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Atmospheric
Terms modified by Atmospheric Selected AbstractsAtmospheric and hydrological transport modelling of SOx emissions in a unique verification contextAICHE JOURNAL, Issue 3 2010B. C. McLellan Abstract In this work, we developed a conceptual model incorporating atmospheric transport and hydrological removal of sulfur compounds from a single isolated source. A process engineering approach with conceptual tanks, reactors, pipes, and valves is used for environmental transport modeling. The work includes verification of the model using current data and historical soil sulfur data from a study 23 yrs earlier, collected from sites in a forest and within 20 km from an isolated coal-fired power plant. This verification opportunity is unique in that the power plant is the single major pollutant source within the airshed. In the conceptual process engineering model, environmental relationships with local soil conditions and climate are modeled. The model is validated for three sampling sites, and a sensitivity analysis shows that rainfall has the greatest variance among several other parameters, including sulfur emissions, dry deposition rate, runoff factor, permeability factor, and airshed dimensions. The model is shown to be suitable for a location-specific sustainability metrics application, but it has limitations that further research could improve on including the incorporation of more complexity with the modeling of ground and surface water flows, atmospheric and soil reactions, and vegetation effects. © 2009 American Institute of Chemical Engineers, AIChE J, 2010 [source] Interactions between atmospheric CO2 concentration and phosphorus nutrition on the formation of proteoid roots in white lupin (Lupinus albus L.)PLANT CELL & ENVIRONMENT, Issue 8 2002C. D. Campbell Abstract Atmospheric [CO2] affects photosynthesis and therefore should affect the supply of carbon to roots. To evaluate interactions between carbon supply and nutrient acquisition, the [CO2] effects on root growth, proteoid root formation and phosphorus (P) uptake capacity were studied in white lupin (Lupinus albus L.) grown hydroponically at 200, 410 and 750 µmol mol,1 CO2, under sufficient (0·25 mm P) and deficient (0·69 µm P) phosphorus. Plant size increased with increasing [CO2] only at high P. Both P deficiency and increasing [CO2] increased the production of proteoid clusters; the increase in response to increased [CO2] was proportionally greater from low to ambient [CO2] than from ambient to high. The activity of phosphoenol pyruvate carboxylase in the proteoid root, the exudation of organic acids from the roots, and the specific uptake of P increased with P deficiency, but were unaffected by [CO2]. Increasing [CO2] from Pleistocene levels to those predicted for the next century increased plant size and allocation to proteoid roots, but did not change the specific P uptake capacity per unit root mass. Hence, rising [CO2] should promote nutrient uptake by allowing lupins to mine greater volumes of soil. [source] Retrieval validation during the European Aqua Thermodynamic ExperimentTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S3 2007Daniel K. Zhou Abstract Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sensors aboard Earth observing satellites are critical to weather prediction and scientific research. The retrieval algorithms and retrieved parameters from satellite sounders must be validated to demonstrate the capability and accuracy of both observation and data processing systems. The European Aqua Thermodynamic Experiment (EAQUATE) was conducted not only for validation of the Atmospheric InfraRed Sounder on the Aqua satellite, but also for assessment of validation systems of both ground-based and aircraft-based instruments that will be used for other satellite systems, such as the Infrared Atmospheric Sounding Interferometer on the European MetOp satellite, the Cross-track Infrared Sounder from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project and the continuing series of NPOESS satellites. Detailed intercomparisons were conducted and presented using different retrieval methodologies: measurements from airborne ultraspectral Fourier transform spectrometers, aircraft in situ instruments, dedicated dropsondes and radiosondes, ground-based Raman lidar, as well as the European Centre for Medium-range Weather Forecasting modelled thermal structures. The results of this study not only illustrate the quality of the measurements and retrieval products, but also demonstrate the capability of the validation systems put in place to validate current and future hyperspectral sounding instruments and their scientific products. Copyright © 2007 Royal Meteorological Society [source] Short-term erosion rates from a 7Be inventory balanceEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2003Christopher G. Wilson Abstract Detailed soil erosion studies bene,t from the ability to quantify the magnitude of erosion over time scales appropriate to the process. An inventory balance for 7Be was used to calculate sediment erosion in a 30·73 m2 plot during a series of runoff-producing thunderstorms occurring over three days at the Deep Loess Research Station in Treynor, Iowa, USA. The inventory balance included determination of the pre- and post-storm 7Be inventories in the soil, the atmospheric in,ux of 7Be during the event, and pro,les of the 7Be activity in the soil following the atmospheric deposition. The erosion calculated in the plot using the 7Be inventory balance was 0·058 g cm,2, which is 23 per cent of the annual average erosion determined using 137Cs inventories. The calculated erosion from the mass balance is similar to the 0·059 g cm,2 of erosion estimated from the amount of sediment collected at the outlet of the 6 ha ,eld during the study period and the delivery ratio (0·64). The inventory balance of 7Be provides a new means for evaluating soil erosion over the time period most relevant to quantifying the prediction of erosion from runoff. Copyright © 2003 John Wiley & Sons, Ltd. [source] Harbor seals (Phoca vitulina) in British Columbia, Canada, and Washington State, USA, reveal a combination of local and global polychlorinated biphenyl, dioxin, and furan signalsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Peter S. Ross Abstract The harbor seal (Phoca vitulina) can serve as a useful indicator of food web contamination by persistent organic pollutants (POPs) because of its high trophic level, wide distribution in temperate coastal waters of the Northern Hemisphere, and relative ease of capture. In 1996 through 1997, we live-captured 60 harbor seal pups from three regions, spanning remote (Queen Charlotte Strait, BC, Canada), moderately industrialized (Strait of Georgia, BC, Canada), and heavily industrialized (Puget Sound, WA, USA) marine basins straddling