability of the atmosphere–vegetation system in the warm, almost ice-free early Eocene climate and in the interglacial, pre-industrial climate by analysing the dependence of the system on the initial vegetation cover. The Earth system model of the Max Planck Institute for Meteorology is initialised with either dense forests or bare deserts on all continents. Starting with desert continents, an extended desert remains in Central Asia in early Eocene climate. Starting with dense forest coverage, this desert is much smaller because the initially dense vegetation cover enhances water recycling in Central Asia relative to the simulation with initial deserts. With a smaller Asian desert, the Asian monsoon is stronger than in the case with a larger desert. The stronger Asian monsoon shifts the global tropical circulation leading to coastal subtropical deserts in North and South America which are significantly larger than with a large Asian desert. This result indicates a global teleconnection of the vegetation cover in several regions. In present-day climate, a bi-stability of the atmosphere–vegetation system is found for Northern Africa only. A global teleconnection of bi-stabilities in several regions is absent highlighting that the stability of the vegetation–atmosphere system depends on climatic and tectonic boundary conditions.
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Kleidon, A., K. Fraedrich e C. Low. "Multiple steady-states in the terrestrial atmosphere-biosphere system: a result of a discrete vegetation classification?" Biogeosciences 4, n. 5 (28 agosto 2007): 707–14. http://dx.doi.org/10.5194/bg-4-707-2007.
Testo completoAbstract (sommario):
Abstract. Multiple steady states in the atmosphere-biosphere system can arise as a consequence of interactions and positive feedbacks. While atmospheric conditions affect vegetation productivity in terms of available light, water, and heat, different levels of vegetation productivity can result in differing energy- and water partitioning at the land surface, thereby leading to different atmospheric conditions. Here we investigate the emergence of multiple steady states in the terrestrial atmosphere-biosphere system and focus on the role of how vegetation is represented in the model: (i) in terms of a few, discrete vegetation classes, or (ii) a continuous representation. We then conduct sensitivity simulations with respect to initial conditions and to the number of discrete vegetation classes in order to investigate the emergence of multiple steady states. We find that multiple steady states occur in our model only if vegetation is represented by a few vegetation classes. With an increased number of classes, the difference between the number of multiple steady states diminishes, and disappears completely in our model when vegetation is represented by 8 classes or more. Despite the convergence of the multiple steady states into a single one, the resulting climate-vegetation state is nevertheless less productive when compared to the emerging state associated with the continuous vegetation parameterization. We conclude from these results that the representation of vegetation in terms of a few, discrete vegetation classes can result (a) in an artificial emergence of multiple steady states and (b) in a underestimation of vegetation productivity. Both of these aspects are important limitations to be considered when global vegetation-atmosphere models are to be applied to topics of global change.
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Kleidon, A., K. Fraedrich e C. Low. "Multiple steady-states in the terrestrial atmosphere-biosphere system: a result of a discrete vegetation classification?" Biogeosciences Discussions 4, n. 1 (22 febbraio 2007): 687–705. http://dx.doi.org/10.5194/bgd-4-687-2007.
Testo completoAbstract (sommario):
Abstract. Multiple steady states in the atmosphere-biosphere system can arise as a consequence of interactions and positive feedbacks. While atmospheric conditions affect vegetation productivity in terms of available light, water, and heat, different levels of vegetation productivity can result in differing energy- and water partitioning at the land surface, thereby leading to different atmospheric conditions. Here we investigate the emergence of multiple steady states in the terrestrial atmosphere-biosphere system and focus on the role of how vegetation is represented in the model: (i) in terms of a few, discrete vegetation classes, or (ii) a continuous representation. We then conduct sensitivity simulations with respect to initial conditions and to the number of discrete vegetation classes in order to investigate the emergence of multiple steady states. We find that multiple steady states occur in our model only if vegetation is represented by a few vegetation classes. With an increased number of classes, the difference between the number of multiple steady states diminishes, and disappears completely in our model when vegetation is represented by 8 classes or more. Despite the convergence of the multiple steady states into a single one, the resulting climate-vegetation state is nevertheless less productive when compared to the emerging state associated with the continuous vegetation parameterization. We conclude from these results that the representation of vegetation in terms of a few, discrete vegetation classes can result (a) in an artificial emergence of multiple steady states and (b) in a underestimation of vegetation productivity. Both of these aspects are important limitations to be considered when global vegetation-atmosphere models are to be applied to topics of global change.
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Wang, Fuyao, Michael Notaro, Zhengyu Liu e Guangshan Chen. "Observed Local and Remote Influences of Vegetation on the Atmosphere across North America Using a Model-Validated Statistical Technique That First Excludes Oceanic Forcings*". Journal of Climate 27, n. 1 (1 gennaio 2014): 362–82. http://dx.doi.org/10.1175/jcli-d-13-00080.1.
Testo completoAbstract (sommario):
Abstract The observed local and nonlocal influences of vegetation on the atmosphere across North America are quantified after first removing the oceanic impact. The interaction between vegetation and the atmosphere is dominated by forcing from the atmosphere, making it difficult to extract the forcing from vegetation. Furthermore, the atmosphere is not only influenced by vegetation but also the oceans, so in order to extract the vegetation impact, the oceanic forcing must first be excluded. This study identified significant vegetation impact in two climatically and ecologically unique regions: the North American monsoon region (NAMR) and the North American boreal forest (NABF). A multivariate statistical method, a generalized equilibrium feedback assessment, is applied to extract vegetation influence on the atmosphere. The statistical method is validated using a dynamical experiment for the NAMR in a fully coupled climate model, the Community Climate System Model, version 3.5 (CCSM3.5). The observed influence of NAMR vegetation on the atmosphere peaks in June–August and is primarily attributed to both roughness and hydrological feedbacks. Elevated vegetation amount increases evapotranspiration and surface roughness, which leads to a local decline in sea level pressure and generates an atmospheric teleconnection response. This atmospheric response leads to moister and cooler (drier and warmer) conditions over the western and central United States (Gulf states). The observed influence of the NABF on the atmosphere peaks in March–May, related to a thermal feedback. Enhanced vegetation greenness increases the air temperature locally. The atmosphere tends to form a positive Pacific–North American (PNA)-like pattern, and this anomalous atmospheric circulation and associated moisture advection lead to moister (drier) conditions in the western (eastern) United States.
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Yang, Peiqi, Wout Verhoef e Christiaan van der van der Tol. "Unified Four-Stream Radiative Transfer Theory in the Optical-Thermal Domain with Consideration of Fluorescence for Multi-Layer Vegetation Canopies". Remote Sensing 12, n. 23 (28 novembre 2020): 3914. http://dx.doi.org/10.3390/rs12233914.
