Dissertations / Theses: 'Land surface - atmosphere interactions'

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Kelly, Patrick. "Evaluation of Land-Atmosphere Interactions in Models of the North American Monsoon." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_theses/118.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Evans, Jason Peter, and jason evans@yale edu. "Modelling Climate - Surface Hydrology Interactions in Data Sparse Areas." The Australian National University. Centre for Resource and Environmental Studies, 2000. http://thesis.anu.edu.au./public/adt-ANU20020313.032142.

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The interaction between climate and land-surface hydrology is extremely important in relation to long term water resource planning. This is especially so in the presence of global warming and massive land use change, issues which seem likely to have a disproportionate impact on developing countries. This thesis develops tools aimed at the study and prediction of climate effects on land-surface hydrology (in particular streamflow), which require a minimum amount of site specific data. This minimum data requirement allows studies to be performed in areas that are data sparse, such as the developing world. ¶ A simple lumped dynamics-encapsulating conceptual rainfall-runoff model, which explicitly calculates the evaporative feedback to the atmosphere, was developed. It uses the linear streamflow routing module of the rainfall-runoff model IHACRES, with a new non-linear loss module based on the Catchment Moisture Deficit accounting scheme, and is referred to as CMD-IHACRES. In this model, evaporation can be calculated using a number of techniques depending on the data available, as a minimum, one to two years of precipitation, temperature and streamflow data are required. The model was tested on catchments covering a large range of hydroclimatologies and shown to estimate streamflow well. When tested against evaporation data the simplest technique was found to capture the medium to long term average well but had difficulty reproducing the short-term variations. ¶ A comparison of the performance of three limited area climate models (MM5/BATS, MM5/SHEELS and RegCM2) was conducted in order to quantify their ability to reproduce near surface variables. Components of the energy and water balance over the land surface display considerable variation among the models, with no model performing consistently better than the other two. However, several conclusions can be made. The MM5 longwave radiation scheme performed worse than the scheme implemented in RegCM2. Estimates of runoff displayed the largest variations and differed from observations by as much as 100%. The climate models exhibited greater variance than the observations for almost all the energy and water related fluxes investigated. ¶ An investigation into improving these streamflow predictions by utilizing CMD-IHACRES was conducted. Using CMD-IHACRES in an 'offline' mode greatly improved the streamflow estimates while the simplest evaporation technique reproduced the evaporative time series to an accuracy comparable to that obtained from the limited area models alone. The ability to conduct a climate change impact study using CMD-IHACRES and a stochastic weather generator is also demonstrated. These results warrant further investigation into incorporating the rainfall-runoff model CMD-IHACRES in a fully coupled 'online' approach.

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Gao, Xiaogang. "Modeling of rainfall distribution, hydrologic processes and examination of model sensitivity in the context of atmosphere-land surface interactions." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186563.

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In order to improve current climate models, two issues have been recognized to be significant: (1) properly representing the precipitation distribution within a GCM grid square, (2) evaluating and improving the existing land surface hydrologic schemes. This dissertation is devoted to these issues. Precipitation affects the climate system in a variety of ways and occurs over areas that are usually smaller than the GCM grid square. This complicates the modeling of land surface processes. There are, however, stable seasonal statistical patterns underlying the observed data for a GCM grid square. A stochastic scheme was therefore proposed for the assimilation of the statistical patterns (extracted from historical data) into the land surface scheme to enhance the simulation. The required high resolution precipitation data may be obtained from satellite imagery for global application. Systematic sensitivity analyses for the Biosphere-Atmosphere Transfer Scheme (BATS) was described in this dissertation. Two types of experiments were conducted to examine the BATS performance. The first type consisted of varying 'perturbation variables' and exploring corresponding variations in energy/water states and fluxes. The employed method stressed (1) long term and multiple measures of model behavior, (2) the dominant processes under certain conditions and the proper ranges for model parameters estimates. The second type experiments applied BATS to a GCM grid covering the Lower Colorado River Basin and examined the effect of intragrid variability on land surface hydrology. The results from different spatial resolutions are compared. BATS sensitivity to initialization, atmospheric forcings, land surface properties and the computational grid size are discussed.

