Dissertations / Theses on the topic 'Land Atmosphere'
To see the other types of publications on this topic, follow the link: Land Atmosphere.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Land Atmosphere.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Martello, Robert 1968. "Land atmosphere interaction and atmospheric mixed layer height evolution." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38774.
Full text
2
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.
Full text
3
Wei, Jiangfeng. "Land-atmosphere interaction and climate variability." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05162007-151312/.
Full textAbstract:
Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008.Stieglitz, Marc, Committee Member ; Guillas, Serge, Committee Member ; Fu, Rong, Committee Member ; Curry, Judith, Committee Member ; Dickinson, Robert, Committee Chair.
4
Cronin, Timothy (Timothy Wallace). "Land-atmosphere interaction and radiative-convective equilibrium." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90605.
Full textAbstract:
Thesis: Ph. D. in Climate Physics and Chemistry, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 161-171).
I present work on several topics related to land-atmosphere interaction and radiative-convective equilibrium: the first two research chapters invoke ideas related to land-atmosphere interaction to better understand radiative-convective equilibrium; the last two research chapters use the framework of radiative-convective equilibrium to better understand land-atmosphere interaction. First, I calculate how averaging the incident solar radiation can lead to biases in idealized climate models. I derive an expression for the absorption-weighted solar zenith angle, which minimizes the bias in mean absorbed shortwave radiation, and I find that it is closely matched by the insolation-weighted zenith angle. Common use of daytime-weighted zenith angle likely leads to high biases in albedo by ~3%. Second, I explore the time scales of approach to radiative-convective equilibrium with both a simple linearized two-variable model, and a single-column model with full physics. I show that there is a long time scale of approach to radiative-convective equilibrium that is order hundreds of days even when the surface heat capacity vanishes. The impact of water vapor on the effective atmospheric heat capacity can more than double this time scale for warm temperatures and low surface heat capacities. Third, I develop an analytic theory for the sensitivity of near-surface temperature to properties of the land surface. I show that the theory compares well against a simple numerical model of the coupled boundary layer-surface system, as well as a more complex two-column model, and discuss application of the theory to questions of how changes in land use or ecosystem function may affect climate change. Finally, I find that the diurnal cycle of convection is important for the spatial distribution of rainfall in idealized simulations of radiative-convective equilibrium with a cloud-resolving model. In a region that is partly an island and mostly ocean, precipitation over the island falls primarily in a regular, strong, afternoon thunderstorm, with a time-mean rainfall rate more than double the domain average. I explore mechanisms for this island rainfall enhancement, investigate the importance of island size for my results, and find that the upper troposphere warms with the inclusion of an island, which may have implications for the large-scale tropical circulation.
by Timothy Cronin.
Ph. D. in Climate Physics and Chemistry
5
Kala, Jatin. "Land-atmosphere interactions in Southwest Western Australia." Thesis, Kala, Jatin ORCID: 0000-0001-9338-2965 (2011) Land-atmosphere interactions in Southwest Western Australia. PhD thesis, Murdoch University, 2011. https://researchrepository.murdoch.edu.au/id/eprint/10624/.
Full textAbstract:
The Southwest of Western Australia (SWWA) is a region of extensive land cover change with an estimated 13 million hectares of native vegetation cleared since European settlement. Whilst previous studies have suggested meteorological and climatological implications of this change in land use, no studies have explicitly focussed on the detailed mechanisms behind the impacts of land-cover change on individual meteorological phenomena. This thesis seeks to identify the physical mechanisms inducing changes within the atmosphere by using the Regional Atmospheric Modeling System (RAMS V6.0) to simulate the impact of land use change on meteorological phenomena at different scales and evaluate these model results against high resolution atmospheric soundings, station observations, and gridded rainfall analyses where appropriate. Sensitivity tests show that land-cover change results in an increase in low-level atmospheric moisture advection associated with the southern sea-breeze due to a reduction in surface roughness. It also results in a decrease in convective precipitation associated with cold-fronts and convective clouds associated with the surface heat trough, due to an increase in wind speed, and a decrease in turbulent kinetic energy and vertically integrated moisture convergence within the PBL. Large-eddy simulations further highlight the role of land-cover change and soil moisture, as well as the contributions of surface versus entrainment fluxes on the growth of the PBL and development of convective clouds. These results are discussed within the broader context of the meteorology of the region.
6
Mohr, Karen Irene. "An investigation of land/atmosphere interactions : soil moisture, heat fluxes, and atmospheric convection /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992875.
Full text
7
White, Cary Blake, and Cary Blake White. "Soil Moisture Variability in Land Surface-Atmosphere Interactions." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/626791.
Full textAbstract:
Meteorological measurements in the Walnut Gulch catchment in Arizona were used
to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area
with a grid resolution of 480 m for a continuous 18-month period which included two
seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the
acceptability (for modeling purposes) of assuming uniformity in all meteorological variables
other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain
gauges. These meteorological data were used as forcing variables for an equivalent array of
stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the
evolution of soil moisture and surface energy fluxes in response to the prevalent,
heterogeneous pattern of convective precipitation. The calculated area-average behavior was
compared with that given by a single aggregate BATS simulation forced with area-average
meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating
differences in the transpiration and the intercepted rainfall components of total evaporation
during rain storms. However, the calculated area-average surface energy fluxes given by the
two simulations in rain-free conditions with strong heterogeneity in soil moisture were
always close to identical, a result which is independent of whether default or site-specific
vegetation and soil parameters are used. Because the spatial variability in soil moisture
throughout the catchment has the same order of magnitude as the amount of rain falling in
a typical convective storm (commonly 10% of the vegetation's root zone saturation), in a
semi-arid environment, any non-linearity in the relationship between transpiration and the
soil moisture available to the vegetation has limited influence on area-average surface fluxes.
8
Gentine, Pierre. "Spectral behavior of the coupled land-atmosphere system." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/61243.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
The main objective of this thesis is to understand the daily cycle of the energy coupling between the land and the atmosphere in response to a forcing of incoming radiation at their common boundary, the land surface. This is of fundamental importance as that the initial/ boundary conditions of the land-surface state variables (e.g. soil moisture, soil temperature) exert strong control at various temporal scales on hydrologic, climatic and weather related processes. Hence diagnosing these state variables is crucial for extreme hydrological forecasting (flood/ drought), agronomic crop management as well as weather and climatic forecasts. Consequently in this thesis, the daily behavior of a simple land-atmosphere model is examined. A conceptual and linearized land-atmosphere model is first introduced and its response to a daily input of incoming radiation at the land surface is investigated. The solution of the different state and fluxes in the Atmospheric Boundary Layer (ABL) and in the soil are expressed as temporal Fourier series with vertically dependent coefficients. These coefficients highlight the impact of both the surface parameters and the frequency of the radiation on the heat propagation in the ABL and in the soil. The simplified model is shown to compare well with field measurements thus accounting for the main emergent behaviors of the system. The first chapter of the thesis describes the theoretical background of the equations governing the evolution of temperature and humidity in the ABL and in the soil. In the second chapter, the pioneering work of Lettau (1951), which inspired our approach is summarized. In his work Lettau studied the response of a simplified linearized land-atmosphere model to a sinusoidal net radiation forcing at the land surface. The third chapter of the thesis describes the SUDMED project, which took place in Morocco in 2003. During this project a wheat field was fully instrumented with continuous measurements of soil moisture, radiative fluxes, turbulent heat fluxes and soil heat flux. This site will be taken as a reference for model comparison. The fourth chapter of the thesis presents the three studies with distinctive goals. In these studies our linearized land-atmosphere model is first introduced. Then the propagation of the land-surface diurnal heating is presented and the model is compared to observations from the SUDMED project. Finally the repercussion of a land-surface energy budget error noise is investigated. Finally in the last chapter of the thesis we discuss possible evolution and improvements of the analytical coupled model presented in this thesis. In particular, it is emphasized that the non-linearity of the the boundary-layer height is of great importance for the predictability of the ABL state.
by Pierre Gentine.
Ph.D.
9
Ghent, Darren John. "Land surface modelling and Earth observation of land/atmosphere interactions in African savannahs." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10274.
