The Impact of Cloud Representation on the Sub-Seasonal Forecasts of Atmospheric Teleconnections and Preferred Circulation Regimes in the Northern Hemisphere     

Cristiana Stan  David M. Straus 《大气与海洋》2013,51(3):233-248

Abstract

The impact of cloud representation on the simulation of mid-latitude recurrent large-scale flows and forecast skill of mid-latitude atmospheric teleconnections is evaluated using the Community Climate System Model, version 4 (CCSM4), and the super-parameterized CCSM4 (SP-CCSM4). Patterns of low-level atmospheric circulation anomalies and convection associated with the Madden–Julian oscillation (MJO) are affected by the method used for the representation of cloud processes. The configuration of the model using super-parameterization for the representation of cloud processes produces MJO-related patterns that agree better with observations than the configuration of the model using a conventional cloud parameterization scheme. The recurrent circulation regimes of the mid-latitudes are also sensitive to the representation of cloud processes. In the North Atlantic sector, the inability of CCSM4 to simulate the Scandinavian blocking regime is corrected in the super-parameterized version of the model. In the North Pacific sector, the strength of the clustering (measured by a variance ratio) is too large in CCSM4 compared with observations and SP-CCSM4. The SP-CCSM4 model has better forecast skill for the MJO amplitude and phase than the model with conventional representation of moist convective processes. In turn, the improved forecast skill of the super-parameterized model results in better forecast skill for mid-latitude teleconnections in 500 hPa geopotential height anomalies forced by the MJO convection.  相似文献   

Editorial     

Gyan N. Pande  Stan Pietruszczak 《Computers and Geotechnics》2010,37(7-8):827

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Occurrence and Distribution of Organic Contaminants in the Aquatic System in Berlin. Part I: Drug Residues and other Polar Contaminants in Berlin Surface and Groundwater     

Th. Heberer  K. Schmidt-Bumler  H.-J. Stan 《洁净——土壤、空气、水》1998,26(5):272-278

Several polar contaminants were found in screening analyses of 30 representative surface water samples collected from rivers, lakes, and canals in Berlin. Residues of pharmaceuticals and N-(phenylsulfonyl)-sarcosine originating from various sewage treatment plants effluents were found at concentrations up to the μg/L-level in the surface water, whereas the concentrations of polar pesticides such as dichlorprop and mecoprop were always below 0.1 μg/L. The pharmaceuticals most frequently detected in the surface water samples include clofibric acid, diclofenac, ibuprofen, propiphenazone, and two other drug metabolites. Additional investigations of groundwater wells of a drinking water plant have shown that polar contaminants such as drug residues or N-(phenylsulfonyl)-sarcosine easily leach through the subsoil into the groundwater aquifers when contaminated surface water is used for groundwater recharge in drinking water production.  相似文献   

The effect of minor to moderate biodegradation on C₅ to C₉ hydrocarbons in crude oils     

Simon C George  Christopher J Boreham  Sandra A Minifie  Stan C Teerman 《Organic Geochemistry》2002,33(12)

