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Bryant, Anna C. "Parameterizing surface fluxes in the Arctic." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA397342.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, Sept. 2001.Thesis advisor: Guest, Peter S. "September 2001." Includes bibliographical references (p. 63-64). Also available in print.
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Panin, Gennadij N., Gerd Tetzlaff, Armin Raabe, Hans-Jürgen Schönfeldt, and A. E. Nasonov. "Inhomogeneity of the land surface and the parameterization of surface fluxes." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213104.
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Modem measurement methods ofthe surface turbulent fluxes (STF) of heat, moisture and momentum in the near surface atmospheric layer by the eddy correlation method and their calculation, relay on the validity of the similarity theory of Monin-Obukhov, which requests stationarity and horizontal homogeneity. Experimental data taken at specially selected sites allowed to develop this concept. Recently performed experiments, purposely conducted in non-ideal conditions showed an underestimation ofthe STF values. To systematise this effect it is suggested to parameterize such underestimation as the influence of inhomogeneity and nonstationarity of the landscape and the atmosphere around the point of observation. This scheme might prove to be useful for the design of new validation experiments in non-ideal terrainModeme Meßmethoden zur Erfassung der turbulenten Oberflächenflüsse für fühlbare und latente Wärme sowie Impuls mit Hilfe der Eddy-Korrelations-Methode basieren für die bodennahe Grenzschicht auf der Monin-Obukhov-Turbulenztheorie, die stationäre und horizontal homogene Verhältnisse voraussetzt. Über speziell ausgewählten Oberflächen wurde dieses Konzept häufig mit Erfolg überprüft. Experimente jedoch, die gezielt unter inhomogenen Verhältnissen durchgeführt werden, zeigen oft eine Unterschätzung der turbulenten Oberflächenflüsse. Es wird vorgeschlagen, diese Unterschätzungen als einen Einfluß inhomogener Umbegungsbedingungen und instationärer atmosphärischer Prozesse zu interpretieren und zu systematisieren. Dieses Schema kann dazu beitragen, eine neue Art von Validierungsexperimenten unter natürlichen Verhältnissen einer inhomogenen Umgebung zu entwerfen
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Panin, Gennadij N., Gerd Tetzlaff, Armin Raabe, Hans-Jürgen Schönfeldt, and A. E. Nasonov. "Inhomogeneity of the land surface and the parameterization of surface fluxes." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 4 = Meteorologische Arbeiten aus Leipzig ; 2 (1996), S. 204-215, 1996. https://ul.qucosa.de/id/qucosa%3A15066.
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Modem measurement methods ofthe surface turbulent fluxes (STF) of heat, moisture and momentum in the near surface atmospheric layer by the eddy correlation method and their calculation, relay on the validity of the similarity theory of Monin-Obukhov, which requests stationarity and horizontal homogeneity. Experimental data taken at specially
selected sites allowed to develop this concept. Recently performed experiments, purposely conducted in non-ideal conditions showed an underestimation ofthe STF values. To systematise this effect it is suggested to parameterize such underestimation as the influence of inhomogeneity and nonstationarity of the landscape and the atmosphere around the point of observation. This scheme might prove to be useful for the design of new validation experiments in non-ideal terrain.Modeme Meßmethoden zur Erfassung der turbulenten Oberflächenflüsse für fühlbare und latente Wärme sowie Impuls mit Hilfe der Eddy-Korrelations-Methode basieren für die bodennahe Grenzschicht auf der Monin-Obukhov-Turbulenztheorie, die stationäre und horizontal homogene Verhältnisse voraussetzt. Über speziell ausgewählten Oberflächen wurde dieses Konzept häufig mit Erfolg überprüft. Experimente jedoch, die gezielt unter inhomogenen Verhältnissen durchgeführt werden, zeigen oft eine Unterschätzung der turbulenten Oberflächenflüsse. Es wird vorgeschlagen, diese Unterschätzungen als einen Einfluß inhomogener Umbegungsbedingungen und instationärer atmosphärischer Prozesse zu interpretieren und zu systematisieren. Dieses Schema kann dazu beitragen, eine neue Art von Validierungsexperimenten unter natürlichen Verhältnissen einer inhomogenen Umgebung zu entwerfen.
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Santoso, Edi. "Surface fluxes and vertical profiles in the radix layer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0028/NQ38975.pdf.
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Bateni, Sayed Mohyeddin. "Estimation of turbulent surface heat fluxes using sequences of remotely sensed land surface temperature." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66850.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 330-366).
Fluxes of heat and moisture at the land-surface play a significant role in the climate system. These fluxes interact with the overlying atmosphere and influence the characteristics of the planetary boundary layer (e.g. temperature and water vapor content), ultimately influencing the presence and growth of low level clouds and precipitation. Nevertheless, there is currently no network of in situ sensors that can map these fluxes globally. Recently a number of studies have focused on the estimation of surface energy flux components based on the assimilation of land surface temperature (LST) within a variational data assimilation (VDA) framework. This study provides the theoretical basis for why sequences of LST contain the necessary information to estimate surface fluxes with minimal reliance on ancillary data and empirical parameterizations. Furthermore this study addresses one of the main drawbacks of the existing VDA models. They use the simple force-restore equation for soil heat diffusion as a physical constraint. The force-restore equation provides a simplified description of the LST dynamics. Also, its performance is highly affected by the specification of a deep ground temperature. These shortcomings cause significant errors in the diurnal dynamics of heat diffusion in the soil and ultimately the retrieval of components of surface energy balance. This study advances the VDA scheme by using the full heat diffusion equation as a constraint in lieu of the forcerestore approximation. The new VDA scheme is tested over several experimental field sites. The results show that inclusion of the heat diffusion equation decreases the phase error associated with the ground heat flux diurnal cycle, and improves surface heat flux estimation. The VDA scheme is further advanced by incorporating model uncertainty in order to account for measurement and model errors. Tests indicate that the VDA scheme with model uncertainty captures measurement errors as well as structural model errors. In order to provide coupled estimates of surface heat fluxes and vegetation dynamics, remotely sensed LST and fraction of photosynthetically active radiation are assimilated into a surface energy balance and a vegetation dynamics model. The application of the assimilation over West Africa shows that the scheme provides reliable estimates of important vegetation dynamics parameters that are required for understanding the role of plant phenology on surface energy balance and vice-versa.
by Sayed Mohyeddin Bateni.
Ph.D.
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Snelgrove, Kenneth Ross. "Implications of Lateral Flow Generation on Land-Surface Scheme Fluxes." Thesis, University of Waterloo, 2002. http://hdl.handle.net/10012/865.
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This thesis details the development and calibration of a model created by coupling a land surface simulation model named CLASS with a hydrologic model named WATFLOOD. The resulting model, known as WatCLASS, is able to serve as a lower boundary for an atmospheric model. In addition, WatCLASS can act independently of an atmospheric model to simulate fluxes of energy and moisture from the land surface including streamflow. These flux outputs are generated based on conservation equations for both heat and moisture ensuring result continuity. WatCLASS has been tested over both the data rich BOREAS domains at fine scales and the large but data poor domain of the Mackenzie River at coarse scale. The results, while encouraging, point to errors in the model physics related primarily to soil moisture transport in partially frozen soils and permafrost. Now that a fully coupled model has been developed, there is a need for continued research by refining model processes and test WatCLASS's robustness using new datasets that are beginning to emerge.
Hydrologic models provide a mechanism for the improvement of atmospheric simulation though two important mechanisms. First, atmospheric inputs to the land surface, such as rainfall and temperature, are transformed by vegetation and soil systems into outputs of energy and mass. One of these mass outputs, which have been routinely measured with a high degree of accuracy, is streamflow. Through the use of hydrologic simulations, inputs from atmospheric models may be transformed to streamflow to assess reliability of precipitation and temperature. In this situation, hydrologic models act in an analogous way to a large rain gauge whose surface area is that of a watershed. WatCLASS has been shown to be able to fulfill this task by simulating streamflow from atmospheric forcing data over multi-year simulation periods and the large domains necessary to allow integration with limited area atmospheric models.
A second, more important, role exists for hydrologic models within atmospheric simulations. The earth's surface acts as a boundary condition for the atmosphere. Besides the output of streamflow, which is not often considered in atmospheric modeling, the earth's surface also outputs fluxes of energy in the form of evaporation, known as latent heat and near surface heating, known as sensible heat. By simulating streamflow and hence soil moisture over the land surface, hydrologic models, when properly enabled with both energy and water balance capabilities, can influence the apportioning of the relative quantities of latent and sensible heat flux that are required by atmospheric models. WatCLASS has shown that by improving streamflow simulations, evaporation amounts are reduced by approximately 70% (1271mm to 740mm) during a three year simulation period in the BOREAS northern old black spruce site (NSA-OBS) as compared to the use of CLASS alone.
To create a model that can act both as a lower boundary for the atmosphere and a hydrologic model, two choices are available. This model can be constructed from scratch with all the caveats and problems associated with proving a new model and having it accepted by the atmospheric community. An alternate mechanism, more likely to be successfully implemented, was chosen for the development of WatCLASS. Here, two proven and well tested models, WATFLOOD and CLASS, were coupled in a phased integration strategy that allowed development to proceed on model components independently. The ultimate goal of this implementation strategy, a fully coupled atmospheric - land surface - hydrologic model, was developed for MC2-CLASS-WATFLOOD. Initial testing of this model, over the Saguenay region of Quebec, has yet to show that adding WATFLOOD to CLASS produces significant impacts on atmospheric simulation. It is suspected, that this is due to the short term nature of the weather simulation that is dominated by initial conditions imposed on the atmospheric model during the data assimilation cycle.