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Bartlett, Paul Alexander. "Modelling with CLASS, representing surface-atmosphere interaction in temperate and boreal forests using the Canadian Land Surface Scheme." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65664.pdf.

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Parsakhoo, Zahra Sadat [Verfasser], Yaping [Gutachter] Shao, and Hendrik [Gutachter] Elbern. "Modelling Multi-Scale Atmosphere And Land-Surface Interactions-A Large-Ensemble Approach- / Zahra Sadat Parsakhoo ; Gutachter: Yaping Shao, Hendrik Elbern." Köln : Universitäts- und Stadtbibliothek Köln, 2019. http://d-nb.info/1202920306/34.

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16

Luo, Yan. "Regional aspects of the North American land surface-atmosphere interactions and their contributions to the variability and predictability of the regional hydrologic cycle." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3408.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.
Thesis research directed by: Atmospheric and Oceanic Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Sanchez-Mejia, Zulia Mayari, and Shirley A. Papuga. "Empirical Modeling of Planetary Boundary Layer Dynamics Under Multiple Precipitation Scenarios Using a Two-Layer Soil Moisture Approach: An Example From a Semiarid Shrubland." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626481.

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In semiarid regions, where water resources are limited and precipitation dynamics are changing, understanding land surface-atmosphere interactions that regulate the coupled soil moisture-precipitation system is key for resource management and planning. We present a modeling approach to study soil moisture and albedo controls on planetary boundary layer height (PBLh). We used Santa Rita Creosote Ameriflux and Tucson Airport atmospheric sounding data to generate empirical relationships between soil moisture, albedo, and PBLh. Empirical relationships showed that similar to 50% of the variation in PBLh can be explained by soil moisture and albedo with additional knowledge gained by dividing the soil profile into two layers. Therefore, we coupled these empirical relationships with soil moisture estimated using a two-layer bucket approach to model PBLh under six precipitation scenarios. Overall we observed that decreases in precipitation tend to limit the recovery of the PBL at the end of the wet season. However, increases in winter precipitation despite decreases in summer precipitation may provide opportunities for positive feedbacks that may further generate more winter precipitation. Our results highlight that the response of soil moisture, albedo, and the PBLh will depend not only on changes in annual precipitation, but also on the frequency and intensity of this change. We argue that because albedo and soil moisture data are readily available at multiple temporal and spatial scales, developing empirical relationships that can be used in land surface-atmosphere applications have great potential for exploring the consequences of climate change.

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Klein, Cornelia [Verfasser], and Harald [Akademischer Betreuer] Kunstmann. "Interactions of regional atmospheric and land surface processes with the West African monsoon system / Cornelia Klein ; Betreuer: Harald Kunstmann." Augsburg : Universität Augsburg, 2017. http://d-nb.info/1127528130/34.

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Ardilouze, Constantin. "Impact de l'humidité du sol sur la prévisibilité du climat estival aux moyennes latitudes." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0048/document.

