Soil moisture modeling and scaling using passive microwave remote sensing

Soil moisture in the shallow subsurface is a primary hydrologic state governing land-atmosphere interaction at various scales. The primary objectives of this study are to model soil moisture in the root zone in a distributed manner and determine scaling properties of surface soil moisture using passive microwave remote sensing. The study was divided into two parts. For the first study, a root zone soil moisture assessment tool (SMAT) was developed in the ArcGIS platform by fully integrating a one-dimensional vadose zone hydrology model (HYDRUS-ET) with an ensemble Kalman filter (EnKF) data assimilation capability. The tool was tested with dataset from the Southern Great Plain 1997 (SGP97) hydrology remote sensing experiment. Results demonstrated that SMAT displayed a reasonable capability to generate soil moisture distribution at the desired resolution at various depths of the root zone in Little Washita watershed during the SGP97 hydrology remote sensing experiment. To improve the model performance, several outstanding issues need to be addressed in the future by: including "effective" hydraulic parameters across spatial scales; implementing subsurface soil properties data bases using direct and indirect methods; incorporating appropriate hydrologic processes across spatial scales; accounting uncertainties in forcing data; and preserving interactions for spatially correlated pixels. The second study focused on spatial scaling properties of the Polarimetric Scanning Radiometer (PSR)-based remotely sensed surface soil moisture fields in a region with high row crop agriculture. A wavelet based multi-resolution technique was used to decompose the soil moisture fields into larger-scale average soil moisture fields and fluctuations in horizontal, diagonal and vertical directions at various resolutions. The specific objective was to relate soil moisture variability at the scale of the PSR footprint (800 m X 800 m) to larger scale average soil moisture field variability. We also investigated the scaling characteristics of fluctuation fields among various resolutions. The spatial structure of soil moisture exhibited linearity in the log-log dependency of the variance versus scale-factor, up to a scale factor of -2.6 (6100 m X 6100 m) irrespective of wet and dry conditions, whereas dry fields reflect nonlinear (multi-scaling) behavior at larger scale-factors

Seismological data acquisition and signal processing using wavelets

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This work deals with two main fields: a) The design, built, installation, test, evaluation, deployment and maintenance of Seismological Network of Crete (SNC) of the Laboratory of Geophysics and Seismology (LGS) at Technological Educational Institute (TEI) at Chania. b) The use of Wavelet Transform (WT) in several applications during the operation of the aforementioned network. SNC began its operation in 2003. It is designed and built in order to provide denser network coverage, real time data transmission to CRC, real time telemetry, use of wired ADSL lines and dedicated private satellite links, real time data processing and estimation of source parameters as well as rapid dissemination of results. All the above are implemented using commercial hardware and software which is modified and where is necessary, author designs and deploy additional software modules. Up to now (July 2008) SNC has recorded 5500 identified events (around 970 more than those reported by national bulletin the same period) and its seismic catalogue is complete for magnitudes over 3.2, instead national catalogue which was complete for magnitudes over 3.7 before the operation of SNC. During its operation, several applications at SNC used WT as a signal processing tool. These applications benefited from the adaptation of WT to non-stationary signals such as the seismic signals. These applications are: HVSR method. WT used to reveal undetectable non-stationarities in order to eliminate errors in site’s fundamental frequency estimation. Denoising. Several wavelet denoising schemes compared with the widely used in seismology band-pass filtering in order to prove the superiority of wavelet denoising and to choose the most appropriate scheme for different signal to noise ratios of seismograms. EEWS. WT used for producing magnitude prediction equations and epicentral estimations from the first 5 secs of P wave arrival. As an alternative analysis tool for detection of significant indicators in temporal patterns of seismicity. Multiresolution wavelet analysis of seismicity used to estimate (in a several years time period) the time where the maximum emitted earthquake energy was observed

Land Surface Verification Toolkit (LVT) - A Generalized Framework for Land Surface Model Evaluation