To model the hydrologic system, using the domain of an atmospheric model, requires that methods be developed to characterize land surface forms that influence hydrologic response. Methods, such as GRU (Grouped Response Unit) developed for WATFLOOD, need to be extended to taken advantage of alternate data forms, such as soil and topography, in a way that allows parameters to be selected a priori. Use of GIS (Geographical Information System) and large data bases to assist in development of these relationships has been started here. Some success in creating DEMs, (Digital Elevation Model) which are able to reproduce watershed areas, was achieved. These methods build on existing software implementations to include lake boundaries information as a topographic data source. Other data needs of hydrologic models will build on relationships between land cover, soil, and topography to assist in establishing grouping of these variables required to determine hydrologic similarity. This final aspect of the research is currently in its infancy but provides a platform from which to explore for future initiatives.
Original contributions of this thesis are centered on the addition of a lateral flow generation mechanism within a land surface scheme. This addition has shown a positive impact on flux returns to the atmosphere when compared to measured values and also provide increased realism to the model since measured streamflow is reproduced. These contributions have been encapsulated into a computer model known as WatCLASS, which together with the implementation plan, as presented, should lead to future atmospheric simulation improvements.
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Franks, Stewart William. "The representation of land surface - atmosphere fluxes for atmospheric modelling." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387430.
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Song, Shaojie Massachusetts Institute of Technology. "Quantifying mercury surface fluxes by combining atmospheric observations and models." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107107.
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Thesis: Ph. D. in Atmospheric Chemistry, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 115-134).
Mercury (Hg) is a critical environmental concern. Although an important component of its biogeochemical cycle, large uncertainties still exist in the estimates of surface fluxes of mercury. Three projects presented in this thesis improve our understanding of mercury surface fluxes at different spatial scales by combining atmospheric observations and models. First, a global scale inverse model study uses observations at multiple ground-based stations and simulations from a three-dimensional chemical transport model (GEOS-Chem) to obtain a total mercury emission of about 5.8 Gg yr-¹, in which the ocean contributes about a half. The global terrestrial ecosystem is found to be neither a net source nor a net sink of Hg⁰ (gaseous elemental mercury). The optimized Asian anthropogenic emissions (0.7-1.8 Gg yr-¹) are very likely higher than bottom-up estimates, implying missing sources, higher activity levels, and/or lower control efficiencies in these inventories. Optimizing two physicochemical ocean parameters improves the model's ability in reproducing the seasonal pattern of observed Hg⁰. The inversion also suggests that the legacy mercury releases tend to reside in the terrestrial system rather than in the ocean. Second, the comparison of nested grid GEOS-Chem model simulations with aircraft observations support results from the global inversion, and further suggests that the Northwest Atlantic Ocean is a net source of Hg⁰, with high evasion fluxes in summer (related to the high precipitation rates and deposition fluxes of oxidized mercury), whereas the terrestrial ecosystem in the eastern United States is likely a net sink of Hg⁰ during summer. Third, a one-dimensional chemical transport model is built and used to simulate the mercury diurnal variabilities observed at Dome Concordia on the Antarctic plateau. The model simulation best reproducing the Hg⁰ observations shows that in summer mercury is rapidly cycled between the shallow atmospheric boundary layer and the surface snowpack. A two-step bromine initiated scheme oxidizes Hg⁰ Oxidized mercury is deposited, photoreduced in the surface snow, and reemitted as Hg⁰ back into the atmosphere.
by Shaojie Song.
Ph. D. in Atmospheric Chemistry
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Carlson, Benjamin Richards. "Development of a Passive Surface Flux Meter to estimate spatially distributed nutrient mass fluxes." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/2452.
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Due to recent changes in agricultural practices the nutrient load in our waterways has increased causing eutrophication and hypoxia. Many legislative actions have taken place because of this problem, including the Clean Water Act of 1972 (CWA), and many different nutrient reduction plans. The CWA governs that impaired waterways must be monitored to meet total maximum daily loads (TMDL) for each watershed. TMDL's must be assessed using data collected over a period of time so that reduction techniques can be administered. TMDL assessments are usually conducted by the United States Geological Survey (USGS) through many different monitoring programs. The USGS programs include collecting streamflow and nutrient concentration data and using the information to estimate nutrient loads. Generally, grab sampling is the method of choice for concentrations. Grab samples do not accurately assess the total load as generally only 6-8 samples can be collected over a year due to financial and logistical constraints, while concentrations vary within a span of hours and days. Research applications involve the use of automated sensors (e.g., ISCO) that allow for more frequent sampling in order to overcome this issue but are expensive to purchase and maintain. Thus the development of an inexpensive, passive sampler would be of much interest in estimating load. The Passive Surface Flux Meter (PSFM), an integrative sampler that estimates the total solute load over a storm event, is such an alternative. The PSFM is composed of two sorbents one to collect the contaminant of choice and another to determine the flow through the device. Ion-exchange resin was used to collect nitrates, while Granular Activated Carbon dosed with a suite of alcohols were used to determine flow through the sampler. This thesis sets forth the fundamental theories behind the PSFM, and investigates its ability to measure nutrient fluxes in the field. In-situ deployments within Clear Creek watershed in Iowa were conducted using a modification of the PSFM design by Boland (2011). There was a strong linear relationship between the loads estimated by the PSFM, and "true" load based on USGS stream gage data, and Nitratax sensor data. This implies that the device could be calibrated to work in the field. However, it was determined that the design underestimated the true load in the stream by 29%. This was attributed to the nonlinear relationship between the external velocity and the flow through the sampler, which weighted the results towards the high flow events. To overcome this constraint, a new design is proposed in which flow through the sampler varies linearly with the transient head at the inlet. Flume experiments done under different flow depths proved that linearity conditions were satisfied. Using the results from the laboratory experiments recommendations were made for design of an in-situ deployment of the new design.
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Padowski, Julie C. "Direct measurement of water and solute mass fluxes using a passive surface water flux meter." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013283.
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Rodgers, David G. "Validating Canadian land surface scheme heat fluxes under subarctic tundra conditions." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29471.
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This study tests the ability of the Canadian Land Surface Scheme (CLASS) to simulate sensible and latent heat fluxes over two subarctic tundra sites in the Trail Valley Creek (TVC) drainage basin, North West Territories, Canada. CLASS simulations with and without the new organic soil parameterisation developed for peatland conditions were compared with three summer months of measurements at each site. The sites are located in a cryoturbated region and are underlain by continuous permafrost and feature mineral soil hummocks and organic soil inter-hummock zones. Results from the peatland version of CLASS showed significant improvement over the standard version although in both cases, there was an underestimation of latent heat fluxes and overestimation of sensible heat fluxes. The observed soil moisture contents are almost constant at both sites. Field photographs show the sites are located in low-lying areas, one in a local depression and the other at the bottom of a valley. Thus, it is reasonable to assume that the constant soil moisture content is maintained by lateral flow from adjacent hillslopes. This assumption could be further supported by the influence of mineral earth hummocks in TVC drainage basin. CLASS is a one-dimensional column model and it is not possible to explicitly represent lateral flow. Thus a nudging module is added to the peatland version of CLASS to reflect this horizontal water movement. Simulations were further improved with this modification. This additional module is a simple and effective way to represent the effect of lateral flow.
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Cushanick, Matthew S. "Impact of convection on surface fluxes observed during LASP/DYNAMO 2011." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44544.
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Approved for public release; distribution is unlimitedThe NOAA WP-3D aircraft made extensive measurements over the tropical Indian Ocean during the Littoral Air-Sea Processes (LASP)/Dynamics of Madden-Julian Oscillation (DYNAMO) experiment. The low-level measurements from the WP-3D are analyzed here to examine the impact of tropical convection and its associated cold pool in modifying surface exchange of momentum and energy. Analysis of surface fluxes under convection and non-convection demonstrates the increased variability of surface fluxes under convection. Fluxes below convection are larger in magnitude, variable, and demonstrate no clear contribution from specific length scales. The lack of clear transport in the turbulence scales under convection highlights that additional processes beyond turbulence transport are occurring, which points to the role of precipitation evaporation below the cloud base. In contrast, surface fluxes under non-convective conditions are smaller and have a clear positive contribution throughout the turbulence region. Comparison of eddy correlation method with the COARE bulk surface flux parameterization indicates large scattering for the convective cases. Stress and latent heat flux from the COARE algorithm show good comparison with the eddy correlation fluxes, while the sensible heat flux seem to be consistently over-predicted, which may be a result of uncertainties in the measured sea surface temperature.
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Blyth, Eleanor M. "The effect of small scale heterogeneity on surface heat and moisture fluxes." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239806.
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McCary, John. "Incorporating surficial aquifer ground-water fluxes into surface-water resource management studies." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001095.
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Oliphant, Andrew J. "Spatial and temporal variability of surface energy fluxes in an alpine catchment." Thesis, University of Canterbury. Geography, 2000. http://hdl.handle.net/10092/5716.
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One of the most important issues facing mesoscale modelling and atmospheric energy budget studies in complex terrain, is addressing the complicated pattern of energy fluxes that occur at the boundary of the Earth's surface. This study was designed to improve understanding of the characteristics and mechanisms of spatial and temporal variability in surface energy fluxes within a large alpine catchment. An observational dataset of time series and space series of surface radiation and energy fluxes in a 2500 km-2 catchment in the Southern Alps of New Zealand was generated. Observations were made for a period of fourteen months at a single site in the MacKenzie Basin and at nine locations in the Tekapo catchment on clear-sky summer days, during a month-long intensive observation period. The seasonal range in Q* was found to be 14.2 MJ m-2 dy-1, resulting primarily from the annual cycle of K*, which provided greater variability than L* by a factor of three. The range in Q* due to synoptic influences was of a similar magnitude and was found to be most significantly a function of cloudiness, which was seen to vary significantly from one end of the study area to the other. Daily Bowen ratio (β) values ranged from 6.85 during the 1997/98 summer to -0.13 for the 1998 winter and 9.38 for the 1998/99 summer. A consistent logarithmic relationship was found between β and soil moisture content for all data, irrespective of season or synoptic situation. Overall, the largest impact on surface energy fluxes on the temporal scale was found to result from synoptic controls on the magnitude of net radiation, and secondly from seasonal control on the partitioning of turbulent fluxes.