A suite of 18 oils from the Barrow Island oilfield, Australia, and a non-biodegraded reference oil have been analysed compositionally in order to detail the effect of minor to moderate biodegradation on C₅ to C₉ hydrocarbons. Carbon isotopic data for individual low molecular weight hydrocarbons were also obtained for six of the oils. The Barrow Island oils came from different production wells, reservoir horizons, and compartments, but have a common source (the Upper Jurassic Dingo Claystone Formation), with some organo-facies differences. Hydrocarbon ratios based on hopanes, steranes, alkylnaphthalenes and alkylphenanthrenes indicate thermal maturities of about 0.8% R_c for most of the oils. The co-occurrence in all the oils of relatively high amounts of 25-norhopanes with C₅ to C₉ hydrocarbons, aromatic hydrocarbons and cyclic alkanes implies that the oils are the result of multiple charging, with a heavily biodegraded charge being overprinted by fresher and more pristine oil. The later oil charge was itself variably biodegraded, leading to significant compositional variations across the oilfield, which help delineate compartmentalisation. Biodegradation resulted in strong depletion of n-alkanes (>95%) from most of the oils. Benzene and toluene were partially or completely removed from the Barrow Island oils by water washing. However, hydrocarbons with lower water solubility were either not affected by water washing, or water washing had only a minor effect. There are three main controls on the susceptibility to biodegradation of cyclic, branched and aromatic low molecular weight hydrocarbons: carbon skeleton, degree of alkylation, and position of alkylation. Firstly, ring preference ratios at C₆ and C₇ show that isoalkanes are retained preferentially relative to alkylcyclohexanes, and to some extent alkylcyclopentanes. Dimethylpentanes are substantially more resistant to biodegradation than most dimethylcyclopentanes, but methylhexanes are depleted faster than methylpentanes and dimethylcyclopentanes. For C₈ and C₉ hydrocarbons, alkylcyclohexanes are more resistant to biodegradation than linear alkanes. Secondly, there is a trend of lower susceptibility to biodegradation with greater alkyl substitution for isoalkanes, alkylcyclohexanes, alkylcyclopentanes and alkylbenzenes. Thirdly, the position of alkylation has a strong control, with adjacent methyl groups reducing the susceptibility of an isomer to biodegradation. 1,2,3-Trimethylbenzene is the most resistant of the C₃ alkylbenzene isomers during moderate biodegradation. 2-Methylalkanes are the most susceptible branched alkanes to biodegradation, 3-methylalkanes are the most resistant and 4-methylalkanes have intermediate resistance. Therefore, terminal methyl groups are more prone to bacterial attack compared to mid-chain isomers, and C₃ carbon chains are more readily utilised than C₂ carbon chains. 1,1-Dimethylcyclopentane and 1,1-dimethylcyclohexane are the most resistant of the alkylcyclohexanes and alkylcyclopentanes to biodegradation. The straight-chained and branched C₅–C₉ alkanes are isotopically light (depleted in ¹³C) relative to cycloalkanes and aromatic hydrocarbons. The effects of biodegradation consistently lead to enrichment in ¹³C for each remaining hydrocarbon, due to preferential removal of ¹²C. Differences in the rates of biodegradation of low molecular weight hydrocarbons shown by compositional data are also reflected in the level of enrichment in ¹³C. The carbon isotopic effects of biodegradation show a decreasing level of isotopic enrichments in ¹³C with increasing molecular weight. This suggests that the kinetic isotope effect associated with biodegradation is site-specific and often related to a terminal carbon, where its impact on the isotopic composition becomes progressively ‘diluted’ with increasing carbon number.  相似文献   

40Ar/39Ar and U-Pb dating in the eastern Pilbara,Australia; temporal constraints on structural and metamorphic events between 3.5 and 2.8 Ga (extended abstract)     

Zegers  Tanja E.  Wijbrans  Jan R.  Nelson  Dave R.  White  Stan H. 《Geologie en Mijnbouw》1997,76(4):353-355

Geologie en Mijnbouw -  相似文献   

Analysis of Pulp Mill EOP Bleaching Process Effluent by Thin-layer Chromatography with Automated Multiple Development (AMD-HPTLC)     

F. Dethlefs  H.-J. Stan 《洁净——土壤、空气、水》1996,24(2):77-84

High-performance thin-layer chromatography with automated multiple development (AMD-HPTLC) was applied for the examination of pulp mill bleachery effluents from an alkali-oxygen-peroxide (EOP) bleaching stage of a sulfite pulp. A gradient based on methanol and dichloro-methane was developed for the separation of the effluent compounds over a wide range of migration distances. A series of reference substances such as lignin phenols and other aromatic acids, aldehydes, and alcohols as well as two resin acids were investigated in parallel using the AMD-HPTLC method. Characterization of the effluent compounds was possible using the migration distances and the recorded spectra. The composition of different samples of effluent were found to be very similar. The application of the AMD-HPTLC to effluent fractions from acidic liquid-liquid extraction using diethyl ether and from RP C18 solid-phase extraction allowed us to follow the behaviour of the effluent compounds in the extraction procedure.  相似文献   