Model evaluation and verification are key in improving the usage and applicability of simulation models for real-world applications. In this article, the development and capabilities of a formal system for land surface model evaluation called the Land surface Verification Toolkit (LVT) is described. LVT is designed to provide an integrated environment for systematic land model evaluation and facilitates a range of verification approaches and analysis capabilities. LVT operates across multiple temporal and spatial scales and employs a large suite of in-situ, remotely sensed and other model and reanalysis datasets in their native formats. In addition to the traditional accuracy-based measures, LVT also includes uncertainty and ensemble diagnostics, information theory measures, spatial similarity metrics and scale decomposition techniques that provide novel ways for performing diagnostic model evaluations. Though LVT was originally designed to support the land surface modeling and data assimilation framework known as the Land Information System (LIS), it also supports hydrological data products from other, non-LIS environments. In addition, the analysis of diagnostics from various computational subsystems of LIS including data assimilation, optimization and uncertainty estimation are supported within LVT. Together, LIS and LVT provide a robust end-to-end environment for enabling the concepts of model data fusion for hydrological applications. The evolving capabilities of LVT framework are expected to facilitate rapid model evaluation efforts and aid the definition and refinement of formal evaluation procedures for the land surface modeling community

Analysis of gravity waves generated at the top of a drainage flow

Drainage or katabatic flows are common mesoscale circulations established as a result of differential radiative cooling of near-surface air masses in sloping terrain. The initial irruption of these flows, with sudden shifts in wind speed and direction, may result in vertical displacements of air parcels from their equilibrium position, which prove to be a common source of internal gravity waves. This paper illustrates this mechanism and describes the main features of the oscillations following the study of observational data gathered throughout one night during the Stable Atmospheric Boundary Layer Experiment in Spain 2006 (SABLES2006) field campaign.This research has been funded by the Spanish Ministry of Science and Innovation (Projects CGL2004-03109, CGL 2006-12474- C03-03, and CGL2009-12797-C03-03). The GR58/08 program (supported by BSCH and UCM) has also partially financed this work through the Research Group ‘‘Micrometeorology and Climate Variability’’ (910437)

The climatic significance of tropical forest edges and their representation in global climate models

An emerging theme in global climate modelling is whether land covers created in the clearance of tropical humid forests influence water exchange between remnant forest patches and the atmosphere, and, if so, how this affects regional and global water exchange. Fieldwork presented in this thesis ascertains whether the amount of water transferred to the atmosphere from a humid tropical forest situated in Sabah, Northern Borneo, Malaysia, differs between its edge and interior due to the influence of surrounding clearings through horizontal heat transfer. Using satellite imagery to measure the shape and size of tropical forests, field measurements of water transfer were extrapolated to continental and global levels to infer how differences in water exchange with the atmosphere between forest edges and interiors may influence regional and global forest-atmosphere water exchange. Mean sap flow in trees within 50 meters of a forest-clearing boundary was found to be 73% greater than that in trees further into the forest; an observation supported by the decreased canopy temperature also recorded there. Evaporation from the forest canopy constituted a high fraction of annual rainfall (33%), but showed no edge effect similar to that of sap flow. Edge plots, however, expressed evapotranspiration rates 22% lower than forest interiors (657-890 mm yr-1), owing to the lower number and size of trees there. One edge plot, however, exhibited evapotranspiration 49.5% greater than that of forest interiors. Gradients of air temperature, vapour pressure deficit and wind speed from the adjacent clearing to the forest interior indicated that warm, dry air moving from the clearing to the forest was the most credible cause of increased sap flow of trees near the forest edge. This hypothesis was supported by a strong correlation between the amount of vapour in the air moving from the clearing and tree water use. It was estimated that the influence of differences in water transfer to the atmosphere between the edges and interiors of tropical forest would not alter global water transfer to the atmosphere by more than 0.25-4%, or by 4-7% in the most fragmented tropical continent, Africa. However, it remains unclear whether the inclusion of tropical forest edge effects within climate models is necessary, as the pioneering nature of this thesis, and of existing studies reviewed within it, means that solid conclusions will be dependent upon future work. This thesis concludes with suggestions for future research that will most effectively consolidate the provisional conclusions and recommendations herein