Spatial series of observations focused on the five dominant surface classes in the catchment including, rock, lake water and three classes of vegetation. From this dataset, energy balances were derived for each surface class, to assess the spatial variability associated with heterogeneity of surface properties. A large range in surface flux density was found, related to radiative, thermal, hydrological and vegetative properties of the surface. The lake surface recorded the highest daily total Q* values of the five surface types, rock surfaces recorded the lowest and the three vegetated surfaces recorded very similar flux densities. The most significant influences were the mean diurnal albedo and the ratio between L↑and absorbed allwave radiation. Significant differences also existed between the surface types in the diurnal range of albedo. Modelling of surface radiation flux components was conducted using SRAD, a topographically based radiation model. Output from the model compared well with observations, with closer agreement found for daily mean than instantaneous fluxes. In both observational and modelled results, K↓ was found to contribute most significantly to the radiation budget both in terms of the mean and variability of flux magnitudes. By contrast, longwave radiation fluxes contributed little variability to the spatial distribution of Q*. The variability in K↓, was associated most strongly with slope aspect, secondly with slope angle, thirdly with shading, and lastly with elevation. The largest range associated with slope throughout the year was found during at the equinox when a range of 20.3 MJ m-2 dy-1 existed between south-facing 60° slopes and northfacing 40° slopes. Turbulent heat flux maps were constructed using modelled Q* maps and observed turbulent flux densities non-dimensionalised by Q*. Maps of the latter were derived from observations over each surface type and surface cover maps, generated using supervised classification of IRS-1C imagery. Large spatial variability in surface energy flux density was found to exist at any given time, although these were greatest near mid-day. Spatial variability was found to be controlled equally by spatial variability of Q* and surface heterogeneity. The role of topographic complexity on the spatial distribution of fluxes was investigated by comparing three. sub-areas of the Tekapo catchment that showed strongly contrasting topographical properties. Increase in topographic complexity was associated with decrease in mean Q*, but a large increase in spatial variability. Similar, but less extreme results were found for turbulent fluxes. However, despite the large ranges in flux densities found throughout the catchment, spatial averages of turbulent fluxes for the three sub-areas were relatively consistent, providing some confidence for the use of spatial averaging for sub-grid areas of numerical models. It is hoped that future research can build on the evidence,
methodologies and hypotheses generated by this research. In particular, it is envisioned that future observations in other mountain settings will help determine the extent to which the findings of this study can be applied generally to areas of complex terrain.
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Harlander, Uwe. "On periodic solutions found in simple ocean models with fixed surface fluxes." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-213065.
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In einer kürzlich erschienenen Arbeit haben Greatbatch und Zhang darauf hingewiesen, daß interdekadische Oszillationen in einem Ozean-Becken-Modell gefunden werden können, falls dieses mit festgehaltenen Wärmeflüssen angetrieben wird. Diese Oszillationen haben Ahnlichkeit mit jenen, welche Delworth et al. in einem gekoppelten Ozean-Atmosphären-Modell fanden. In der vorliegenden Arbeit werden Mechanismen verglichen, die in drei einfachen Ozeanmodellen mit festgehaltenen Antrieben zu Schwingungen führen. Die Experimente mit einem drei-dimensionalen Becken-Modell werden ausführlich beschrieben. In diesen Experimenten zeigt sich der voll dreidimensionale Charakter der Schwingungen. Die Oszillationen stehen im Zusammenhang mit einer Reduktion der Ausbreitungsgeschwindigkeit von kalten Randstörungen im nordwestlichen Teil des Ozeanbeckens. Der Grund dafür ist ein anomal großes Gebiet tiefreichender Konvektion in dieser Region. Kräftige Temperaturanomalien enstehen dann infolge von anomaler Advektion. Ganz wesentlich für das Vorkommen von ungedämpften Oszillationen ist eine Verlängerung der Zeitspanne mit starker (schwacher) meridionaler Zirkulation im drei-dimensionalen Modell (\"Schleifen\"-Modell) durch einen Überkompensationsmechanismus. Letzendlich bestätigen diese Experimente die Ansicht von Winton, daß sich die Oszillationen in drei-dimensionalen Modellen nicht mit einfachen \"Schleifen\"-Modellen nachvollziehen lassenIn a recent paper Greatbatch and Zhang reported the finding of interdecadal oscillations in an idealized ocean basin forced by constant heat flux. This oscillation has many similarities to that found by Delworth et al. in a coupled ocean-atmosphere model. We have used three simple models with fixed surface fluxes, a box model, a Welander-like loop model and a three-level three-dimensional ocean basin model, in order to compare mechanisms associated with interdecadal oscillations in these models. Our experiments with the basin model revealed the three-dimensional character of the oscillations in three-dimensional models. Self-sustained oscillations are associated with a reduction of the propagation speed of cold anomalies in the north-western corner of the model because of anomalous strong convection in that region. Then anomalous gyre circulation leads to the development of strong temperature anomalies. The extension of the period of strong (low) overturning in the three-dimensional (loop) model by some overcompensation mechanism is crucial for the occurrence of self-sustained oscillations. In conclusion we confirm Wintons view that fixed flux variability is not a meridional plane phenomenon related to loop oscillators
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Harlander, Uwe. "On periodic solutions found in simple ocean models with fixed surface fluxes." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 4 = Meteorologische Arbeiten aus Leipzig ; 2 (1996), S. 151-169, 1996. https://ul.qucosa.de/id/qucosa%3A15062.
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In einer kürzlich erschienenen Arbeit haben Greatbatch und Zhang darauf hingewiesen, daß interdekadische Oszillationen in einem Ozean-Becken-Modell gefunden werden können, falls dieses mit festgehaltenen Wärmeflüssen angetrieben wird. Diese Oszillationen haben Ahnlichkeit mit jenen, welche Delworth et al. in einem gekoppelten Ozean-Atmosphären-Modell fanden. In der vorliegenden Arbeit werden Mechanismen verglichen, die in drei einfachen Ozeanmodellen mit festgehaltenen Antrieben zu Schwingungen führen. Die Experimente mit einem drei-dimensionalen Becken-Modell werden ausführlich beschrieben. In diesen Experimenten zeigt sich der voll dreidimensionale Charakter der Schwingungen. Die Oszillationen stehen im Zusammenhang mit einer Reduktion der Ausbreitungsgeschwindigkeit von kalten Randstörungen im nordwestlichen Teil des Ozeanbeckens. Der Grund dafür ist ein anomal großes Gebiet tiefreichender Konvektion in dieser Region. Kräftige Temperaturanomalien enstehen dann infolge von anomaler Advektion. Ganz wesentlich für das Vorkommen von ungedämpften Oszillationen ist eine Verlängerung der Zeitspanne mit starker (schwacher) meridionaler Zirkulation im drei-dimensionalen Modell (\"Schleifen\"-Modell) durch einen Überkompensationsmechanismus. Letzendlich bestätigen diese Experimente die Ansicht von Winton, daß sich die Oszillationen in drei-dimensionalen Modellen nicht mit einfachen \"Schleifen\"-Modellen nachvollziehen lassen.In a recent paper Greatbatch and Zhang reported the finding of interdecadal oscillations in an idealized ocean basin forced by constant heat flux. This oscillation has many similarities to that found by Delworth et al. in a coupled ocean-atmosphere model. We have used three simple models with fixed surface fluxes, a box model, a Welander-like loop model and a three-level three-dimensional ocean basin model, in order to compare mechanisms associated with interdecadal oscillations in these models. Our experiments with the basin model revealed the three-dimensional character of the oscillations in three-dimensional models. Self-sustained oscillations are associated with a reduction of the propagation speed of cold anomalies in the north-western corner of the model because of anomalous strong convection in that region. Then anomalous gyre circulation leads to the development of strong temperature anomalies. The extension of the period of strong (low) overturning in the three-dimensional (loop) model by some overcompensation mechanism is crucial for the occurrence of self-sustained oscillations. In conclusion we confirm Wintons view that fixed flux variability is not a meridional plane phenomenon related to loop oscillators.
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Cook, Joseph. "Microbially mediated carbon fluxes on the surface of glaciers and ice sheets." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2882/.
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Measurements from Austre Brøggerbreen (Svalbard, 2009) and the Greenland Ice Sheet (GrIS, near Kangerlussuaq, 2010) are used to examine microbially mediated supraglacial carbon fluxes and feedbacks between these fluxes and the abiotic conditions at the ice surface. Linear relationships between mass and area of cryoconite deposits indicate constant sediment layer thicknesses at a range of Arctic locations. This is suggested to result from a tendency for cryoconite to form a layer of single grains, with the thickness determined by grain diameter. A thermodynamic mechanism of single grain layer (SGL) maintenance is proposed, in which holes expand laterally to accommodate increased sediment volumes. This is shown to reduce ice surface albedo and promote photosynthesis because the greatest possible surface area for irradiance of cryoconite is maintained. Since cryoconite only contributes to supraglacial carbon fluxes while it resides upon ice surfaces, two major mechanisms of sediment evacuation are examined: melt-out and hydraulic removal. Energy balance modelling indicates that melt out is unlikely unless high air temperature and low incident radiation persist for multiple days. Stream migration is proposed to be the most likely mechanism of sediment removal; however for the majority of holes, multi-year residence times can be expected. This thesis also provides new estimates of microbially mediated carbon fluxes from the GrIS. New models estimate carbon fluxes from a section of GrIS for which spatially variable parameter values were derived from point-to-point interpolation of field data. An algal ecosystem is included for the first time. The results indicate that cryoconite can fix about four times more carbon than previously predicted, and surface algal ecosystems fix about eleven times more carbon than cryoconite. Biologically mediated carbon fluxes on the GrIS are therefore shown to be much higher than previously thought. Further, the GrIS is shown to be in a relatively stable state of net autotrophy.
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Wu, Lichuan. "Impact of surface gravity waves on air-sea fluxes and upper-ocean mixing." Licentiate thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-276466.