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Les épisodes de sécheresse et de canicule qui frappent épisodiquement les régions tempérées ont des conséquences préjudiciables sur les plans sanitaire, économique, social et écologique. Afin de pouvoir enclencher des stratégies de préparation et de prévention avec quelques semaines ou mois d'anticipation, les attentes sociétales en matière de prévision sont élevées, et ce d'autant plus que les projections climatiques font craindre la multiplication de ces épisodes au cours du 21ème siècle. Néanmoins, la saison d'été est la plus difficile à prévoir aux moyennes latitudes. Les sources connues de prévisibilité sont plus ténues qu'en hiver et les systèmes de prévision climatique actuels peinent à représenter correctement les mécanismes de téléconnexion associés. Un nombre croissant d'études a mis en évidence un lien statistique dans certaines régions entre l'humidité du sol au printemps et les températures et précipitations de l'été qui suit. Ce lien a été partiellement confirmé dans des modèles numériques de climat mais de nombreuses interrogations subsistent. L'objectif de cette thèse est donc de mieux comprendre le rôle joué par l'humidité du sol sur les caractéristiques et la prévisibilité du climat de l'été dans les régions tempérées. Grâce notamment au modèle couplé de circulation générale CNRM-CM, nous avons mis en œuvre des ensembles de simulations numériques qui nous ont permis d'évaluer le degré de persistance des anomalies d'humidité du sol printanière. En effet, une longue persistance est une condition nécessaire pour que ces anomalies influencent le climat à l'échelle de la saison, via le processus d'évapotranspiration de la surface. En imposant dans notre modèle des conditions initiales et aux limitées idéalisées d'humidité du sol, nous avons mis en évidence des régions du globe pour lesquelles l'état moyen et la variabilité des températures et des précipitations en été sont particulièrement sensibles à ces conditions. C'est notamment le cas sur une grande partie de l'Europe et de l'Amérique du nord, y compris à des latitudes élevées. Pour toutes ces régions, l'humidité du sol est une source prometteuse de prévisibilité potentielle du climat à l'horizon saisonnier, bien que de fortes incertitudes demeurent localement sur le degré de persistance de ses anomalies. Une expérience de prévisibilité effective coordonnée avec plusieurs systèmes de prévision montre qu'une initialisation réaliste de l'humidité du sol améliore la prévision de températures estivales principalement dans le sud-est de l'Europe. Dans d'autres régions, comme l'Europe du Nord, le désaccord des modèles provient de l'incertitude sur la persistance des anomalies d'humidité du sol. En revanche, sur les Grandes Plaines américaines, aucun modèle n'améliore ses prévisions qui restent donc très médiocres. La littérature ainsi que nos évaluations de sensibilité du climat à l'humidité du sol ont pourtant identifié cette région comme un "hotspot" du couplage entre l'humidité du sol et l'atmosphère. Nous supposons que l'échec de ces prévisions est une conséquence des forts biais chauds et secs présents dans tous les modèles sur cette région en été, qui conduisent à un dessèchement excessif des sols. Pour le vérifier, nous avons développé une méthode qui corrige ces biais au cours de l'intégration des prévisions avec CNRM-CM6. Les prévisions qui en résultent sont nettement améliorées sur les Grandes Plaines. La compréhension de l'origine des biais continentaux en été et leur réduction dans les prochaines générations de modèles de climat sont des étapes essentielles pour tirer le meilleur parti de l'humidité du sol comme source de prévisibilité saisonnière dans les régions tempérées
Severe heat waves and droughts that episodically hit temperate regions have detrimental consequences on health, economy and society. The design and deployment of efficient preparedness strategies foster high expectations for the prediction of such events a few weeks or months ahead. Their likely increased frequency throughout the 21st century, as envisaged by climate projections, further emphasizes these expectations. Nevertheless, the summer season is the most difficult to predict over mid-latitudes. Well-known sources of predictability are weaker than in winter and current climate prediction systems struggle to adequately represent associated teleconnection mechanisms. An increasing number of studies have shown a statistical link over some regions between spring soil moisture and subsequent summer temperature and precipitation. This link has been partly confirmed in climate numerical models, but many questions remain. The purpose of this PhD thesis is to better understand the role played by soil moisture onthe characteristics and predictability of the summer climate in temperate regions. By means of the CNRM-CM coupled general circulation model, we have designed a range of numerical simulations which help us evaluate the persistence level of spring soil moisture anomalies. Indeed, a long persistence is a necessary condition for these anomalies to influence the climate at the seasonal scale, through the process of evapotranspiration. By imposing in our model idealized initial and boundary soil moisture conditions, we have highlighted areas of the globe for which the average state and the variability of temperatures and precipitation in summer is particularly sensitive to these conditions. This is the case in particular for Europe and North America, including over high latitudes. Soil moisture is therefore a promising source of potential seasonal climate predictability for these regions, although the persistence of soil moisture anomalies remains locally very uncertain. An effective predictability coordinated experiment, bringing together several prediction systems, shows that a realistic soil moisture initialization improves the forecast skill of summer temperatures mainly over southeast Europe. In other regions, such as Northern Europe, the disagreement between models comes from uncertainty about the persistence of soil moisture anomalies. On the other hand, over the American Great Plains, even the forecasts with improved soil moisture initialization remain unsuccessful. Yet, the literature as well as our assessment of climate sensitivity to soil moisture have identified this region as a "hotspot" of soil moisture - atmosphere coupling. We assume that the failure of these predictions relates to the strong hot and dry bias present in all models over this region in summer, which leads to excessive soil drying. To verify this assumption, we developed a method that corrects these biases during the forecast integration based on the CNRM-CM6 model. The resulting forecasts are significantly improved over the Great Plains. Understanding the origin of continental biases in the summer and reducing them in future generations of climate models are essential steps to making the most of soil moisture as a source of seasonal predictability in temperate regions

