Indications of change of climate from the analysis of air temperature time series in Athens,Greece     

Bas D. Katsoulis 《Climatic change》1987,10(1):67-79

Air temperature data of Athens are analysed to point out the variations caused by natural controls and anthropogenic activities. The study of the temperature records from 1858 to 1982 at Athens, on the southeast coast of Greece, supports the findings of earlier studies which indicate that the period of the 1920's to the 1950's were, climatologically, warmer than the preceding 60 yr and after about 1960. In particular, minimum temperatures show an increase from the 1920's to the 1980's, possibly due to the urbanization of the area. The climatological trends are clearly indicated in the data, when averaged over 30 yr and/or a numerical low-pass filtering technique is used. However, the sizes of the trends in climate are smaller than the interannual variations in the temperature measures. Over periods of several generations these small variations in climate cannot have had any effect on human activity when compared with the large effects caused by the interannual variability in the temperature.  相似文献   

Towards Adaptive Grids for Atmospheric Boundary-Layer Simulations   总被引：1，自引：0，他引：1  

J. Antoon van Hooft  Stéphane Popinet  Chiel C. van Heerwaarden  Steven J. A. van der Linden  Stephan R. de Roode  Bas J. H. van de Wiel 《Boundary-Layer Meteorology》2018,167(3):421-443

We present a proof-of-concept for the adaptive mesh refinement method applied to atmospheric boundary-layer simulations. Such a method may form an attractive alternative to static grids for studies on atmospheric flows that have a high degree of scale separation in space and/or time. Examples include the diurnal cycle and a convective boundary layer capped by a strong inversion. For such cases, large-eddy simulations using regular grids often have to rely on a subgrid-scale closure for the most challenging regions in the spatial and/or temporal domain. Here we analyze a flow configuration that describes the growth and subsequent decay of a convective boundary layer using direct numerical simulation (DNS). We validate the obtained results and benchmark the performance of the adaptive solver against two runs using fixed regular grids. It appears that the adaptive-mesh algorithm is able to coarsen and refine the grid dynamically whilst maintaining an accurate solution. In particular, during the initial growth of the convective boundary layer a high resolution is required compared to the subsequent stage of decaying turbulence. More specifically, the number of grid cells varies by two orders of magnitude over the course of the simulation. For this specific DNS case, the adaptive solver was not yet more efficient than the more traditional solver that is dedicated to these types of flows. However, the overall analysis shows that the method has a clear potential for numerical investigations of the most challenging atmospheric cases.  相似文献   

Influence of tidal regime,diurnal phase,habitat and season on feeding of an intertidal crab     

Claudia Bas  Juan P. Lancia  Tomás Luppi  Agustina Méndez‐Casariego  Marcelo Kittlein  Eduardo Spivak 《Marine Ecology》2014,35(3):319-331

The relationship between diet and feeding activity of intertidal crabs, and environmental cycles (tidal, daily and seasonal), habitat and level of the intertidal zone (high/low) was studied using Neohelice granulata (Brachyura, Varunidae) as a model. This is a semi‐terrestrial burrowing crab occupying different habitats in the Southwestern Atlantic coasts and estuaries from bare low intertidal mudflats to high intertidal salt marshes, and from fine, organic matter rich sediment to very coarse sediment with low content of organic matter. The study was carried out in two contrasting habitats of three sites with diverse sets of physical and biological conditions. Diet and feeding of adult N. granulata were indirectly studied through the proportion of food items and the presence/absence of food in crab stomachs, respectively. This species has a dual mode of feeding: predominantly herbivorous (live plants or plant litter in salt marshes) or deposit feeder (superficial sediment and detritus in mudflats), but the quantity and quality of ingested food varies among habitats and sites. A trend to omnivory (including algae and conspecifics) was detected in relation to low quality of resources. Feeding activity modulated by a complex interaction of factors varied according to spatial and/or temporal changes in some natural cycles. Males and non‐ovigerous females fed preferably after dark and during submersion periods, but also after emersion periods if mudflat sediment remained wet; salt marsh crab feeding is somewhat independent of light and tidal cycles. Ovigerous females almost never fed. Both diet and feeding activity of this crab seem to be flexible traits adapted to different combinations of physical and biological factors.  相似文献   

Scenarios for vulnerability: opportunities and constraints in the context of climate change and disaster risk     