the Canada-United States border. Biopsy samples of blubber were taken and analyzed for congener-specific polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p -dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) by using high-resolution gas chromatography-high-resolution mass spectrometry. Harbor seals in Puget Sound were heavily contaminated with PCBs, whereas seals from the Strait of Georgia had relatively high concentrations of PCDDs and PCDFs. Pattern evaluation and principal components analysis suggested that proximity to sources influenced the mixture to which seals were exposed, with those inhabiting more remote areas being exposed to lighter PCB congeners (those with lower Henry's law constant and KOW) that disperse more readily through atmospheric and other processes. Total toxic equivalents to 2,3,7,8-tetrachlorodibenzo- p -dioxin for the PCBs, PCDDs, and PCDFs suggest that Puget Sound seals are at greatest risk for adverse health effects, and that PCBs represent the class of dioxinlike contaminants of greatest concern at all sites. [source] Modelling the response of sprinklers in compartment firesFIRE AND MATERIALS, Issue 3 2001A. K. Gupta Alpert's expressions are used extensively to calculate the maximum temperature and velocity in the ceiling-jet at any distance, r, from the fire axis. These expressions are valid for unconfined ceilings insofar as the environment outside the ceiling-jet is uniform in temperature and is atmospheric ambient. In compartments the outward flow of hot gases is checked by the presence of bounding walls and so a layer of hot gases is formed in the upper portion of the compartment. The environment outside the ceiling-jet is no longer ambient atmospheric. Expressions due to Alpert becomes unsuitable, unless the effects of the accumulated hot layer are included in these expressions. The effect of the upper layer temperature has been taken by assuming that since the ceiling-jet is completely submerged in the upper hot gas layer, the entrained gases are drawn from this layer only instead of the ambient atmospheric air at T,. Thus T, has been replaced by TL in the Alpert's empirical expression for ceiling-jet temperatures. The proposed equation is then used to calculate the response time of sprinklers fitted in compartments of varying sizes. Calculations have been done for identical conditions to those employed by Evans and compared. Comparison has also been made with Cooper's LAVENT model predictions. The study shows that the present model is capable of predicting the maximum, as well as average, temperatures in the ceiling-jets submerged in the hot gas layer. Copyright © 2001 John Wiley & Sons, Ltd. [source] A Strategic Framework for Monitoring Coastal Change in Australia's Wet-dry Tropics , Concepts and ProgressGEOGRAPHICAL RESEARCH, Issue 2 2009C. MAX FINLAYSON Abstract A strategic framework for monitoring natural and human-induced change in the coastal plains of the Alligator Rivers Region in the wet-dry tropics of northern Australia is presented. The framework also supports refinement of methods used to monitor the vulnerability of coastal areas to change, including human-induced climate change and sea-level rise. The information derived through the framework can be used to assess scenarios, highlight the potential significance and implications of changes, and assist land managers formulate management responses. The framework incorporates several large-scale studies for monitoring atmospheric and hydrodynamic processes as well as mapping and monitoring projects specific to environmental change in the freshwater wetlands and the floodplains of the Region. Monitoring is proposed to address processes influencing the stability and rate of change of the floodplain environments. These include large-scale processes, such as inter-annual variability in weather conditions affecting the morphology of the coastal plains, shoreline and riverbank stabilisation, headward expansion of tidal creeks, and salinisation of freshwater basins. Information management is also addressed, and a Geographic Information System structure proposed for effective data collation, analysis and management. The information management system will facilitate data sharing and participation of multiple agencies and organisations interested in coastal change, especially where a landscape perspective or whole ecosystem approach is advocated. [source] Reduced early growing season freezing resistance in alpine treeline plants under elevated atmospheric CO2GLOBAL CHANGE BIOLOGY, Issue 3 2010MELISSA MARTIN Abstract The frequency of freezing events during the early growing season and the vulnerability to freezing of plants in European high-altitude environments could increase under future atmospheric and climate change. We tested early growing season freezing sensitivity in 10 species, from four plant functional types (PFTs) spanning three plant growth forms (PGFs), from a long-term in situ CO2 enrichment (566 vs. 370 ppm) and 2-year soil warming (+4 K) experiment at treeline in the Swiss Alps (Stillberg, Davos). By additionally tracking plant phenology, we distinguished indirect phenology-driven CO2 and warming effects from direct physiology-related effects on freezing sensitivity. The freezing damage threshold (lethal temperature 50) under ambient conditions of the 10 treeline species spanned from ,6.7±0.3 °C (Larix decidua) to ,9.9±0.6 °C (Vaccinium gaultherioides). PFT, but not PGF, explained a significant amount of this interspecific variation. Long-term exposure to elevated CO2 led to greater freezing sensitivity in multiple species but did not influence phenology, implying that physiological changes caused by CO2 enrichment were responsible for the effect. The elevated CO2 effect on freezing resistance was significant in leaves of Larix, Vaccinium myrtillus, and Gentiana punctata and marginally significant in leaves of Homogyne alpina and Avenella flexuosa. No significant CO2 effect was found in new shoots of Empetrum hermaphroditum or in leaves of Pinus uncinata, Leontodon helveticus, Melampyrum pratense, and V. gaultherioides. Soil warming led to advanced leaf expansion and reduced freezing resistance in V. myrtillus only, whereas Avenella showed greater freezing resistance when exposed to warming. No effect of soil warming was found in any of the other species. Effects of elevated CO2 and soil warming on freezing sensitivity were not consistent within PFTs or PGFs, suggesting that any future shifts in plant community composition due to increased damage from freezing events will likely occur at the individual species level. [source] Responses of dryland soil respiration and soil carbon pool size to abrupt vs. gradual and individual vs. combined changes in soil temperature, precipitation, and atmospheric [CO2]: a simulation analysisGLOBAL CHANGE BIOLOGY, Issue 9 2009WEIJUN SHEN Abstract With the large