Testo completoAbstract (sommario):
Vegetation radiative transfer models (RTMs) are important tools to understand biosphere-atmosphere interactions. The four-stream theory has been successfully applied to solve the radiative transfer problems in homogeneous canopies for both incident solar radiation, thermal and fluorescence emission since 1984. In this note, we describe the development of a unified radiative transfer theory for optical scattering, thermal and fluorescence emission in multi-layer vegetation canopy, and provide a detailed mathematical derivation for the fluxes inside and leaving the canopy. This theory can be used to develop vegetation models for remote sensing applications and plant physiological processes, such as photosynthesis and transpiration. It can also be used to solve the radiative transfer problems in soil-water, soil-water-atmosphere, or soil-vegetation-atmosphere ensembles, besides the soil-vegetation system presented in the note.
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Calvet, Jean-Christophe, Patricia de Rosnay e Stephen G. Penny. "Editorial for the Special Issue “Assimilation of Remote Sensing Data into Earth System Models”". Remote Sensing 11, n. 18 (19 settembre 2019): 2177. http://dx.doi.org/10.3390/rs11182177.
Testo completoAbstract (sommario):
This Special Issue is a collection of papers reporting research on various aspects of coupled data assimilation in Earth system models. It includes contributions presenting recent progress in ocean–atmosphere, land–atmosphere, and soil–vegetation data assimilation.
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Dekker, S. C., H. J. de Boer, V. Brovkin, K. Fraedrich, M. J. Wassen e M. Rietkerk. "Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales". Biogeosciences 7, n. 4 (12 aprile 2010): 1237–45. http://dx.doi.org/10.5194/bg-7-1237-2010.
Testo completoAbstract (sommario):
Abstract. Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.
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Milcu, Alexandru, Martin Lukac, Jens-Arne Subke, Pete Manning, Andreas Heinemeyer, Dennis Wildman, Robert Anderson e Phil Ineson. "Biotic carbon feedbacks in a materially closed soil–vegetation–atmosphere system". Nature Climate Change 2, n. 4 (11 marzo 2012): 281–84. http://dx.doi.org/10.1038/nclimate1448.
Testo completoTesi sul tema "Vegetation-Atmosphere System"
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Hughes, John K. "The dynamic response of the global atmosphere-vegetation coupled system". Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397768.
Testo completo
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Rabbel, Inken [Verfasser]. "Analyzing feedbacks in a forest soil-vegetation-atmosphere system / Inken Rabbel". Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1188731319/34.
Testo completo
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Chatterjee, Sumantra. "ESTIMATING EVAPOTRANSPIRATION USING REMOTE SENSING: A HYBRID APPROACH BETWEEN MODIS DERIVED ENHANCED VEGETATION INDEX, BOWEN RATIO SYSTEM, AND GROUND BASED MICRO-METEOROLOGICAL DATA". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1271602329.
Testo completo
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Bolinius, Damien Johann. "Methods to measure mass transfer kinetics, partition ratios and atmospheric fluxes of organic chemicals in forest systems". Doctoral thesis, Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-136008.
Testo completoAbstract (sommario):
Vegetation plays an important role in the partitioning, transport and fate of hydrophobic organic contaminants (HOCs) in the environment. This thesis aimed at addressing two key knowledge gaps in our understanding of how plants exchange HOCs with the atmosphere: (1) To improve our understanding of the uptake of HOCs into, and transfer through, leaves of different plant species which can significantly influence the transport and fate of HOCs in the environment; and (2) To evaluate an experimental approach to measure fluxes of HOCs in the field. The methods presented in papers I, II and III contribute to increasing our understanding of the fate and transport of HOCs in leaves by offering straightforward ways of measuring mass transfer coefficients through leaves and partition ratios of HOCs between leaves, leaf lipids and lipid standards and reference materials like water, air and olive oil. The passive dosing study in paper III in particular investigated the role of the composition of the organic matter extracted from leaves in determining the capacity of the leaves to hold chemicals and found no large differences between 7 different plant species, even though literature data on leaf/air partition ratios (Kleaf/air) varies over 1-3 orders of magnitude. In paper IV we demonstrated that the modified Bowen ratio method can be extended to measure fluxes of persistent organic pollutants (POPs) if the fluxes do not change direction over the course of the sampling period and are large enough to be measured. This approach thus makes it possible to measure fluxes of POPs that usually require sampling times of days to weeks to exceed method detection limits. The experimental methods described in this thesis have the potential to support improved parameterization of multimedia models, which can then be evaluated against fluxes measured in the field using the modified Bowen ratio approach.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
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Gutierrez, Cori Omar. "Relationship and feedback between LULC changes and hydroclimatic variability in Amazonia". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS123.
