bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Oscillation Analysis of Floating Bridge Panel at Different Water Depths
Authors: Madhuri S. , Muni Reddy M. G. , Manchala Savithri
Published: March 2016

There are different kinds of bridges to cross from obstructions. Bridges which are constructed to cross water body needs special attention in the analysis and design. Usually these bridges are being constructed with large amount of construction material and leading to increase in construction cost. As the structures are fixed and the deck levels are fixed, sometimes alternative proposals like rising of deck level are being proposed and implemented for navigational purposes across the bridges. The dynamic characteristics of the floating bridge play a major role in the response of the bridge under water flow or any wave action. In order to assess the dynamic characteristic of a floating bridge numerical studies are performed at different water depths by developing a MATLAB code using Newmark's Beta method. The concept of a floating bridge takes the advantage of buoyancy of water to support the dead and live loads thus reduce the construction material when compared with the conventional fixed bridges. The proposed floating bridge consist different number of panels. One or two panels can be detached from the floating bridge to allow the navigation of boats or ships across the bridge. Experimental and numerical free oscillation studies are performed at a water depth of 32.7m and results are compared well. Numerical studies are performed for 50 and 80m of water depth and results are presented.
Evaluation of Different Hydrate Prediction Software and Impact of Different MEG Products on Gas Hydrate Formation and Inhibition
Authors: AlHarooni K. M. , Barifcani A. , Pack D. , Iglauer S.
Published: March 2016

New hydrate profile correlations for methane gas hydrates were obtained computationally (using three different hydrate prediction software packages) and experimentally (with three different MEG products from different suppliers). Methane gas with pure distilled water was the benchmark case used for the software comparison at pressures of 50 to 300 bar. In order to compare the hydrate inhibition performance of the MEG products, aqueous 10 wt% MEG solutions were tested using the isobaric method at a pressure range of 50 to 200 bar.

Furthermore, the kinetics of MEG hydrate inhibition were studied experimentally for methane gas using a stirred cryogenic sapphire cell. Hydrate formation start, hydrate dissociation initiation and hydrate dissociation end points were identified and analysed. The results were correlated with the hydrate formation start points predicted by three well known selected hydrate prediction software packages (which all use the Peng-Robinson equation of state). Moreover, the hydrate inhibition performance of the three MEG products was evaluated to determine the superior MEG product that provides the best hydrate inhibition performance.

Our analysis shows that the hydrate formation points predicted computationally are not identical to the hydrate formation start points measured in this work. Software "A" and software "B" predicted results matching with the average curve of the experimental hydrate formation start and hydrate dissociation start points, and with a deviation value of 0.06 °C for software "A" and a deviation value of 0.03 °C for software "B". However, software "C" predicted results almost identical with the experimental dissociation start points, and with an average deviation value of 0.54 °C.

The methane gas hydrate profiles for the three different MEG products (X-MEG, Y-MEG and Z-MEG) indicated that X-MEG was the most efficient inhibitor as it shifted the hydrate curve most to the left; X-MEG shifted the hydrate formation curve by an average temperature of 2.07 °C when compared to the benchmark curve (100% water); while Z-MEG shifted the curve by an average temperature of 1.81 °C and Y-MEG shifted the curve by an average temperature of 1.71 °C.

We conclude that not all software packages predict the same results although they are all based on the same equation of state. Furthermore not all MEG products supplied have the same hydrate inhibition efficiency. Importantly, choosing the best MEG supplier will reduce the OPEX by reducing the amount of MEG used, and it will accommodate more relaxed operating conditions of lower temperatures and higher pressures.
Numerical Modelling of Seismically Induced Settlement for Ichthys Riser Support Structure
Authors: Erbrich C. , Wallbridge P. , Yamamoto N.
Published: March 2016

The Ichthys Riser Support Structure (RSS) is a very large subsea structure for supporting up to 25 flexible risers and umbilicals as they transition from the seabed to a semi-submersible Central Processing Facility. The Ichthys field is in a region affected by both local shallow crustal earthquakes and major subduction earthquakes emanating from the Australian/Eurasian plate boundary. Large beds of uncemented carbonate silts and sands are present at Ichthys, which are highly prone to excess pore pressure accumulation and liquefaction under cyclic loads. Any structure placed on the seabed will suffer from both co-seismic and post seismic settlement after an energetic earthquake event.