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Surface gravity waves play a vital role in the air-sea interaction. They can alter the turbulence ofthe bottom atmospheric layer as well as the upper-ocean layer. Accordingly, they can affect themomentum flux, heat fluxes, as well as the upper-ocean mixing. In most numerical models, waveinfluences are not considered or not fully considered. The wave influences on the atmosphereand the ocean are important for weather forecasts and climate studies. Here, different aspects ofwave impact on the atmosphere and the ocean are introduced into numerical models.In the first study, a wave-state-dependent sea spray generation function and Charnock co-efficient were applied to a wind stress parameterization under high wind speeds. The newlyproposed wind stress parameterization and a sea spray influenced heat flux parameterizationwere applied to an atmosphere-wave coupled model to study their influence on the simulationof mid-latitude storms. The new wind stress parameterization reduces wind speed simulationerror during high wind speed ranges and intensifies the storms. Adding the sea spray impacton heat fluxes improves the model performance concerning the air temperature. Adding the seaspray impact both on the wind stress and heat fluxes results in best model performance in allexperiments for wind speed, and air temperature.In the second study, the influence of surface waves on upper-ocean mixing was parameter-ized into a 1D k − ε ocean turbulence model though four processes (wave breaking, Stokes driftinteraction with the Coriolis force, Langmuir circulation, and stirring by non-breaking waves)based mainly on existing investigations. Considering all the effects of surface gravity waves,rather than just one effect, significantly improves model performance. The non-breaking-wave-induced mixing and Langmuir turbulence are the most important terms when considering theimpact of waves on upper-ocean mixing. Sensitivity experiments demonstrate that vertical pro-files of the Stokes drift calculated from 2D wave spectrum improve the model performancesignificantly compared with other methods of calculating the vertical profiles of the Stokes drift.Introducing the wave influences in modelling systems, the results verified against measure-ments. Concluding from these studies for the further model development, the wave influencesshould be taken into account to improve the model performance.
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Lauwo, Simon Yesse. "A modeling investigation of ground and surface water fluxes for Konza Tallgrass Prairie." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/470.
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Webster, Cameron. "The effects of biochar application on carbon dioxide and methane soil surface fluxes." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46262.
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Soils contain the largest terrestrial organic carbon (C) stock, representing two-thirds or more of terrestrial C. Soils can act as a source or sink for carbon dioxide (CO???) and methane (CH???). One common technique for studying soil surface effluxes of CO??? (FCO???) and of CH??? (FCH???) is the soil chamber. This involves placing an enclosure over the soil surface and measuring the change in headspace concentration of the gas of interest over time. Due to the air-filled pore spaces within the near-surface soil, and adsorption of gases of interest onto chamber walls, the effective volume (Veff) of the chamber which contributes to FCO??? and FCH??? measurements is generally higher than the geometric volume (Vg) of the chamber. It is necessary that Veff be known in order to estimate fluxes accurately. This study coupled a flow-through non-steady-state automated chamber system to a laser-based cavity ring-down spectrometer (CRDS) to estimate Veff of the chamber system using separate standard additions of CO??? and CH??? calibration gases.
The system was then mounted onto soil cylinders which had been filled with a forest soil from Vancouver Island, British Columbia, Canada. There has been recent interest in the ability of biochar to provide multiple environmental benefits upon application to soil, including the long-term sequestration of C. There are conflicting studies as to the effect of biochar on FCO??? and FCH??? and overall greenhouse gas (GHG) emissions.
After making background measurements of FCO??? and FCH??? in soil columns, biochar was applied to one of the columns and the resulting FCO??? and FCH??? were measured. The results from this study showed that the coupling of the CRDS to the automated chamber system proved to be successful. The estimated Veff during CO??? and CH??? calibration gas injections agreed with past studies as the Veff was 5 to 10% larger than the geometric volume of the chamber. Following biochar application, the amended soil produced 36.9% more CO??? and consumed 20.4% less CH??? than the control over the four month experiment. The results showed that soil water content was an important factor in controlling FCO??? and FCH??? following biochar amendment.
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Gerbi, Gregory Peter. "Observations of turbulent fluxes and turbulence dynamics in the ocean surface boundary layer." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45778.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2008.Includes bibliographical references (p. 110-119).
This study presents observations of turbulence dynamics made during the low winds portion of the Coupled Boundary Layers and Air-Sea Transfer experiment (CBLAST-Low). Observations were made of turbulent fluxes, turbulent kinetic energy, and the length scales of flux-carrying and energy-containing eddies in the ocean surface boundary layer. A new technique was developed to separate wave and turbulent motions spectrally, using ideas for turbulence spectra that were developed in the study of the bottom boundary layer of the atmosphere. The observations of turbulent fluxes allowed the closing of heat and momentum budgets across the air-sea interface. The observations also show that flux-carrying eddies are similar in size to those expected in rigid-boundary turbulence, but that energy-containing eddies are smaller than those in rigid-boundary turbulence. This suggests that the relationship between turbulent kinetic energy, depth, and turbulent diffusivity are different in the ocean surface boundary layer than in rigid-boundary turbulence. The observations confirm previous speculation that surface wave breaking provides a surface source of turbulent kinetic energy that is transported to depth where it dissipates. A model that includes the effects of shear production, wave breaking and dissipation is able to reproduce the enhancement of turbulent kinetic energy near the wavy ocean surface. However, because of the different length scale relations in the ocean surface boundary layer, the empirical constants in the energy model are different from the values that are used to model rigid-boundary turbulence. The ocean surface boundary layer is observed to have small but finite temperature gradients that are related to the boundary fluxes of heat and momentum, as assumed by closure models. However, the turbulent diffusivity of heat in the surface boundary layer is larger than predicted by rigid-boundary closure models. Including the combined effects of wave breaking, stress, and buoyancy forcing allows a closure model to predict the turbulent diffusivity for heat in the ocean surface boundary layer.
by Gregory Peter Gerbi.
Ph.D.
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Miyamoto, Yoshiaki. "ROLES OF SEA SURFACE FLUXES ON THE MAINTENANCE AND INTENSIFICATION OF TROPICAL CYCLONES." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142389.
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Geli, Hatim M. E. "Modeling Spatial Surface Energy Fluxes of Agricultural and Riparian Vegetation Using Remote Sensing." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1165.
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Modeling of surface energy fluxes and evapotranspiration (ET) requires the understanding of the interaction between land and atmosphere as well as the appropriate representation of the associated spatial and temporal variability and heterogeneity. This dissertation provides new methodology showing how to rationally and properly incorporate surface features characteristics/properties, including the leaf area index, fraction of cover, vegetation height, and temperature, using different representations as well as identify the related effects on energy balance flux estimates including ET.
The main research objectives were addressed in Chapters 2 through 4 with each presented in a separate paper format with Chapter 1 presenting an introduction and Chapter 5 providing summary and recommendations. Chapter 2 discusses a new approach of incorporating temporal and spatial variability of surface features. We coupled a remote sensing-based energy balance model with a traditional water balance method to provide improved estimates of ET. This approach was tested over rainfed agricultural fields ~ 10 km by 30 km in Ames, Iowa. Before coupling, we modified the water balance method by incorporating a remote sensing-based estimate for one of its parameters to ameliorate its performance on a spatial basis. Promising results were obtained with indications of improved estimates of ET and soil moisture in the root zone.
The effects of surface features heterogeneity on measurements of turbulence were investigated in Chapter 3. Scintillometer-based measurements/estimates of sensible heat flux (H) were obtained over the riparian zone of the Cibola National Wildlife Refuge (CNWR), California. Surface roughness including canopy height (hc), roughness length, and zero-plane displacement height were incorporated in different ways, to improve estimates of H. High resolution, 1-m maps of ground surface digital elevation model and canopy height, hc, were derived from airborne LiDAR sensor data to support the analysis.
The effects of using different pixel resolutions to account for surface feature variability on modeling energy fluxes, e.g., net radiation, soil, sensible, and latent heat, were studied in Chapter 4. Two different modeling approaches were applied to estimate energy fluxes and ET using high and low pixel resolution datasets obtained from airborne and Landsat sensors, respectively, provided over the riparian zone of the CNWR, California. Enhanced LiDAR-based hc maps were also used to support the modeling process. The related effects were described relative to leaf area index, fraction of cover, hc, soil moisture status at root zone, groundwater table level, and vegetation stress conditions.
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Isaac, Peter Robert, and peter isaac@flinders edu au. "Estimating Surface-Atmosphere Exchange at Regional Scales." Flinders University. School of Chemistry, Physics and Earth Sciences, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20060412.170700.
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This thesis examines a method for estimating the daytime fluxes of heat, water vapour and carbon dioxide at regional scales by using simple models to combine spatially resolved surface properties with bulk meteorological quantities measured at a central location. The central themes of this thesis are that the spatial and temporal variability of regional scale fluxes are contained in the surface properties and meteorology respectively and that the surface properties can be interpolated across a heterogeneous landscape using remotely sensed data. The regional scale fluxes estimated using this technique are compared to the values from three other methods and this allows some conclusions to be made regarding the relative strengths and weaknesses of each method. The surface property approach yields robust estimates of the fluxes that will be useful in researching exchange processes at regional scales, providing input parameters for, and validation of, the biosphere components of General Circulation Models and testing inventory estimates of CO2 budgets.
The surface properties are derived using data from 33 aircraft flights and eight ground-based sites along a 96 km transect established during the 1995 Observations At Several Interacting Scales experiment held near Wagga Wagga, New South Wales, Australia. Surface properties examined are the evaporative fraction (ratio of evapotranspiration to available energy), the Bowen ratio (ratio of sensible heat flux to evapotranspiration), the maximum stomatal conductance (maximum stomatal opening under optimal conditions) and the water-use efficiency (ratio of CO2 flux to evapotranspiration). Maximum stomatal conductance is calculated using a simple model of the stomatal response to light and water vapour deficit assuming soil evaporation occurs at the equilibrium rate. The diurnal trend and day-to-day variability in the surface properties is found to be significantly less than the spatial variability. All of the surface properties examined show some sensitivity to the synoptic conditions.