extent and great amount of soil carbon (C) storage, drylands play an important role in terrestrial C balance and feedbacks to climate change. Yet, how dryland soils respond to gradual and concomitant changes in multiple global change drivers [e.g., temperature (Ts), precipitation (Ppt), and atmospheric [CO2] (CO2)] has rarely been studied. We used a process-based ecosystem model patch arid land simulator to simulate dryland soil respiration (Rs) and C pool size (Cs) changes to abrupt vs. gradual and single vs. combined alterations in Ts, Ppt and CO2 at multiple treatment levels. Results showed that abrupt perturbations generally resulted in larger Rs and had longer differentiated impacts than did gradual perturbations. Rs was stimulated by increases in Ts, Ppt, and CO2 in a nonlinear fashion (e.g., parabolically or asymptotically) but suppressed by Ppt reduction. Warming mainly stimulated heterotrophic Rs (i.e., Rh) whereas Ppt and CO2 influenced autotrophic Rs (i.e., Ra). The combined effects of warming, Ppt, and CO2 were nonadditive of primary single-factor effects as a result of substantial interactions among these factors. Warming amplified the effects of both Ppt addition and CO2 elevation whereas Ppt addition and CO2 elevation counteracted with each other. Precipitation reduction either magnified or suppressed warming and CO2 effects, depending on the magnitude of factor's alteration and the components of Rs (Ra or Rh) being examined. Overall, Ppt had dominant influence on dryland Rs and Cs over Ts and CO2. Increasing Ppt individually or in combination with Ts and CO2 benefited soil C sequestration. We therefore suggested that global change experimental studies for dryland ecosystems should focus more on the effects of precipitation regime changes and the combined effects of Ppt with other global change factors (e.g., Ts, CO2, and N deposition). [source] Reorganization of a large marine ecosystem due to atmospheric and anthropogenic pressure: a discontinuous regime shift in the Central Baltic SeaGLOBAL CHANGE BIOLOGY, Issue 6 2009CHRISTIAN MÖLLMANN Abstract Marine ecosystems such as the Baltic Sea are currently under strong atmospheric and anthropogenic pressure. Besides natural and human-induced changes in climate, major anthropogenic drivers such as overfishing and anthropogenic eutrophication are significantly affecting ecosystem structure and function. Recently, studies demonstrated the existence of alternative stable states in various terrestrial and aquatic ecosystems. These so-called ecosystem regime shifts have been explained mainly as a result of multiple causes, e.g. climatic regime shifts, overexploitation or a combination of both. The occurrence of ecosystem regime shifts has important management implications, as they can cause significant losses of ecological and economic resources. Because of hysteresis in ecosystem responses, restoring regimes considered as favourable may require drastic and expensive management actions. Also the Baltic Sea, the largest brackish water body in the world ocean, and its ecosystems are strongly affected by atmospheric and anthropogenic drivers. Here, we present results of an analysis of the state and development of the Central Baltic Sea ecosystem integrating hydroclimatic, nutrient, phyto- and zooplankton as well as fisheries data. Our analyses of 52 biotic and abiotic variables using multivariate statistics demonstrated a major reorganization of the ecosystem and identified two stable states between 1974 and 2005, separated by a transition period in 1988,1993. We show the change in Baltic ecosystem structure to have the characteristics of a discontinuous regime shift, initiated by climate-induced changes in the abiotic environment and stabilized by fisheries-induced feedback loops in the food web. Our results indicate the importance of maintaining the resilience of an ecosystem to atmospherically induced environmental change by reducing the anthropogenic impact. [source] The importance of low atmospheric CO2 and fire in promoting the spread of grasslands and savannasGLOBAL CHANGE BIOLOGY, Issue 7 2003W. J. BOND Abstract The distribution and abundance of trees can be strongly affected by disturbance such as fire. In mixed tree/grass ecosystems, recurrent grass-fuelled fires can strongly suppress tree saplings and therefore control tree dominance. We propose that changes in atmospheric [CO2] could influence tree cover in such metastable ecosystems by altering their postburn recovery rates relative to flammable herbaceous growth forms such as grasses. Slow sapling recovery rates at low [CO2] would favour the spread of grasses and a reduction of tree cover. To test the possible importance of [CO2]/fire interactions, we first used a Dynamic Global Vegetation Model (DGVM) to simulate biomass in grassy ecosystems in South Africa with and without fire. The results indicate that fire has a major effect under higher rainfall conditions suggesting an important role for fire/[CO2] interactions. We then used a demographic model of the effects of fire on mesic savanna trees to test the importance of grass/tree differences in postburn recovery rates. We adjusted grass and tree growth in the model according to the DGVM output of net primary production at different [CO2] relative to current conditions. The simulations predicted elimination of trees at [CO2] typical of the last glacial period (180 ppm) because tree growth rate is too slow (15 years) to grow to a fire-proof size of ca. 3 m. Simulated grass growth would produce an adequate fuel load for a burn in only 2 years. Simulations of preindustrial [CO2] (270 ppm) predict occurrence of trees but at low densities. The greatest increase in trees occurs from preindustrial to current [CO2] (360 ppm). The simulations are consistent with palaeo-records which indicate that trees disappeared from sites that are currently savannas in South Africa in the last glacial. Savanna trees reappeared in the Holocene. There has also been a large increase in trees over the last 50,100 years. We suggest that slow tree recovery after fire, rather than differential photosynthetic efficiencies in C3 and C4 plants, might have been the significant factor in the Late Tertiary spread of flammable grasslands under low [CO2] because open, high light environments would have been a prerequisite for the spread of C4 grasses. Our simulations suggest further that low [CO2] could have been a significant factor in the reduction of trees during glacial times, because of their slower regrowth after disturbance, with fire favouring the spread of grasses. [source] Responses of leaf nitrogen concentration and specific leaf area to atmospheric CO2 enrichment: a retrospective synthesis across 62 speciesGLOBAL CHANGE BIOLOGY, Issue 7 2002Xiwei Yin Abstract Knowledge of leaf responses to elevated atmospheric [CO2] (CO2 concentration) is integral to understanding