This paper presents dynamic non-linear numerical analyses (2D and 3D FEA) of the coupled soil and structure that were performed in order to estimate the seismically induced settlement and the potential extent of soil liquefaction beneath the RSS, which is founded on a large skirted raft foundation. Extensive site specific laboratory test data, defining the material behaviour during and after cycling, was collected to provide the necessary input to this analysis.

Significant areas of liquefaction (in the form of cyclic mobility, not flow liquefaction) were found under DLE conditions and hence the combined co-seismic and post-seismic foundation settlements were predicted to be substantial although tilts were modest due to low eccentricity of the centre of gravity. The RSS was demonstrated to be tolerant to such large settlements and hence the results were shown to be acceptable in this case.
Challenges in Riser Design - The Ichthys Gas Field Development
Authors: Coone Niall
Published: March 2016

The Ichthys Gas Field is located 220 kilometers offshore from the North West coast of Western Australia. The field is located within a cyclone-prone region and has two permanently moored floating production units in a water depth of approximately 250m.

The floating systems consist of a semi-submersible Central Processing Facility (CPF) and a Floating Production Storage and Offloading (FPSO) facility. This paper presents an overview of the riser solutions developed for each facility while documenting challenges faced in design, cognisant of installation limitations and complex interface management within a large EPCI project. Both facility riser systems contain aspects that are first of their kind within the region and were developed with the added complexity of a 40-year riser design life and the requirement to withstand a 10,000 year return period survival cyclonic event.

Within a single mooring sector to the North of the CPF, 25 risers are supported on a single riser support structure (RSS) in a fixed-S configuration. The RSS, which is the subject of another paper [1], has an arch length of 130 m to support the risers at a height of 110 m above the seabed. This paper explains the design aspects of the system including optimizing riser spacing and riser gutter geometry in close proximity with varying minimum bending radii. A robust design was required that allowed for future phase riser installation and riser replacement.

A lazy-S riser configuration was developed to support 15 risers from the FPSO. The solution consisted of three mid depth buoys (MDBs), one in each mooring sector. The MDB design is the subject of another paper [2]. Design challenges included significant dynamic response of the permanently moored FPSO in 10,000 year return period survival cyclonic conditions. MDB dynamic response was found to be significantly impacted by added mass, which provided challenges in maintaining positive tether tension and minimizing interface loads into the MDB structure and foundation. Diffraction analysis of the MDB structure was used to determine accurately the added mass coefficient in order to refine interface loads into the MDB and its foundation.
Improving Jack-Up Rig Spudcan Penetration Predictions in Malaysian Waters
Authors: Rohani M. J. , Sha'ari F. A. , Rahman A. A. , Ismail W. M. Wan , Chan N. , Tho K. K.
Published: March 2016

A review of the performance of jack-up rig spudcan penetration predictions in Malaysian Waters over the past ten years is performed with the aim of improving the predictions for future deployments. This work is part of an ongoing initiative to further improve the safety and efficiency of jack-up rig deployments in Malaysian Waters.

During the first phase of the study, field measured spudcan penetrations at maximum preload from 100 jack-up rig emplacements in different subsoil conditions are compared against the corresponding spudcan penetration predictions. These spudcan penetration predictions, which originated from third parties and are presented anonymously, consist entirely of Class-A predictions made prior to the jack-up emplacement. A significant scatter is noted between predicted and actual spudcan penetrations. Possible causes of discrepancy between predicted and actual spudcan penetration depths in Malaysian Waters are postulated.

In a significant proportion of the cases reviewed, the final spudcan penetration is found to be governed by bearing capacity in clay. Consequently, bearing capacity solutions for clays detailed in SNAME (2008) and ISO (2012) were reviewed. The bearing capacity equations in SNAME (2008) and ISO (2012) are based on the work of Hansen (1970) and Skempton (1951) respectively. Both SNAME (2008) and ISO (2012) noted that the value of undrained cohesive shear strength can be taken as the average value over a distance of B/2 from beneath the level where the maximum spudcan diameter is in contact with soil. The undrained shear strength profiles in Malaysian Waters are found to be more irregular as compared to those encountered in Gulf of Mexico. It is therefore the objective of the current study to assess the influence of undrained shear strength averaging distance for soil condition encountered in oil and gas producing regions offshore Malaysian Waters and to recommend the most applicable value for use in Malaysian Waters.