The relationships between the surface properties and the Normalised Difference Vegetation Index (NDVI) are examined using a 130 km by 50 km sub-scene from a Landsat 5 Thematic Mapper (TM) image obtained five days before the start of the experiment period. The ground-based and aircraft observations are used to calculate the source-area influencing each measurement and this is combined with the Landsat 5 TM data to produce an average, source-area weighted NDVI for each ground-based site and each aircraft location. The source-area model is important because it provides the link between the observations and the remotely sensed data by identifying the surface patch that influences the measurements. Linear relationships are found between the source-area weighted NDVI and the surface properties. The observed relationships are used to interpolate the surface properties over the region covered by the satellite image and spatial variations in water loss and CO2 uptake by the surface vegetation are identified that are not resolved by the ground-based network.
Analysis of the ground-based data showed that the spatial variability of the bulk meteorological quantities used in the surface property approach was much less than the diurnal trend in these data. With the small temporal variation in the surface properties noted before, this confirms the utility of assigning the spatial and temporal variability of the fluxes to the surface properties and the meteorology respectively.
The combination of surface properties derived from the aircraft data and meteorology measured at a single location at the centre of the transect shows good skill in predicting the observed fluxes. Furthermore, the discrepancies between the predictions and the observations are explained by the different source-areas of the aircraft and ground-based data and much of the bias is removed when the surface properties are scaled from the NDVI of the aircraft source-area to the NDVI of the ground-based sites. Regional scale fluxes of heat and water vapour calculated using the surface property approach agree with averages of the ground-based data and this indicates that the ground-based network was representative of the OASIS region. Estimates of regional scale CO2 fluxes are not available from the ground-based network due to the lack of measurements at the driest ground-based site but the surface property approach yields plausible values. The results demonstrate the utility of extrapolating surface properties across heterogeneous landscapes using remotely sensed data.
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Trat, Diep N. "Frontogenesis and surface heat fluxes associated with a case of rapid cyclogenesis during ERICA." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59990.
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The presence of the Gulf Stream in the cold season, and a cold air outbreak following a previous cyclone passage are two important precursors of a case of rapid cyclogenesis on 13-14 December 1988. The study showed that a large area of conditional instability in the lower troposphere, and an area of symmetric instability primarily over the sea, coinciding with small values of isentropic potential vorticity below the 290$ sp circ$K level were associated with strong surface heat fluxes.During the time prior to the onset of this cyclogenesis, the surface frontogenetical forcing was dominated by diabatic frontogenesis, and later, by geostrophic frontogenesis, though the diabatic heating still contributed substantially to this forcing. The cyclone formed and continued to travel along a prominent axis of frontogenetic forcing. Kinematically-computed vertical motions, derived from both conventional and special ERICA soundings, show good agreement with analyses and diagnostics in the domain.
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Atkinson, Erin C. "Field-testing of a passive surface water flux meter for the direct measurement of water and solute mass fluxes." [Gainesville, Fla.] : University of Florida, 2007. http://purl.fcla.edu/fcla/etd/UFE0021166.
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Savvakis, Vasileios. "Evaluation of FLake’s Performance on Water Temperatures and Surface Heat Fluxes at Lake Erken, Sweden." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-380766.
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In many numerical weather prediction models, the presence of lakes is simulated crudely, with their effect being neglected in the resulting simulations. However, it has been shown how lakes effect not only their surrounding climate directly, but have an effect to the overall weather evolution and ecosystem. It is therefore vital to improve existing models to take lakes into account, by coupling with smaller models specificaly compiled for a reas with lakes. There have been several sophisticated models to parameterizelakes in a geographical area, which are, on the other hand, computationally expensive and time consuming. A model built specifically on simple physical assumptions, named FLake, aims to provide a solution that is not heavy computationally, but is accurate enough and contains all the necessary physics surrounding the heat budget and temperature of a given lake. For this project, FLake was tried on a lake close to Uppsala, named Erken, where the validity of the model was tested against data archives from Erken Laboratory’s measurement tower. The resulting simulations were very promising regarding the water temperatures, as well as giving out acceptable results for the surface heat fluxes above the lake and the duration of the ice period, as it was modeled by FLake and compared with ice data archives.
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Tisell, Camilla. "An investigation of the surface fluxes and other parameters inthe regional climate model RCA1 during ice conditions." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303758.
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In this study data from the regional climate model RCA1 is compared to measured data to investigate how good the model is during ice conditions and mainly how well the turbulent surface fluxes are described by the model. Comparisons of the sensible heat flux and the momentum flux as well as mean parameters are included. The measured data used are from the Bothnian Bay measured during the BASIS field experiment in February to March 1998. RCA1 (Rossby Centre regional Atmospheric model) is a regional climate model for Northern Europe based on HIRLAM and forced by ERA-40 data. Two different grid points of the RCA1 44 km grid have been chosen with geographical coordinates as close as possible to the two measuring sites. The first site is a small peninsula south of the town Umeå at the east coast of Sweden and the second one is the ship R/V Aranda anchored in the sea ice outside the Finnish west coast. The model presents generally too large negative (downward) sensible heat fluxes and too large momentum fluxes over ice. The largest difference between modelled and measured sensible heat fluxes are seen after warm front passages due to melting conditions. There are some uncertainties in the comparison of modelled fluxes and measured fluxes at Umeå due to a complex and varying ice cover around this measuring site. The vertical structure in the atmosphere has also been studied and modelled temperature, wind and humidity profiles were compared to radiosondes at the Umeå site. Two periods with on-ice flow and off-ice flow was analysed and one of the main differences was that for the on-ice situation an internal boundary layer was built up over the ice. Modelled profiles are generally smoother then measured profiles and inversions and other small-scale phenomena like low-level jets are almost never described correctly by the model but there are tendencies of the phenomena to occur.Sammanfattning av ”En undersökning i hur bra den regionala klimatmodellen RCA1 beskriver olika parametrar över is, i huvudsak de turbulenta flödena”. I denna undersökning har den regionala klimatmodellen RCA1 jämförts med mätdata för att se hur bra modellen är över is och framförallt hur bra den beskriver de turbulenta flödena över is. RCA1 är en regional klimatmodell för norra Europa baserad på HIRLAM och som drivs av ERA-40 data. Modelldata har jämförts med mätdata från två platser i Bottenviken, en liten halvö utanför Umeå på den svenska östkusten och forskningsfartyget Aranda som var fastankrad i havsisen utanför Finlands västkust. Mätningarna gjordes under BASIS fältexperiment i februari till mars 1998. Modellen ger generellt för stora negativa (nedåtriktade) sensibla värmeflöden över is och likaså för stora impulsflöden över is. Den största skillnaden mellan modellvärden och mätningar förekom efter det att varmfronter passerat och detta beror delvis på smältförhållanden. I jämförelsen av de turbulenta flödena beräknade av RCA och de uppmäta turbulenta flödena från Umeå finns det vissa osäkerheter pga. den komplicerade issituationen runt denna mätplats med mycket varierande isförhållanden. Den vertikala strukturen i atmosfären har också undersökts och temperatur, vind och fuktighetsprofiler har jämförts. Två perioder varav en där det blåste från havet mot isen (on-ice) och en där det blåste från isen mot havet (off-ice) valdes ut och en av skillnaderna var att det bildades ett internt gränsskikt över isen i on-ice perioden. Modellen har en tendens att släta ut profilerna och småskaliga fenomen som inversionsskikt, inversionshöjder och low-level jets är nästan aldrig korrekt beskrivna i modellen men det finns tendenser till inversioner och vindmaximum.
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Campbell, Elliott. "Optimal recovery of regional CO2 surface fluxes by data assimilation of anthropogenic and biogenic tracers." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/182.
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Faivre, Robin. "Multi-sensor remote sensing parameterization of heat fluxes over heterogeneous land surfaces." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAD017/document.
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La paramétrisation du transfert de chaleur par télédétection, basée sur le schéma SEBS, s'est déjà avérée très adaptée pour l'estimation de l'évapotranspiration (ET) sur des surfaces naturelles homogènes. Cependant, l'utilisation d'une telle méthode pour des paysages hétérogènes (e.g. régions semi-arides ou surfaces agricoles) est plus délicate, puisque le principe de la théorie de la similarité est compromis par la présence de différentes sources de chaleur et de hauteurs variées. Dans un premier temps, cette thèse a pour objectif de proposer et d'évaluer différents modèles basés sur la géométrie de la végétation qui permettent d'estimer la longueur de rugosité pour le transfert de quantité de mouvement à la surface (z0m), cette dernière étant un paramètre clé dans la caractérisation du transfert de chaleur. En revanche, une telle investigation ne peut être menée qu'à une petite échelle et à l'aide de données de télédétection très haute résolution permettant ainsi une description très détaillée de la surface. Ensuite, le second aspect de ce travail est de caractériser le transfert de chaleur dans le cas d'études régionales. Puis, la capacité de SEBS à estimer les flux de chaleur turbulents à de grandes échelles spatiales et temporelles sera évaluée. Pour ce faire, l’approche multi-échelle de SEBS (MSSEBS) a été implémentée afin de traiter une zone de 2,4 millions km2, incluant le Plateau du Tibet et l’amont des principaux fleuves d’Asie du sud-est. La combinaison de données horaires de température de surface FY-2 avec un rayonnement net journalier et des paramètres de surface avancés, permet de produire une série temporelle d’ET sur le Plateau du Tibet pour la période 2008-2010, et à une fréquence journalièreThe parameterization of heat transfer by remote sensing, and based on SEBS scheme for turbulent heat fluxes retrieval, already proved to be very convenient for estimating evapotranspiration (ET) over homogeneous land surfaces. However, the use of such a method over heterogeneous landscapes (e.g. semi-arid regions or agricultural land) becomes more difficult, since the principle of similarity theory is compromised by the presence of different heat sources with various heights. This thesis aims at first to propose and evaluate some models based on vegetation geometry for retrieving the surface roughness length for momentum transfer (z0m), which is a key parameter in the characterization of heat transfer. Such an investigation can only be led at a small scale with very-high resolution remote sensing data, for a precise description of the land surface. Therefore, the second aspect of this work is to determine how to address the characterization of heat transfer for regional studies. Then, the reliability of SEBS for estimating turbulent heat fluxes at large spatial and temporal scales has been evaluated. To do so, the Multi-Scale SEBS approach (MSSEBS) has been implemented for a 2.4 million km2 area including the Tibetan Plateau and the headwaters of the major rivers of East and South Asia. The addition of gap-filled hourly FY-2 LST data to advanced daily averaged net radiation and land surface parameters, allows to compute time-series of land surface ET over the Tibetan Plateau during the period 2008-2010, and on a daily basis
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Fan, Yalin. "Effects of surface waves on air-sea momentum and energy fluxes and ocean response to hurricanes /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3276981.