interactions between vegetation and global change. This work deals with responses of leaf mass-based nitrogen concentration (Nm) and specific leaf area (SLA). It assesses the statistical significance of factors perceived as influential on the responses, and quantifies how the responses vary with the significant factors identified, based on 170 data cases of 62 species compiled from the literature. Resultant equations capture about 41% of the variance in the data for percent responses of Nm and SLA, or about 95% of the variance for Nm and SLA at 57,320% normal [CO2]; these performance statistics also hold for leaf area-based N concentration and specific leaf weight. The equations generalize that: (i) both Nm and SLA decline as [CO2] increases; (ii) proportional decline of Nm is greater with deciduous woody species and with plants of normally low Nm, increases with pot size in growth chamber and greenhouse settings and with temperature and photosynthetic photon flux density (PPFD), and is mitigated by N fertilization; and (iii) proportional decline of SLA depends on pot size and PPFD similarly to Nm, increases with leaf life span and water vapour pressure deficit in enclosed experiments, and decreases with prolonged exposure to elevated [CO2] among broadleaf woody species in field conditions. The results highlight great uncertainty in the percent-response data and reveal the potential feasibility to estimate Nm and SLA at various magnitudes of elevated [CO2] from a few key plant and environmental factors of broad data bases. [source] Selective Atmospheric Pressure Chemical Vapor Deposition Route to CdS Arrays, Nanowires, and NanocombsADVANCED FUNCTIONAL MATERIALS, Issue 2 2004P. Ge Abstract CdS arrays, nanowires, and nanocombs were selectively prepared through an atmospheric pressure chemical vapor deposition (APCVD) process with CdCl2 and S as sources. The morphologies could be controlled by adjusting the deposition position, the temperature, and the flux of the carrier gas. The phase structure, morphologies, and photoluminescence properties of the CdS products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra. The formation mechanism of the nanowires is discussed on the basis of the experimental results. The adopted synthetic route is expected to be applied in the synthesis of other metal sulfide one-dimensional (1D) nanostructures. [source] Subglacial drainage system structure and morphology of Brewster Glacier, New ZealandHYDROLOGICAL PROCESSES, Issue 3 2009Ian Willis Abstract A global positioning system and ground penetrating radar surveys is used to produce digital elevation models of the surface and bed of Brewster Glacier. These are used to derive maps of subglacial hydraulic potential and drainage system structure using three different assumptions about the subglacial water pressure (Pw): (i) Pw = ice overburden; (ii) Pw = half ice overburden; (iii) Pw = atmospheric. Additionally, 16 dye-tracing experiments at 12 locations were performed through a summer melt season. Dye return curve shape, together with calculations of transit velocity, dispersivity and storage, are used to infer the likely morphology of the subglacial drainage system. Taken together, the data indicate that the glacier is underlain by a channelised but hydraulically inefficient drainage system in the early summer in which water pressures are close to ice overburden. By mid-summer, water pressures are closer to half-ice overburden and the channelised drainage system is more hydraulically efficient. Surface streams that enter the glacier close to the location of major subglacial drainage pathways are routed quickly to the channels and then to the glacier snout. Streams that enter the glacier further away from the drainage pathways are routed slowly to the channels and then to the snout because they first flow through a distributed drainage system. Copyright © 2008 John Wiley & Sons, Ltd. [source] Modelling two-dimensional steady-state groundwater flow and flow sensitivity to boundary conditions in blanket peat complexesHYDROLOGICAL PROCESSES, Issue 2 2005D. R. Lapen Abstract This study used a two-dimensional steady-state finite-element groundwater flow model to simulate groundwater flow in two Newfoundland blanket peat complexes and to examine flow system sensitivity to changes in water table recharge and aquifer properties. The modelling results were examined within the context of peat-forming processes in the two complexes. Modelled flow compared favourably with observed flow. The sensitivity analyses suggested that more highly decomposed bog peat along bog margins probably has/had a positive impact on net peat accumulation within bog interiors. Peat with lower hydraulic conductivity along bog margins effectively impedes lateral drainage, localizes water table drawdown to extreme bog margins, and elevates water tables along bog interiors. Peat formation and elevated water tables in adjacent poor fens/laggs currently rely on placic and ortstein horizons impeding vertical drainage and water flow inputs from adjacent bogs. Modest reductions in atmospheric recharge were found to govern bog-flow-system geometries in a way that would adversely affect paludification processes in adjacent fens/laggs. Copyright © 2004 John Wiley & Sons, Ltd. [source] Sources of stream sulphate in headwater catchments in Otter Creek Wilderness, West Virginia, USAHYDROLOGICAL PROCESSES, Issue 4 2001Ross D. Fitzhugh Abstract Upland forested catchments in the Appalachian Plateau region receive among the greatest rates of atmospheric sulphur (S) deposition in the eastern USA, although coal mines and S-bearing minerals in bedrock may also contribute to stream acidity in this region. Watershed mass balance and stable S isotopic values (,34S) of sulphate (SO42,) were used to assess the contributions to stream SO42, from atmospheric and lithogenic sources at Yellow Creek (YC), a headwater catchment on the Appalachian Plateau in West Virginia. Oxygen isotopic values (,18O) of water were used to study catchment hydrology. Stream output of SO42, was c. 60% of atmospheric S deposition during a relatively dry year, whereas atmospheric S input was nearly balanced by stream output during a year with above normal amounts of precipitation. The temporal patterns and values of ,34S were similar between bulk precipitation and stream water at two upper elevation sites. At the lowest elevation site, stream ,34S values were similar to bulk precipitation values during the dormant season but were slightly lower than precipitation during the low-flow summer, probably as the result of a greater proportion of stream water being derived from deep hydrological flowpaths that have contacted S-bearing minerals with low ,34S values in coal seams. Stream ,34S values at YC were significantly higher than at Coal Run, a catchment containing abandoned coal prospects and having a greater