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Montes, Carlo. "Modélisation spatialisée des échanges surface-atmosphère à l'échelle d'une région agricole méditerranéenne." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20085/document.

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En régions méditerranéennes, la gestion de l'eau à partir d'outils d'aide à la décision requiert la connaissance des échanges d'énergie et de masse entre la surface et l'atmosphère, dont l'évapotranspiration, qui représente la composante majeure du cycle hydrologique. Les avancées récentes, en termes de modélisation des Transferts Sol-Végétation-Atmosphère (TSVA) pour des couverts homogènes et d'assimilation des données de télédétection, principalement à l'échelle subrégionale, permettent d'envisager le passage à l'échelle régionale pour des couverts complexes de type cultures en rang. L'objectif de ce travail est de développer une modélisation versatile et de la caler par télédétection à l'échelle régionale sur un bassin versant viticole. Les investigations sont menées sur le bassin versant de la Peyne, dans le cadre de l'ORE OMERE. Une analyse bibliographique a permis de sélectionner un modèle TSVA à vocation régionale avec un nombre réduit de paramètres. L'implémentation de ce modèle est motivée par des objectifs de versatilité mais aussi d'inclusion dans une plateforme de simulation. Parallèlement, l'évapotranspiration a été spatialisée à l'échelle régionale par synergie des données télédétectées infrarouge thermique ASTER et Landsat. Les chroniques d'évapotranspiration obtenues sont ensuite utilisées pour caler le modèle TSVA
In Mediterranean regions, decision making tools for water management require knowledge of water and mass exchanges between land surface and atmosphere, where evapotranspiration is the main component of the hydrological cycle. Recent advances, in terms of modeling and remote sensing, mainly at the subregional scale for homogeneous canopies, allow foreseeing the regional extent for complex landscapes such as row crops. This work aims to propose and calibrate a versatile modeling at the regional scale over a vineyard watershed, the calibration relying on remote sensing. A literature review allows selecting a SVAT model with a regional scope and a limited number of parameters. Model implementation is motivated by versatility and further inclusion into a simulation platform. Then, evapotranspiration is spatialized synergistically by using thermal infrared data from ASTER and Landsat remote sensors. Next, the time series obtained for evapotranspiration are used for calibrating the selected SVAT model. These investigations are conducted over the Peyne watershed, within the framework of the OMERE Observatory for environmental research

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Gibelin, Anne-Laure. "Cycle du carbone dans un modèle de surface continentale : modélisation, validation et mise en oeuvre à l'échelle globale." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00164054.

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ISBA-A-gs est une option du modèle de surface continentale du CNRM, ISBA, qui simule les échanges de carbone entre la biosphère terrestre et l'atmosphère. Au cours de cette thèse, le modèle est utilisé pour la première fois à l'échelle globale en mode forcé. Plusieurs simulations globales sont réalisées pour évaluer la sensibilité des flux turbulents et du LAI à un doublement de CO2 et au changement climatique prévu pour la fin du XXIe siècle.
Une nouvelle option du modèle, nommée ISBA-CC, est aussi développée afin de simuler de manière plus réaliste la respiration de l'écosystème, en distinguant la respiration autotrophe et la respiration hétérotrophe.
La validation de la dynamique de la végétation et des flux de carbone échangés, à la fois à l'échelle globale à l'aide de données satellitaires, et à l'échelle locale sur 26 sites de mesure du réseau FLUXNET, montre que le modèle de surface est suffisamment réaliste pour être couplé à un modèle de circulation générale, afin de simuler les interactions entre la surface continentale, l'atmosphère et le cycle du carbone.

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Liu, Yuqiong. "Parameter Estimations For Locally Coupled Land Surface-Atmosphere Models." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/191262.

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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.

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Astudillo, Orlando. "Rôle des interactions océan-atmosphère-continent sur la dynamique de la couche limite marine dans la région d'upwelling du Chili central." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30360.