Testo completoAbstract (sommario):
La forêt amazonienne joue un rôle essentiel en tant que régulateur du système climatique et principal puits de carbone terrestre. Il contrôle les processus hydroclimatiques et atténue les effets des sécheresses grâce au couplage végétation-atmosphère. En fait, les forêts amazoniennes peuvent potentiellement affecter les régimes de précipitations grâce à des processus biophysiques tels que le recyclage de l'eau. Cependant, ces capacités ont été réduites au cours des dernières décennies en raison des perturbations du système climat-végétation ainsi que de l'intensification des sécheresses. Cela a accentué un processus de transition biophysique d'un écosystème à prédominance forestière vers une savane. Par conséquent, compte tenu de ces complexités, il est extrêmement important de comprendre la direction des changements.À l'aide de plusieurs ensembles de données et du modèle couplé ORCHIDEE-LMDZ, cette thèse approfondit l'étude des interactions entre l'hydroclimatologie et la végétation amazonienne. En outre, il cherche à élargir notre compréhension des modifications du système végétation-atmosphère et de ses liens avec le climat et des changements du LULC. De même, en tenant compte des taux croissants de déforestation, il étudie les effets et les rétroactions résultant d'un scénario de perte forestière à grande échelle sur les processus hydrologiques.Les résultats montrent que, dans le sud-ouest de l'Amazonie, les forêts passant d'un état influencé par la disponibilité énergétique à un état dépendant de la disponibilité en eau tout au long de l'année. Pendant la saison des pluies, la croissance de la végétation est principalement influencée par la disponibilité en énergie plutôt que par la disponibilité en eau. Cependant, en dehors de cette période, les forêts réagissent positivement aux précipitations et au stockage terrestre de l'eau, ce qui suggère que la végétation dépend principalement de l'approvisionnement hydrique. Toutefois, une analyse spatiale révèle que la déforestation récente modifie ces transitions et déstabilise l'équilibre naturel du système climat-végétation.La nature de ces déséquilibres en Amazonie n'est pas complètement claire. En examinant les liens entre les flux d'eau/énergie et les conditions de végétation, nous explorons si ces changements sont inhérents au climat ou résultent de processus anthropiques. 67% du sud-ouest a connu une transition vers un état majoritairement sec en raison du climat (forçage externe), tandis que 21% a connu une transition vers un état dominé par la déforestation (forçage interne). Cependant, les moteurs externes et internes entraînent simultanément des changements. En quantifiant les forçages, nous montrons que les synergies ont amené 74% du sud-ouest de l'Amazonie à un état de stress hydrique élevé. Or, ces dernières années, 30% des changements sont strictement dominés par des forçages internes. Cela suggère que les processus internes jouent un rôle croissant dans la transition vers des états caractérisés par un stress hydrique forestier élevé, particulièrement là où la déforestation et la pression anthropique augmentent.À l'aide du modèle couplé ORCHIDEE-LMDZ, les effets de la déforestation projetée de l'Amazonie d'ici 2050 sur le cycle de l'eau et la sécheresse sont examinés. La déforestation diminue les précipitations, réduit l'évapotranspiration et augmente le ruissellement. De plus, elle accentue le stress hydrique, notamment dans le sud-ouest de l'Amazonie (retour positif). La demande en eau dans l'atmosphère, à la surface et même dans la zone racinaire du sol s'intensifie pendant la saison sèche. Pendant la saison des pluies, le déficit d'humidité atmosphérique devient encore plus aigu vers les Andes tropicales, sur la région de l'Altiplano. Ces résultats permettent de mieux comprendre les effets possibles du déboisement massif sur la disponibilité en eau et la résilience de l'Amazonie dans un contexte où les changements se produisent à un rythme accéléréThe Amazon rainforest plays a vital role by functioning as a regulator of the climate system and as the main terrestrial carbon sink. It drives hydroclimatic processes and mitigates the effects of droughts through vegetation-atmosphere coupling. Indeed, Amazon forests have the potential to impact rainfall patterns through biophysical processes like water recycling. However, these capacities have been reduced during the last decades due to disturbances in the climate-vegetation system together with the intensification of droughts. All this has accentuated a process of biophysical transition from a predominantly forested ecosystem to a Savanna. Therefore, given these complexities, understanding the direction of changes is of vital importance.Using multiple datasets and the coupled ORCHIDEE and LMDZ models, this thesis delves into the study of the interactions between Amazon hydroclimatology and vegetation. In addition, it seeks to expand our understanding of modifications in the vegetation-atmosphere system and its links with climate and LULC changes. Likewise, taking into account the increasing rates of deforestation, it investigates the effects and feedback resulting from a large-scale forest loss scenario on hydrological processes.The results show that, over the southwestern Amazon, forests undergo a transition from being influenced by energy availability to depending on water availability throughout the year. During the rainy season, vegetation growth is primarily influenced by energy availability rather than water availability. Nevertheless, outside of this period, forests respond positively to precipitation and terrestrial water storage, suggesting that vegetation is primarily dependent on water supply. However, a spatial analysis reveals that recent deforestation modifies these transitions and destabilizes the natural balance in the climate-vegetation system.The nature of these imbalances in the Amazon is not entirely clarified. Through an approach based on the relationships of water/energy fluxes and vegetation conditions over the last four decades, it is explored whether these changes are intrinsic to climate variability or are driven by anthropogenic processes. 67% of the southwestern Amazon has experienced a transition towards a predominantly dry state due to climatic factors (external forcing), while 21% has transitioned towards a state dominated by deforestation (internal forcing). However, external and internal forcings are not independent processes, as both mechanisms drive changes simultaneously. By weighing the magnitudes of these forcings, we show that the synergies have led 74% of the southwestern Amazon toward a state of greater water stress. Nevertheless, during recent years, although combined external-internal processes continue to exert significant control over changes, 30% of these are strictly dominated by internal forcing. This suggests that internal processes are playing an increasingly relevant role in the transition towards a state characterized by high forest water stress, especially in areas where deforestation and anthropogenic pressure are increasing.Using the coupled ORCHIDEE and LMDZ models, the effects of projected Amazon deforestation by 2050 on the hydrological cycle and dryness are examined. Deforestation decreases precipitation, reduces evapotranspiration and increases runoff. Furthermore, deforestation accentuates water stress especially in the southwestern Amazon (positive feedback). Water demands in the atmosphere, on the land surface and even in the soil root zone intensify during the dry season. During the wet season, the deficit of specific atmospheric humidity becomes even more acute towards the tropical Andes over the Altiplano region. These findings provide a more thorough understanding of the possible effects of massive forest removal on the water availability and resilience of the Amazon in a context where changes are occurring at an accelerated rate
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Brimelow, Julian Charles. "On the use of modelling, observations and remote sensing to better understand the Canadian prairie soil-crop-atmosphere system". 2011. http://hdl.handle.net/1993/4462.
Testo completoAbstract (sommario):
Thunderstorms have been identified as an important component of the hydrological cycle on the Canadian Prairies, a region that is postulated to have the potential to exert a detectable influence on convective precipitation in the summer. However, very little work has been undertaken exploring and elucidating those aspects of biophysical forcing on the Canadian Prairies that affect lightning activity during the summer months, the constraints under which any linkages operate, and the mechanisms by which surface anomalies modify the structure and moisture content of the convective boundary layer (CBL) so as to modulate lightning activity.
Evapotranspiration (ET) from the soil and vegetation canopy is known to be important for modulating the moisture content in the CBL, and this in turn has important implications for the initiation and intensity of deep, moist convection. The Second Generation Prairie Agrometeorological Model (PAMII) of Raddatz (1993) has been used extensively for the purpose of quantifying the evolution of soil moisture and ET in response to atmospheric drivers on the Canadian Prairies. However, the ability of PAMII to simulate the evolution of root-zone soil moisture and ET during the growing season has yet to be verified against a comprehensive set of in-situ observations.
In this thesis, we address the above knowledge gaps using unique datasets comprising observed lightning flash data, satellite-derived Normalized Difference Vegetation Index (NDVI) data, observed atmospheric soundings, in-situ soil moisture observations and estimates of daily ET from eddy-covariance systems.