amount of S-bearing minerals than YC. Results suggested that lithogenic S is a relatively minor source and that atmospheric deposition is the principal source of stream SO42,, and thus stream acidity, at YC. Copyright © 2001 John Wiley & Sons, Ltd. [source] Simulation of two-dimensional turbulent flows in a rotating annulusINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2004Brian D. Storey Abstract Rotating water tank experiments have been used to study fundamental processes of atmospheric and geophysical turbulence in a controlled laboratory setting. When these tanks are undergoing strong rotation the forced turbulent flow becomes highly two dimensional along the axis of rotation. An efficient numerical method has been developed for simulating the forced quasi-geostrophic equations in an annular geometry to model current laboratory experiments. The algorithm employs a spectral method with Fourier series and Chebyshev polynomials as basis functions. The algorithm has been implemented on a parallel architecture to allow modelling of a wide range of spatial scales over long integration times. This paper describes the derivation of the model equations, numerical method, testing and performance of the algorithm. Results provide reasonable agreement with the experimental data, indicating that such computations can be used as a predictive tool to design future experiments. Copyright © 2004 John Wiley & Sons, Ltd. [source] An Arctic and antarctic perspective on recent climate changeINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2007John Turner Abstract We contrast recent climatic and environmental changes and their causes in the Arctic and the Antarctic. There are continuing increases in surface temperatures, losses of sea ice and tundra, and warming of permafrost over broad areas of the Arctic, while most of the major increase in Antarctic temperatures is on the Antarctic Peninsula associated with sea ice loss in the Bellingshausen,Amundsen Seas sector. While both natural atmospheric and oceanic variability, and changes in external forcing including increased greenhouse gas concentrations, must be considered in the quest for understanding such changes, the interactions and feedbacks between system components are particularly strong at high latitudes. For the 1950s to date in the Arctic and for 1957 to date in the Antarctic, positive trends in large-scale atmospheric circulation represented by the Arctic oscillation (AO) and Antarctic oscillations (AAO) and the Pacific North American (PNA) pattern contribute to the long-term temperature trends. However, continuing Arctic trends during the last decade of near neutral AO will require alternate explanations. The trend in the AAO since 1950 is larger than expected from natural variability and may be associated with the decrease in stratospheric ozone over Antarctic. The persistence shown in many Arctic and Antarctic Peninsula components of climate and their influence through possible feedback supports continuation of current trends over the next decade. One can expect large spatial and temporal differences, however, from the relative contributions of intrinsic variability, external forcing, and internal feedback/amplifications. It is particularly important to resolve regional feedback processes in future projections based on modeling scenarios. Copyright © 2006 Royal Meteorological Society. [source] Features of cross-Pacific climate shown in the variability of China and US precipitationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2005Q. Li Abstract In this study, we have analyzed the climate features of China and the United States with a focus on the differences, similarities, connectivity, and predictability of precipitation and the relationships between precipitation and large-scale patterns of natural variability. China precipitation is characterized by large seasonality, with a maximum in summer and a minimum in winter. The seasonality of precipitation shows an increasing linear tendency in northwest China, with a change of about 20% from 1901 to 1998. A relatively weaker increasing tendency also appears in the Big Bend of Yellow River (BBYR) and the Tibetan Plateau, while southwest China experiences a decreasing tendency. Furthermore, the seasonality in the BBYR shows particularly significant interdecadal variability, while that of southern and eastern China has decreased slightly in the recent decades. Compared to China, the United States as a whole has less precipitation in summer but more precipitation in other seasons. Here, the seasonality of precipitation is only about 24% of that in China. The annual mean precipitation is 64.1 mm per month in the United States, compared to 54.6 mm per month in China. The seasonality of precipitation exhibits a decreasing tendency in the southeast, Pacific Northwest, and Gulf Coast and an increasing tendency in the Great Lakes. The seasonality in the Great Plains exhibits large interdecadal variability. The long-term variations of precipitation are highly seasonally dependent. In summer, a decreasing trend is observed in north China and an increasing trend is found in eastern-central China. However, these trends are almost opposite in spring. In addition, the fall precipitation decreases with time nearly everywhere in China except for the middle and lower reaches of the Yangtze River Valley. Results also indicate that the El Niño/Southern Oscillation (ENSO), the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Pacific Decadal Oscillation (PDO), and the North Pacific (NP) fluctuation affect strongly the variations of China and US precipitation. Although these influences vary with regions and seasons, we in particular emphasize the importance of AO and NAO for China precipitation and NP and PDO for US precipitation. In fall, ENSO and PDO are the two phenomena that influence predominantly precipitation variability in both China and the United States We also identify the common phenomena that influence China and US regional precipitation and provide a better understanding of the physical mechanism for precipitation variability through the associated changes in atmospheric and oceanic conditions. Furthermore, we develop a linear regression model, based on multiple regression method by combining the regionally and seasonally varying impacts, to increase the skill of precipitation prediction. Copyright © 2005 Royal Meteorological Society [source] Classification of synchronous oceanic and atmospheric El Niño-Southern Oscillation (ENSO) events for palaeoclimate reconstructionINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2005Joëlle L. Gergis Abstract Since the mid-1970s, ENSO has changed in character to a predominance of El Niño conditions, the extreme phase of which appears coincidental with increases in global temperature records. Instrumental time series (<150 years) are too short to adequately