A Monte Carlo Model Of The Nocturnal Surface Temperatures In Urban Canyons

A model for the urban canyon is formulated for meteorologicalconditions of weak winds at night time. Thermal radiation, conductivity and convection are simulated by means of the Monte Carlo method. These are the main physical processesof energy transfer that give rise to the characteristic temperaturedistribution in these systems. The model has been satisfactory tested under ideal conditions for which analytical solutions exist.The predictions of the model under morerealistic conditions accurately reproduce the observationalresults. A strong temperature gradient across streets, with the canyon corners up to 4 °C warmer than the canyon centre, is found for the deepest canyons. This theoretical predictionhas been successfully verified with measurementstaken in a number of streets of the city of Granada in Spain.     

On the inclusion of ground-based gravity measurements to the calibration process of a global rainfall-discharge reservoir model: case of the Durzon karst system (Larzac, southern France)

This work examines the relevance of the inclusion of ground-based gravity data in the calibration process of a global rainfall-discharge reservoir model. The analysis is performed for the Durzon karst system (Larzac, France). The first part of the study focuses on the hydrological interpretation of the ground-based gravity measurements. The second part of the study investigates further the information content of the gravity data with respect to water storage dynamics modelling. The gravity-derived information is found unable to either reduce equifinality of the single-objective, discharge-based model calibration process or enhance model performance through assimilation.     

Pennsylvanian carbonate platforms adjacent to deltaic systems in an active marine foreland basin (Escalada Fm., Cantabrian Zone,NW Spain)

The Pennsylvanian marine foreland basin of the Cantabrian Zone (NW Spain) is characterized by the unique development of kilometre‐size and hundred‐metre‐thick carbonate platforms adjacent to deltaic systems. During Moscovian time, progradational clastic wedges fed by the orogen comprised proximal alluvial conglomerates and coal‐bearing deltaic sequences to distal shelfal marine deposits associated with carbonate platforms (Escalada Fm.) and distal clay‐rich submarine slopes. A first phase of carbonate platform development (Escalada I, upper Kashirian‐lower Podolskian) reached a thickness of 400 m, nearly 50 km in width and developed a distal high‐relief margin facing a starved basin, nearly 1000‐m deep. Carbonate slope clinoforms dipped up to 30° and consisted of in situ microbial boundstone, pinching out downslope into calciturbidites, argillaceous spiculites and breccias. The second carbonate platform (Escalada II, upper Podolskian‐lower Myachkovian) developed beyond the previous platform margin, following the basinward progradation of siliciclastic deposits. Both carbonate platforms include: (1) a lower part composed of siliciclastic‐carbonate cyclothems characterized by coated‐grain and ooid grainstones; and (2) a carbonate‐dominated upper part, composed of tabular and mound‐shaped wackestone and algal‐microbial boundstone strata alternating at the decametre scale with skeletal and coated‐grain grainstone beds. Carbonate platforms initiated in distal sectors of the foreland marine shelf during transgressions, when terrigenous sediments were stored in the proximal part, and developed further during highstands of 3rd‐order sequences in a high‐subsidence context. During the falling stage and lowstand systems tracts, deltaic systems prograded across the shelf burying the carbonate platforms. Key factors involved in the development of these unique carbonate platforms in an active foreland basin are: (1) the large size of the marine shelf (approaching 200 km in width); (2) the subsidence distribution pattern across the marine shelf, decreasing from proximal shoreline to distal sectors; (3) Pennsylvanian glacio‐eustacy affecting carbonate lithofacies architecture; and (4) the environmental conditions optimal for fostering microbial and algal carbonate factories.     

Nonlinear Shallow Water Theories for Coastal Waves

Ocean waves entering the near-shore zone undergo nonlinear and dispersive processes. This paper reviews nonlinear models, focusing on the so-called Serre equations. Techniques to overcome their limitations with respect to the phase speed are presented. Nonlinear behaviours are compared with theoretical results concerning the properties of Stokes waves. In addition, the models are tested against experiments concerning periodic wave transformation over a bar topography and of the shoaling of solitary waves on a beach.     

The use of environmental integrative indicators to assess seabed disturbance in estuaries and coasts: Application to the Humber Estuary, UK

The coastal zone is subject to many and varied changes resulting from human activities and natural processes. Existing or emerging agreements and legislation acknowledge the relevance of indicators for monitoring these. In the UK, following a series of recent workshops, potential indicators of nearshore disturbance have been identified and grouped into three broad indices: 'Coastline Morphological Change', 'Resource Use Change' and 'Environmental Quality and its Perception'. The present study developed these indicators further and tested their use by applying them to 18 sections in the Humber Estuary, Eastern England. The results obtained reflect the current knowledge of the state of the Humber environment and show the potential of integrative indicators but indicate that further studies are required to assess the relative importance of the indicators and their value in reflecting the ability of the ecosystems to sustain natural habitats and populations at a good conservation status.     