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Les systèmes de courant de bords est (EBUS) sont les régions océaniques des latitudes tropicales à moyennes le long des côtes ouest des continents. Ils abritent des écosystèmes marins très productifs en raison de la circulation atmosphérique de surface dirigée vers l'équateur qui font remonter des eaux profondes froides (upwelling) enrichies en éléments nutritifs à l'origine de la vie marine le longde la côte. Si les processus océaniques fondamentaux de l'upwelling côtier sont bien connus (transport et pompage d'Ekman), la modélisation océanique des EBUS reste problématique en raison des difficultés pour prendre en compte de manière réaliste des phénomènes à fine échelle spatiale dans la zone de transition entre le littoral et l'océan du large. Dans cette thèse, nous nous sommes concentrés sur le système d'upwelling dit de Humboldt (côtes du Pérou et du Chili) et sur l'influence des caractéristiques méso-échelles des vents près de la côte, en particulier la décroissance vers la cotes du vent (appelé "drop-off") qui détermine l'importance relative des processus d'Ekman, et donc, la structure spatiale de la zone d'upwelling. Une approche combinée basée sur l'analyse de données satellitaires et sur la modélisation régionale, océanique et atmosphérique, est utilisée pour étudier la sensibilité de la circulation océanique le long de la côte Chili central aux caractéristiques du drop-off. Dans un premier temps, la circulation atmosphérique de surface moyenne à saisonnière le long du littoral du Pérou et du Chili est documentée pour la première fois à partir des données altimétriques de quatre missions satellites (ENVISAT, JASON1, JASON2 et SARAL). L'analyse révèle l'existence d'une réduction marquée de la vitesse du vent le long de la côte, bien que le taux de réduction varie en fonction de la latitude. Malgré la répétitivité relativement faible des satellites, nous montrons que les données altimétriques permettent néanmoins d'échantillonner le cycle saisonnier du drop-off. L'estimation de l'upwelling côtier à partir de ces données suggère que le pompage d'Ekman tend en moyenne à dominer par rapport au transport d'Ekman le long de la côte péruvienne, alors que le long de la côte chilienne, le transport d'Ekman est le processus dominant. Dans un second temps, un modèle atmosphérique régional (WRF) à différentes résolutions horizontales (36 km, 12 km et 4 km) dans une configuration imbriquée zoomée sur la région centrale du Chili a été développé afin de produire des champs atmosphériques présentant des caractéristiques différentes du drop-off. Les solutions du modèle atmosphérique sont d'abord évaluées par rapport aux observations, indiquant un plus grand réalisme près de la côte que les réanalyses atmosphériques. Le rotationnel du vent cyclonique simulé le long de la côte associé au drop-off présente des échelles transversales comprises entre 8 et 45 km avec une variabilité latitudinale significative, en accord avec les vents altimétriques. Lorsque la résolution du modèle est augmentée, le drop-off est généralement d'autant plus confiné à la côte et le modèle indique une saisonnalité marquée avec un maximum d'intensité au printemps-automne. La contribution relative de la divergence côtière et du pompage d'Ekman présente une modulation latitudinale liée aux détails de l'orographie et de la ligne de côte
Eastern Boundary Upwelling Systems (EBUS) are the tropical to mid-latitudes oceanic regions along the west coast of the continents. They host very productive marine ecosystems owing to the mean equatorward low-level atmospheric circulation that uplifts cool subsurface nutrient-enriched waters that trigger marine life along the coast. While the fundamental oceanic processes behind such process are well known (i.e. Ekman transport and pumping), the oceanic modeling of the EBUS has remained problematic owing to difficulties in accounting realistically for phenomena at fine spatial scales in the transition zone between the littoral and the off-shore ocean. In this thesis we have focused on the Peru-Chile Upwelling System (so-called Humboldt system) and on the influence of the cross-shore mesoscale features of the winds near the coast, particularly the shoreward wind drop-off, which determinate the relative importance of the Ekman processes, and thus, the spatial and temporal structure of the upwelling. A combined approach based on satellite data analysis and regional modeling, both oceanic and atmospheric, is used to investigate the sensitivity of the oceanic circulation along the coast of central Chile to the characteristics of the wind drop-off. As a first step, the mean to seasonal near-shore surface atmospheric circulation along the coast of Peru and Chile is documented for the first time based on the altimeter data from four satellite missions (ENVISAT, JASON1, JASON2 and SARAL). The analysis reveals the existence of a marked shoreward reduction in the wind speed all along the coast, although the reduction rate is latitudinally dependent. Despite the relatively weak repetitivity of the satellites, it is shown that the altimetric data are able to sample the seasonal cycle of the wind drop-off at some locations. The estimate of coastal upwelling from these data suggests that Ekman pumping tends on average to dominate with respect to Ekman transport over the Peruvian coast, whereas over the central-Chilean coast, the Ekman transport is the dominant process. In a second step, a regional atmospheric model (WRF) at different horizontal resolutions (36km, 12km and 4km) in a nested configuration zoomed over the central-Chile region was developed in order to produce atmospheric fields with different characteristics of the wind-stress curl (drop-off) along the coast. The atmospheric model solutions are first evaluated against the satellite observations, showing a much larger realism than atmospheric Reanalyses near the coast. In particular, the simulated cyclonic wind curl along the coast related to the wind drop-off exhibit length scales between 8 and 45 km with a significant latitudinal variability, which is in agreement with the altimetric winds. The higher model resolution, the more confined to the coast the wind drop-off, with the latter evidencing a marked seasonality with a maximum intensity in spring-fall and minimum in winter. The relative contribution of the coastal divergence and Ekman pumping exhibits a latitudinal modulation linked to details in the orography and coastlines

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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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MELO, Ewerton Cleudson de Sousa. "Simulação numérica das interações biosfera-atmosfera em área de caatinga: uma análise da expansão agrícola em ambiente semiárido." Universidade Federal de Campina Grande, 2011. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1437.