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Ghobadian, Marjan [Verfasser], and Detlef [Akademischer Betreuer] Stammer. "Inferring Air-Sea Carbon Dioxide Fluxes from Scatterometer Sea Surface Backscatter / Marjan Ghobadian ; Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1161847340/34.
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Xiao, Xue Ph D. Massachusetts Institute of Technology. "Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45603.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 199-210).
The four chloromethanes - methyl chloride (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), are chlorine-containing gases contributing significantly to stratospheric ozone depletion and having adverse health effects. Large uncertainties in estimates of their source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of surface fluxes of these species. The Model of Atmospheric Transport and CHemistry (MATCH), driven by NCEP interannually varying meteorological fields, is then used to simulate the trace gas mole fractions using the a priori emissions and to quantify the time series of sensitivities of tracer concentrations to different aseasonal, seasonal, and regional sources and sinks.We implement the Kalman filter (with the unit pulse response method) to estimate both constant (if applicable) and time-varying surface fluxes on regional/global scales at a monthly resolution for the three short-lived species between 2000-2004, and the continental industrial emissions and global oceanic sink for CCl4 at a 3-month resolution between 1996-2004. The high frequency observations from AGAGE, SOGE, NIES and NOAA/GMD HATS and other low frequency flask observations are used to constrain the source and sink magnitudes estimated as multiplying factors for the a priori fluxes and contained in the state vector in the Kalman filter. The CH3Cl inversion results indicate large CH3Cl emissions of 2240 ± 370 Gg yr-1 from tropical plants. The inversion implies greater seasonal oscillations of the natural sources and sink of CH3Cl compared to the a priori. Seasonal cycles have been derived for both the oceanic (for CHCl3 and CH2Cl2) and terrestrial (for CHCl3) sources, with summer maxima and winter minima emissions. Our inversion results show significant industrial sources of CH2Cl2 and CCl4 from the Southeast Asian region. Our inversions also exhibit the strong effects of the 2002/2003 globally wide-spread heat and drought conditions on the emissions of CH3Cl from tropical plants and global salt marshes, on the soil fluxes of CH3Cl and CHCl3, on the biomass burning sources of CH3Cl and CH2Cl2, and on the derived oceanic flux of CHCl3.
by Xue Xiao.
Ph.D.
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Chen, Yu-Han 1973. "Estimation of methane and carbon dioxide surface fluxes using a 3-D global atmospheric chemical transport model." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/18068.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004.Includes bibliographical references (p. 172-180).
Methane (CH₄) and carbon dioxide (CO₂) are the two most radiatively important greenhouse gases attributable to human activity. Large uncertainties in their source and sink magnitudes currently exist. We estimate global methane surface emissions between 1996 and 2001, using a top-down approach that combines observed and simulated atmospheric CH₄ concentrations. As a secondary study, we describe our participation in a CO₂ inverse-modeling intercomparison. The available methane time-series data used in this work include observations from 13 high-frequency stations (in-situ) and 74 low-frequency sites (flask). We also construct an annually-repeating reference emissions field from pre-existing datasets of individual methane processes. For our forward simulations, we use the 3-D global chemical transport model MATCH driven by NCEP meteorology. A prescribed, annually-repeating OH field scaled to fit methyl chloroform observations is used as the methane sink. A total methane source of approximately 600 Tg yr⁻¹ best reproduces the methane growth rate between 1993-2001. Using the reference emissions, MATCH can reproduce the observed methane variations at many sites. Interannual variations in transport, including those associated with ENSO and the NAO, are found to be important at certain locations. We adapt the Kalman Filter to estimate methane flux magnitudes and uncertainties between 1996 and 2001. Seven seasonal processes (3 wetland, rice, and 3 biomass burning) are optimized at each month, while three aseasonal processes (animals/waste, coal, and gas) are optimized as constant emissions. These optimized emissions represent adjustments to the reference emissions. For the entire period, the inversion reduces coal and gas emissions, and
(cont.) increases rice and biomass burning emissions. The optimized seasonal emission has a strong peak in July, largely due to increased emissions from rice producing regions. The inversion also attributes the large 1998 increase in atmospheric CH₄ to global wetland emissions, consistent with a bottom-up study based on a wetland process model. The current observational network can significantly constrain northern emitting regions, but is less effective at constraining tropical emitting regions due to limited observations. We further assessed the inversion sensitivity to different observing sites and model sampling strategies. Better estimates of global OH fluctuations are also necessary to fully describe the interannual behavior of methane observations. Carbon dioxide inversions were conducted as part of the Transcom 3 (Level 1) modeling intercomparison. We further explored the sensitivity of our CO₂ inversion results to different parameters.
by Yu-Han Chen.
Ph.D.
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Tzortzi, Eleni. "Sea surface salinity in the Atlantic Ocean from the SMOS mission and its relation to freshwater fluxes." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/377301/.
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Spatially dense sea surface salinity (SSS) measurements have recently begun to be made from space through the ESA SMOS mission. In this PhD, the sub-annual to interannual SSS distribution and variability is characterized, and its relationship with surface freshwater fluxes, i.e. Evaporation minus Precipitation (E-P) and river outflow (R) is investigated. Given its link to the Meridional Overturning Circulation, the focus is on the Tropical/ Subtropical Atlantic, which encompasses the dynamically different E-dominated Subtropics and P-dominated Tropics. The global and Atlantic SSS variability on different time scales and controlling processes are reviewed, including a description of how SSS is remotely sensed by satellites. The research initially examines the Tropical Atlantic SSS variability using the first year (2010) of SMOS data. This reveals that the variability in 2010 is dominated by eastern/western basin SSS regions ("poles") close to the major Amazon/Orinoco and Congo/Niger rivers. The poles show seasonal ranges up to 6.5 pss and out-of-phase by 6 months seasonal cycles that largely compensate each other, playing a key role in the Tropical Atlantic salinity budget. The growing SMOS record also reveals new aspects of the interannual variability of the SSS seasonal cycle during 2010-2012 and its phase-relationship with E, P, and R. It also shows that the E/W poles' seasonal compensation holds at multi-annual time scales. Next, a novel analysis of the spatio-temporal characteristic scales of SSS from SMOS over the Tropical/Subtropical Atlantic basin is presented. By examining how quickly consistent SSS changes evolve, regions with time persistent and, likewise, spatially homogeneous SSS variations, on sub-annual to interannual time scales, are identified. The spatial scales of SSS in the region are anisotropic, and persist for up to 3-4 months over most of the basin. Determination of SSS time and space scales of variability also provides insights into the controlling mechanisms of SSS. Finally, focusing on the freshwater forcing term of the salt budget equation, E-P is estimated from satellite SSS variations to explore whether and where SMOS can capture the main characteristics of E-P distribution in the region.
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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.
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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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Burnett, Benjamin F. "Exploratory Eddy Covariance Measurements of Surface Heat and CO2 Fluxes in the Roughness Sublayer of an Urban Environment." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/401.
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In this study eddy covariance was used to measure sensible heat, latent heat, and carbon dioxide fluxes for the months of August, September, and October of 2009 within the roughness sublayer (RSL) of the urban center of Portland, OR. Vehicle traffic and solar radiation were also measured for the month of October. Flux measurements were compared with measurements from other urban areas as a test of reasonableness. CO₂ fluxes were nearly always positive and were strongly correlated with the weekday diurnal traffic cycle. CO₂ fluxes averaged 6.6 μmol/m^²s, which is less than other published measurements in urban areas. Sensible and latent heat fluxes followed the expected diurnal profile associated with solar radiation. Average sensible heat flux decreased as the season changed from summer to fall, moving from an average of 39 W/m^² in August to 12 W/m^² in October. A corresponding increase in latent heat flux was observed during this period, changing from an average of 10 W/m^² in August to 17 W/m^² in October. Heat flux behavior and amplitude was consistent with other urban measurements, though amplitude varies considerably from city to city. Stationarity was shown to positively influence measured CO₂ fluxes, but to have little effect on measured heat fluxes. Preliminary comparisons of October sensible heat and CO₂ fluxes to an inventory-based estimate of vehicle emissions indicate that eddy covariance measurements underestimate the true fluxes by 50%.
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Papa, Rita. "Micrometeorological approaches to measure and model surface energy fluxes of irrigated citrus orchards in a semi-arid environment." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1336.
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The object of the research project was to propose and develop innovative theoretical methods for evaluating mass and energy exchange processes within one of the most relevant crop of the agricultural Sicilian context. The study was conceived as a long monitoring program of micrometeorological features of the study orange orchard at different spatial scales (plant, orchard, farm). Different micrometeorological methods, mainly based on Surface Renewal theory, were studied and tested, in order to provide reliable and low cost estimates of sensible heat fluxes within the plant-atmosphere system. Micrometeorological techniques were integrated with in situ measurements of transpiration by up-scaled sap flow techniques, physiological plant features and microclimatic characteristics of the study area. Derived actual crop evapotranspiration fluxes, by means of the resolution of the energy balance equation opportunely corrected for closure, and crop coefficient values were analyzed. All these efforts may contribute to address irrigation water scheduling towards water saving measures.
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Brunke, Michael. "Assessing and Improving the Representation of Hydrologic Processes in Atmospheric, Ocean, and Land Modeling and Dataset Generation." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/560855.
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Water is essential to life on Earth. Since water exists in all three phases (solid, liquid, and gas) on Earth, it exists in various reservoirs throughout the planet that compose the hydrologic cycle, and its movement through these reservoirs requires energy. Thus, water is a key component of the energy balance of the Earth. Despite its importance, its representation in modeling and dataset generation is problematic. Here, the depiction of three phenomena, ocean surface turbulent fluxes, humidity inversions, and groundwater, are assessed, and suggestions for improvements of their representations are made. First, ocean surface turbulent fluxes, including those of moisture (latent heat flux), heat (sensible heat flux), and momentum (wind stress), from reanalysis, satellite-derived, and combined products which are commonly used to produce climatologies and to evaluate global climate models are compared to in situ observations from ship cruises to ascertain which products are the least problematic. The National Aeronautics and Space Administration’s reanalysis, the Modern Era Retrospective Analysis for Research and Applications, is the least problematic for all three fluxes, while a couple of others are the least problematic for only one of the three fluxes. Also, the product biases are disaggregated into uncertainties from the grid cell mean quantities, or bulk variables, used plus the residual uncertainties which includes the algorithm uncertainties due to the parameterization used to relate the small-scale turbulent processes to the large-scale bulk variables. The latter contribute the most to the majority of product latent heat fluxes, while both uncertainties can contribute the most to product sensible heat fluxes and wind stress. Thus, both algorithms and bulk variables need to be improved in ocean surface flux datasets. Second, humidity inversion climatologies in five reanalyses are evaluated. Humidity inversions, similar to its thermal counterpart, are layers in which specific humidity increases with height rather than the usual decrease with height. These are especially persistent in the polar regions in autumn and winter. However, Arctic inversions are the strongest in summer corresponding to the time of year that low cloud cover is the highest. Comparing the reanalysis inversions to radiosonde observations reveals some problems with the realization of humidity inversions in reanalyses including the misrepresentation of the diurnal cycle and of the overproduction of inversions in areas outside the polar regions. Finally, the simulation of groundwater in the Community Land Model (CLM) as used in the Community Earth System Model is made more realistic by including variable soil thickness. Because the bottom of the model soil column is placed at effectively bedrock, the unconfined aquifer model currently used in CLM is removed and a zero bottom water flux is put in place. The removal of the unconfined aquifer allows the simulation of groundwater to not be treated separately from soil moisture. The model is most affected where the number of soil layers is reduced from the original constant 10 layers and largely unaffected where the number of soil layers is increased except for baseflow where the mean annual range in rainfall is large.
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Katz, Jeremy. "Evaluation of Surface Layer Parameterizations Using In-Situ Observations." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2604.
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Appropriate calculation of surface turbulent fluxes between the atmosphere and the underlying surface is one of the major challenges in geosciences. In practice, the surface turbulent fluxes are estimated from the mean surface meteorological variables based on the bulk transfer model combined with Monnin-Obukhov Similarity (MOS) theory. Few studies have been done to examine the extent that to which this flux parameterization framework can be applied to different weather and surface conditions. A novel validation method is developed in this thesis research, which is applied to evaluate the surface flux parameterization using in-situ observations. The main findings are: (a) the theoretical prediction that uses MOS theory does not match well with those directly computed from the observations collected in the coastal region. (b) Large spread in exchange coefficients mainly occurs in the calm wind regime with strong stability. (c) Large turbulent eddies, which depend largely on the mean flow and surface conditions, tend to break the constant flux assumption in the surface layer.
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Sachs, Oliver. "Benthic organic carbon fluxes in the Southern Ocean regional differences and links to surface primary production and carbon export." Bremerhaven Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2008. http://d-nb.info/997391650/34.
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Wang, Aihui, Xubin Zeng, and Donglin Guo. "Estimates of Global Surface Hydrology and Heat Fluxes from the Community Land Model (CLM4.5) with Four Atmospheric Forcing Datasets." AMER METEOROLOGICAL SOC, 2016. http://hdl.handle.net/10150/621989.
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Global land surface hydrology and heat fluxes can be estimated by running a land surface model (LSM) driven by the atmospheric forcing dataset. Previous multimodel studies focused on the impact of different LSMs on model results. Here the sensitivity of the Community Land Model, version 4.5 (CLM4.5), results to the atmospheric forcing dataset is documented. Together with the model default global forcing dataset (CRU-NCEP, hereafter CRUNCEP), three newly developed, reanalysis-based, near-surface meteorological datasets (i.e., MERRA, CFSR, and ERA-Interim) with the precipitation adjusted by the Global Precipitation Climatology Project monthly product were used to drive CLM4.5. All four simulations were run at 0.5 degrees x0.5 degrees grids from 1979 to 2009 with the identical initialization. The simulated monthly surface hydrology variables, fluxes, and the forcing datasets were then evaluated against various observation-based datasets (soil moisture, runoff, snow depth and water equivalent, and flux tower measurements). To partially avoid the mismatch between model gridbox values and point measurements, three approaches were taken. The model simulations based on three newly constructed forcing datasets are overall better than the simulation from CRUNCEP, in particular for soil moisture and snow quantities. The ensemble mean from the CLM4.5 simulations using the four forcing datasets is generally superior to individual simulations, and the ensemble mean latent and sensible heat fluxes over global land (60 degrees S-90 degrees N) are 42.8 and 40.3 W m(-2), respectively. The differences in both precipitation and other atmospheric forcing variables (e.g., air temperature and downward solar radiation) contribute to the differences in simulated results. The datasets are available from the authors for further evaluation and for various applications.
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Urgnani, Rossella. "Measurements and analysis of vertical distribution, surface fluxes, and chemical composition of atmospheric aerosol in two Italian Alpine valleys." Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/350599.
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The results of research activities performed in two Italian Alpine valleys (Chiese Valley, Trentino; Camonica Valley, Lombardy) are presented. The four intensive field campaigns held during summer 2019 and winter 2020 covered different topics: wintertime black carbon (BC) concentrations, techniques for measuring PM10 and temperature vertical profiles, surface size-resolved aerosol fluxes, aerosol concentrations, and chemical composition. Firstly, the contribution of two significant PM sources (traffic and biomass burning) to wintertime total black carbon concentrations was estimated, and the effect of meteorological factors on BC levels was assessed. In both pilot areas, traffic resulted as the predominant BC source during the daytime, while biomass burning weighed more than 50% at night. Atmospheric mixing and strong winds contributed to the removal of BC from the atmosphere, while wet scavenging was not effective if accompanied by low wind and friction velocities along with a significant increase in emission sources. Other aerosol sources, such as secondary particulate matter formation in the atmosphere, manure, fertilizers, or lithospheric erosion, were instead appointed in both seasons through the chemical speciation of the inorganic aerosol fraction, which had deposited on the filters of a multi-stage Electrical Low-Pressure Impactor (Elpi+, Dekati, FI) during an entire campaign. Results showed that SIA (secondary inorganic aerosol) components were the most abundant inorganic water-soluble ions in the collected samples. Secondly, three techniques for measuring PM10 and temperature vertical distributions were applied and compared. The first method enabled continuous monitoring by positioning 5 battery-powered stations, equipped with low-cost sensors, on the mountain slope overlooking the valleys. These measurements extended up to about 1000 m above the valley floor and were accompanied by drone profiles in summer and tethered balloon soundings in winter, both of them equipped with the same sensors installed in the slope stations. The research aimed at evaluating the effectiveness of the temperature and PM10 slope pseudo-vertical profiles in reproducing soundings measured in the valley centre. Slope stations successfully replicated the vertical profiles, especially in the morning/evening hours, thus representing a good and inexpensive alternative for long-lasting campaigns or even excellent support to traditional methods. Finally, the role of a typical alpine agro-economic ecosystem (pasture/grass field) in the atmosphere-Earth surface aerosol exchange was evaluated, studying aerosol size-segregated fluxes (9 classes, 10 nm ≤ GMD ≤ 0.76 m) with the eddy covariance technique, employing the aforementioned Dekati (FI) Elpi+ multi-stage impactor. Surprisingly, the pasture did not behave as an aerosol sink, favouring aerosol removal from the atmosphere, but rather contributed to the formation of secondary particulate matter through ammonia, NOX, and organic sulphides emissions from soil and vegetation. Deposition phenomena were registered under atmospheric stability or low turbulence conditions, but emission phenomena were very frequent, especially during winter. Thanks to the ion chromatography analysis of the inorganic particulate soluble fraction deposited on the impactor filters, aerosol fluxes were also linked to aerosol chemical composition and sources, thus hypothesizing nucleation, growth, and coagulation processes as responsible for the formation of concentration gradients in the atmosphere and the observation of deposition fluxes in the ultrafine range. The data collected and described in the present thesis had an interesting follow-up within the EU Alpine Space project BB-CLEAN, within which the activities developed. In particular, the experimental data were used by modellists to calibrate a meteorological and dispersion modelling chain that provided 48-hour PM concentration forecasts to a smartphone app, indicating when the activation of biomass burning heating systems might be sustainable. The researchers of the BB-CLEAN project also employed the model to evaluate some scenarios that envisaged the reduction of PM emissions from biomass burning appliances (e.g., through system upgrades, app use, and realization of a district heating network). Simulations showed that some of these scenarios could lead to a significant decrease in PM concentrations. However, no scenario can be elected as an absolute best, as policymakers should consider the characteristics of their respective municipalities when faced with the need to decide which scenario to implement.
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Pianezze, Joris. "Modélisation de la structure verticale de la turbulence optique en milieu naturel." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00830505.