Parameterisation of the near surface by combined geophysical and direct push techniques in the frame of geotechnical site investigation

Knowledge of the spatial distribution of geotechnical parameters in the near surface is essential in engineering geology. Latest developments in engineering geophysics and direct push-based (DP) data acquisition provide a large set of techniques for non-invasive and in situ data recording for high-resolution parameterisation. Different traditional but sparse geotechnical surveying and analysis tools are typically used at selected locations such as drillings and sieve analysis, respectively. State-of-the-art laboratory techniques and supporting field measurements are used to gather the relevant soil properties for soil type classification helping to assign this information to homogeneous sections of the ground (layers). Site-specific data interpretation however becomes challenging because actual field conditions (in situ) differ from those appropriated in the laboratory, owing to the high spatial heterogeneity of near-surface unconsolidated sediments. We performed intensive fieldwork at two test sites (Löbnitz and Taucha) representing typical construction grounds in Central Germany. We tested electrical resistivity tomography, ground penetrating radar, refraction seismic, multichannel analysis of surface waves, and mobile DP-based seismic traveltime tomography. A combination can overcome the deficiencies restrictions of the particular individual methods, compensating the deficiencies of each method, helping therefore to minimise any drawbacks or limitations that depend on the contrast of and between the physical properties, which each technique is sensitive to. In developing mobile seismic tomography, we overcame prior restrictions imposed by existing on-site boreholes by using DP-devices as carrier systems. The derived geotechnical parameters allows us to carry out uncertainties evaluated by additional applied DP-methods gathering high-resolution data for ground truthing. Furthermore, we show that DP-based in situ-obtained soil colour yields information about the vertical stratigraphic pattern. So far, no methods exist that stipulate how best to handle such high-resolution data from colorimeter probes. We present improvements of direct data acquisition, numerical transformation, filtering, and interpretation. We found that filtered colour surrogates provide more detailed information about the soil which corresponds to its geological set-up. The results help us gain a new understanding of soil colours as a technically reliable proxy that is applicable in geotechnical site characterisation. The findings encourage an enable the reliable characterisation of a highly heterogeneous ground, especially for appraising information uncertainty at different scales. Compared with traditional sparse geotechnical measurements, we obtain more information for definition of clearly homogeneous sections (layers). The combined data interpretation compensates for any disadvantages of a single method. Thus, we expect a significant positive impact for near-surface characterisation in the frame of engineering geological investigations.In der Ingenieurgeologie sind Kenntnisse über die Verteilung von geotechnischen Parametern im oberflächennahen Untergrund von entscheidender Bedeutung. Neueste Entwicklungen im Bereich der Ingenieurgeophysik und von Direct-Push-Verfahren (DP) bieten umfangreiche technische Möglichkeiten für nichtinvasive bzw. In-situ-Parametrisierung. Es kommen unterschiedliche, eher grobe, geotechnische Standartuntersuchungs- und Analyseverfahren zum Einsatz, z.B. Bohrungen und Siebanalysen. Standardisierte Labormethoden und unterstützende Geländemessungen zur Bestimmung relevanter Bodeneigenschaften sowie zur Bodentypbestimmung können Homogenbereichen (Schichten) im Untergrund zugeordnet werden. Die standortabhängige Interpretation dieser Daten ist jedoch schwierig, da die natürlichen Eigenschaften am Standort (in situ) auf Grund der stark heterogenen Natur oberflächennaher Lockergesteine von den Laborbedingungen abweichen. An zwei Standorten (Löbnitz und Taucha) wurden umfangreiche Feldarbeiten durchgeführt. Als Repräsentanten typischer Baugrundsituationen in Mitteldeutschland, wurden hier die Elektr. Widerstandstomographie, Bodenradar, Refraktionsseismik, multichannel analysis of surface waves sowie eine mobile, DP-basierte seismische Laufzeittomographie getestet. Der kombinierte Einsatz gleicht Beschränkungen und Nachteile einzelner Verfahren aus, welche sich aus dem Kontrast bzw. der spezifischen Sensitivität gegenüber dem jeweilig gemessen physikalischen Parameter ergeben. Durch den Einsatz von DP-Systemen in der Entwicklung einer mobilen, seismischen Tomographie kann die Abhängigkeit zu stationär vorhandenen Bohrlöchern überwunden werden. Die abgeleiteten geotechnischen Parameter erlauben eine Unsicherheitsabschätzung, evaluiert durch hochauflösende Daten zusätzlich durchgeführter DP-Methoden. Ferner ermöglichen DP-basierte In-situ-Bodenfarbmessungen mittels Colorimetersonden eine stratigraphische Modelbildung. Bisher sind für solcherart hochaufgelöster Daten keine Auswerteroutinen bekannt. Die Arbeit stellt Entwicklungen im Bereich der Datenakquisition, der numerischen Umrechnung, Filterung sowie Interpretation vor. Die gefilterten Farbdaten bilden als zusätzliche Bodeneigenschaft die geologischen Gegebenheiten ab. Die Ergebnisse belegen den Mehrwert von Bodenfarben als technisch belastbarer Kennwert zur Anwendung in der geotechnischen Standorterkundung. Die Schlussfolgerungen ermöglichen eine belastbare Parametrisierung stark heterogener Untergründe, insbesondere für Unsicherheitsabschätzung auf verschiedenen Skalen. Gegenüber traditionellen, eher groben geotechnischen Messverfahren erhöht sich der Informationsgewinn zu klar abgrenzbaren Homogenbereichen (Schichten). Die gemeinsame Dateninterpretation gleicht die Nachteile einzelner Methoden aus. Die Ergebnisse haben erhebliche Bedeutung für die oberflächennahe Charakterisierung im Rahmen ingenieurgeologischer Untersuchungen