Full textAbstract:
Land/atmosphere feedback processes play a significant role in determining climate forcing on monthly to decadal timescales. Considerable uncertainty however exists in land surface model representation of these processes. This investigation represents an innovative approach to understanding key land surface processes in African savannahs in the framework of the UK‘s most important land surface model – the Joint UK Land Environment Simulator (JULES). Findings from an investigation into the carbon balance of Africa for a 25-year period from 1982 to 2006 inclusive show that JULES estimated Africa to behave as a carbon sink for most of the 1980‘s and 1990‘s punctuated by three periods as a carbon source, which coincided with the three strongest El Niño events of the period. From 2002 until 2006 the continent was also estimated to be a source of carbon. Overall, the JULES simulation suggests a weakening of the African terrestrial carbon sink during this period primarily caused by hot and dry conditions in savannahs. Applying the model further, land surface temperature (LST) displayed large uncertainty with respect to savannah field measurements from Kruger National Park, South Africa, and JULES systematically underestimated LST with respect to Earth Observation data continent-wide. The postulation was that a reduction in the uncertainty of surface-to-atmosphere heat and water fluxes could be achieved by constraining JULES simulations with satellite-derived LST using an Ensemble Kalman Filter. Findings show statistically significant reductions in root mean square errors with data assimilation than without; for heat flux simulations when compared with Eddy Covariance measurements, and surface soil moisture when compared with derivations from microwave scatterometers. The improved representation of LST was applied to map daily fuel moisture content – one of the most important wildfire determinants - over the mixed tree/grass landscapes of Africa, whereby values were strongly correlated with field measurements acquired from three savannah locations.
10
Liu, Yuqiong. "Parameter Estimations For Locally Coupled Land Surface-Atmosphere Models." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/191262.
Full textAbstract:
As land-surface modeling moves from the off-line mode to the coupled mode, it is also highly desirable to extend the off-line calibration of land-surface models to coupled applications. Using the NCAR SCCM as an example, this study proposed and implemented some effective schemes for the application of automatic parameter estimation procedures in a locally coupled environment, where other relevant issues such as parameterization tests, sensitivity analyses, and off-line calibrations were also involved. A parameterization deficiency having serious negative impacts on the performance of the NCAR SCCM was identified and rectified in this work, which led to significantly improved model performances and formed the basis for the subsequent sensitivity analysis and calibration experiments. To facilitate the calibration studies, an independent sensitivity analysis was conducted to identify some sensitive model parameters, followed by a multi-objective sensitivity analysis using the MOGSA algorithm to obtain better understanding of the model. Some off-line calibrations using the NCAR LSM were also conducted for comparison purposes. In the locally coupled environment, both land-surface and atmospheric variables/parameters were involved in the calibration processes of 14 different predesigned calibration cases. In brief, the results show that atmospheric parameters are of critical importance for the calibration of a coupled land surface-atmosphere model, and atmospheric forcing variables generally contain more useful information for calibration than land-surface fluxes/variables. In the coupled environment, step-wise calibration schemes, with land-surface and atmospheric parameters optimized successively in the off-line and coupled modes, respectively, appear to be superior to the single-step calibration schemes which optimize land-surface and atmospheric parameters simultaneously in the coupled environment, in that the former can provide better converged optimal solutions with less uncertainties. In addition, the results also show that better optimization effects can be achieved in the partially decoupled environment by replacing the model-generated precipitation and net radiation with the corresponding observations to drive the land-surface part of the model, indicating the dominant importance of precipitation and radiation in a coupled land surface-atmosphere model.
11
Zabel, Florian. "Land-atmosphere coupling between a land surface hydrological model and a regional climate model." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-151446.
Full text
12
Shibuo, Yoshihiro. "Modelling water and solute flows at land-sea and land-atmosphere interfaces under data limitations." Doctoral thesis, Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6834.
Full text
13
Manrique-Sunen, A. "The treatment of vegetation in land surface models : implications for predictions of land-atmosphere exchange." Thesis, University of Reading, 2016. http://centaur.reading.ac.uk/68719/.
Full textAbstract:
Plant processes affect fluxes of energy, moisture and CO2 between the land and the atmosphere. Land surface models need to correctly represent the vegetation functioning and its response to environmental conditions. Due to anthropogenic carbon emissions rising, and global warming, plant processes are being affected and in turn modulate the terrestrial carbon sink. However, models still disagree on the response of plants to changing conditions. This work analyses how vegetation is treated in two land surface models: the Joint UK Land Environment Simulator (JULES) and Carbon Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (CTESSEL). The aim is to analyse how environmental variables control the vegetation processes at daily and seasonal timescales at present day climate and the changes that arise in a scenario of double atmospheric CO2 and higher temperature. The analyses are carried out at the leaf level and at the canopy level. To investigate the responses at the leaf level, the photosynthesis scheme used in each model was extracted, thereby providing a submodel that can be run in stand alone mode. The photosynthesis submodel provides a means to analyse the leaf level response of each photosynthesis model to environment variables as well as the internal model parameters that characterise each plant type. In JULES the environmental controls on photosynthesis are explicitly introduced by three limiting regimes: light, rubisco (carbon) or export limiting regime. In CTESSEL the carbon and light limitations are implicitly represented but there is no export limitation. Due to the lack of export limiting regime, CTESSEL presents higher sensitivity to CO2 concentration resulting in a stronger CO2 fertilization effect. The carbon and energy fluxes produced by the full land surface models were tested and compared at 10 European FLUXNET sites. The main differences between modellled carbon fluxes were found to be the treatment of soil moisture stress and the lack of export limiting regime in CTESSEL. The optimum temperature for photosynthesis in models is the result of model parameters’ dependence on temperature and the combination of limiting regimes. The optimum temperature for photosynthesis was found to be a determining element in the strength and sign of the vegetation modelled feedback to climate change.
14
Goncalves, de Goncalves Luis Gustavo. "LAND SURFACE-ATMOSPHERE INTERACTIONS IN REGIONAL MODELING OVER SOUTH AMERICA." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/195893.
Full textAbstract:
Land surface processes play an important role when modeling weather and climate, and understanding and representing such processes in South America is a particular challenge because of the large variations in regional climate and surface features such as vegetation and soil. Numerical models have been used to explore the climate and weather of continental South America, but without appropriate initiation of land surface conditions model simulations can rapidly diverge from reality. This initiation problem is exacerbated by the fact that conventional surface observations over South America are scarce and biased towards the urban centers and coastal areas. This dissertation explores issues related to the apt representation of land surface processes and their impacts in numerical simulations with a regional atmospheric model (specifically the Eta model) over South America. The impacts of vegetation heterogeneity in regional weather forecast were first investigated. A South American Land Data Assimilation System (SALDAS) was then created analogous to that currently used in North America to estimate soil moisture fields for initializing regional atmospheric models. The land surface model (LSM) used in this SALDAS is the Simplified Simple Biosphere (SSiB). Precipitation fields are critical when calculating soil moisture and, because conventional surface observations are scarce in South America, some of the most important remote sensed precipitation products were evaluated as potential precipitation forcing for the SALDAS. Spin up states for SSiB where then compared with climatological estimates of land surface fields and significant differences found. Finally, an assessment was made of the value of SALDAS-derived soil moisture fields on Eta model forecasts. The primary result was that model performance is enhanced over the entire continent in up to 72h forecasts using SALDAS surface fields
15
Yang, Zhao, and Zhao Yang. "Land-Atmosphere Interactions Due to Anthropogenic and Natural Changes in the Land Surface: A Numerical Modeling." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/623069.