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Les milieux complexes sont une source d'incertitude importante notamment lorsqu'il s'agit de développer des modèles climatique ou météorologique. Le développement de la couche limite atmosphérique à l'intérieur d'une vallée encaissée, incluant des vents de vallée et de pente, n'est, par exemple, pas résolu, ce qui a un impact considérable sur la prévision de la convection, du transport de polluants, etc... La simulation des grandes échelles de la turbulence (SGE) est un outil qui a montré sa capacité à reproduire finement les structures turbulentes dans ce type de contextes au travers des approches idéalisées. L'extension de la SGE aux milieux naturels est réalisée dans cette thèse qui s'articule en trois parties. La première partie présente les équations et les notions nécessaires à la compréhension des problèmes de turbulence dans la couche limite atmosphérique. On s'attache à décrire le cadre des lois issues de la théorie des similitudes et le cadre de la turbulence optique. La seconde partie présente des résultats issus de deux simulations idéales dans lesquelles nous comparons les résultats issus de la simulation avec d'une part les lois issues de la théorie des similitudes et d'autre part les données radar disponible lors de la campagne IHOP. L'utilisation d'un maillage raffinée près du sol permet d'améliorer les profils verticaux des champs turbulents en améliorant la prédiction des gradients à l'interface sol/atmosphère. De plus, le profil de couche limite est bien reproduit par les profils du paramètre de structure des fluctuations de l'indice de réfraction de l'air simulé si on compare avec les résultats issus du radar. Globalement, la dynamique des champs turbulents résolus par le modèle reproduise une dynamique et des ordres de grandeurs corrects conformes à nos attentes. Une fois l'évaluation du modèle effectuée, une simulation a été mise en place autour de la campagne d'observation VOTALP située dans le sud de la Suisse. Cette simulation comprend 5 domaines emboités allant de 16 kms de résolution horizontales pour le plus grand domaine à 100m pour le plus petit domaine. L'important dispositif déployé durant la campagne VOTALP située dans une vallée dans le sud de la Suisse a permis de confronter les résultats issus de la modélisation à haute résolution avec ces données d'observation. Les résultats obtenus ont, entre autre, montré que la simulation à haute résolution est un outil adapté pour l'étude des phénomènes de basses couches et notamment la turbulence optique en milieu complexe.
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Walker, Rachel. "Large-eddy Simulation of the Inner Continental Shelf Under the Combined Effects of Surface Temperature Fluxes, Tidal Currents and Langmuir Circulation." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5590.
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In a shallow shelf region, turbulent motion can have a major effect on coastal processes including ecosystem functioning, surface gas exchange and sediment resuspension. Many factors contribute to such turbulence; wind and wave forcing, buoyancy induced by surface heat fluxes and tidal forcing all play a key role in generating vertical mixing in this shallow region. Alongside these independent sources of turbulence, combinations thereof can lead to full-depth turbulent structures acting secondary to the mean flow and leading to enhanced vertical mixing throughout the entire water column.
Field and laboratory experiments can often prove to be costly and time consuming, and reproducing or maintaining the complex flow dynamics of real world ocean flows is a constant challenge to these methods of research. As such, those interested in developing realistic and useful models of the marine environment to further understand its behavior often rely on 3-dimensional mathematical modeling and simulation. In this dissertation, simulations will be presented of turbulent flow and associated vertical mixing in a domain representative of the shallow coastal ocean, sufficiently far off shore that the land-ocean boundary does not significantly affect the flow behavior. This will be done using a large-eddy simulation (LES) method; solving the governing Navier-Stokes equations over a finite grid designed to capture the large, energy containing turbulent scales, and modeling the smaller, sub-grid scales.
The simulations to be presented feature combinations of coastal forcing mechanisms which are either presently unexplored or the analysis of which has been hindered by the complexity of field measurements and the challenge of isolating independent causes of turbulent motion. This will include surface heat fluxes, tidal forcing and Langmuir (or wave) forcing, acting both in isolation and in conjunction with each other, in order to bridge existing gaps in knowledge and provide a more complete understanding of the generation of full-depth turbulent structures in this shallow coastal water column.
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Timm, Andréa Ucker. "Estimativa dos fluxos de energia superficiais utilizando o modelo de superfície noah modificado para culturas alagadas." Universidade Federal de Santa Maria, 2011. http://repositorio.ufsm.br/handle/1/3898.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe following study quantifies the seasonal and annual distribution of energy balance components (sensible heat fluxes, latent, soil, and net radiation) in this flooded irrigated rice ecosystem in Southern Brazil for three different periods (Fallow 1: 22 July 2003 to 24 November 2003; Rice: 25 November 2003 to 04 April 2004 and Fallow 2: 05 April 2004 to 21 July 2004). In addition, it has been applied the Noah Land Surface Model with the objective of estimating the surface energy fluxes. An important challenge is to implement a new version of Noah Land Surface Model applied to flooded agricultural land called Noah-Paddy. The stabilization of the models has been performed using the atmospheric forcing data obtained from South American Land Data Assimilation System (SALDAS) for the period 22 July 2000 to 21 July 2003. The models were simulated using the observed atmospheric forcing from a micrometeorological tower installed on a flooded irrigated rice paddies located in the city of Paraíso do Sul - RS. The initial conditions were obtained from the last time step of the spin-up experiment performed with atmospheric forcing data of SALDAS. The models results were compared with experimental data for surface energy fluxes. From the simulated results generated by the Noah Land Surface Model, it seems that when the rice crop is flooded, the model does not satisfactorily represents the experimental data. However, using the Noah-Paddy model the components of surface energy balance are more realistic for the system surface-water-atmosphere. The most important contribution performed in this research was to describe the diffent physical processes originated by the presence of a body of water between the soil surface and the atmosphere. This physical system occorr always in flooded agricultural crops in wich the rice paddies field are predominant.
No presente trabalho, quantifica-se a distribuição sazonal e anual das componentes do balanço de energia (fluxos de calor sensível, latente, do solo e saldo de radiação) em um ecossistema de arroz irrigado por inundação localizado no Sul do Brasil para três períodos distintos ao longo do ano (Pousio 1: 22Jul2003 a 24Nov2003; Arroz: 25Nov2003 a 04Abr2004 e Pousio 2: 05Abr2004 a 21Jul2004). Além disso, é utilizado o Modelo de Superfície Noah (Noah LSM) com o objetivo de estimar os fluxos de energia superficiais. Um dos desafios mais importantes é a implementação de uma nova versão do Noah LSM aplicado para áreas agrícolas alagáveis chamado Noah-Paddy. A estabilização dos modelos foi realizada utilizando dados de forçantes atmosféricas do South American Land Data Assimilation System (SALDAS) para o período de 22Jul2000 a 21Jul2003. Os modelos foram executados usando dados de forçantes atmosféricas observados obtidos a partir da torre micrometeorológica instalada sobre uma cultura de arroz irrigado por inundação localizada em Paraíso do Sul - RS. As condições iniciais foram obtidas a partir do último passo de tempo do experimento spin-up realizado com os dados de forçantes atmosféricas do SALDAS. O desempenho dos modelos estudados foi comparado com dados experimentais de fluxos de energia superficiais. A partir dos resultados obtidos pela simulação do Noah LSM verifica-se que, quando a cultura do arroz está irrigada, o modelo não representa satisfatoriamente os dados experimentais. Porém, utilizando o Noah-Paddy as trocas de energia superficiais são representadas de forma mais realísticas para o sistema superfície-água-atmosfera. A contribuição mais importante realizada neste trabalho foi a descrição dos diferentes processos físicos originados pela presença de uma massa de água entre a superfície do solo e a atmosfera. Esse sistema físico ocorre sempre em culturas agrícolas alagadas nas quais as plantações de arroz são predominantes.
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Babenhauserheide, Arne [Verfasser], and J. [Akademischer Betreuer] Orphal. "Inverse modelling of carbon dioxide surface fluxes - estimating uncertainties due to model design and observational constraints / Arne Babenhauserheide. Betreuer: J. Orphal." Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1093559012/34.
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Sachs, Oliver [Verfasser]. "Benthic organic carbon fluxes in the southern ocean : Regional differences and links to surface primary production and carbon export / Oliver Sachs." Bremerhaven : AWI, Alfred-Wegener-Institut für Polar- und Meeresforschung, 2008. http://d-nb.info/1010121391/34.
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Humes, Karen Sue, and Soroosh Sorooshian. "THE ESTIMATION AND SCALING OF LAND-SURFACE FLUXES OF LATENT AND SENSIBLE-HEAT WITH REMOTELY SENSED DATA OVER A GRASSLAND SITE." Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1993. http://hdl.handle.net/10150/617639.
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The overall topic of the research described in this dissertation was the
partitioning of available energy at the Earth's surface into sensible and latent heat
flux, with an emphasis on the development of techniques which utilize remotely
sensed data. One of the major objectives was to investigate the modification of
existing techniques, developed over agricultural surfaces, to "natural" ecosystems (i.e.,
non -agricultural vegetation types with variable and incomplete canopy cover).
Ground -based measurements of surface fluxes, vegetation cover, and surface
and root -zone soil moisture from the First ISLSCP (International Land Surface
Climatology Program) Field Experiment (FIFE) were used to examine the factors
controlling the partitioning of energy at ground stations with contrasting surface
characteristics.
Utilizing helicopter -based and satellite -based data acquired directly over
ground -based flux stations at the FINE experimental area, relatively simple
algorithms were developed for estimating the soil heat flux and sensible heat flux
from remotely sensed data. The root mean square error (RMSE) between the
sensible heat flux computed with the remotely sensed data and the sensible heat flux
measured at the ground stations was 33 Wm 2. These algorithms were then applied
on a pixel -by -pixel basis to data from a Landsat -TM (Thematic Mapper) scene
acquired over the FIFE site on August 15, 1987 to produce spatially distributed
surface energy- balance components for the FIFE site.
A methodology for quantifying the effect of spatial scaling on parameters
derived from remotely sensed data was presented. As an example of the utility of this approach, NDVI values for the 1,IFE experimental area were computed with
input data of variable spatial resolution. The differences in the values of NDVI
computed at different spatial resolutions were accurately predicted by an equation
which quantified those differences in terms of variability in input observations.