Multi-scale controls on spatial patterns of soil water storage in the hummocky regions of North America

The intensification of land-water management due to agriculture, forestry, and urbanization is a global phenomenon increasing the pressure on world’s water resources and threatening water security in North America. The Prairie Pothole Region of North America covers approximately 775,000 km2 and contains millions of wetlands that serve important hydrological and ecological functions. The unique hummocky topography and the variable effect of different processes contribute to high spatio-temporal variability in soil water, posing major challenges in hydrological studies. The objectives of this study were to a) examine the spatial pattern of soil water storage and its scale and location characteristics; and b) to identify its controls at multiple scales. Soil water content at 20 cm intervals down to 140 cm was measured along a transect extending over several knoll–depression cycles in a hummocky landscape. High water storage in depressions and low water storage on the knolls created a spatial pattern that was inversely related to elevation. Spatial patterns were strongly similar within any given season (intra-season rank correlation coefficient as high as 0.99), moreso than between the same season over different years (inter-annual rank correlation coefficient as high as 0.97). Less similar spatial patterns were observed between different seasons (inter-season rank correlation coefficients as high as 0.90). While the intra-season and inter-annual spatial patterns were similar at scales >18 m, the inter-season spatial patterns were similar at much large scales (>72 m). This may be due to the variations in landform elements and micro-topography. The similarity at scales >72 m were present at any time and depth. However, small- and medium-scale spatial patterns changed with depth and with season due to a change in the hydrological processes. The relative dominance of a given set of processes operating both within a season and for the same season over different years yielded strong intra-season and inter-annual similarity at scales >18 m. Moreover, similarity was stronger with increasing depth, and was thought to be due to the dampening effect of overlying soil layers that are more dynamic. Similarity of spatial patterns over time helps to identify the location that best represents the field averaged soil water and improves sampling efficiency. Change in the similarity of scales of spatial pattern helps identify the change in sampling domain as controlled by hydrological processes. The scale information can be used to improve prediction for use in environmental management and modeling of different surface and subsurface hydrological processes. The similarity of spatial pattern between the surface and subsurface layers help make inferences on deep layer hydrological processes as well as groundwater dynamics from surface water measurements