Full textAbstract:
Alterations to the land surface can be attributed to both human activity and natural variability. Human activities, such as urbanization and irrigation, can change the conditions of the land surface by altering albedo, soil moisture, aerodynamic roughness length, the partitioning of net radiation into sensible and latent heat, and other surface characteristics. On the other hand, natural variability, manifested through changes in atmospheric circulation, can also induce land surface changes. These regional scale land surface changes, induced either by humans or natural variability, can effectively modify atmospheric conditions through land-atmosphere interactions. However, only in recent decades have numerical models begun to include representations of the critical processes driving changes at the land surface, and their associated effects on the overlying atmosphere. In this work we explore three mechanisms by which changes to the land surface–both anthropogenic and naturally induced–impact the overlying atmosphere and affect regional hydroclimate. The first land-atmosphere interaction mechanism explored here is land-use and land-cover change (LULCC) due to urban expansion. Such changes alter the surface albedo, heat capacity, and thermal conductivity of the surface. Consequently, the energy balance in urban regions is different from that of natural surfaces. To evaluate the changes in regional hydroclimate that could arise due to projected urbanization in the Phoenix–Tucson corridor, Arizona, my first study applied the Weather Research and Forecasting (WRF) with an Urban Canopy Model (UCM; which includes a detailed urban radiation scheme) coupled to the Noah land surface model to this region. Land-cover changes were represented using land-cover data for 2005 and projections to 2050, and historical North American Regional Reanalysis (NARR) data were used to specify the lateral boundary conditions. Results suggest that temperature changes are well defined, reflecting the urban heat island (UHI) effect within areas experiencing LULCC, whereas changes in precipitation are less certain (statistically less robust). However, the study indicates the likelihood of reductions in precipitation over the mountainous regions northeast of Phoenix and decreased evening precipitation over the newly urbanized area. The second land-atmosphere interaction mechanism explored here is irrigation which, while being an important anthropogenic factor affecting the local to regional water cycle, is not typically represented in regional climate models. In this (second) study, I incorporated an irrigation scheme into the Noah land surface scheme coupled to the WRF model. Using a newly developed water vapor tracer package (developed by Miguez-Macho et al. 2013), the study tracks the path of water vapor that evapotranspires from the irrigated regions. To assess the impact of irrigation over the California Central Valley (CCV) on the regional climate of the U.S. Southwest, I ran six simulations (for three dry and three wet years), both with and without the irrigation scheme. Incorporation of the irrigation scheme resulted in simulated surface air temperature and humidity that were closer to observations, decreased the depth of the planetary boundary layer over the CCV, and increased the convective available potential energy. The results indicated an overall increase in precipitation over the Sierra Nevada Range and the Colorado River Basin during the summer, with water vapor rising from the irrigated region moving mainly northeastward and contributing to precipitation in Nevada and Idaho. The results also indicate an increase in precipitation on the windward side of the Sierra Nevada Range and over the Colorado River Basin. The former is possibly linked to a sea-breeze type circulation near the CCV, while the latter is likely associated with a wave pattern related to latent heat release over the moisture transport belt. In the third study, I investigated the role of large-scale and local-scale processes associated with heat waves using the Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and evaluate the performance of the regional climate model ensemble used in the North America Regional Climate Change Program (NARCCAP) in reproducing these processes. The Continental US is divided into different climate divisions (following the convention of the National Climate Assessment) to investigate different mechanisms associated with heat waves. At the large scale, warm air advection from terrestrial sources is a driving factor for heat waves in the Northeast and Midwest. Over the western United States, reduced maritime cool air advection results in local warming. At the local scale, an antecedent precipitation deficit leads to the continuous drying of soil moisture, more energy being partitioned into sensible heat flux and acting to warm surface air temperatures, especially over the Great Plains. My analysis indicates that the NARCCAP simulated large-scale meteorological patterns and temporal evolution of antecedent local-scale terrestrial conditions are very similar to those of MERRA. However, NARCCAP overestimates the magnitude and underestimates the frequency of Northeastern and Midwestern US heat waves, partially due to anomalous heat advection through large-scale forcing. Overall, the aforementioned studies show that utilization of new parameterizations in land surface models, such as the urban canopy scheme and the irrigation scheme, allow us to understand the detailed physical mechanisms by which anthropogenic changes in the land surface can affect regional hydroclimate, and may thus help with informed decision making and climate adaptation/mitigation. In addition to anthropogenic changes of the land surface, humans are of course affecting the overlying atmosphere. Currently, NARCCAP is the best available tool we have to help us understand the effects of changes greenhouse gas induced climate change at the regional scale. The regional climate models participating in NARCCAP are able to realistically represent the dominant processes associated with heat waves, including the atmospheric circulation changes and the land-atmosphere interactions that drive heat waves. This lends credibility, when analyzing the projections of these models with increased GHG emissions, to the assessment of changes in heat waves under a future climate.
16
Zhang, Yan. "Influence of biomass burning aerosol on land-atmosphere interactions over Amazonia." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-07122005-120105/.
Full text
17
Bain, Caroline Louise. "Interactions between the Land Surface and the Atmosphere over West Africa." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491661.
Full textAbstract:
The north-south gradient in surface temperature and rainfall in West Africa leads to the summertime monsoon circulation. Here, the full extent of the relationship between the land surface and the atmosphere is discussed with particular reference to the impact that soil moisture has on the atmosphere at different spatial scales. Observations from the AMMA field campaign in 2005 and 2006 are combined with satellite analysis and model simulations to discuss various interactions between the land surface and the atmosphere. Tethered balloon observations from Mali in August 2005 are used to assess the characteristics of the nocturnal boundary layer. It is observed that a stronger surface temperature inversion after sunset leads to a faster nocturnal jet, and these findings are further investigated using surface station data. Case studies of two nights of observations are used to discuss the variation of observed boundary layer structures. It is found that on nights where the nocturnal jet is weaker, the winds align with African Easterly Wave (AEW) circulations on the larger scale. . Following this, the impact that AEWs had on sl1rface properties is examined. Flux data from Niamey showed little statistical correlation with wave passage. It is suggested this could be partly due to the study year having more westerly initiating waves than climatology. The inducement of circulations by soil moisture inhomogeneities are discussed in regard to previous literature, where a moist cool surface leads to high pressure and anticyclonic circulation. The relation of this theory to the synoptic scale is investigated using a case study from 25-29 July 2006. During this time, an unusually-structured AEW left a distinct synoptic 'wave' pattern of soil moisture in the Sahel region due to its modulation of convection. The structure of this wave and the initial conditions which lead to the soil moisture pattern are discussed. The atmospheric impact of the soil moisture wave is investigated using the Met Office Unified Model. It is found that th~ enhanced soil moisture leads to a cooler, moister, . thinner boundary layer. This leads to divergent winds at low levels and a reduction in the monsoon flow due to the reduction in the north-south pressure gradient. There is indication that low-level anticyclonic circulations are enhanced. The enhanced soil moisture wave also leads to an increase in easterly winds at the African Easterly Jet level: it is shown that this is due to a decrease in boundary layer height and a reduction in turbulence. Inspection of wave energetics shows the case study wave appears to be in a decaying phase. There is evidence that the soil moisture wave increases the thermal decay by decreasing the temperature behind the trough in the warm region, reducing the temperature eddies and re-establishing the zonal temperature gradient. This study has implications for weather forecasting as the results suggest that patterns in soil moisture on the large scale are able to alter atmospheric dynamics at the synoptic scale within the time frame of a few days. This leads to further questions as to whether a realistic representation of soil moisture in mo.dels would lead to an improvement in the simulation 'of tropical synoptic dynamics.
18
Macdonald, J. A. "Soil and environmental variables affecting the land-atmosphere exchange of methane." Thesis, University of Edinburgh, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654211.
Full textAbstract:
Rates of methane (CH4) oxidation (-) and emission were measured from a range of soil types and land uses to investigate the soil and environmental variables which affected the land-atmosphere exchange of CH4. The influence of soil characteristics, land use, inputs of nitrogen (N) and sulphur (S) and temporal variations in soil water content and temperature on CH4 flux were examined in the field using a static chamber technique, and in the laboratory using soil cores. The flux of CH4 was measured from a range of sites in the UK, Cameroon and Borneo, including temperate and tropical forest, agricultural land, moorland and blanket bog. In mineral soils, rates of CH4 oxidation ranged from a maximum uptake of -27.2 ng m-2 s-1 in an undisturbed forest in Cameroon, to a small net emission of 0.8 ng m-2 s-1 from an agricultural field in Scotland. In peats, soil water content controlled the magnitude and direction of flux within sites by affecting the degree of anaerobicity of the peat and hence the depth of the CH4 oxidising layer. Other factors such as peat depth and substrate quality influenced inter-site variability. The contribution of CH4 produced by termites to the CH4 budget was investigated in undisturbed and disturbed forests in Cameroon and Borneo. In summary, rates of CH4 oxidation from mineral soils were low and covered a small range relative to CH4 emission rates from peat. Rates of CH4 oxidation were significantly inhibited by anthropogenic disturbance such as deforestation, conversion to agriculture, and inputs of N. Spatial variability was controlled by the bulk density of the soil, both in temperate and tropical climates, demonstrating the importance of the gaseous diffusion status of the soil and the secondary role of temperature in regulating oxidation rates. Seasonal variability affected both CH4 emission and oxidation rates. The relative influence of soil water content and temperature on the CH4 flux varied between sites and was dependent on the soil type.
19
Brubaker, Kaye L. (Kaye Lorraine). "Nonlinear dynamics of water and energy balance in land-atmosphere interaction." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36513.
Full text
20
Sirkin, David Michael. "Thermohaline circulation stability in a copuled land-ocean-atmosphere box model." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/57858.
Full text
21
Barros, Ana Paula. "Modeling of orographic precipitation with multilevel coupling of land-atmosphere interactions /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/10144.
Full text
22
Lytle, William. "Coupled Evaluation of Below- and Above-Ground Energy and Water Cycle Variables from Reanalysis Products Over Five Flux Tower Sites in the U.S." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/595636.