Joern Birkmann  Susan L. Cutter  Dale S. Rothman  Torsten Welle  Matthias Garschagen  Bas van Ruijven  Brian O’Neill  Benjamin L. Preston  Stefan Kienberger  Omar D. Cardona  Tiodora Siagian  Deny Hidayati  Neysa Setiadi  Claudia R. Binder  Barry Hughes  Roger Pulwarty 《Climatic change》2015,133(1):53-68

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The role of negative CO2 emissions for reaching 2 °C—insights from integrated assessment modelling     

Detlef P. van Vuuren  Sebastiaan Deetman  Jasper van Vliet  Maarten van den Berg  Bas J. van Ruijven  Barbara Koelbl 《Climatic change》2013,118(1):15-27

Limiting climate change to 2 °C with a high probability requires reducing cumulative emissions to about 1600 GtCO₂ over the 2000–2100 period. This requires unprecedented rates of decarbonization even in the short-run. The availability of the option of net negative emissions, such as bio-energy with carbon capture and storage (BECCS) or reforestation/afforestation, allows to delay some of these emission reductions. In the paper, we assess the demand and potential for negative emissions in particular from BECCS. Both stylized calculations and model runs show that without the possibility of negative emissions, pathways meeting the 2 °C target with high probability need almost immediate emission reductions or simply become infeasible. The potential for negative emissions is uncertain. We show that negative emissions from BECCS are probably limited to around 0 to 10 GtCO₂/year in 2050 and 0 to 20 GtCO₂/year in 2100. Estimates on the potential of afforestation options are in the order of 0–4 GtCO₂/year. Given the importance and the uncertainty concerning BECCS, we stress the importance of near-term assessments of its availability as today’s decisions has important consequences for climate change mitigation in the long run.  相似文献   

A method for tsunami risk assessment: a case study for Kamakura,Japan     

Non Okumura  Sebastiaan N. Jonkman  Miguel Esteban  Bas Hofland  Tomoya Shibayama 《Natural Hazards》2017,88(3):1451-1472

This paper presents a methodology for tsunami risk assessment, which was applied to a case study in Kamakura, Japan. This methodology was developed in order to evaluate the effectiveness of a risk-reducing system against such hazards, also aiming to demonstrate that a risk assessment is possible for these episodic events. The tsunami risk assessment follows these general steps: (1) determination of the probability of flooding, (2) calculation of flood scenarios, (3) assessment of the consequences and (4) integration into a risk number or graph. The probability of flooding was approximated based on the data provided by local institutes, and the flood scenarios were modeled in 1D using the Simulating WAves till SHore model. Results showed that a tsunami in Kamakura can result in thousands of casualties. Interventions such as improvements in evacuation systems, which would directly reduce the number of casualties, would have a large influence in risk reduction. Although this method has its limits and constraints, it illustrates the value it can add to existing tsunami risk management in Japan.  相似文献   

Hanger replacement influence on seismic response of suspension bridges: Implementation to the Bosphorus Bridge subjected to multi-support excitation     

Selcuk Bas  Chuan-Zhi Dong  Nurdan M. Apaydin  Alper Ilki  F. Necati Catbas 《地震工程与结构动力学》2020,49(14):1496-1518

The effects of hanger replacement from inclined to vertical configuration on seismic response of long-span suspension bridges are investigated considering multi-support earthquake excitation. The Bosphorus Bridge is investigated due to its recent comprehensive rehabilitation, mainly involving hanger replacement. The finite-fault stochastic simulation method (FINSIM) is utilized for multi-point earthquake time-history generation. The developed finite element (FE) model both for the inclined and vertical hanger arrangement are verified through the structural health monitoring (SHM) data. Based on the comparative analysis, the tension force of vertical hangers is found to be lower than that of inclined hangers, whereas the tension force of the main and back-stay cables remains the same. The compressive axial force of the deck decreases relatively in the case of the vertical hanger arrangement, whereas the cross-sectional forces at the tower base section increase. The approach viaducts are not affected by the vertical hanger arrangement. According to the demand/capacity ratios for damage estimation under the max. earthquake (2475 years return period), structural damage on the tower base section may be expected for both hanger arrangements, while these sections perform well under design scenario earthquake. The expansion joint of the bridge with inclined hangers is also estimated to be damaged; however, this displacement is lower in the case of the vertical hanger arrangement due to the viscous dampers. The findings also reveal that a change in hanger form of a suspension bridge can necessitate other structural retrofit, such as using viscous dampers to limit longitudinal displacements of the deck and retrofitting the bridge towers.  相似文献