address the significance of late twentieth-century ENSO variability, thus, multi-century palaeoclimate reconstructions derived from long proxy records are sought. Despite the global influence exerted by ENSO on society, limited consensus exists within the scientific community as to which index best defines the timing, duration and strength of events. Here we address issues associated with the complexity of ENSO characterisation by comparing the ,event capture' ability of two currently used indices of ENSO. It is suggested that the use of a sole ENSO index is undesirable as a given index is only indicative of one physical aspect of the phenomenon, and as such is unlikely to be representative of the wider interactions experienced in the coupled ocean-atmospheric system. In an attempt to describe more of the nature and evolution of ENSO events, the Coupled ENSO Index (CEI) classification scheme was devised to identify synchronous oceanic (Niño 3.4 SST) and atmospheric (Southern Oscillation Index) anomalies associated with ENSO for the instrumental period (1871,2003). The CEI is of practical relevance to the ENSO community as it provides an amplitude preserving instrumental baseline for the calibration of proxy records to reconstruct both components of the ENSO system. Analysis of the nature of instrumental ENSO events from the CEI suggests that the frequency and intensity of post-1970 ENSO events (when 50% of all extreme events identified occur) appears the most anomalous in the context of at least the past century. It is hoped that the CEI will facilitate palaeo-ENSO research to systematically resolve the long-term context of past ENSO behaviour to assess whether the apparently anomalous nature of late twentieth-century variability is unprecedented within existing palaeoclimate archives. Copyright © 2005 Royal Meteorological Society. [source] Variability of total and solid precipitation in the Canadian Arctic from 1950 to 1995INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2002Rajmund Przybylak Abstract Trends in solid and total precipitation, as well as in the ratio of solid to total precipitation (hereinafter S/T ratio), in the Canadian Arctic in recent decades have been investigated. In addition, the influence of air temperature and circulation factors (atmospheric and oceanic) on the above-mentioned precipitation characteristics have been examined. Recently updated and adjusted data by the Canadian Climate Centre from 16 stations located in the Canadian Arctic and two stations from the sub-Arctic were used for the investigation. The southern boundary of the study area was taken after Atlas Arktiki (Tresjinkov, A. 1985. Glavnoye Upravlenye Geodeziy i Kartografiy: Moscow; 204 pp). The majority of the data cover the period from 1950 to 1995. A statistically significant increase in all kinds of areally averaged seasonal and annual precipitation for the Canadian Arctic over the period 1950,95 has been found. On the other hand, the S/T ratio did not change significantly, except for summer values, and its behaviour was also in accord with small variations noted in air temperature. An increase in air temperature in the Canadian Arctic most often led to a rise in all kinds of annual precipitation sums, but only when the warmest and coldest years were chosen based on individual stations. The pattern of the relationship is significantly more complicated, and can even be opposite to that presented above, when the sets of the warmest and coldest years are chosen based on the areally averaged annual temperature for the Canadian Arctic. Significantly more stable results of changes were found for the S/T ratio, which in warmer periods was usually lower. However, more detailed and reliable investigations of temperature,precipitation relationships conducted for individual stations showed that though the S/T ratio in warmer periods may well be lower, this only applies to the southern (warmer) part of the Canadian Arctic (<70 °N). During periods with high positive values of the North Atlantic Oscillation Index (NAOI), a decrease in precipitation is observed in the south-eastern part of the Canadian Arctic, i.e. in the area where strong cooling was also observed. During El Niño events most of the Canadian Arctic had both greater precipitation and a higher S/T ratio than during La Niña events. The most unequivocal results of precipitation and S/T ratio changes were found for changes in the Arctic Ocean circulation regimes. In almost the whole study area, a lower precipitation and S/T ratio were noted during the anticyclonic circulation regime in the Arctic Ocean. Copyright © 2002 Royal Meteorological Society [source] Observed and SST-forced seasonal rainfall variability across tropical AmericaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2001Vincent Moron Abstract Three experiments starting from different initial conditions have been made with the ECHAM-4 atmospheric General Circulation Model (GCM) integrated at T30 resolution forced with the observed sea-surface temperature (SST) over the period 1960,1994. The tropical America modes of seasonal rainfall anomalies whose time variation is most accurately simulated by the GCM have been searched for using Singular Value Decomposition Analyses (SVDA) and Canonical Correlation Analysis (CCA) between observed and model fields. The leading modes revealed by SVDA and CCA are highly similar, even though the ordering of the modes showed some fluctuation. A first skilful rainfall anomaly mode has weights of the same sign almost everywhere in tropical America, except along the western coast and the sub-tropical margins. This mode appears in all of the four seasons assessed. A second major skilful mode is usually a bipolar north,south (N,S) rainfall anomaly pattern (clear in December,March, DJFM; March,May, MAM; and June,September, JJAS). A large portion of the skill of the first rainfall anomaly mode (same sign anomalies across tropical America except small patches along the western coast) is through variance that is in common with the Southern Oscillation Index (SOI). In addition to forcing from the central/eastern tropical Pacific SST, there also appears a contribution from contrasting SST anomalies in the tropical Atlantic. This rainfall mode is usually a regional portion of a more large-scale mode encompassing at least the whole tropical zone (especially in DJFM, MAM and September,November, SON). Analysis of the relationship of this mode with GCM circulation features reveals that a rainfall deficit (respectively excedent) over the main rainbelt of the tropical America region is associated with strengthening (respectively weakening) of the sub-tropical westerly jet streams, a global warming (respectively cooling) of the tropical atmosphere, an anomalous divergence (respectively convergence) in the lower levels and an anomalous convergence (respectively divergence) in the