A thorough quantitative validation of simulations of root-zone soil moisture and ET from PAMII was undertaken against in-situ soil moisture measurements and ET from eddy-covariance systems at sites on the Canadian Prairies. Our analysis demonstrates that PAMII shows skill in simulating the evolution of bulk root-zone soil moisture content and ET during the growing season, and for contrasting summer conditions (i.e., wet versus dry). As part of the soil moisture validation, a novel multi-model pedotransfer function ensemble technique was developed to quantify the uncertainty in soil moisture simulations arising from errors in the specified soil texture and associated soil hydraulic properties.
An innovative approach was used to explore linkages between the terrestrial surface and deep, moist convection on the Canadian Prairies, using datasets which avoid many of the problems encountered when studying linkages between soil moisture and thunderstorm activity. This was achieved using lightning flash data in unison with remotely sensed NDVI data. Specifically, statistical analysis of the data over 38 Census Agricultural Regions (CARs) on the Canadian Prairies for 10 summers from 1999 to 2008 provided evidence for a surface-convection feedback on the Canadian Prairies, in which drought tends to perpetuate drought with respect to deep, moist convection. The constraints in which such a feedback operates (e.g., areal extent and magnitude of the NDVI anomalies) were also identified. For example, our data suggest that NDVI anomalies and lightning duration are asymmetric, with the relationship between NDVI and lightning duration strengthening as the area and amplitude of the negative NDVI anomaly (less vegetation vigour) increases.
Finally, we focused on how surface anomalies over the Canadian Prairies can condition the CBL so as to inhibit or facilitate thunderstorm activity, while also considering the role of synoptic-scale forcing on modulating summer thunderstorm activity. We focused on a CAR located over central Alberta for which observed lightning flash data, NDVI data, and in-situ sounding data were available for 11 summers from 1999 to 2009. Our analysis suggests that storms over this region are more likely to develop and are longer-lived or more widespread when they develop in an environment in which the surface and upper-air synoptic-scale forcings are synchronized. On days when a surface or upper-air feature is present, storms are more likely to be triggered when NDVI is much above average, compared to when NDVI is much below average. We propose a conceptual model, based almost entirely on observations, which integrates our findings to describe how a reduction in vegetation vigour modulates the partitioning of available energy into sensible and latent heat fluxes at the surface, thereby modulating the lifting condensation level heights, which in turn affect lightning duration.
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Tagarelli, Vito. "Analysis of the slope-vegetation-atmosphere interaction for the design of the mitigation measures of landslide risk in clayey slopes". Doctoral thesis, 2019. http://hdl.handle.net/11589/161130.
Testo completoAbstract (sommario):
L’attività di ricerca affrontata dal dottorando riguarda l'evoluzione delle condizioni di equilibrio nel tempo in riferimento alla stabilità di frane clima-indotte. L'approccio seguito è principalmente legato al confronto tra analisi numeriche e dati di monitoraggio di campo, che sono di fondamentale importanza per poter determinare la veridicità delle previsioni numeriche.
La ricerca mira innanzitutto ad identificare i principali fattori interni ed esterni da considerare per il replicare correttamente numericamente, le evidenze sul campo. Come tale in questa fase del lavoro, lo scopo è quello di diagnosticare l'attuale attività stagionale osservata ricorrentemente e documentata in un caso di studio (la frana di Pisciolo) tramite monitoraggi di sito. Attraverso strategie numeriche diverse e gradualmente più complesse si è effettuato un calcolo del processo franoso. In particolare, sono state condotte analisi numeriche idrauliche e idromeccaniche, volte a mettere in luce i punti di forza e di debolezza di ciascuna strategia numerica nella modellazione dell’attività attuale della frana in studio.
La rappresentatività del pendio di Pisciolo con riferimento a diversi meccanismi di frana nell'Appennino sud-orientale, rende questo caso di particolare interesse, poiché le conclusioni sito-specifiche sono valide anche per casi di studio meno studiati, o meno monitorati.
Questa circostanza è molto rilevante, dal momento che consente una trasposizione di concetti e strategie di progettazione dal caso specifico (la frana di Pisciolo) ad altri casi di studio, anche senza studi dettagliati sito-specifici.
L'obiettivo finale di questo lavoro di ricerca è di fornire consigli per quanto concerne due diverse strategie di mitigazione; in particolar modo il dottorando si è occupato della progettazione di sistemi di allerta e di interventi di bioingegneria in relazione al meccanismo di frana di riferimento.
Il sistema di allerta è progettato con riferimento a diversi corpi di frana, da superficiale a profondo, evidenziando le differenze sia per quanto riguarda le variabili di soglia di riferimento sia che i valori di soglia. Questa analisi viene effettuata me-diante modellazione numerica idraulica seguita dal calcolo del fattore di sicurezza con il metodo del limite di equilibrio.
L'input forzante climatico per queste analisi è ottenuto da dati climatici reali, dal 2001 al 2016, per i quali sono disponibili precipitazioni e temperature minime e massime da annali climatici forniti da una stazione di monitoraggio climatico vicina al versante di Pisciolo. I risultati della diagnosi del meccanismo di frana consentono di comprendere che anche la condizione climatica preesistente può influire sul successivo risultato di un certo input climatico. Di conseguenza tra tutti gli anni monitorati disponibili, sono stati scelti due anni diversi come rappresentativi di uno molto piovoso e di uno molto secco; questi sono stati applicati prima dell'applicazione dell'anno climatico in esame.
L'analisi dell'efficienza di un intervento di ingegneria naturalistica o di bioingegneria è stata anch’essa analizzata in questa attività di ricerca; in particolare, è stato effettuato uno studio preliminare sull'uso di colture radicate sul suolo per la stabilizzazione di corpi superficiali e profondi.
A questo scopo, un campo prova (circa 2000 m2) è stato allestito al piede del meccanismo franoso di Pisciolo, allo scopo di determinare l'efficienza idraulica di alcuni piante selezionate. I vari tipi di colture sono stati seminati nell’area del test e il monitoraggio delle variabili climatiche, dello stato di copertura superficiale (zona insatura) e dello stato del suolo più profondo (zona saturata) è iniziato a gennaio 2018 ed è tuttora in corso.
Una piattaforma numerica di equazioni differenziali per risolvere il numerica-mente il calcolo termo-idraulico è stato descritto, con lo scopo futuro di calcolare in maniera inversa i flussi verso l’atmosfera evaporativi e traspirativi indotti dalle piante.