Full textAbstract:
Reanalysis products are widely used to study the land-atmosphere exchanges of energy, water, and carbon fluxes, and have been evaluated using in situ data above or below ground. Here measurements for several years at five flux tower sites in the U.S. (with a total of 315,576 hours of data) are used for the coupled evaluation of both below- and above-ground processes from three global reanalysis products and six global land data assimilation products. All products show systematic errors in precipitation, snow depth, and the timing of the melting and onset of snow. Despite the biases in soil moisture, all products show significant correlations with observed daily soil moisture for the periods with unfrozen soil. While errors in 2 meter air temperature are highly correlated with errors in skin temperature for all sites, the correlations between skin and soil temperature errors are weaker, particularly over the sites with seasonal snow. While net shortwave and longwave radiation flux errors have opposite signs across all products, the net radiation and ground heat flux errors are usually smaller in magnitude than turbulent flux errors. On the other hand, the all-product averages usually agree well with the observations on the evaporative fraction, defined as the ratio of latent heat over the sum of latent and sensible heat fluxes. This study identifies the strengths and weaknesses of these widely-used products, and helps understand the connection of their errors in above- versus below-ground quantities.
23
Luke, Catherine M. "Modelling aspects of land-atmosphere interaction : thermal instability in peatland soils and land parameter estimation through data assimilation." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3229.
Full textAbstract:
The land (or ‘terrestrial’) biosphere strongly influences the exchange of carbon, energy and water between the land surface and the atmosphere. The size of the land carbon store and the magnitude of the interannual variability of the carbon exchange make models of the land surface a vital component in climate models. This thesis addresses two aspects of land surface modelling: soil respiration and phenology modelling, using different techniques with the goal of improving model representation of land-atmosphere interaction. The release of heat associated with soil respiration is neglected in the vast majority of large-scale models but may be critically important under certain circumstances. In this thesis, the effect of this heat release is considered in two ways. Firstly, a deliberately simple model for soil temperature and soil carbon, including biological heating, is constructed to investigate the effect of thermal energy generated by microbial respiration on soil temperature and soil carbon stocks, specifically in organic soils. Secondly, the mechanism for biological self-heating is implemented in the Joint UK Land Environment Simulator (JULES), in order to investigate the impacts of the extra feedback in a complex model. With the intention of improving estimates of the parameters governing modelled land surface processes, a data assimilation system based on the JULES land surface model is presented. The ADJULES data assimilation system uses information from the derivative of JULES (or adjoint) to search for a locally optimum parameter set by calibrating against observations. In this thesis, ADJULES is used with satellite-derived vegetation indices to improve the modelling of phenology in JULES.
24
Kelly, Patrick. "Evaluation of Land-Atmosphere Interactions in Models of the North American Monsoon." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_theses/118.
Full textAbstract:
Improving diurnal errors in surface-based heating processes in models might be a promising step towards improved seasonal simulation of the North American Monsoon (NAM). This study isolates model errors in the surface energy budget and examines diurnal heating implications for seasonal development of the NAM 500hPa anticyclone and 850-500hPa thickness ridge using observations and multi-model output. Field data from the 2004 North American Monsoon Experiment (NAME) and satellite estimates are used to evaluate land-atmosphere interactions in regional and global models as part of the North American Monsoon Model Assessment Project 2 (NAMAP2). Several key findings about heating in the NAM emerge: ? Models exhibit considerable differences in surface radiation of the NAM, beginning with albedo (Fig. 3.1). All models have highly-biased albedo throughout summer (Fig. 3.2). ? Observed net surface radiation is around 125 Wm-2 over land in the NAM region in summer (Table 3.5). Models overestimate it by an average of about 20 Wm-2, despite their high albedo, apparently due to deficiencies in cloud radiative forcing. ? Partitioning of this net radiation into latent and sensible fluxes to the atmosphere differs substantially among models. Sensitivity of this partitioning to rainfall also varies widely among models, and appears clearly excessive in some models relative to observations (Fig. 4.10). ? Total sensible heating exceeds latent heating in the NAM (Table 4.1), since it covers a much larger area than the rainy core region (Fig. 4.11). ? Inter-model differences in sensible heating can be traced consistently from surface heat flux (Table 5.1), to PBL diurnal evolution (Fig. 5.1), to diurnal thickening of the lower troposphere (Fig. 5.2). ? Seasonal biases in the NAM?s synoptic structure correspond well to diurnal heating biases (Fig. 5.3, Fig. 5.5), suggesting that diurnal cycle studies from a single field season may suffice to inform physical process improvements that could impact seasonal simulation and forecasting. These NAMAP2 results highlight the range of uncertainty and errors in contemporary models, including those defining US national weather forecasting capability. Model experimentation will be necessary to fully interpret the lessons and harvest the fruits of this offline inter-comparison exercise.
25
Arain, Muhammad Altaf. "Spatial aggregation of vegetation parameters in a coupled land surface-atmosphere model." Thesis, The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0049_m_sip1_w.pdf&type=application/pdf.
Full text
26
McAtee, Brendon Kynnie. "Surface-atmosphere interactions in the thermal infrared (8 - 14um)." Thesis, Curtin University, 2003. http://hdl.handle.net/20.500.11937/408.
Full textAbstract:
Remote sensing of land surface temperature (LST) is a complex task. From a satellite-based perspective the radiative properties of the land surface and the atmosphere are inextricably linked. Knowledge of both is required if one is to accurately measure the temperature of the land surface from a space-borne platform. In practice, most satellite-based sensors designed to measure LST over the surface of the Earth are polar orbiting. They scan swaths of the order of 2000 km, utilizing zenith angles of observation of up to 60°. As such, satellite viewing geometry is important when comparing estimates of LST between different overpasses of the same point on the Earth's surface. In the case of the atmosphere, the optical path length through which the surfaceleaving radiance propagates increases with increasing zenith angle of observation. A longer optical path may in turn alter the relative contributions which molecular absorption and emission processes make to the radiance measured at the satellite sensor. A means of estimating the magnitudes of these radiative components in relation to the viewing geometry of the satellite needs to be developed if their impacts on the at-sensor radiance are to be accurately accounted for. The problem of accurately describing radiative transfer between the surface and the satellite sensor is further complicated by the fact that the surface-leaving radiance itself may also vary with sensor viewing geometry. Physical properties of the surface such as emissivity are known to vary as the zenith angle of observation changes. The proportions of sunlit and shaded areas with the field-of-view of the sensor may also change with viewing geometry depending on the type of cover (eg vegetation), further impacting the surface emissivity.Investigation of the change in surface-leaving radiance as the zenith angle of observation varies is then also important in developing a better understanding of the radiative interaction between the land surface and the atmosphere. The work in this study investigates the atmospheric impacts using surface brightness temperature measurements from the ATSR-2 satellite sensor in combination with atmospheric profile data from radiosondes and estimates of the downwelling sky radiance made by a ground-based radiometer. A line-by-line radiative transfer model is used to model the angular impacts of the atmosphere upon the surfaceleaving radiance. Results from the modelling work show that if the magnitude of the upwelling and downwelling sky radiance and atmospheric transmittance are accurately known then the surface-emitted radiance and hence the LST may be retrieved with negligible error. Guided by the outcomes of the modelling work an atmospheric correction term is derived which accounts for absorption and emission by the atmosphere, and is based on the viewing geometry of the satellite sensor and atmospheric properties characteristic of a semi-arid field site near Alice Springs in the Northern Territory (Central Australia). Ground-based angular measurements of surface brightness temperature made by a scanning, self calibrating radiometer situated at this field site are then used to investigate how the surface-leaving radiance varies over a range of zenith angles comparable to that of the ATSR-2 satellite sensor.Well defined cycles in the angular dependence of surface brightness temperature were observed on both diumal and seasonal timescales in these data. The observed cycles in surface brightness temperature are explained in terms of the interaction between the downwelling sky radiance and the angular dependence of the surface emissivity. The angular surface brightness temperature and surface emissivity information is then applied to derive an LST estimate of high accuracy (approx. 1 K at night and 1-2 K during the day), suitable for the validation of satellite-derived LST measurements. Finally, the atmospheric and land surface components of this work are combined to describe surface-atmosphere interaction at the field site. Algorithms are derived for the satellite retrieval of LST for the nadir and forward viewing geometries of the ATSR-2 sensor, based upon the cycles in the angular dependence of surface brightness temperature observed in situ and the atmospheric correction term developed from the modelling of radiative transfer in the atmosphere. A qualitative assessment of the performance of these algorithms indicates they may obtain comparable accuracy to existing dual angle algorithms (approx. 1.5 K) in the ideal case and an accuracy of 3-4 K in practice, which is limited by knowledge of atmospheric properties (eg downwelling sky radiance and atmospheric transmittance), and the surface emissivity. There are, however, strong prospects of enhanced performance given better estimates of these physical quantities, and if coefficients within the retrieval algorithms are determined over a wider range of observation zenith angles in the future.
27
Zabel, Florian [Verfasser], and Wolfram [Akademischer Betreuer] Mauser. "Land-atmosphere coupling between a land surface hydrological model and a regional climate model / Florian Zabel. Betreuer: Wolfram Mauser." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1029662487/34.