upper levels over tropical America and in the region of the Atlantic Inter-tropical Convergence Zone (ITCZ). Such global features are not so apparent for the dominant mode of JJAS, even though the correlations with El Niño,Southern Oscillation (ENSO) indicators (as SOI or NINO3 SST index) are as high as for the other seasons. The bipolar N,S rainfall anomaly mode in tropical America is mostly related to anomalous N,S gradient of SST anomalies in the tropical Atlantic. The atmospheric circulation anomalies emphasize changes in 850 hPa meridional winds in the tropical Atlantic. However, there is also interannual variance of this rainfall mode in both the model and observations that is unexplained by tropical Atlantic SSTs, but which is explained by central/eastern tropical Pacific SSTs and, potentially, SSTs from other tropical and extratropical areas. This is especially true in MAM. Some differences in the details of the model and observed teleconnection patterns are noted. Such differences can be used to statistically adjust the model simulations using the CCA or SVDA modes as basis patterns. Both statistical approaches have been applied and the results are consistent between the two. The increase of skill is stronger when temporal correlation (the pattern correlation) between the model and observed pattern is high (low) as for JJAS. The skill is moderate to high around the whole Amazon basin, but remains relatively low inside the Amazon basin, though reliability of the observations themselves may influence this result. Averaged over all the seasons, about 15,35% (35,55%) of the interannual grid-box (regional) seasonal rainfall variance is skilfully simulated from the observed SST forcing. Copyright © 2001 Royal Meteorological Society [source] Thermodynamic optimization of global circulation and climateINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2005Adrian Bejan Abstract The constructal law of generation of flow structure is used to predict the main features of global circulation and climate. The flow structure is the atmospheric and oceanic circulation. This feature is modelled as convection loops, and added to the earth model as a heat engine heated by the Sun and cooled by the background. It is shown that the dissipation of the power produced by the earth engine can be maximized by selecting the proper balance between the hot and cold zones of the Earth, and by optimizing the thermal conductance of the circulation loops. The optimized features agree with the main characteristics of global circulation and climate. The robustness of these predictions, and the place of the constructal law as a self-standing principle in thermodynamics, are discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source] A theoretical study of the rotational structure of the ,(0,0) band of NOINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2010A. M. Velasco Abstract This study has been focused on the ,(0,0) band of the nitric oxide molecule, associated with the absorption electronic transition D2,+,X 2,, in the energetic vacuum ultraviolet region. A temperature of 295 K has been considered. The Molecular Quantum Defect Orbital (MQDO) methodology, with which reliable spectroscopic data have been reached in the ,(0,0), ,(0,0), and ,(1,0) bands of the same molecule, has also been used for these calculations. We hope that the present results might be of straightforward use in atmospheric and interstellar chemistry. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Interference rejection in non-Gaussian noise for satellite communications using non-linear beamformingINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003Chang Qing Xu Abstract In this paper, non-linear beamforming based on the method of radial basis functions (RBF) is proposed to combine with constant modulus algorithm (CMA) for interference cancellation in non-Gaussian noise. First, a signal space is constructed from the input array data vectors utilizing RBF. A set of exponential functions is used to transform the Euclidean norm of the input array data vectors into the signal space. Then, CMA is employed to eliminate the interference. Both Gaussian and non-Gaussian noise are considered in the experiment. The numerical results indicate that this scheme is effective and robust in terms of interference cancellation. A deep null can be formed to the direction of interference for both Gaussian and non-Gaussian noise. Furthermore, these results are compared with that of DBF with CMA based on FFT technique, a widely used linear beamforming technique. The comparison shows that a DBF array antenna with CMA based on the method of RBF outperforms its counterpart based on FFT technique. The most interesting result is that the proposed method has a robust interference cancellation performance in non-Gaussian noise whereas the FFT technique fails to do so. This observation can be very useful in satellite communications because that non-Gaussian noise such as atmospheric and man-made noise are often encountered in satellite communications. Copyright © 2003 John Wiley & Sons, Ltd. [source] Visualization of the foaming mechanism of polyethylene blown by chemical blowing agents under ambient pressureADVANCES IN POLYMER TECHNOLOGY, Issue 4 2007Remon Pop-Iliev Abstract Understanding the fundamental mechanisms that govern the foaming process is the most essential universal prerequisite for developing effective processing strategies for fabricating high-quality foamed plastic products using any type of foaming technology. Despite chemically blown foaming of thermoplastics under atmospheric pressure has been successfully implemented in rotational foam molding over the last decade, the related open literature does not provide substantial research addressing the fundamentals of this unique foaming mechanism. The present study focuses on clarifying the fundamental foaming mechanisms that govern the successful manufacture of thermoplastic foams using a chemical blowing agent under low-pressure (atmospheric) conditions. The presented research is mainly based on observing a series of visualization experiments conducted using a custom-made visualization system including an optical microscope and a computerized CCD camera imaging system, which was utilized for investigating the behavior of foamable polyethylene samples prepared by using the compression-molding method. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:213,222, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20102 [source] Current issues with fish and fisheries: editor's overview and introductionJOURNAL OF APPLIED ECOLOGY, Issue 2 2003S. J. Ormerod Summary 1.,By any measure, fishes are among the world's most important natural resources. Annual exploitation from wild populations exceeds 90 million tonnes, and fish supply over 15% of global protein needs as part of total annual trade exceeding $US 55 billion. Additionally, with over 25 000 known species, the biodiversity and ecological roles of fishes are being increasingly recognised in aquatic conservation, ecosystem management, restoration and aquatic environmental regulation. 