The next phase of the study also aims to evaluate the need for revised calibration factors to SNAME (2008) / ISO (2012) based equations and to define the tolerance for acceptance of the leg penetration analysis (LPA) predictions in Malaysia Waters.
A Well Testing Analysis Methodology and Application for Tight Reservoirs
Authors: Zhao Xiaoliang , Liao Xinwei , Chen Zhiming , Mu Lingyu , Zhang Fengyuan , Zhou Yejun , Zhou Xingze , Zhao Ning
Published: March 2016

For tight oil reservoirs, because of ultra-low permeability, the radial flow is difficult to be obtained in pressure build-up testing which results in multi-solution of flow model and interpretation results. How to determine the right model and identify the right interpretation result are the key questions. This paper presents a well test interpretation methodology based on time and space scales to increase accuracy of well-test interpretation results. Two steps are performed to determine reasonable flow model and interpretation results based on time and space scales. For the time scales, the history of well testing data for a single well are interpreted and the interpretation results are compared first. Then for space scales, the well test data in space for multi-wells are analyzed. At this stage, the interpretation results of adjacent wells are compared. The reservoir geological data and the production history are used as a reference to appraise the well test interpretation results. After these two steps, the reasonable interpretation model and interpretation results can be determined. Two cases selected from Changqing oilfields whose permeabilities are almost under 0.5mD and fluid flow rates are very low are analyzed and the great application effect is attained. This methodology is applied in Changqing oilfields extensively and is proved to be a great methodology in ultra-low permeability oil reservoirs. It can be expanded to other unconventional reservoirs, such as tight gas, shale gas and so on. The innovation is that this paper derives a well testing analysis methodology to determine right model and identify the right interpretation result based on time and space scales. It can decrease the errors which are caused by multi-solution of flow model and many interpretation results.
First Meta-Sedimentary Basement Reservoir Formation Evaluation in Offshore Sarawak: A Detail Insight on Fracture Morphology
Authors: Ming Wu Ivan Zhia , Parashar Sarvagya , Lee Chung Yee , Kamarul Zaman M. Naquib , Amri M. Bukhari M. Khairul , Jabbar Siti Fatimah , Lowrans Calvin , Mansur Hussen
Published: March 2016

Exploration and production companies in the South China Sea region have focused increasing attention on basement reservoirs. In the current study, a modest step was to taken to identify the fracture pattern and its associated physical properties, which help provide the potential zone of the formation sampling and pressure gradient analysis. An exploratory well located offshore Sarawak, Malaysia recently encountered oil in the meta-sediment basement—confirming the basement plays in this region.

Borehole microresistivity images and acoustic data with background geology characterized rock texture, lithofacies, and fracture network. Integration of sidewall core and microresistivity image data characterized litho-units having complex architecture. Open fracture zones were validated in images and acoustic logs. Borehole image-derived fracture properties calibrated with sonic-derived results were used to estimate gross voidage. Average porosity in fractured basement rock is usually low; hence, fracture transitivity/permeability is important for estimating fluid movement. To characterize basement rock, fractural properties and geometry, such as permeability, aperture, density, and flow potential, should be attributed properly with respect to the different facies association present.

The exploratory well was mainly drilled through the quartzite and phyllite section. Microresistivity image data helped decipher the different texture patterns with the two litho-units and also identify the internal structural features associated with each. The major types of structural features were identified, including partial fracture, open fracture, and closed fracture. Statistical analysis showed the major strike orientation for the open fracture was toward the NW-SE; whereas, the minor trend was NNE-SSW with a mean dip of 45° magnitude. Partial fractures also exhibited a similar trend, with the major strike NNE-SSW and minor trend NW-SE with mean dips of 52° magnitude. Average open fracture aperture was determined to be in the range of 0.2 to 0.4 mm, with an approximate secondary porosity range between 2 to 3% and permeability of 0.01 md.

This was the first integrated approach for evaluating a meta-sediments basement in the offshore Sarawak area. This methodology emphasized advanced integration and is essential for evaluating such complex reservoirs, providing a stepping stone for future well trajectory planning in the study area.
Proper Planning Supported by Latest Technology Leads to Drilling the Longest 8.5-in. Section in an Extended-Reach Well: Case Study
Authors: Chima Jude , Umarin Isa , Kunhiveetil Dhanraj , Otaif Hassan , Al Dabyah Ali , Zubairi Bilal
Published: March 2016

Over the past years, extended-reach drilling (ERD) field development has significantly increased globally, and its benefits are well recognized. ERD techniques are increasingly used to intersect hydrocarbon targets that are difficult to access due to logistic issues. While these wells are challenging to drill, complete, and service, the benefits can be wide ranging. These benefits drive the development of technology and techniques to continuously expand the ERD envelope and increase the complexity of profiles to reach more challenging targets. The directional drilling and evaluation service supplier plays an important role.