Full text
28
Sgoff, Christine [Verfasser], Juerg [Gutachter] Schmidli, and Roland [Gutachter] Potthast. "Assimilating synthetic land surface temperature in a fully coupled land-atmosphere system / Christine Sgoff ; Gutachter: Juerg Schmidli, Roland Potthast." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2021. http://nbn-resolving.de/urn:nbn:de:hebis:30:3-613301.
Full text
29
Martinez, Agudelo John Alejandro. "On the Hydroclimate of Southern South America: Water Vapor Transport and the Role of Shallow Groundwater on Land-Atmosphere Interactions." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/595679.
Full textAbstract:
The present work focuses on the sources and transport of water vapor to the La Plata Basin (LPB), and the role of groundwater dynamics on the simulation of hydrometeorological conditions over the basin. In the first part of the study an extension to the Dynamic Recycling Model (DRM) is developed to estimate the water vapor transported to the LPB from different regions in South America and the nearby oceans, and the corresponding contribution to precipitation over the LPB. It is found that more than 23% of the precipitation over the LPB is from local origin, while nearly 20% originates from evapotranspiration from the southern Amazon. Most of the moisture comes from terrestrial sources, with the South American continent contributing more than 62% of the moisture for precipitation over the LPB. The Amazonian contribution increases during the positive phase of El Niño and the negative phase of the Antarctic Oscillation. In the second part of the study the effect of a groundwater scheme on the simulation of terrestrial water storage, soil moisture and evapotranspiration (ET) over the LPB is investigated. It is found that the groundwater scheme improves the simulation of fluctuations in the terrestrial water storage over parts of the southern Amazon. There is also an increase in the soil moisture in the root zone over those regions where the water table is closer to the surface, including parts of the western and southern Amazon, and of the central and southern LPB. ET increases in the central and southern LPB, where it is water limited. Over parts of the southeastern Amazon the effects of the groundwater scheme are only observed at higher resolution, when the convergence of lateral groundwater flow in local topographical depressions is resolved by the model. Finally, the effects of the groundwater scheme on near surface conditions and precipitation are explored. It is found that the increase in ET induced by the groundwater scheme over parts of the LPB induces an increase in near surface specific humidity, accompanied by a decrease in near surface temperature. During the dry season, downstream of the regions where ET increases, there is also a slight increase in precipitation, over a region where the model has a dry bias compared with observations. During the early rainy season, there is also an increase in the local convective available potential energy. Over the southern LPB, groundwater induces an increase in ET and precipitation of 13 and 10%, respectively. Over the LPB, the groundwater scheme tends to improve the warm and dry biases of the model. It is suggested that a more realistic simulation of the water table depth could further increase the simulated precipitation during the early rainy season.
30
Nagai, Haruyasu. "Development of a New Atmosphere-Soil-Vegetation Model to Study Heat, Water, and CO2 Exchanges between the Atmosphere and Land-surface." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147889.
Full text
31
Gustafsson, David. "Boreal land surface water and heat balance : Modelling soil-snow-vegetation-atmosphere behaviour." Doctoral thesis, KTH, Mark- och vattenteknik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3406.
Full textAbstract:
The water and heat exchange in thesoil-snow-vegetation-atmosphere system was studied in order toimprove the quantitative knowledge of land surface processes.In this study, numerical simulation models and availabledatasets representing arable land, sub-alpine snowpack, andboreal forest were evaluated at both diurnal and seasonaltimescales. Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden during three winters and two summersfrom 1997 to 2000 within the WINTEX project. A one-dimensionalsimulation model (COUP) was used to simulate the water and heatbalance of the field. Comparison of simulated and measured heatfluxes in winter showed that parameter values governing theupper boundary condition were more important for explainingmeasured fluxes than the formulation of the internal mass andheat balance of the snow cover. The assumption of steady stateheat exchange between the surface and the reference height wasinadequate during stable atmospheric conditions. Independentestimates of the soil heat and water balance together with thecomparison of simulated and measured surface heat fluxes showedthat the eddy-correlation estimates of latent heat fluxes fromthe arable field were on average 40 % too low. The ability of a multi-layered snowpack model (SNTHERM) tosimulate the layered nature of a sub-alpine snowpack wasevaluated based on a dataset from Switzerland. The modelsimulated the seasonal development of snow depth and densitywith high accuracy. However, the models ability to reproducethe strong observed snowpack layering was limited by theneglection of the effect of snow microstructure on snowsettling, and a poor representation of water redistributionwithin the snowpack. The representation of boreal forest in the land surfacescheme used within a weather forecast (ECMWF) model was testedwith a three-year dataset from the NOPEX forest site in centralSweden. The new formulation with separate energy balances forvegetation and the soil/snow beneath the tree cover improvedthe simulation of seasonal and diurnal variations in latent andsensible heat flux. Further improvements of simulated latentheat fluxes were obtained when seasonal variation in vegetationproperties was introduced. Application of the COUP model withthe same dataset showed that simulation of evaporation fromintercepted snow contributed to a better agreement with themeasured sensible heat flux above forests, but also indicatedthat the measurements might have underestimated latent heatflux. The winter sensible heat flux above the forest wasfurther improved if an upper limit of the aerodynamicresistance of 500 s m-1 was applied for stable conditions. A comparison of the water and heat balance of arable landand forest confirmed the general knowledge of the differencesbetween these two surface types. The forest contributed withconsiderably more sensible heat flux to the atmosphere than thearable land in spring and summer due to the lower albedo andrelatively less latent heat flux. Latent heat flux from theforest was higher in winter due to the evaporation ofintercepted snow and rain. The net radiation absorbed by theforest was 60 % higher than that absorbed by the arable land,due to the lower surface albedo in winter. Key words:soil; snow; land surface heat exchange;forest; arable land; eddy-correlation.QC 20100614
32
Sagerfors, Jörgen. "Land-atmosphere exchange of CO₂, water and energy at a boreal minerotrophic mire /." Umeå : Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200704.pdf.
Full text
33
Knist, Sebastian [Verfasser]. "Land-atmosphere interactions in multiscale regional climate change simulations over Europe / Sebastian Knist." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1173789669/34.
Full text
34
Gong, Cuiling 1964. "The role of land-atmosphere-ocean interactions in rainfall variability over West Africa." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38753.
Full text
35
He, Yufeng. "Real-world solutions for improving estimates of land-atmosphere exchanges in heterogeneous landscapes." Thesis, Bangor University, 2016. https://research.bangor.ac.uk/portal/en/theses/realworld-solutions-for-improving-estimates-of-landatmosphere-exchanges-in-heterogeneous-landscapes(5bca7965-6d2d-46ab-8645-82f32dc51fd2).html.
Full textAbstract:
Accurately quantifying land-atmosphere exchanges is essential at every spatial scale, from aiding a better understanding of climate change globally to informing land management decisions at the smallest scale (e.g. agricultural land management). This quantification may be dealt with relatively easily for homogeneous land surfaces, but in the real world, landscapes are spatially heterogeneous and simple approaches are often inadequate. This thesis uses mathematically advanced methods and/or models to find robust solutions to landatmosphere exchange problems that accommodate spatial heterogeneity. A two-stage sampling strategy (2SS) was developed to reduce the uncertainties in the estimation of chamber-based GHG fluxes when sample size is inadequate to fully capture spatial heterogeneity. A Monte Carlo simulation showed that 2SS improves the estimation of soil GHG fluxes in all but the most homogeneous situations, with the improvement being directly related to the amount of spatial heterogeneity present. EC-based measurements of GHG fluxes invariably contain data gaps that require filling to generate long-term cumulative fluxes, i.e. integrating over a temporally heterogeneous timeseries. Gap-filling methods introduce uncertainty. A robust method based on image inpainting is introduced to fill gaps via a two-dimensional representation of a onedimensional data, i.e. the flux fingerprint. Results show that this unsupervised method, using a more compact and simple form, compares favourably with a widely-used traditional method and can outperform it when applied to de-noised data. The most robust measurements of surface carbon fluxes will be generated when using two independent measurement methods simultaneously. To investigate CO2 and CH4 fluxes from a heterogeneous fen, EC- and chamber-based measurements of surface carbon fluxes were implemented from 2013 to 2015. To implement a direct comparison between these measurements made at differing scales, the chamber-measured data were up-scaled, both temporally by model-based interpolations and spatially by flux footprint modelling. Results show a good linear correlation in CO2 flux and a near zero correlation in CH4 flux between methods. Further analysis on CH4 flux, however, show that the two differed only by a Gaussian distribution, implying the existence of white noise in the signal. The cumulative CO2 flux for the whole season measured by chambers was -376.5 g/m2, 33% higher than the estimated measured by EC (-281.8 g/m2). Similarly, the final cumulative CH4 flux was 4.01 g/m2 by chamber-based estimates, 43% more than EC (2.81 g/m2). The final part of this study investigates the surface flux of momentum in a structured heterogeneous land surface. A logarithmic normal distribution was developed to model the wind speed reduction around a tree-based windbreak. The model showed an excellent fit to field observations made at a real-world windbreak on farm land. A graphical method that describes a 3-d space of wind-chill temperature vs. ambient temperature and wind speed was created to quantify the potential thermal benefits gained by introducing windbreaks and reducing wind speed. The wind-chill thermal tolerance (WTT) of sheep was estimated and compared for a lowland and an upland site. Distinct differences to reduced wind speed were found between the sites, with greater thermal benefits at the upland site. The methods and models generated and developed in this study contribute to an improved quantification of land-atmosphere exchanges, and have potential to be applied to surface fluxes generally, either of mass (GHGs) or energy (heat, momentum), and to landscapes other than those dominated by vegetation. For example, the statistical idea of the two-stage sampling approach provides a generic solution to sample size deficiency in heterogeneous land surfaces; The inpainting-based gap-filling method, as an image processing technique, may be applicable to any signals that can be represented as an image, i.e. a two-dimensional space in which individual locations (pixels) have numerical attributes that can be used as RGB values; The WTT plot/analysis, used here in the context of sheep in upland sites, provides an intuitive and powerful scheme for analysing the thermal tolerance of any animal in any energetically heterogeneous landscape.