The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO2   总被引：3，自引：0，他引：3  

Anthony W. King  Wilfred M. Post  Stan D. Wullschleger 《Climatic change》1997,35(2):199-227

We use a georeferenced model of ecosystem carbon dynamics to explore the sensitivity of global terrestrial carbon storage to changes in atmospheric CO₂ and climate. We model changes in ecosystem carbon density, but we do not model shifts in vegetation type. A model of annual NPP is coupled with a model of carbon allocation in vegetation and a model of decomposition and soil carbon dynamics. NPP is a function of climate and atmospheric CO₂ concentration. The CO₂ response is derived from a biochemical model of photosynthesis. With no change in climate, a doubling of atmospheric CO₂ from 280 ppm to 560 ppm enhances equilibrium global NPP by 16.9%; equilibrium global terrestrial ecosystem carbon (TEC) increases by 14.9%. Simulations with no change in atmospheric CO₂ concentration but changes in climate from five atmospheric general circulation models yield increases in global NPP of 10.0–14.8%. The changes in NPP are very nearly balanced by changes in decomposition, and the resulting changes in TEC range from an increase of 1.1% to a decrease of 1.1%. These results are similar to those from analyses using bioclimatic biome models that simulate shifts in ecosystem distribution but do not model changes in carbon density within vegetation types. With changes in both climate and a doubling of atmospheric CO₂, our model generates increases in NPP of 30.2–36.5%. The increases in NPP and litter inputs to the soil more than compensate for any climate stimulation of decomposition and lead to increases in global TEC of 15.4–18.2%.  相似文献   

Facies architecture of the mixed carbonate/siliciclastic inner continental shelf of west-central Florida: implications for Holocene barrier development   总被引：2，自引：0，他引：2  

Gregg R. Brooks  Larry J. Doyle  Beau C. Suthard  Stan D. Locker  Albert C. Hine   《Marine Geology》2003,200(1-4):325-349

Sediment vibracores and surface samples were collected from the mixed carbonate/siliciclastic inner shelf of west–central Florida in an effort to determine the three-dimensional facies architecture and Holocene geologic development of the coastal barrier-island and adjacent shallow marine environments. The unconsolidated sediment veneer is thin (generally <3 m), with a patchy distribution. Nine facies are identified representing Miocene platform deposits (limestone gravel and blue–green clay facies), Pleistocene restricted marine deposits (lime mud facies), and Holocene back-barrier (organic muddy sand, olive-gray mud, and muddy sand facies) and open marine (well-sorted quartz sand, shelly sand, and black sand facies) deposits. Holocene back-barrier facies are separated from overlying open marine facies by a ravinement surface formed during the late Holocene rise in sea level. Facies associations are naturally divided into four discrete types. The pattern of distribution and ages of facies suggest that barrier islands developed approximately 8200 yr BP and in excess of 20 km seaward of the present coastline in the north, and more recently and nearer to their present position in the south. No barrier-island development prior to approximately 8200 yr BP is indicated. Initiation of barrier-island development is most likely due to a slowing in the Holocene sea-level rise ca. 8000 yr BP, coupled with the intersection of the coast with quartz sand deposits formed during Pleistocene sea-level highstands. This study is an example of a mixed carbonate/siliciclastic shallow marine depositional system that is tightly constrained in both time and sea-level position. It provides a useful analog for the study of other, similar depositional systems in both the modern and ancient rock record.  相似文献   