Each ERD well has a unique set of challenges. Common to all ERD projects is that many aspects of drilling engineering principles are not only pushed to the limit, but become highly interrelated and sensitive to smaller changes than conventional wells. For this reason, a team approach to planning and executing ERD activities should be considered critical. Each team member should bring to the project relevant experience, knowledge, a range of field-proven technology, and a solid global support structure.

Drilling successful ERD wells in challenging conditions depends on various factors, which include careful planning and use of the latest technology. Planning involves understanding the geological structure, not only within the reservoir section, but also in the overburden where typically most of the time efficiency gains can be achieved. The last step in planning is designing an efficient bottomhole assembly (BHA) based on previous experiences, lessons learned and inputs from various teams. Good planning is supported by use of new technologies, especially tools that give real-time information, enabling quick and informed decisions to ensure safe and efficient drilling in a challenging environment. The paper discusses the planning and decision-making process to drill ERD wells by using latest real-time technologies in drilling challenging wells. This paper will describe the experiences and huge success of drilling the longest 8.5-in. hole section in an ERD well, drilled and cased smoothly through challenging formations.
Influence of Improved Soil Layer with Deep Mixing Method on the Penetration Performance of Spudcan Foundations in Multilayer Clays
Authors: Won Jonghwa , Park Jong-Sik , Joo Young Seok , Ryu Mincheol
Published: March 2016

This paper provides the design basis and case study of soil improvement to secure the stability of jack up rig under operation and fabrication condition to effectively mitigate the risk associated with unexpected spudcan penetration. The two penetration curves of spudcan foundation are presented to confirm soil improvement influence using DMM (Deep Mixing Method) with native soil material. The results from 3D large deformation finite element (LDFE) analyses are reported on vertical penetration of skirted spudcan into multilayer clays. The LDFE analyses were carried out using the Coupled Eulerian-Lagrangian (CEL) approach and the modified simple elastic-perfectly plastic Tresca soil model. The seabed sediments were simulated as single layer soft clay with undrained shear strength increasing linearly with depth, two-layer stiff clayey sand overlying soft clay and sandy gravel. The circular block of soil improvement is partially located in the third sandy clay layer under the spudcan penetration path with specific thickness. The result with native soil condition is validated against ISO recommendation and the penetration curve for reinforced section is also overlaid concurrently. The punch-through phenomeneon predicted in the assessement by ISO method is replicated in the numerical analysis. The validation exercise of the original case shows a good agreement and the present numerical approach is capable of predicting the behavior of a spudcan penetration in multi-layered soil. The partially reinforced layer shows the load distribution during spudcan penetration. It provides the reduction of penetration depth under a given preload and seabed conditions efficiently. To ensure the structural stability of jack up rig, the uncertainties of site condition during installation should be removed such as partially trapped soft soil or soft thin layer at the footing location. The presented numerical approach can provide reasonable design basis for soil treatment to mitigate stability risk.
Characterizing the activation of the Wnt signaling pathway in hilar cholangiocarcinoma using a tissue microarray approach
Authors: Chen W. , Liang J. , Huang L. , Cai J. , Lei Y. , Lai J. , Liang L. , Zhang K.
Published: March 2016

Hilar cholangiocarcinoma (HCCA) is an invasive hepatic malignancy that is difficult to biopsy; therefore, novel markers of HCCA prognosis are needed. Here, the level of canonical Wnt activation in patients with HCCA, intrahepatic cholangiocarcinoma (IHCC), and congenital choledochal cysts (CCC) was compared to understand the role of Wnt signaling in HCCA. Pathology specimens from HCCA (n=129), IHCC (n=31), and CCC (n=45) patients were used to construct tissue microarrays. Wnt2, Wnt3, Î²-catenin, TCF4, c-Myc, and cyclin D1 were detected by immunohistochemistry. Parallel correlation analysis was used to analyze differences in protein levels between the HCCA, IHCC, and CCC groups. Univariate and multivariate analyses were used to determine independent predictors of successful resection and prognosis in the HCCA group. The protein levels of Wnt2, Î²-catenin, TCF4, c-Myc, and cyclin D1 were significantly higher in HCCA compared to IHHC or CCC. Wnt signaling activation (Wnt2+, Wnt3+, nuclear Î²-catenin+, nuclear TCF4+) was significantly greater in HCCA tissues than CCC tissues. Univariable analyses indicated that expression of cyclin D1 as well as Wnt signaling activation, and partial Wnt activation (Wnt2+ or Wnt3+ and nuclear Î²-catenin+ or nuclear TCF4+) predicted successful resection, but only cyclin D1 expression remained significant in multivariable analyses. Only partial Wnt activation was an independent predictor of survival time. Proteins in the canonical Wnt signaling pathway were present at higher levels in HCCA and correlated with tumor resecility and patient prognosis. These results suggest that Wnt pathway analysis may be a useful marker for clinical outcome in HCCA.
Transgenic expression of dentin phosphoprotein inhibits skeletal development
Authors: Zhang H. , Liu P. , Wang S. , Liu C. , Jani P. , Lu Y. , Qin C.
Published: March 2016