36
McAtee, Brendon Kynnie. "Surface-atmosphere interactions in the thermal infrared (8 - 14um)." Curtin University of Technology, Department of Applied Physics, 2003. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14481.
Full textAbstract:
Remote sensing of land surface temperature (LST) is a complex task. From a satellite-based perspective the radiative properties of the land surface and the atmosphere are inextricably linked. Knowledge of both is required if one is to accurately measure the temperature of the land surface from a space-borne platform. In practice, most satellite-based sensors designed to measure LST over the surface of the Earth are polar orbiting. They scan swaths of the order of 2000 km, utilizing zenith angles of observation of up to 60°. As such, satellite viewing geometry is important when comparing estimates of LST between different overpasses of the same point on the Earth's surface. In the case of the atmosphere, the optical path length through which the surfaceleaving radiance propagates increases with increasing zenith angle of observation. A longer optical path may in turn alter the relative contributions which molecular absorption and emission processes make to the radiance measured at the satellite sensor. A means of estimating the magnitudes of these radiative components in relation to the viewing geometry of the satellite needs to be developed if their impacts on the at-sensor radiance are to be accurately accounted for. The problem of accurately describing radiative transfer between the surface and the satellite sensor is further complicated by the fact that the surface-leaving radiance itself may also vary with sensor viewing geometry. Physical properties of the surface such as emissivity are known to vary as the zenith angle of observation changes. The proportions of sunlit and shaded areas with the field-of-view of the sensor may also change with viewing geometry depending on the type of cover (eg vegetation), further impacting the surface emissivity.Investigation of the change in surface-leaving radiance as the zenith angle of observation varies is then also important in developing a better understanding of the radiative interaction between the land surface and the atmosphere. The work in this study investigates the atmospheric impacts using surface brightness temperature measurements from the ATSR-2 satellite sensor in combination with atmospheric profile data from radiosondes and estimates of the downwelling sky radiance made by a ground-based radiometer. A line-by-line radiative transfer model is used to model the angular impacts of the atmosphere upon the surfaceleaving radiance. Results from the modelling work show that if the magnitude of the upwelling and downwelling sky radiance and atmospheric transmittance are accurately known then the surface-emitted radiance and hence the LST may be retrieved with negligible error. Guided by the outcomes of the modelling work an atmospheric correction term is derived which accounts for absorption and emission by the atmosphere, and is based on the viewing geometry of the satellite sensor and atmospheric properties characteristic of a semi-arid field site near Alice Springs in the Northern Territory (Central Australia). Ground-based angular measurements of surface brightness temperature made by a scanning, self calibrating radiometer situated at this field site are then used to investigate how the surface-leaving radiance varies over a range of zenith angles comparable to that of the ATSR-2 satellite sensor.
Well defined cycles in the angular dependence of surface brightness temperature were observed on both diumal and seasonal timescales in these data. The observed cycles in surface brightness temperature are explained in terms of the interaction between the downwelling sky radiance and the angular dependence of the surface emissivity. The angular surface brightness temperature and surface emissivity information is then applied to derive an LST estimate of high accuracy (approx. 1 K at night and 1-2 K during the day), suitable for the validation of satellite-derived LST measurements. Finally, the atmospheric and land surface components of this work are combined to describe surface-atmosphere interaction at the field site. Algorithms are derived for the satellite retrieval of LST for the nadir and forward viewing geometries of the ATSR-2 sensor, based upon the cycles in the angular dependence of surface brightness temperature observed in situ and the atmospheric correction term developed from the modelling of radiative transfer in the atmosphere. A qualitative assessment of the performance of these algorithms indicates they may obtain comparable accuracy to existing dual angle algorithms (approx. 1.5 K) in the ideal case and an accuracy of 3-4 K in practice, which is limited by knowledge of atmospheric properties (eg downwelling sky radiance and atmospheric transmittance), and the surface emissivity. There are, however, strong prospects of enhanced performance given better estimates of these physical quantities, and if coefficients within the retrieval algorithms are determined over a wider range of observation zenith angles in the future.
37
Fischer, Erich Markus. "The role of land-atmosphere interactions for European summer heat waves : past, present and future /." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:30604.
Full text
38
Jang, Eun-Hwa. "Source identification and reactivity study on atmosphere polycyclic aromatic hydrocarbons." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5648/.
Full textAbstract:
Polycyclic aromatic hydrocarbons (PAH) are ubiquitous compounds produced through incomplete combustion processes from various sources in different proportions. They are of concern because of their recognized mutagenic and carcinogenic properties. There are a number of receptor modelling (RM) studies that identify sources of urban atmospheric PAH, despite concerns over the application of RM to the relatively reactive PAH. This thesis utilizes Positive Matrix Factorization (PMF) with extensive PAH datasets, and compares the results with local and national emission inventories. An atmospheric chemical reactivity study for PAH is also investigated; highlighting the importance of taking reactivity into consideration when applying source apportionment models. The results demonstrate that traffic sources are significantly responsible for the PAH mass (∑PAH) at UK urban sites throughout the year. A substantial fraction of benzo[a]pyrene emissions was apportioned to solid fossil fuel combustion sources, showing significant seasonal variations. A conceptual simulation of PAH ratios has been investigated using urban and rural data. Results were in good agreement between simulated ratios and empirically obtained values. The results provide a better understanding of PAH reactivity and their atmospheric fate, indicating the potential for long-range transport of high molecular weight PAH.
39
Morrison, Ross David. "Land/atmosphere carbon dioxide exchange at semi-natural and regenerating peatlands in East Anglia, UK." Thesis, University of Leicester, 2013. http://hdl.handle.net/2381/27972.
Full textAbstract:
This thesis presents the first direct flux measurements of land/atmosphere carbon dioxide (CO[subscript 2]) exchange at managed lowland peatlands in the East Anglian Fens, UK. The dynamics and magnitude of land/atmosphere CO[subscript 2] exchange were quantified at semi-natural and regenerating ex-arable fens located at the Wicken Fen Nature Reserve in Cambridgeshire. Eddy covariance measurements were made at the semi-natural fen throughout two thermally and hydrologically dissimilar periods during 2009 and 2010, and at the regenerating former-arable fen over the complete annual cycle of 2010. The study sites were characterised by strong seasonal variation in CO[subscript 2] exchange. The semi-natural fen was a net source of 85.47±25.78 g CO[subscript 2]-C m[superscript -2] between 20th March and 31st December 2009, and a small net sink of -22.66±18.85 g CO[subscript 2]-C m[superscript -2] for the same period of 2010. Photosynthesis and ecosystem respiration were both higher during warm conditions of 2009 compared to 2010, but enhanced rates of ecosystem production were outweighed by large CO[subscript 2] losses during warm and dry conditions in autumn. The large interannual variability in CO[subscript 2] exchange illustrates the sensitivity of semi-natural fens to climatic variability and change, and highlights the need to maintain high water levels to prevent large losses of soil carbon to the atmosphere as CO[subscript 2]. The regenerating fen functioned as a small net source of 21.24±17.11 g CO[subscript 2]-C m[superscript -2] yr[superscript -1]. On the basis of values currently used to represent CO[subscript 2] losses from arable fens, the annual CO[subscript 2] balance for the ex-arable fen in 2010 indicates the net CO[subscript 2] benefit of fenland rehabilitation was an avoided loss of -87.7±17.11g CO[subscript 2]-C m[superscript -2] yr[superscript -1]. The results from the regenerating site imply that a more adaptive water management strategy will be needed if the environmental conditions required for peat formation and net carbon capture are to be restored.