Pur non essendo conclusivo, questo studio può essere scientificamente rilevante, ed è quindi auspicabile che esso abbia ripercussioni sul lato pratico, risultando utile per future linee guida per la progettazione di interventi di bioingegneria simili a quello in studio.The present research activity deals with the evolution of the equilibrium conditions in time with reference to climate-induced landslides. The approach followed herein is mainly linked to the comparison between numerical analyses and field monitoring data which are of major importance to state the success of the numerical predictions. The research is first aimed at identifying the main internal and external factors to be accounted for numerically replicating the field evidence. As such in this step of the work, the purpose is to diagnose the current seasonal activity observed in a case study (the Pisciolo slope) in terms of hydraulic and mechanical behavior. In particular, a boundary value problem has been numerically solved with different and gradually more complex numerical strategies. Specifically, hydraulic and hydro-mechanical numerical analyses have been carried out, aimed at highlighting the strengths and weaknesses of each numerical strategy in modeling the current activity of the Pisciolo slope. The representativeness of the Pisciolo slope with respect to several landslide mechanisms in the South-Eastern Apennine, makes this case study of particular interest, since the site-specific conclusions drawn may be also valid for other mechanisms. This circumstance appears to be very relevant, since it allows for transposition of concepts and design strategies from a representative slope to others, even without very detailed site-specific studies. The final aim of this research work is to give advice on two different mitigation measures, addressing the design of early warning systems and bio-engineering interventions for the landslide mechanism of reference. The early warning system is designed with reference to different landslide bodies, from shallow to deep, highlighting the differences on both the reference threshold variables and threshold values. This analysis is carried out by means of hydraulic numerical modeling followed by the computation of the safety factor with the limit equilibrium method. The climatic forcing input for these analyses is obtained from real climatic data, from 2001 to 2016, for which rainfall and minimum and maximum temperatures were available from climatic annals provided by a climatic monitoring station close the Pisciolo slope. The results of the diagnosis of the landslide mechanism allow realizing that also the pre-existent climatic condition may affect the subsequent impact of a certain climatic input. As such, among all the monitored years available, two different years have been chosen as representative of a very rainy and a very dry one; those have been applied prior the application of the climatic year under investigation. The analysis of the efficiency of a bio-engineering intervention has been of interest in this research activity; in particular, the use of deep-rooted crops on the soil cover for stabilizing shallow and deep bodies is studied herein. As such, a test site (approx. 2000 m2) has been installed at the toe of the Pisciolo landslide, aimed at determining the hydraulic efficiency of some selected crop types. The various crop types have been seeded into the test site, and the monitoring of climatic variables, the shallow cover state (unsaturated zone), and the deeper soil state (saturated zone) has been activated in January 2018 and is still on-going. A numerical platform of differential equations for solving the thermo-hydraulic boundary value problem is described, with the future aim to back-calculate the upward fluxes of evaporation and plant-induced transpiration. Although not being conclusive, this study may be scientifically relevant and is then intended to have repercussions on the practical side, being useful for future guidelines for the design of bio-engineering interventions.
Libri sul tema "Vegetation-Atmosphere System"
1
Claussen, Martin, Anne Dallmeyer e Jürgen Bader. Theory and Modeling of the African Humid Period and the Green Sahara. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.532.
Testo completoAbstract (sommario):
There is ample evidence from palaeobotanic and palaeoclimatic reconstructions that during early and mid-Holocene between some 11,700 years (in some regions, a few thousand years earlier) and some 4200 years ago, subtropical North Africa was much more humid and greener than today. This African Humid Period (AHP) was triggered by changes in the orbital forcing, with the climatic precession as the dominant pacemaker. Climate system modeling in the 1990s revealed that orbital forcing alone cannot explain the large changes in the North African summer monsoon and subsequent ecosystem changes in the Sahara. Feedbacks between atmosphere, land surface, and ocean were shown to strongly amplify monsoon and vegetation changes. Forcing and feedbacks have caused changes far larger in amplitude and extent than experienced today in the Sahara and Sahel. Most, if not all, climate system models, however, tend to underestimate the amplitude of past African monsoon changes and the extent of the land-surface changes in the Sahara. Hence, it seems plausible that some feedback processes are not properly described, or are even missing, in the climate system models.Perhaps even more challenging than explaining the existence of the AHP and the Green Sahara is the interpretation of data that reveal an abrupt termination of the last AHP. Based on climate system modeling and theoretical considerations in the late 1990s, it was proposed that the AHP could have ended, and the Sahara could have expanded, within just a few centuries—that is, much faster than orbital forcing. In 2000, paleo records of terrestrial dust deposition off Mauritania seemingly corroborated the prediction of an abrupt termination. However, with the uncovering of more paleo data, considerable controversy has arisen over the geological evidence of abrupt climate and ecosystem changes. Some records clearly show abrupt changes in some climate and terrestrial parameters, while others do not. Also, climate system modeling provides an ambiguous picture.The prediction of abrupt climate and ecosystem changes at the end of the AHP is hampered by limitations implicit in the climate system. Because of the ubiquitous climate variability, it is extremely unlikely that individual paleo records and model simulations completely match. They could do so in a statistical sense, that is, if the statistics of a large ensemble of paleo data and of model simulations converge. Likewise, the interpretation regarding the strength of terrestrial feedback from individual records is elusive. Plant diversity, rarely captured in climate system models, can obliterate any abrupt shift between green and desert state. Hence, the strength of climate—vegetation feedback is probably not a universal property of a certain region but depends on the vegetation composition, which can change with time. Because of spatial heterogeneity of the African landscape and the African monsoon circulation, abrupt changes can occur in several, but not all, regions at different times during the transition from the humid mid-Holocene climate to the present-day more arid climate. Abrupt changes in one region can be induced by abrupt changes in other regions, a process sometimes referred to as “induced tipping.” The African monsoon system seems to be prone to fast and potentially abrupt changes, which to understand and to predict remains one of the grand challenges in African climate science.
2
Verschuur, Gerrit L. Impact! Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195101058.001.0001.