Dentin sialophosphoprotein (DSPP) is proteolytically processed into an NH2-terminal fragment called dentin sialoprotein (DSP) and a COOH-terminal fragment known as dentin phosphoprotein (DPP). These two fragments are believed to perform distinct roles in formation of bone and dentin. To investigate the functions of DPP in skeletal development, we generated transgenic mice to overexpress hemagglutinin (HA)-tagged DPP under the control of a 3.6 kb type I collagen (Col1a1) promoter (designated as Col1a1-HA-DPP). The Col1a1-HA-DPP transgenic mice were significantly smaller by weight, had smaller skeletons and shorter long bones than their wild type littermates, as demonstrated by X-ray radiography. They displayed reduced trabecular bone formation and narrower zones of proliferative and hypertrophic chondrocytes in the growth plates of the long bones. Histological analyses showed that the transgenic mice had reduced cell proliferation in the proliferating zone, but lacked obvious defects in the chondrocyte differentiation. In addition, the transgenic mice with a high level of transgene expression developed spontaneous long bone fractures. In conclusion, overexpressing DPP inhibited skeletal development, suggesting that the balanced actions between the NH2- and COOH-terminal fragments of DSPP may be required for normal skeletal development.
Changes in muscularis propria of anterior vaginal wall in women with pelvic organ prolapse
Authors: Vetuschi A. , D'Alfonso A. , Sferra R. , Zanelli D. , Pompili S. , Patacchiola F. , Gaudio E. , Carta G.
Published: March 2016

The objective of this study was to evaluate the morphological and immunohistochemical alterations of tissue removed from the upper third of anterior vaginal wall in a sample group of the female population presenting homogenous risk factors associated with Pelvic Organ Prolapse (POP). The case study consisted of 14 patients with POP and there were 10 patients in the control group. Patient selection was carried on the basis of specific criteria and all of the patients involved in the study presented one or more of the recognized POP risk factors. Samples were taken from POP patients during vaginal plastic surgery following Â colpohysterectomy, and from control patients during closure of the posterior fornix following hysterectomy. Samples were processed for histological and Â immunohistochemical analyses for Collagen I and Collagen III, Î±-Smooth Muscle Actin (Î±-SMA), Platelet-Derived-Growth-Factor (PDGF), matrix metalloproteinase 3 (MMP3), Caspase3. Immunofluorescence analyses for Collagen I and III and PDGF were also carried out. In prolapsed specimens our results show a disorganization of smooth muscle cells that appeared to have been displaced by an increased collagen III deposition resulting in rearrangement of the muscularis propria architecture. These findings suggest that the increase in the expression of collagen fibers in muscularis could probably due to a phenotypic switch resulting in the dedifferentiation of smooth muscle cells into myofibroblasts. These alterations could be responsible for the compromising of the dynamic functionality of the pelvic floor.Â
Interleukin-6 Kinetics Can Be Useful for Early Treatment Monitoring of Severe Bacterial Sepsis and Septic Shock
Authors: Klag Thomas , Cantara Giulio , Sechtem Udo , Athanasiadis Anastasios
Published: March 2016

Early appropriate anti-microbial therapy is necessary to improve outcomes of septic patients. We describe 20 case histories of patients with severe bacterial sepsis regarding kinetics of several biomarkers. We found that interleukin-6 is able to predict survival and might be able to evaluate appropriateness of anti-microbial therapy.
Validation of the Swiss methane emission inventory by atmospheric observations and inverse modelling
Authors: Henne Stephan , Brunner Dominik , Oney Brian , Leuenberger Markus , Eugster Werner , Bamberger Ines , Meinhardt Frank , Steinbacher Martin , Emmenegger Lukas
Published: March 2016