40
Biasutti, Michela. "On the annual cycle over the atlantic sector : the relative role of land and ocean. /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10016.
Full text
41
Liu, Shuguang, Ben Bond-Lamberty, Lena R. Boysen, James D. Ford, Andrew Fox, Kevin Gallo, Jerry Hatfield, et al. "Grand Challenges in Understanding the Interplay of Climate and Land Changes." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/624354.
Full textAbstract:
Half of Earth's land surface has been altered by human activities, creating various consequences on the climate and weather systems at local to global scales, which in turn affect a myriad of land surface processes and the adaptation behaviors. This study reviews the status and major knowledge gaps in the interactions of land and atmospheric changes and present 11 grand challenge areas for the scientific research and adaptation community in the coming decade. These land-cover and land-use change (LCLUC)-related areas include 1) impacts on weather and climate, 2) carbon and other biogeochemical cycles, 3) biospheric emissions, 4) the water cycle, 5) agriculture, 6) urbanization, 7) acclimation of biogeochemical processes to climate change, 8) plant migration, 9) land-use projections, 10) model and data uncertainties, and, finally, 11) adaptation strategies. Numerous studies have demonstrated the effects of LCLUC on local to global climate and weather systems, but these putative effects vary greatly in magnitude and even sign across space, time, and scale and thus remain highly uncertain. At the same time, many challenges exist toward improved understanding of the consequences of atmospheric and climate change on land process dynamics and services. Future effort must improve the understanding of the scale-dependent, multifaceted perturbations and feedbacks between land and climate changes in both reality and models. To this end, one critical cross-disciplinary need is to systematically quantify and better understand measurement and model uncertainties. Finally, LCLUC mitigation and adaptation assessments must be strengthened to identify implementation barriers, evaluate and prioritize opportunities, and examine how decisionmaking processes work in specific contexts.
42
Zhang, Chi Tian Hanqin. "Terrestrial carbon dynamics of southern United States in response to changes in climatic, atmosphere, and land-use/land cover from 1895 to 2005." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Forestry_and_Wildlife_Sciences/Dissertation/Zhang_Chi_13.pdf.
Full text
43
Sanchez-Mejia, Zulia M. "Monsoon dependent ecosystems| Implications of the vertical distribution of soil moisture on land surface-atmosphere interactions." Thesis, The University of Arizona, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3590060.
Full textAbstract:
Uncertainty of predicted change in precipitation frequency and intensity motivates the scientific community to better understand, quantify, and model the possible outcome of dryland ecosystems. In pulse dependent ecosystems (i.e. monsoon driven) soil moisture is tightly linked to atmospheric processes. Here, I analyze three overarching questions; Q1) How does soil moisture presence or absence in a shallow or deep layer influence the surface energy budget and planetary boundary layer characteristics?, Q2) What is the role of vegetation on ecosystem albedo in the presence or absence of deep soil moisture?, Q3) Can we develop empirical relationships between soil moisture and the planetary boundary layer height to help evaluate the role of future precipitation changes in land surface atmosphere interactions? . To address these questions I use a conceptual framework based on the presence or absence of soil moisture in a shallow or deep layer. I define these layers by using root profiles and establish soil moisture thresholds for each layer using four years of observations from the Santa Rita Creosote Ameriflux site. Soil moisture drydown curves were used to establish the shallow layer threshold in the shallow layer, while NEE (Net Ecosystem Exchange of carbon dioxide) was used to define the deep soil moisture threshold. Four cases were generated using these thresholds: Case 1, dry shallow layer and dry deep layer; Case 2, wet shallow layer and dry deep layer; Case 3, wet shallow layer and wet deep layer, and Case 4 dry shallow and wet deep layer. Using this framework, I related data from the Ameriflux site SRC (Santa Rita Creosote) from 2008 to 2012 and from atmospheric soundings from the nearby Tucson Airport; conducted field campaigns during 2011 and 2012 to measure albedo from individual bare and canopy patches that were then evaluated in a grid to estimate the influence of deep moisture on albedo via vegetation cover change; and evaluated the potential of using a two-layer bucket model and empirical relationships to evaluate the link between deep soil moisture and the planetary boundary layer height under changing precipitation regime. My results indicate that (1) the presence or absence of water in two layers plays a role in surface energy dynamics, (2) soil moisture presence in the deep layer is linked with decreased ecosystem albedo and planetary boundary layer height, (3) deep moisture sustains vegetation greenness and decreases albedo, and (4) empirical relationships are useful in modeling planetary boundary layer height from dryland ecosystems. Based on these results we argue that deep soil moisture plays an important role in land surface-atmosphere interactions.
44
Hill, Timothy C. "A modelling approach to carbon, water and energy feedbacks and interactions across the land-atmosphere interface." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/2201.
Full textAbstract:
The climate is changing and the rate of this change is expected to increase. In the 20th century global surface temperatures rose by 0.6 (±0.2) K. Based on current model predictions, and economic forecasts, global temperature increases of 1.4 to 5.8 K are expected over the period 1990 – 2100. One of the main drivers for this temperature increase is the build up of CO2 in the atmosphere which has been increasing since pre-industrial times. Pre-industrial concentrations of CO2 were bounded between 180 ppm and 300 ppm, however the current concentrations of 380 ppm are far in excess of these bounds. Further more, forecasts indicates that a further doubling in the next century is a distinct possibility. However making predictions about the future climate is difficult. Predicting the trajectory that the climate will take uses assumptions of economic growth, technological advances and ecological and physical processes. If we are to make informed decisions regarding the future of the planet, we have to account not only for future anthropogenic emissions and land use, but we also have to identify the response of the Earth system. By its very nature the Earth is immensely complex; processes, interactions and feedbacks exist which operate on vastly different spatial and temporal scales. Each of these processes has an associated level of uncertainty. This uncertainty propagates through models and the processes and feedbacks they simulate. One of our jobs as environmental scientists is to quantify and then reduce these uncertainties. Consequently it is critical to quantify the interactions of the land-surface and the atmosphere. The role of the land-surface is critical to the response of the Earth’s climate. All general circulation models and regional scale models need representations of the land-surface. A lot of the work concerning the land-surface aims to determine the land-surface partitioning of energy, the evapotranspiration of water and if the land-surface is a sink or a source of CO2. To do achieve this we need to understand (1) the underlying processes governing the response of the land-surface, (2) the response of these processes to perturbations from climate change and humans, (3) the temporal and spatial heterogeneity in these processes, and (4) the feedbacks that land-surface processes have with the climate. In this thesis I use a coupled atmosphere-biosphere model to show current understanding of the carbon, water and energy dynamics of the biosphere and the atmosphere to be consistent with both PBL and stand-based measurements. I then use the CAB model to investigate the strength of different feedbacks between the atmosphere and biosphere. Finally the model is then used in a Monte Carlo Bayesian inversion scheme to invert atmospheric measurements to infer information about surface parameters.
45
Liang, Chun Xia. "Can planting trees make it rain?: the impact of trees on precipitation through land-atmosphere feedback." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/11686.
Full textAbstract:
Land surface atmosphere feedback is the interaction between land and atmosphere. Three studies have been conducted to investigate the vegetation-rainfall feedback. The first study is to detect the signal of land cover change from rainfall data in two regions in the Murray Darling Basin (MDB) with known land surface intervention. A semi-parametric regression model and a regression model with non-parametric step trend test are applied to identify changes in rainfall data and correlate these changes to land cover intervention. Both methods have identified some rainfall changes in the Snowy Mountain ranges in NSW/VIC after the 2003 severe bushfires in this area. A simple model, “CLASS”, is used in the second study to simulate day time boundary layer dynamics and atmospheric conditions. The model is applied to Kyeamba (short grasses) and Tumbarumba (Eucalyptus forest), during 09 - 11 November, 2006. Sensitivity experiments do not find a preferential land cover type for the lifting condensation level. Even though latent heat flux and humidity are usually higher over forest, the boundary layer development over forest is not significantly stronger than the grassland. In the last study, rainfall sensitivity to land surface conditions is assessed using a simple equilibrium model. A Sobol’s sensitivity analysis shows the lateral moisture fluxes have the highest impact on rainfall, followed by initial soil moisture and initial LAI. Afforestation cannot enhance long term summer precipitation in the MDB, unless there is a constant supply of high lateral moisture. The current research does not find a strong relationship between the forest and precipitation. Loss of tree covers might decrease precipitation in some areas of the MDB but this relation is not significant, especially in areas with low rainfall. High moisture convergence is required for afforestation to affect rainfall.