Testo completoAbstract (sommario):
Most scientists now agree that some sixty-five million years ago, an immense comet slammed into the Yucatan, detonating a blast twenty million times more powerful than the largest hydrogen bomb, punching a hole ten miles deep in the earth. Trillions of tons of rock were vaporized and launched into the atmosphere. For a thousand miles in all directions, vegetation burst into flames. There were tremendous blast waves, searing winds, showers of molten matter from the sky, earthquakes, and a terrible darkness that cut out sunlight for a year, enveloping the planet in freezing cold. Thousands of species of plants and animals were obliterated, including the dinosaurs, some of which may have become extinct in a matter of hours. In Impact, Gerrit L. Verschuur offers an eye-opening look at such catastrophic collisions with our planet. Perhaps more important, he paints an unsettling portrait of the possibility of new collisions with earth, exploring potential threats to our planet and describing what scientists are doing right now to prepare for this awful possibility. Every day something from space hits our planet, Verschuur reveals. In fact, about 10,000 tons of space debris fall to earth every year, mostly in meteoric form. The author recounts spectacular recent sightings, such as over Allende, Mexico, in 1969, when a fireball showered the region with four tons of fragments, and the twenty-six pound meteor that went through the trunk of a red Chevy Malibu in Peekskill, New York, in 1992 (the meteor was subsequently sold for $69,000 and the car itself fetched $10,000). But meteors are not the greatest threat to life on earth, the author points out. The major threats are asteroids and comets. The reader discovers that astronomers have located some 350 NEAs ("Near Earth Asteroids"), objects whose orbits cross the orbit of the earth, the largest of which are 1627 Ivar (6 kilometers wide) and 1580 Betula (8 kilometers). Indeed, we learn that in 1989, a bus-sized asteroid called Asclepius missed our planet by 650,000 kilometers (a mere six hours), and that in 1994 a sixty-foot object passed within 180,000 kilometers, half the distance to the moon. Comets, of course, are even more deadly. Verschuur provides a gripping description of the small comet that exploded in the atmosphere above the Tunguska River valley in Siberia, in 1908, in a blinding flash visible for several thousand miles (every tree within sixty miles of ground zero was flattened). He discusses Comet Swift-Tuttle--"the most dangerous object in the solar system"--a comet far larger than the one that killed off the dinosaurs, due to pass through earth's orbit in the year 2126. And he recounts the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994, as some twenty cometary fragments struck the giant planet over the course of several days, casting titanic plumes out into space (when Fragment G hit, it outshone the planet on the infrared band, and left a dark area at the impact site larger than the Great Red Spot). In addition, the author describes the efforts of Spacewatch and other groups to locate NEAs, and evaluates the idea that comet and asteroid impacts have been an underrated factor in the evolution of life on earth. Astronomer Herbert Howe observed in 1897: "While there are not definite data to reason from, it is believed that an encounter with the nucleus of one of the largest comets is not to be desired." As Verschuur shows in Impact, we now have substantial data with which to support Howe's tongue-in-cheek remark. Whether discussing monumental tsunamis or the innumerable comets in the Solar System, this book will enthrall anyone curious about outer space, remarkable natural phenomenon, or the future of the planet earth.
Capitoli di libri sul tema "Vegetation-Atmosphere System"
1
Shuttleworth, W. James. "The Soil-Vegetation-Atmosphere Interface". In Energy and Water Cycles in the Climate System, 323–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-76957-3_13.
Testo completo
2
Satoh, Takashi, Michiaki Sugita, Tsutomu Yamanaka, Maki Tsujimura e Reiichiro Ishii. "Water Dynamics Within the Soil–Vegetation–Atmosphere System in a Steppe Region Covered by Shrubs and Herbaceous Plants". In The Mongolian Ecosystem Network, 43–63. Tokyo: Springer Japan, 2012. http://dx.doi.org/10.1007/978-4-431-54052-6_5.
Testo completo
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"Transport processes in the soil-vegetation-lower atmosphere system". In Fluid Mechanics of Environmental Interfaces, 345–66. CRC Press, 2012. http://dx.doi.org/10.1201/b13079-20.
Testo completo
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"Transport processes in the soil-vegetation-lower atmosphere system". In Fluid Mechanics of Environmental Interfaces, 215–36. Taylor & Francis, 2008. http://dx.doi.org/10.4324/9780203895351-16.
Testo completo
5
Artaxo, Paulo. "The Atmospheric Component of Biogeochemical Cycles in the Amazon Basin". In The Biogeochemistry of the Amazon Basin. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195114317.003.0006.
Testo completoAbstract (sommario):
Tropical forests, with their high biological activity, have the potential to emit large amounts of trace gases and aerosol particles to the atmosphere. The accelerated development and land clearing that is occurring in large areas of the Amazon basin suggest that anthropogenic effects on natural biogeochemical cycles are already occurring (Gash et al. 1996). The atmosphere plays a key role in this process. The tropics are the part of the globe with the most rapidly growing population, the most dramatic industrial expansion and the most rapid and pervasive change in land use and land cover. Also the tropics contain the largest standing stocks of terrestrial vegetation and have the highest rates of photosynthesis and respiration. It is likely that changes in tropical land use will have a profound impact on the global atmosphere (Andreae 1998, Andreae and Crutzen 1997). A significant fraction of nutrients are transported or dislocated through the atmosphere in the form of trace gases, aerosol particles, and rainwater (Keller et al. 1991). Also the global effects of carbon dioxide, methane, nitrous oxide, and other trace gases have in the forest ecosystems a key partner. The large emissions of isoprene, terpenes, and many other volatile organic compounds could impact carbon cycling and the production of secondary aerosol particles over the Amazon region. Vegetation is a natural source of many types of aerosol particles that play an important role in the radiation budget over large areas (Artaxo et al. 1998). There are 5 major reservoirs in the Earth system: atmosphere, biosphere (vegetation, animals), soils, hydrosphere (oceans, lakes, rivers, groundwater), and the lithosphere (Earth crust). Elemental cycles of carbon, oxygen, nitrogen, sulfur, phosphorus, and other elements interact with the different reservoirs of the Earth system. The carbon cycle has important aspects in tropical forests due to the large amount of carbon stored in the tropical forests and the high rate of tropical deforestation (Jacob 1999). In Amazonia there are two very different atmospheric conditions: the wet season (mostly from November to June) and the dry season (July-October) (see Marengo and Nobre, this volume). Biomass burning emissions dominate completely the atmospheric concentrations over large areas of the Amazon basin during the dry season (Artaxo et al. 1988).
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Houghton, R. A. "Effects of Land-Use Change, Surface Temperature, and CO2 Concentration on Terrestrial Stores of Carbon". In Biotic Feedbacks in the Global Climatic System, 333–50. Oxford University PressNew York, NY, 1995. http://dx.doi.org/10.1093/oso/9780195086409.003.0024.
Testo completoAbstract (sommario):
Abstract Two questions are addressed in this chapter. First, are there feedbacks between the earth’s environment and the amount of carbon held in terrestrial ecosystems? More specifically, will a warmer earth with higher concentrations of CO2 in its atmosphere store more or less carbon in vegetation and soil than the current earth? The time frame of interest is years to decades, and consideration is given to metabolic processes (productivity and respiration) rather than to migration of species or ecotones. The question is addressed from the perspective of the global carbon balance over the last 140 years. The answer is tentative: it appears as though there may have been both positive and negative biotic feedbacks.