Abstract. Atmospheric inverse modelling has the potential to provide observation-based estimates of greenhouse gas emissions at the country scale, thereby allowing for an independent validation of national emission inventories. Here, we present a regional-scale inverse modelling study to quantify the emissions of methane (CH4) from Switzerland, making use of the newly established CarboCount-CH measurement network and a high-resolution Lagrangian transport model. In our reference inversion, prior emissions were taken from the "bottom-up" Swiss Greenhouse Gas Inventory (SGHGI) as published by the Swiss Federal Office for the Environment in 2014 for the year 2012. Overall we estimate national CH4 emissions to be 196 ± 18 Gg yr−1 for the year 2013 (1σ uncertainty). This result is in close agreement with the recently revised SGHGI estimate of 206 ± 33 Gg yr−1 as reported in 2015 for the year 2012. Results from sensitivity inversions using alternative prior emissions, uncertainty covariance settings, large-scale background mole fractions, two different inverse algorithms (Bayesian and extended Kalman filter), and two different transport models confirm the robustness and independent character of our estimate. According to the latest SGHGI estimate the main CH4 source categories in Switzerland are agriculture (78 %), waste handling (15 %) and natural gas distribution and combustion (6 %). The spatial distribution and seasonal variability of our posterior emissions suggest an overestimation of agricultural CH4 emissions by 10 to 20 % in the most recent SGHGI, which is likely due to an overestimation of emissions from manure handling. Urban areas do not appear as emission hotspots in our posterior results, suggesting that leakages from natural gas distribution are only a minor source of CH4 in Switzerland. This is consistent with rather low emissions of 8.4 Gg yr−1 reported by the SGHGI but inconsistent with the much higher value of 32 Gg yr−1 implied by the EDGARv4.2 inventory for this sector. Increased CH4 emissions (up to 30 % compared to the prior) were deduced for the north-eastern parts of Switzerland. This feature was common to most sensitivity inversions, which is a strong indicator that it is a real feature and not an artefact of the transport model and the inversion system. However, it was not possible to assign an unambiguous source process to the region. The observations of the CarboCount-CH network provided invaluable and independent information for the validation of the national bottom-up inventory. Similar systems need to be sustained to provide independent monitoring of future climate agreements.
Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake
Authors: Whelan Mary E. , Hilton Timothy W. , Berry Joseph A. , Berkelhammer Max , Desai Ankur R. , Campbell J. Elliott
Published: March 2016

Abstract. Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil–COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from five new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois,  > 800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. While COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.
Long-term visibility variation in Athens (1931–2013): A proxy for local and regional atmospheric aerosol loads
Authors: Founda Dimitra , Kazadzis Stelios , Mihalopoulos Nikolaos , Gerasopoulos Evangelos , Lianou Maria
Published: March 2016

Abstract. This study explores the inter-decadal variability and trends of surface horizontal visibility at the urban area of Athens from 1931 to 2013, using the historical archives of the National Observatory of Athens (NOA). A prominent deterioration of visibility in the city was detected, with the long-term linear trend amounting to −2.8 km decade−1 (p < 0.001), over the entire studied period. This was not accompanied with any significant trend in relative humidity (RH) or precipitation over the same period. A slight recovery of visibility levels seems to be established in the recent decade (2004–2013). It was found that very good visibility (> 20 km) occurred at a frequency of 34 % before the 1950s, while this percentage drops to just 2 % during the recent decade. The rapid impairment of the visual air quality in Athens around 1950, points to the increased levels of air pollution from local and/or regional emission sources, related to high urbanization rates and/or higher rates of anthropogenic emissions increase on a global scale at that period. A marked seasonal cycle was detected in visibility before the 1950s, which attenuates afterwards. Visibility was found to be negatively/positively correlated with relative humidity (RH)/wind speed, the correlation being statistically valid at certain periods. Wind regime and mainly wind direction and corresponding air masses origin was found to highly control visibility levels in Athens. The comparison between visibility in Athens and at a reference, non urban site, revealed similar negative trends over the common period of observations, suggesting that apart from the contribution of local sources, visibility in Athens is highly determined by aerosol loads of regional origin. Satellite derived aerosol optical depth (AOD) retrievals over Athens since 2000, and surface measurements of PM10 confirmed the relation of visibility with aerosol loads.
LA Megacity: a High-Resolution Land-Atmosphere Modelling System for Urban CO2 Emissions
Authors: Feng Sha , Lauvaux Thomas , Newman Sally , Rao Preeti , Ahmadov Ravan , Deng Aijun , Díaz-Isaac Liza I. , Duren Riley M. , Fischer Marc L. , Gerbig Christoph , Gurney Kevin R. , Huang Jianhua , Jeong Seongeun , Li Zhijin , Miller Charles E. , O’Keeffe Darragh , Patarasuk Risa , Sander Stanley P. , Song Yang , Wong Kam W. , Yung Yuk L.
Published: March 2016