Tourism and deforestation in the Mt Everest region of Nepal     

Stan Stevens 《The Geographical journal》2003,169(3):255-277

Over the past 50 years the Sherpa-inhabited Mt Everest region of Nepal has become a premier international mountaineering and trekking destination. Tourism development has brought prosperity to many Sherpas. It has also, however, had adverse impacts on regional forests and alpine vegetation because of the use of firewood by camping groups and inns and the felling of trees to construct inns and other tourist facilities. Concern that tourism was causing widespread deforestation helped catalyse the 1976 establishment of an inhabited protected area, Sagarmatha (Mt Everest) National Park, in the Khumbu region and spurred the implementation of a series of forest conservation and alternative energy development measures both within the national park and in a recently declared buffer zone in the adjacent Pharak region. This paper examines the changing pressures that tourism has placed on regional forests and alpine vegetation over the past half century and their role in regional vegetation change. This analysis is based primarily on detailed accounts of past and present forest use and change obtained during fieldwork conducted in all Khumbu and Pharak villages, along with corroborating evidence from early foreign visitors' accounts and photographs. Contrary to some early reports it now appears there has actually been little deforestation since 1950. The continuing use of firewood by inns, however, has contributed to the thinning of forests in some parts of the national park and to the depletion of shrub juniper in the most heavily visited alpine regions. There has been a greater impact on forests just outside the national park, which have been heavily thinned over an extensive area in order to provide timber to build inns within the national park.  相似文献   

Determination of the motion of an observation point by microtriangulation when measuring the deformation of dams     

Václav B. Staněk 《Studia Geophysica et Geodaetica》1959,3(1):1-24

Резюме При проверке предпосылок для статических расчетов плотинных стен и при контроле запаса их прочности важное значение имеют геодезические методы. Их применение, однако, часто обусловливается достижением требуемой высокой точности. Препятствием для полного использования некоторых геодезических методов является тоже сравнительно большая продолжительность расчетов. Наиболее трудной задачей при определении триг. методом абсолютных смещений плотины в горизонтальном направлении является определение изменений положения наблюдательных пунктов с помощью сети основных (поверителных) точек. До сего времени применяемые методы, основанные на совместном уравнивании всей сети методом наименьших квадратов и преобразований Гельмерта, требуют большой затраты времени, причем результаты с теоретической точки зрения не вполне надежны. Новый, автором настоящсй статьи предложенный, метод дает возможность простым сравнением измеряемых оснований установить смещенные точки и их смещение постепенно определить путем некоторых вычислительных или графических методов. В результате отпадет как трудопмкое уравнивание всей сети, так и необходимые преобразования. Для лучшего сравнения удобно выбирать для всех пунктов одно и то же начало, достаточно удаленное от плотины. Точность ориентировки повысится в результате повышения числа ориентировочных направлений. Повышение их числа достигается без увеличения затрат путем заделки вторых неподвижных сигналов в устои пунктов. Паралактический угол между подвижным и неподвижным сигналами, который должен быть постоянным, является также ценным контрольным средством качества измерений. Новый метод был с успехом использован на плотине Порабка в Польше. Определение смещенных точек еще перед уравниванием процесс не только существенно ускорит, но и уточнит. На плотине в Жерманицах среднее арифметическое средних ошибок определения точки в IV–VI этапах в одной координате равно ±0,2 μμ, максимальная же ошибка ±0,3 μμ. На плотине Порабка 5 пунктов (устоев) было снабжено двумя центрирующими кольцами с известными расстояниями. С их помощью можно контролировать результаты, полученные различными способами расчетов. Как видно из табл. 8, результаты, полученные при применении нового метода, равноценны и даже более точны, чем результаты, полученные путем совместного уравнивания всей сети по направлениям или углам. В разделе „Графическо-вычислительные методы” приводится сравнение результатов, полученных с помощью ныне применяемых методов с новым графическим постепенным методом. Этот метод выгоден в особенности в тех случаях, когда наперед было определено приблизительное положение смещенной точки (например, прямой засечкой); кроме того, лучше всего проявил себя метод направлений (обратных величин расстояний). Для достижения требуемой высокой точности результатов, необходимы не толяко правильная форма сети и точные измерения, но и пригодный способ расчета. Как практика показывает, упрощения и ускорения расчетов не идут всегда в ущерб точности.

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