2.,At the same time, substantial management problems now affect the production, exploitable stocks, global diversity, trophic structure, habitat quality and local composition of fish communities. 3.,In marine systems, key issues include the direct effects of exploitation on fish, habitats and other organisms, while habitat or water quality problems arise also from the atmospheric, terrestrial and coastal environments to which marine systems are linked. In freshwaters, flow regulation and obstruction by dams, fragmentation, catchment management, pollution, habitat alterations, exotic fish introductions and nursery-reared fish are widespread issues. 4.,Management responses to the problems of fish and fisheries include aquatic reserves in both marine and freshwater habitats, and their effectiveness is now being evaluated. Policies on marine exploitation increasingly emphasise fishes as integral components of aquatic ecosystems rather than individually exploitable stocks, but the rationalisation of fishing pressures presents many challenges. In Europe, North America and elsewhere, policies on freshwaters encourage habitat protection, integrated watershed management and restoration, but pressures on water resources will cause continued change. All these management approaches require development and evaluation, and will benefit from a perspective of ecological understanding with ecologists fully involved. 5.,Synthesis and applications. Although making a small contribution to the Journal of Applied Ecology in the past, leading work on aquatic problems and fish-related themes appear increasingly in this and other mainstream ecology journals. As this special profile of five papers shows, significant contributions arise on diverse issues that here include the benefit of aquatic reserves, river restoration for fish, the accumulation of contaminants, interactions with predators, and the fitness of salmonids from nurseries. This overview outlines the current context in which papers on the applied ecology of fish and fisheries are emerging, and it identifies scope for further contributions. [source] Characterization of liquefied wood residues from different liquefaction conditionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Hui Pan Abstract The amount of wood residue is used as a measurement of the extent of wood liquefaction. Characterization of the residue from wood liquefaction provides a new approach to understand some fundamental aspects of the liquefaction reaction. Residues were characterized by wet chemical analyses, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The Klason lignin content of the residues decreased, while the holocellulose and ,-cellulose contents increased as the phenol to wood ratio (P/W) increased. A peak at 1735 cm,1, which was attributed to the ester carbonyl group in xylan, disappeared in the FTIR spectra of the residues from liquefied wood under a sealed reaction system, indicating significantly different effects of atmospheric versus sealed liquefaction. The crystallinity index of the residues was higher than that of the untreated wood particles and slightly increased with an increase in the P/W ratio. The SEM images of the residues showed that the fiber bundles were reduced to small-sized bundles or even single fibers as the P/W ratio increased from 1/1 to 3/1, which indicated that the lignin in the middle lamella had been dissolved prior to the cellulose during liquefaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Thermodynamic calculations for molecules with asymmetric internal rotors.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2008Abstract The thermodynamic properties of three halocarbon molecules relevant in atmospheric and public health applications are presented from ab initio calculations. Our technique makes use of a reaction path-like Hamiltonian to couple all the vibrational modes to a large-amplitude torsion for 1,2-difluoroethane, 1,2-dichloroethane, and 1,2-dibromoethane, each of which possesses a heavy asymmetric rotor. Optimized ab initio energies and Hessians were calculated at the CCSD(T) and MP2 levels of theory, respectively. In addition, to investigate the contribution of electronically excited states to thermodynamic properties, several excited singlet and triplet states for each of the halocarbons were computed at the CASSCF/MRCI level. Using the resulting potentials and projected frequencies, the couplings of all the vibrational modes to the large-amplitude torsion are calculated using the new STAR-P 2.4.0 software platform that automatically parallelizes our codes with distributed memory via a familiar MATLAB interface. Utilizing the efficient parallelization scheme of STAR-P, we obtain thermodynamic properties for each of the halocarbons, with temperatures ranging from 298.15 to 1000 K. We propose that the free energies, entropies, and heat capacities obtained from our methods be used to supplement theoretical and experimental values found in current thermodynamic tables. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] EFFECTS OF COOKING AND DRYING PROCESSES ON PHYSICAL, CHEMICAL AND SENSORY PROPERTIES OF LEGUME BASED BULGURJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2009NERMIN BILGIÇLI ABSTRACT The changes in physical, chemical and sensory properties of common bean (CB) and chickpea (CP) bulgur prepared with different cooking (atmospheric, pressure and microwave) and drying (oven at 60, 70 and 80C; microwave at 350 and 700 W) processes were investigated. Neither the cooking methods nor the drying methods significantly affected the ash and protein contents of CB and CP bulgur. Pressure cooking gave lower phytate phosphorus and higher bulgur yield and volume increase values when compared to the other cooking methods. Average bulgur yields were found as 82% for CB and 84% for CP. Cooking processes decreased the phytic acid content of the bulgurs between 25.2 and 39.5% according to raw legume. Ca, K, Mg, P, Zn, Cu and Fe contents of the bulgurs decreased in variable degrees (8.69,28.5%) when compared to raw materials. Pressure cooked and oven (80C) dried bulgur samples in the case of bulgur pilaf were appreciated by the panelists in terms of overall acceptability. PRACTICAL APPLICATIONS Bulgur is a valuable cereal product with its high nutritional value and long shelf life. In this research, bulgur process was applied successfully on common bean and chickpea, and new legume-based bulgur products improved. The bulgur yield (BY) of the legumes was above 80%. Pressure cooking increased the nutritional, sensory and technological quality of the legume bulgurs. [source] | |||||||||||||||||||||||||||||||