Abstract. Megacities are major sources of anthropogenic fossil fuel CO2 emissions. The spatial extents of these large urban systems cover areas of 10,000 km2 or more with complex topography and changing landscapes. We present a high-resolution land-atmosphere modelling system for urban CO2 emissions over the Los Angeles (LA) megacity area. The Weather Research and Forecasting (WRF)-Chem model was coupled to a very high-resolution FFCO2 emission product, Hestia-LA, to simulate atmospheric CO2 concentrations across the LA megacity at spatial resolutions as fine as ~ 1 km. We evaluated multiple WRF configurations, selecting one that minimized errors in wind speed, wind direction, and boundary layer height as validated by its performance against meteorological data collected during the CalNex-LA campaign (May–June 2010). Our results show no significant difference between moderate- (4-km) and high- (1.3-km) resolution simulations when evaluated against surface meteorological data, but the high-resolution configurations better resolved PBL heights and vertical gradients in the horizontal mean winds. We coupled our WRF configuration with the Vulcan 2.2 (10 km resolution) and Hestia-LA (1.3-km resolution) fossil fuel CO2 emission products to evaluate the impact of the spatial resolution of the CO2 emission products and the meteorological transport model on the representation of spatiotemporal variability in simulated atmospheric CO2 concentrations. We find that high spatial resolution in the fossil fuel CO2 emissions is more important than in the atmospheric model to capture CO2 concentration variability across the LA megacity. Finally, we present a novel approach that employs simultaneous correlations of the simulated atmospheric CO2 fields to qualitatively evaluate greenhouse gas measurements over the LA megacity. Spatial correlations in the atmospheric CO2 fields reflect the coverage of individual measurement sites when a statistically significant number of sites observe emissions from a specific source or location. We conclude that elevated atmospheric CO2 concentrations over the LA megacity are composed of multiple fine-scale plumes rather than a single homogenous urban dome. Furthermore, we conclude that FFCO2 emissions monitoring in the LA megacity requires FFCO2 emissions modelling with ~ 1 km resolution since coarser resolution emissions modelling tends to overestimate the observational constraints on the emissions estimates.
Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in-situ measurements
Authors: Fu G. , Heemink A. W. , Lu S. , Segers A. J. , Weber K. , Lin H. X.
Published: March 2016

Abstract. The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain, resulting in inaccurate volcanic ash forecasts in these distal areas. In our approach, we use real-life aircraft in-situ observations, measured in the North-West part of Germany during the 2010 Eyjafjallajokull eruption, in an ensemble-based data assimilation system combined with a volcanic ash transport model to investigate the potential improvement on the forecast accuracy with regard to the distal volcanic ash plume. We show that the error of the analyzed volcanic ash state can be significantly reduced through assimilating real-life in-situ measurements. After a continuous assimilation, it is shown that the aviation advice for Germany, the Netherlands and Belgium can be significantly improved. We suggest that with suitable aircrafts measuring once per day across the distal volcanic ash plume, the description and prediction of volcanic ash clouds in these areas can be greatly improved.
Impact of Biomass Burning emission on total peroxy nitrates: fire plume identification during the BORTAS campaign
Authors: Aruffo Eleonora , Biancofiore Fabio , Di Carlo Piero , Busilacchio Marcella , Verdecchia Marco , Tomassetti Barbara , Dari-Salisburgo Cesare , Giammaria Franco , Bauguitte Stephane , Lee James , Moller Sarah , Hopkins James , Punjabi Shalini , Andrews Stephen , Lewis Alistair C. , Palmer Paul I. , Hyer Edward , Le Breton Michael , Percival Carl
Published: March 2016