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Graf, William L. "Plutonium in the Rio Grande System". In Plutonium and the Rio Grande. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195089332.003.0012.
Testo completoAbstract (sommario):
The water, sediment, landform, and vegetation systems of the Northern Rio Grande provide the environmental framework within which plutonium moves and is stored. Plutonium enters the Northern Rio Grande from two sources: atmospheric fallout and releases from operations of Los Alamos National Laboratory that enter the main stream by transport through Los Alamos Canyon. This chapter describes the nature and timing of plutonium loading in the river’s sediment system as a means of identifying those years when sedimentation is likely to have accumulated those deposits with the highest concentrations of plutonium. This chapter also discusses plutonium in river water, sediments in transit, and sediments deposited along and stored along the channel, as well as the various mean values of plutonium concentrations found in the region of Los Alamos. The review includes plutonium in the regional environments around Los Alamos, including the compartments of river water, active sediments, flood-plain deposits, and reservoir deposits, as well as the plutonium concentrations in the sediments of Los Alamos Canyon. Most of the plutonium in atmospheric fallout is from the testing of nuclear weapons. Five nations have detonated a total of 484 nuclear devices in the atmosphere, 466 with known dates. These explosions have injected plutonium into the general atmospheric circulation, resulting in a global distribution of fallout as the material returns to the surface. There are three types of fallout: local, tropospheric, and stratospheric. Local or early fallout arrives within a day of the detonation and consists of particles 100 to 200 microns in diameter (fine sand) transported in the lower atmosphere and deposited within several hundred kilometers of the site of the explosion. Finer particles travel greater distances and disperse over greater areas. Tropospheric fallout arrives within a month of the detonation and consists of particles less than 100 microns in diameter (mostly silt size), transported in the lower atmosphere. The global atmospheric circulation transports tropospheric fallout around the world in a band about 30 degrees latitude wide, centered on the site of the explosion. Most of the tropospheric fallout delivers plutonium to the earth’s surface in precipitation, with only about 10 percent occurring as dry fall.
8
Pielke, Roger A., e Nolan J. Doesken. "Climate of the Shortgrass Steppe". In Ecology of the Shortgrass Steppe. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195135824.003.0006.
Testo completoAbstract (sommario):
The climate of a region involves the short- and long-term interaction among the atmospheric, hydrologic, ecologic, oceanographic, and cryospheric components of the earth’s environmental system (Hayden, 1998; Pielke, 1998, 20 01a,b). These interactions occur across a ll spatial and temporal scales, from turbulence generated by diurnal cycles at a landscape scale, to globalscale circulation. The establishment of particular ecosystem types is associated with a nonlinear feedback between the atmosphere and the underlying vegetation (Pielke a nd Vidale, 1995). Wang a nd E ltahir (20 0 0) and Claussen (1998) have demonstrated that vegetation patterning cannot be accurately simulated in a model unless vegetation–atmosphere feedbacks are included. In this chapter we summarize the climate system of the shortgrass steppe. This is a region of large seasonal contrasts, and of interannual and longer term variability. It is also a region that has undergone major human impacts during the past 150 years. We present both average conditions and examples of extreme events in the shortgrass steppe to illustrate the variable climate of this interesting ecosystem. Geographic factors play a large role in determining the climatic characteristics of the shortgrass steppe (Lauenroth and Burke, 1995; Lauenroth and Milchunas, 1992; Lauenroth et al., 1999). Key factors for this region include its mid-latitude position, its relatively high elevations, its interior continental location, and its proximity to the Rocky Mountains, a substantial north–south-oriented mountain barrier immediately to the west. Air masses affecting the region consist of continental polar air from the north, humid continental air masses from the east, humid subtropical air masses from the southeast and south, and Paci8 c maritime air masses from the west. The latter can be signi8 cantly modi8 ed as they cross a series of mountain ranges and interior dry regions before reaching the shortgrass steppe region. Each of these geographic and atmospheric features contributes to the climate of the region. Latitude determines day length and sun angle, and, hence, solar insolation. This, in turn, greatly affects air temperature. Upper level westerly winds increase over the mid-latitudes in the fall and winter in response to strengthening north–south temperature gradients in the atmosphere. Paci8 c air masses are carried eastward over the Rocky Mountains, depositing considerable cool-season precipitation in the mountains, but rarely on the shortgrass steppe.
9
Bararzadeh Ledari, Masoumeh, e Reza Bararzadeh Ledari. "Nature as a Teacher for Abiota Self-Organization in Terms of Entropy Analysis". In Exergy - New Technologies and Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109817.
Testo completoAbstract (sommario):
In this chapter, the various terms of entropy generation in terrestrial systems and the atmosphere are estimated by imitating the entropy analysis of a steam power generation (STPG). The highest entropy generation is associated with the outgoing longwave radiation flux (more than 20–200 times the downward solar radiation). The results indicate that the most significant terms of entropy generation (heat dissipation) in different processes are related to latent and sensible heat fluxes (similar to steam generation and flue gas of the STPG). The vegetation cover (boiler system) destroys a part of solar energy absorption in the form of entropy generated by the formation of water vapor and transpiration (steam turbine). Given that life is formed by the optimal balance between the system, the ecosystem, and the living and nonliving organisms, it is important to study the various entropy fluxes in ecosystems that can lead to ecosystem balance.
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Zhao, Ying, Ji Qi, Qiuli Hu e Yi Wang. "The “Groundwater Benefit Zone”, Proposals, Contributions and New Scientific Issues". In Soil Science - Emerging Technologies, Global Perspectives and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.100299.
Testo completoAbstract (sommario):
The groundwater has great potential for water resource utilization, accounting for about a quarter of vegetation transpiration globally and contributing up to 84% in shallow groundwater areas. However, in irrigated agricultural regions or coastal areas with shallow groundwater levels, due to the high groundwater salinity, the contribution of groundwater to transpiration is small and even harmful. This paper proposes a new conception of groundwater benefit zone in the groundwater-soil–plant-atmosphere continuum (GSPAC) system. Firstly, it analyzes the mutual feedback processes of the underground hydrological process and aboveground farmland ecosystem. Secondly, it elaborates on the regional water and salt movement model proposed vital technologies based on the optimal regulation of the groundwater benefit zone and is committed to building a synergy that considers soil salt control and groundwater yield subsidies. Finally, based on the GSPAC system water-salt coupling transport mechanism, quantitative model of groundwater benefit zone, and technical parameters of regional water-salt regulation and control, the scientific problems and development opportunities related to the conception of groundwater benefit zone have been prospected.