46
Sanchez-Mejia, Zulia Mayari. "Monsoon Dependent Ecosystems: Implications of the Vertical Distribution of Soil Moisture on Land Surface-Atmosphere Interactions." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/299116.
Full textAbstract:
Uncertainty of predicted change in precipitation frequency and intensity motivates the scientific community to better understand, quantify, and model the possible outcome of dryland ecosystems. In pulse dependent ecosystems (i.e. monsoon driven) soil moisture is tightly linked to atmospheric processes. Here, I analyze three overarching questions; Q1) How does soil moisture presence or absence in a shallow or deep layer influence the surface energy budget and planetary boundary layer characteristics?, Q2) What is the role of vegetation on ecosystem albedo in the presence or absence of deep soil moisture?, Q3) Can we develop empirical relationships between soil moisture and the planetary boundary layer height to help evaluate the role of future precipitation changes in land surface atmosphere interactions?. To address these questions I use a conceptual framework based on the presence or absence of soil moisture in a shallow or deep layer. I define these layers by using root profiles and establish soil moisture thresholds for each layer using four years of observations from the Santa Rita Creosote Ameriflux site. Soil moisture drydown curves were used to establish the shallow layer threshold in the shallow layer, while NEE (Net Ecosystem Exchange of carbon dioxide) was used to define the deep soil moisture threshold. Four cases were generated using these thresholds: Case 1, dry shallow layer and dry deep layer; Case 2, wet shallow layer and dry deep layer; Case 3, wet shallow layer and wet deep layer, and Case 4 dry shallow and wet deep layer. Using this framework, I related data from the Ameriflux site SRC (Santa Rita Creosote) from 2008 to 2012 and from atmospheric soundings from the nearby Tucson Airport; conducted field campaigns during 2011 and 2012 to measure albedo from individual bare and canopy patches that were then evaluated in a grid to estimate the influence of deep moisture on albedo via vegetation cover change; and evaluated the potential of using a two-layer bucket model and empirical relationships to evaluate the link between deep soil moisture and the planetary boundary layer height under changing precipitation regime. My results indicate that (1) the presence or absence of water in two layers plays a role in surface energy dynamics, (2) soil moisture presence in the deep layer is linked with decreased ecosystem albedo and planetary boundary layer height, (3) deep moisture sustains vegetation greenness and decreases albedo, and (4) empirical relationships are useful in modeling planetary boundary layer height from dryland ecosystems. Based on these results we argue that deep soil moisture plays an important role in land surface-atmosphere interactions.
47
Sakaguchi, Koichi. "Spatiotemporal Scale Limits and Roles of Biogeochemical Cycles in Climate Predictions." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/268598.
Full textAbstract:
There is much confidence in the global temperature change and its attribution to human activities. Global climate models have attained unprecedented complexity in representing the climate system and its response to external forcings. However, climate prediction remains a serious challenge and carries large uncertainty, particularly when the scale of interest becomes small. With the increasing interest in regional impact studies for decision-making, one of the urgent tasks is to make a systematic, quantitative evaluation of the expected skill of climate models over a range of spatiotemporal scales. The first part of this dissertation was devoted to this task, with focus on the predictive skill in the linear trend of surface air temperature. By evaluating the hindcasts for the last 120 year period in the form of deterministic and probabilistic predictions, it was found that the hindcasts can reproduce broad-scale changes in the surface air temperature, showing reliable skill at spatial scales larger than or equal to a few thousand kilometers (30° x 30°) and at temporal scales of 30 years or longer. However, their skill remains limited at smaller spatiotemporal scales, where we saw no significant improvement over climatology or a random guess. Over longer temporal scales, the feedbacks from the carbon cycle to atmospheric CO₂ concentration become important. Therefore the rest of the dissertation attempts to find key processes in the climate-carbon cycle feedback using one of the leading land-climate models, the National Center for Atmospheric Research Community Land Model. Evaluation of site-level simulations using field observations from the Amazon forest revealed that the current formulation for drought-related mortality, which lacks the ecophysiological link between short- and long-term drought stress, prevent the model from simulating realistic forest response. Global simulations showed that such dynamics of vegetation strongly influences the control of the nitrogen cycle on vegetation productivity, which then alters the sensitivity of the terrestrial biosphere to surface air temperature. This implies that if the state of the terrestrial biosphere is inconsistent with the simulated climate, either biased or prescribed, then its feedback to anthropogenic forcing could be also inconsistent.
48
Wang, Zhaomin. "A simple coupled atmosphere-ocean-sea ice-land surface-ice sheet model for climate and paleoclimate studies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0020/NQ55391.pdf.
Full text
49
Wang, Zhaomin 1963. "A simple coupled atmosphere-ocean-sea ice-land surface-ice sheet model for climate and paleoclimate studies /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36068.
Full textAbstract:
We develop a new coupled atmosphere-ocean-sea ice-land surface-ice sheet model for long-term climate change studies. This five-component model incorporates the seasonal cycle, and the three major ocean basins, the Antarctic Circumpolar Current region and the major continents are resolved. The model variables are sectorially averaged across the different ocean basins and continents.The above coupled model (less the ice sheet component) is first used to simulate the major features of the present day climate. In a global warming (cooling) experiment, the thermohaline circulation (THC) in the North Atlantic Ocean is weakened (intensified) due to the increased (reduced) moisture transport to, and warmer (cooler) sea surface temperatures at northern high latitudes.
Secondly, the above four-component model is employed to investigate the initiation of glaciation, which is accomplished by reducing the solar radiation and increasing the planetary emissivity only in high northern latitudes. When land ice is growing, the THC in the North Atlantic Ocean is intensified, resulting in a warm subpolar North Atlantic Ocean. The intensified THC maintains a large land-ocean thermal contrast at high latitudes, which leads to enhanced land ice accumulation. We conclude that increased fresh water or massive iceberg discharge from land is responsible for a weak or collapsed THC.
Lastly, a dynamic ice sheet model is coupled to the above four-component model. Sensitivity experiments show that a smaller lateral (east-west) ice discharge rate maintains a larger ice volume and extent in our model. Also, a reduced atmospheric CO2 concentration, which is parameterized as an increased planetary emissivity, may lead to the expansion of the ice sheets and hence a larger ice volume and extent. A simple iceberg calving scheme is next introduced to investigate ice sheet-THC interactions on the millennial timescale. We find that the longer the duration of iceberg calving, the longer the time that must elapse before the next calving event can occur. Also, it is shown that the strength of the THC in the North Atlantic Ocean is very sensitive to the discharge rate of the ice sheets. This makes the simulation of the interactions between ice sheets and the THC extremely challenging.
50
Wang, Zhuo. "Using MODIS BRDF/Albedo Data to Evaluate and Improve Land Surface Albedo in Weather and Climate Models." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/195109.
Full textAbstract:
Land surface albedo plays a key role in the surface-atmosphere internaction, because it greatly influences the shortwave radiation absorbed by the surface. Surface albedo depends on soil characteristics and vegetation types. Error in the specification of albedos of soil and vegetation may cause biases in the computation of ground temperature and surface fluxes, therefore accurate albedo estimates are essential for an accurate simulation of the Earth's climate. The study demonstrates the importance of MODIS data in assessing and improving albedo parameterization in weather forecast and climate models as well as the remote sensing retrieval of surface solar fluxes through a series of three papers. First, the NCAR Community Climate System Model (CCSM2) albedo is evaluated using the MODIS BRDF and albedo data. The model and MODIS albedo differences are related to the deficiences in the model simulation of snow cover and soil moisture and in the model's specification of leaf and stem area indexes. They are also partially caused by the deficiency of the two-stream method. Second, motivated by these analyses, a new formulation for surface albedo is developed. Over desert, most land models assume that the bare soil albedo is a function of soil color and soil moisture but independent of solar zenith angle (SZA). However, analysis of MODIS BRDF/albedo data and in situ data indicates that bare soil albedo does vary with SZA. Furthermore this SZA dependence is found to affect the surface energy fluxes and temperature in the offline land surface model sensitivity tests. Finally, the MODIS BRDF algorithm is reformulated to derive a new two-parameter scheme for the computation of land surface albedo and its SZA dependence for use in weather and climate models as well as the remote sensing retrieval of surface solar fluxes. In this formulation, the season- and pixel-dependent black-sky albedo at 60 deg SZA can be directly prescribed using the MODIS BRDF data while the two parameters are taken as a function of vegetation type only. Comparison of this formulation with those used in weather, climate, and data assimilation models (at NCAR, NCEP, and NASA) as well as those used in remote sensing groups (University of Maryland, ISCCP-FD, and CERES/TRMM) reveals the deficiencies in the land surface albedo treatment in these models and remote sensing retrieval algorithm along with suggestions for improvement.