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Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-08-14T10:58:52Z No. of bitstreams: 1 EWERTON CLEUDSON DE SOUSA MELO - TESE (PPGMet) 2016.pdf: 4714414 bytes, checksum: 399def91bcd71b3e8a00a6b001dcfd4b (MD5)
Made available in DSpace on 2018-08-14T10:58:52Z (GMT). No. of bitstreams: 1 EWERTON CLEUDSON DE SOUSA MELO - TESE (PPGMet) 2016.pdf: 4714414 bytes, checksum: 399def91bcd71b3e8a00a6b001dcfd4b (MD5) Previous issue date: 2011-06-30
CNPq
Neste trabalho a versão 6.0 do modelo numérico RAMS (Regional Atmospheric Modeling System) é usada com o objetivo principal de simular a influência da expansão agrícola nas trocas de água e energia em áreas de Caatinga, e quantificar os efeitos das mudanças na cobertura e uso da terra na geração de circulações termicamente induzidas e na atividade convectiva. Os cenários de uso da terra investigados neste estudo foram construídos para representar condições ambientais nativas (sem influências antrópicas), e com alterações decorrentes da construção da represa de Sobradinho, e da expansão de atividades agrícolas e irrigação em região de clima semiárido. O ambiente atmosférico de grande escala é caracterizado pela estrutura dinâmica e termodinâmica típica da área central de um vórtice ciclônico de altos níveis (VCAN). A escolha do período de estudo teve como objetivo garantir condições ambientais com ampla diversidade agrícola em áreas de Caatinga (culturas de sequeiro e agricultura irrigada), e pouca nebulosidade. A evolução temporal da precipitação convectiva acumulada nas simulações da expansão agrícola mostra diferenças marcantes nos efeitos da agricultura de sequeiro e vegetação irrigada. O aumento na taxa da evapotranspiração nas áreas irrigadas eleva consideravelmente o teor de umidade nos baixos níveis da troposfera, reduz a temperatura do ar e diminui a precipitação convectiva. A descontinuidade na umidade e tipo de cobertura vegetal modifica a intensidade e distribuição dos fluxos turbulentos que são importantes na formação dos gradientes de pressão que geram circulações de brisa (brisa lacustre e de vegetação), de forma que o domínio nos transportes verticais de calor e água passa a ser da mesoescala. Verificou-se que as principais forçantes locais na determinação da distribuição espacial dos fluxos turbulentos e da chuva convectiva foram a topografia e a descontinuidade no teor de umidade do solo. Com relação a estabilidade atmosférica percebeu-se a existência de uma relação quase linear entre a Energia Potencial Convectiva Disponível (CAPE) e a temperatura potencial equivalente.
In this work the version 6.0 of the numerical model RAMS (Regional Atmospheric Modeling System) is used with the main objective of simulating the influence of agricultural expansion on the water and energy exchange in Caatinga vegetation areas, and to quantify the effects that changes on soil use and coverage have on the generation of thermally induced circulations and convective activity. The scenarios of soil use investigated are designed to represent native environmental conditions (without anthropogenic influences) and with alterations due to the implementation of the Sobradinho reservoir, and the expansion of agricultural activities and irrigation in a semiarid climate area. The large scale atmospheric ambient is characterized by the dynamic and thermodynamic structure typical of the central area of an upper level cyclonic vortex. The period of study was chosen aiming at environmental conditions with largely diversified agricultural use in Caatinga vegetation areas (agriculture with and without irrigation), and almost cloudless skies. The temporal evolution of the accumulated convective precipitation in the numerical simulations of the agricultural expansion shows large differences in the effects of agriculture with and without irrigation. The irrigated areas higher evapotranspiration rate causes a substantial increase in the moisture content in the lower troposphere, and lower the air temperature and convective precipitation.

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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.

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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/.

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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.

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McAtee, Brendon Kynnie. "Surface-atmosphere interactions in the thermal infrared (8 - 14℗æm) /." Full text available, 2003. http://adt.curtin.edu.au/theses/available/adt-WCU20040324.085644.

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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/.

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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.

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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.

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32

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.

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33

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.

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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.

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Zhuang, Haixiong School of Mathematics UNSW. "Parameterisation of atmosphere-ocean surface interactions, with applications to the Australian monsoon." Awarded by:University of New South Wales. School of Mathematics, 2004. http://handle.unsw.edu.au/1959.4/26170.