Atti di convegni sul tema "Vegetation-Atmosphere System"
1
Miura, Munenori, Kenta Obata e Hiroki Yoshioka. "Vegetation isoline equations for atmosphere-canopy-soil system of layer with second order interaction term". In SPIE Optical Engineering + Applications, a cura di Wei Gao, Thomas J. Jackson e Jinnian Wang. SPIE, 2010. http://dx.doi.org/10.1117/12.860432.
Testo completo
2
SASNAUSKIENĖ, Jurgita, Nomeda SABIENĖ, Vitas MAROZAS, Laima ČESONIENĖ e Kristina LINGYTĖ. "SOIL RESPIRATION IN STANDS OF DIFFERENT TREE SPECIES". In RURAL DEVELOPMENT. Aleksandras Stulginskis University, 2018. http://dx.doi.org/10.15544/rd.2017.106.
Testo completoAbstract (sommario):
Forest ecosystems of different tree species participate actively in climatic and biotic processes, such as photosynthesis, plant and soil respiration, therefore knowledge of soil respiration, especially of CO2 emissions to the atmosphere is of great importance. The aim of the study was to determine soil respiration rate of stands of deciduous (Betula pubescens Ehrh., Quercus robur L.) and coniferous (Larix eurolepis Henry, Thuja occidentalis L.) tree species as well as impact of abiotic (soil temperature, humidity, electrical conductivity, pH) and biotic (abundance of undergrowth, shrub, herbs) factors. Measurements of CO2 emissions, temperature, moisture and electrical conductivity were performed in-situ in the stands of different tree species with portable ADC BioScientific LCpro+ system and digital electrochemical device “Wet” (Delta-T). Soil samples were collected for the physicochemical analysis simultaneously. Chemical analysis of soil samples was done at the lab of the Environmental Research of the Aleksandras Stulginskis University by standard methods. Soil respiration was highest in the stand of Thuja occidentalis and lowest in the stand of Betula pubescens. Soil respiration intensity of the tree stands increased as follow: Thuja˂ Quercus˂ Larix˂ Betula. In the coniferous tree stands, the soil respiration was lower on average 27% comparing to deciduous tree stands. Soil respiration rate increased with increase of herbaceous vegetation cover and temperature. Soil respiration rate was mostly influenced by abundance of herbaceous vegetation (r = 0.91) of all biotic factors investigated, while soil temperature (r = 0.75) of abiotic factors. 60 years old stands of different tree species formed specific conditions what influenced different soil respiration rates.
3
Diwakar, Philip, e Jonathan Berkoe. "Safety and Reliability Studies Using Analysis Tools". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37338.
Testo completoAbstract (sommario):
Computational Fluid Dynamics and Computational Structural Mechanics (also called Finite Element Analysis of FEA) and a combination of the two — Fluid Solid Interaction (FSI) — have long been used for safety of Personnel in Industry. This paper gives four examples of using these tools for designing equipment and mitigations to provide a safe and amenable working environment for personnel. The first example deals with the use of CFD to resize or relocate exhaust stacks — to prevent personnel working on an adjacent elevated platform being exposed to hot gasses or low oxygen levels — under high wind conditions or the presence of an inversion layer in the atmosphere. The second example is on construction of a retractable protective screen — for personal working on an elevated platform — in the event of a leak of combustive gas from an adjoining unit. CFD is used to determine the length and temperature of the flame while FEA is used to determine the impinging forces half way between the combustion source and the workers to select a suitable flexible retractable screen for protection. A third example is on cooling methane and ethane vapors heated during initial ship loading to prevent flaring caused by pressure build up. Flaring causes several environmental issues such as degradation of vegetation and trees, temperature effects on nearby occupied building, large luminescence, atmospheric disturbances and turbulence on passing aircraft, as well as loss of production. The stresses on the piping network, flanges, valves, pads and shoes — which may lift by Joule-Thompson effect caused temperature differentials — are studied using FEA to ensure the safe operation. A final example is on the use of CFD and FEA to determine the sources of flow-induced and cavitation-induced acoustic noise and vibration and water hammer produced by flow restrictions and flashing of liquid to vapor behind a vee-ball control valve and a ball control valve. The frequencies are extracted from CFD and checked against the natural frequencies from modal analysis and experimental bump test for typical resonant frequencies in the system. Mitigations are proposed to ensure lower noise levels and reduce vibrations in the system for the comfort of personnel working in the vicinity.
4
Ren, Guangyao, Xiaoling Pan e Xinchun Liu. "Statistic self-similarity at the border of vegetation patchiness: system behavior of the interior dynamic which adapts the exterior environment". In Third International Asia-Pacific Environmental Remote Sensing Remote Sensing of the Atmosphere, Ocean, Environment, and Space, a cura di Xiaoling Pan, Wei Gao, Michael H. Glantz e Yoshiaki Honda. SPIE, 2003. http://dx.doi.org/10.1117/12.466495.
Testo completoRapporti di organizzazioni sul tema "Vegetation-Atmosphere System"
1
Wilson, D., Daniel Breton, Lauren Waldrop, Danney Glaser, Ross Alter, Carl Hart, Wesley Barnes et al. Signal propagation modeling in complex, three-dimensional environments. Engineer Research and Development Center (U.S.), aprile 2021. http://dx.doi.org/10.21079/11681/40321.
Testo completoAbstract (sommario):
The Signal Physics Representation in Uncertain and Complex Environments (SPRUCE) work unit, part of the U.S. Army Engineer Research and Development Center (ERDC) Army Terrestrial-Environmental Modeling and Intelligence System (ARTEMIS) work package, focused on the creation of a suite of three-dimensional (3D) signal and sensor performance modeling capabilities that realistically capture propagation physics in urban, mountainous, forested, and other complex terrain environments. This report describes many of the developed technical capabilities. Particular highlights are (1) creation of a Java environmental data abstraction layer for 3D representation of the atmosphere and inhomogeneous terrain that ingests data from many common weather forecast models and terrain data formats, (2) extensions to the Environmental Awareness for Sensor and Emitter Employment (EASEE) software to enable 3D signal propagation modeling, (3) modeling of transmitter and receiver directivity functions in 3D including rotations of the transmitter and receiver platforms, (4) an Extensible Markup Language/JavaScript Object Notation (XML/JSON) interface to facilitate deployment of web services, (5) signal feature definitions and other support for infrasound modeling and for radio-frequency (RF) modeling in the very high frequency (VHF), ultra-high frequency (UHF), and super-high frequency (SHF) frequency ranges, and (6) probabilistic calculations for line-of-sight in complex terrain and vegetation.