Some Insights into Topographic,Elastic and Self-gravitation Interaction in Modelling Ground Deformation and Gravity Changes in Active Volcanic Areas

Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic, elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation and gravity changes depend on such effects.     

Impacts of Indian Ocean SST biases on the Indian Monsoon: as simulated in a global coupled model

In this study, the impact of the ocean–atmosphere coupling on the atmospheric mean state over the Indian Ocean and the Indian Summer Monsoon (ISM) is examined in the framework of the SINTEX-F2 coupled model through forced and coupled control simulations and several sensitivity coupled experiments. During boreal winter and spring, most of the Indian Ocean biases are common in forced and coupled simulations, suggesting that the errors originate from the atmospheric model, especially a dry islands bias in the Maritime Continent. During boreal summer, the air-sea coupling decreases the ISM rainfall over South India and the monsoon strength to realistic amplitude, but at the expense of important degradations of the rainfall and Sea Surface Temperature (SST) mean states in the Indian Ocean. Strong SST biases of opposite sign are observed over the western (WIO) and eastern (EIO) tropical Indian Ocean. Rainfall amounts over the ocean (land) are systematically higher (lower) in the northern hemisphere and the south equatorial Indian Ocean rainfall band is missing in the control coupled simulation. During boreal fall, positive dipole-like errors emerge in the mean state of the coupled model, with warm and wet (cold and dry) biases in the WIO (EIO), suggesting again a significant impact of the SST errors. The exact contributions and the distinct roles of these SST errors in the seasonal mean atmospheric state of the coupled model have been further assessed with two sensitivity coupled experiments, in which the SST biases are replaced by observed climatology either in the WIO (warm bias) or EIO (cold bias). The correction of the WIO warm bias leads to a global decrease of rainfall in the monsoon region, which confirms that the WIO is an important source of moisture for the ISM. On the other hand, the correction of the EIO cold bias leads to a global improvement of precipitation and circulation mean state during summer and fall. Nevertheless, all these improvements due to SST corrections seem drastically limited by the atmosphere intrinsic biases, including prominently the unimodal oceanic position of the ITCZ (Inter Tropical Convergence Zone) during summer and the enhanced westward wind stress along the equator during fall.     

North Atlantic atmospheric circulation and surface wind in the Northeast of the Iberian Peninsula: uncertainty and long term downscaled variability

The variability and predictability of the surface wind field at the regional scale is explored over a complex terrain region in the northeastern Iberian Peninsula by means of a downscaling technique based on Canonical Correlation Analysis. More than a decade of observations (1992–2005) allows for calibrating and validating a statistical method that elicits the main associations between the large scale atmospheric circulation over the North Atlantic and Mediterranean areas and the regional wind field. In an initial step the downscaling model is designed by selecting parameter values from practise. To a large extent, the variability of the wind at monthly timescales is found to be governed by the large scale circulation modulated by the particular orographic features of the area. The sensitivity of the downscaling methodology to the selection of the model parameter values is explored, in a second step, by performing a systematic sampling of the parameters space, avoiding a heuristic selection. This provides a metric for the uncertainty associated with the various possible model configurations. The uncertainties associated with the model configuration are considerably dependent on the spatial variability of the wind. While the sampling of the parameters space in the model set up moderately impact estimations during the calibration period, the regional wind variability is very sensitive to the parameters selection at longer timescales. This fact illustrates that downscaling exercises based on a single configuration of parameters should be interpreted with extreme caution. The downscaling model is used to extend the estimations several centuries to the past using long datasets of sea level pressure, thereby illustrating the large temporal variability of the regional wind field from interannual to multicentennial timescales. The analysis does not evidence long term trends throughout the twentieth century, however anomalous episodes of high/low wind speeds are identified.     

SEM-EDX Characterisation of Tropospheric Aerosols in the Negev Desert (Israel)

Individual aerosol particles collected in the Negev desert in Israel during a summer and winter campaign in 1996–1997 were analysed by scanning electron microscopy with energy-dispersive X-ray analysis. Hierarchical cluster analysis was performed to interpret the data on the basis of particle diameter and composition. Eleven particle classes (groups) provided clues on sources and/or particle formation. The summer samples were enriched in sulphates and mineral dusts; the winter samples contained more sea salts, aged sea salts, and industrial particles. The fine size fraction below 1 m diameter was enriched in secondary particles and showed evidence of atmospheric processing. The secondary sulphate particles were mainly attributed to long-range transport. A regional conversion from calcite to calcium sulphate occurred during summer. Industrial particles originating from local pollution appeared during winter.     

Performance of a multi-RCM ensemble for South Eastern South America

The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991–2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons.