Mass consistent models for wind distribution in complex terrain — Fast algorithms for three dimensional problems

Mass consistent models for wind distribution in complex terrain are extremely useful and readily applied to many practical situations, such as the siting of wind turbines, or as input in the estimation of diffusion and transport of pollutants in complex terrain. These models are based on the numerical solution of the steady state three dimensional continuity equation for the mean wind components. The momentum and energy equations are not solved explicitly, but considered indirectly using parametric relations and wind data. In practical applications the equations must be solved numerous times (e.g. for each time interval). Standard techniques for numerical solution of three dimensional problems are frequently very expensive and thus not suitable for practical needs. In the present work, great emphasis is given to the development of fast algorithms, and techniques based on the multigrid approach are shown. Two mass consistent programs are described, the first based on the parametric representation of one of the wind components, and the second based on a few wind measurements and a variational principle. To verify the reliability of the variational approach, a measurement program related to a project of wind energy, is being performed at Har-Ahim, a site located in the Galilee.     

Simulating vegetation effects on flows in 3D using an unstructured grid model: model development and validation

Ocean Dynamics - Prevalence of vegetation (either submerged or emergent) in shallow water significantly affects the flow and turbulence structure in this environment. In this paper, we develop a...     

Effects of Wormhole Configurations on Performance of Cyclic Solvent Injection in Heavy Oil Systems

Natural Resources Research - In this study, the effect of three different wormhole configurations: single-linear, single-branched, and double-branched wormholes on the performance of cyclic solvent...     

Groundwater Depletion and Agricultural Land Use Change in the High Plains: A Case Study from Wichita County,Kansas*

Shifts in resource availability and resulting land use changes are important research themes for coupled human and natural systems and human dimensions of global environmental change. This study examines the relationship between groundwater depletion and agricultural land use change within a single county in the High Plains, where agro-economic systems and populations are dependent on access to reliable groundwater supplies. Results indicate a significant relationship between high proportionate decreases in groundwater and land being removed from irrigation. This case study strengthens the links among local, regional, and global environmental change, and contributes to a greater understanding of the High Plains in the context of regional sustainability and vulnerability concerns.     

Vertical-axis rotation controlled by upper crustal stress based on force balance analysis: A case study of the western Transverse Ranges of California

This paper evaluates driving mechanisms of vertical-axis rotation using data from the western Transverse Ranges in southern California. Simple force balance considerations and comparison of torque applied to a rotating block indicate that shear forces applied to the base of the block are not strong enough to produce the motions and deformation observed at the surface. For the measured dimensions of the crustal blocks and crustal viscosities in southern California, stresses transmitted through the upper crust are one to three orders of magnitude stronger than forces generated in the ductile lower crust. These results suggest that the kinematics of crustal blocks in continental deformation zones are primarily controlled by forces within the upper crust rather than a flow field beneath.     

Heat tracing of heterogeneous hyporheic exchange adjacent to in‐stream geomorphic features

There are many field techniques used to quantify rates of hyporheic exchange, which can vary in magnitude and direction spatially over distances of only a few metres, both within and between morphological features. We used in‐stream mini‐piezometers and heat transport modelling of stream and streambed temperatures to quantify the rates and directions of water flux across the streambed interface upstream and downstream of three types of in‐stream geomorphic features: a permanent dam, a beaver dam remnant and a stream meander. We derived hyporheic flux estimates at three different depths at six different sites for a month and then paired those flux rates with measurements of gradient to derive hydraulic conductivity (K) of the streambed sediments. Heat transport modelling provided consistent daily flux estimates that were in agreement directionally with hydraulic gradient measurements and also identified vertical heterogeneities in hydraulic conductivity that led to variable hyporheic exchange. Streambed K varied over an order of magnitude (1·9 × 10^?6 to 5·7 × 10^?5 m/s). Average rates of hyporheic flux ranged from static (q < ±0·02 m/day) to 0·42 m/day. Heat transport modelling results suggest three kinds of flow around the dams and the meander. Copyright © 2010 John Wiley & Sons, Ltd.     

Integrated assessment of smallholder farming’s vulnerability to drought in the Brazilian Semi-arid: a case study in Ceará

Smallholder farming is among the most vulnerable sectors due to its great social and economic sensitivity. Despite future climate change, current climate variability is already an issue of concern that justifies adaptation efforts. In Brazil, the Semi-Arid Region is a climate hotspot, well known for both historic socioeconomic setbacks, and agriculture failures caused by dry spells and severe droughts. In 2010, the Brazilian government enacted the National Policy on Climate Change, which states as one of its key goals the identification of vulnerabilities and the adoption of adequate measures of adaptation to climate change. The improvement of vulnerability assessment tools is a response to the growing demand of decision makers for regular information and indicators with high spatial and temporal resolution. This article aims at undertaking a comparative assessment of smallholder farming’s vulnerability to droughts. An integrated assessment system has been developed and applied to seven municipalities located in the Brazilian Semi-Arid Region (within the State of Ceará). Results show regional vulnerability contrasts driven by institutional and socioeconomic factors, beyond climatic stressors.     

Climate extremes in the United States: recent research by physical geographers

This paper reports our review of research on domestic climate extremes conducted by US physical geographers over the past 15?years. Sections cover extremes in wind, precipitation, lightning, and temperature, as well as derivative climate extremes (droughts, floods, and storm surges). Themes considered include: the spatial and temporal distribution of the climate extreme; its implications for our understanding of the physical processes that produce it; the spatial and temporal distributions of the extreme’s economic and human costs; lessons for assessment, policy, and management; and scale. We conclude that most of the works reviewed inadequately address the human basis of vulnerability to climate extremes, and encourage physical geographers to work with colleagues from the other subfields of geography and the social sciences to develop the holistic understanding of vulnerability needed to effectively adapt to the more extreme climate projected under climate change.     

An Examination of ENSO’s Effect on the Monthly and Seasonal Climate of Hong Kong from a Statistical Perspective

This study aims to examine the effect of El Nino and La Nina on the monthly and seasonal climate of Hong Kong against the ENSO-neutral situation from a statistical perspective. Monthly and seasonal temperature and rainfall of Hong Kong and monthly number of tropical cyclones (TCs) coming within 500 km of the city over the 59-yr (1950-2008) period are examined under three ENSO situations, namely El Nino, La Nina, and ENSO-neutral. It is found that, compared with the ENSO-neutral situation, El Nino tends...