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Atmosphere-ocean and atmosphere-land interactions are important processes which determine the development of monsoon systems. In this study, a new atmosphere-ocean surface interaction scheme, referred to as AOSIS, is developed and verified with observed data. AOSIS, together with ALSIS (Atmosphere-Land Surface Interaction Scheme), is then coupled into CEMSYS4 (Computational Environmental Modelling System) to investigate the influences of atmosphere-ocean and atmosphere-land surface interactions on the Australian Monsoon, especially the monsoon onset, break and withdrawal. Numerical experiments are carried out and the simulations are compared with the NCEP (National Center for Environmental Prediction, America) data. AOSIS is constructed with three basic components, i.e., a two-layer ocean temperature model, a wind-wave model and a surface flux model. We divide the ocean into a mixed layer and a deep layer. However, the depth of the mixed layer is not constant but varies with time, depending on surface wind shear and buoyancy flux. In AOSIS, we adapted the approach of relating the stages of wave development by wave age and proposed a new expression for calculating the ocean surface roughness length, $z_{0m}$, with consideration of waves. We test AOSIS in a stand along mode against the Moana data and the NCEP data. The comparison with the Moana data shows that AOSIS has considerable skill in simulating SST (sea surface temperature) and energy fluxes, with the simulated values in good agreement with observed data. AOSIS is also successful in simulating the warm and cool effects considered in the COARE (Coupled Ocean-Atmosphere Response Experiment) scheme. Comparison with the NCEP data also confirms that AOSIS simulates SST well. AOSIS and ALSIS are then coupled into CEMSYS4. We apply the system to the simulation of SST and surface energy fluxes over the Australian region and compared the results with the NCEP data. It is found that the simulated SST and energy fluxes are in good agreement with the NCEP data. Further, we study the synoptic events of the Australian Monsoon onset, break and withdrawal and examine the impacts of atmosphere-ocean and atmosphere-land surface interactions on such synoptic events.

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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.

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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

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37

Virmani, Jyotika I. "Ocean-atmosphere interactions on the West Florida shelf." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001141.

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38

Wu, Zhaohua. "Thermally driven surface winds in the tropics /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10075.

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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.

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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.

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41

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.

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42

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.

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43

Winterrath, Tanja. "Numerical investigations on atmosphere-biosphere interactions impact of radiation fog and leaf surface water /." [S.l. : s.n.], 2002. http://archimed.uni-mainz.de/pub/2002/0143/diss.pdf.

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44

Löw, Alexander. "Coupled modelling of land surface microwave interactions using ENVISAT ASAR data." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-27646.

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45

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.

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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.

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46

Sen, Omer Lutfi. "Improving the parameterization of land-surface interactions in GCMs using field data." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284191.

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General Circulation Models are important tools in the study of the earth's climate system. The terrestrial surface forms the lower boundary to such models over continents and a well-defined lower boundary is crucial for reliable climate simulations because the Earth interacts with the atmosphere via this boundary. The primary motivation for this research is to improve the parameterization of these interactions in General Circulation Models using field data and calibration techniques. For this purpose, a recent version of Biosphere-Atmosphere Transfer Scheme was selected, studied, and then calibrated for five different vegetation types using multi-criteria calibration techniques. The associated parameter sets were then tested in a ten-year climate integration with Version 3 of the Community Climate Model. The present study explored the methodology needed to use the growing number of relevant field data sets effectively and efficiently better to parameterize the land surface in a GCM. It showed that such field data can, indeed, be used in this way, not only to improve simulations but also to understand models' capabilities and deficiencies. Calibrating the land surface parameterization significantly improved simulations relative to the original default parameterization but several physically based land surface models studied, once calibrated, were found to give equally good simulations of the land surface processes. The primary results are that it is possible to obtain a single preferred parameter sets for different vegetation types using multi-criteria calibration, and that using calibrated parameter sets in climate models can improve the representation of surface exchanges and the modeled climate given by a GCM.

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47

Huang, Hsin-Yuan. "Investigation of land surface-convective boundary layer interactions using large-eddy simulation." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1835573641&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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48

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.

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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.

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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.

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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.

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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.

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Dissertations / Theses on the topic 'Land surface - atmosphere interactions'

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