Abstract. The total peroxy nitrates (∑PNs) concentrations have been measured using a thermal dissociation laser induced fluorescence (TD-LIF) instrument during the BORTAS campaign, which focused on the impact of boreal biomass burning emissions on air quality in the Northern hemisphere. The strong correlation observed between the ∑PNs concentrations and those of the carbon monoxide (CO), a well-known pyrogenic tracer, suggests the possible use of the ∑PNs concentrations as marker of the biomass burning (BB) plumes. We applied both statistical and percentile methods to the ∑PNs concentrations, comparing the percentage of BB plume selected using these methods with the percentage evaluated applying the approaches usually used in literature. Moreover, adding the pressure threshold (~ 750 hPa) to ∑PNs, HCN and CO, as ancillary parameter, the BB plume identification is improved. An artificial recurrent neural network (ANN) model was adapted to simulate the concentrations of ∑PNs and the HCN including as input parameters ∑PNs, HCN, CO and atmospheric pressure, to verify the specific role of these input data to better identify BB plumes.
Comparing models of microbial–substrate interactions and their response to warming
Authors: Sihi Debjani , Gerber Stefan , Inglett Patrick W. , Inglett Kanika Sharma
Published: March 2016

Abstract. Recent developments in modelling soil organic carbon decomposition include the explicit incorporation of enzyme and microbial dynamics. A characteristic of these models is a positive feedback between substrate and consumers, which is absent in traditional first-order decay models. With sufficiently large substrate, this feedback allows an unconstrained growth of microbial biomass. We explore mechanisms that curb unrestricted microbial growth by including finite potential sites where enzymes can bind and by allowing microbial scavenging for enzymes. We further developed a model where enzyme synthesis is not scaled to microbial biomass but associated with a respiratory cost and microbial population adjusts enzyme production in order to optimise their growth. We then tested short- and long-term responses of these models to a step increase in temperature and find that these models differ in the long-term when short-term responses are harmonised. We show that several mechanisms, including substrate limitation, variable production of microbial enzymes, and microbes feeding on extracellular enzymes eliminate oscillations arising from a positive feedback between microbial biomass and depolymerisation. The model where enzyme production is optimised to yield maximum microbial growth shows the strongest reduction in soil organic carbon in response to warming, and the trajectory of soil carbon largely follows that of a first-order decomposition model. Modifications to separate growth and maintenance respiration generally yield short-term differences, but results converge over time because microbial biomass approaches a quasi-equilibrium with the new conditions of carbon supply and temperature.
Millennial-scale vegetation changes in the tropical Andes using ecological grouping and ordination methods
Authors: Urrego Dunia H. , Hooghiemstra Henry , Rama-Corredor Oscar , Martrat Belen , Grimalt Joan O. , Thompson Lonnie , Bush Mark B. , González-Carranza Zaire , Hanselman Jennifer , Valencia Bryan , Velásquez-Ruiz César
Published: March 2016

Abstract. We compare eight pollen records reflecting climatic and environmental change from northern and southern sites in the tropical Andes. Our analysis focuses on the last 30 000 years, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations and moisture availability. Our analysis focuses on the signature of millennial-scale climate variability in the tropical Andes, in particular Heinrich stadials (HS) and Greenland interstadials (GI). The pollen records show an overall warming trend during the Pleistocene–Holocene transition, but the onset of post-glacial warming differs in timing among records. We identify rapid responses of the tropical vegetation to millennial-scale climate variability. The signatures of HS and the Younger Dryas are generally recorded as downslope upper forest line (UFL) migrations in our transect, and are likely linked to air temperature cooling. The GI1 signal is overall comparable between northern and southern records and indicates upslope UFL migrations and warming in the tropical Andes. Our marker for lake level changes indicated a north-to-south difference that could be related to moisture availability. The air temperature signature recorded by the Andean vegetation was consistent with millennial-scale cryosphere and sea surface temperature changes but suggests a potential difference between the magnitude of temperature change in the ocean and the atmosphere. We also show that arboreal pollen percentage (AP %) and detrended correspondence analysis (DCA) scores are two complementary approaches to extract environmental variability from pollen records.
The PRISM4 (mid-Piacenzian) palaeoenvironmental reconstruction
Authors: Dowsett Harry , Dolan Aisling , Rowley David , Pound Matthew , Salzmann Ulrich , Robinson Marci , Chandler Mark , Foley Kevin , Haywood Alan
Published: March 2016

Abstract. The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions and means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a palaeoenvironmental reconstruction of the mid-Piacenzian (~ 3 Ma) containing data for palaeogeography, land and sea-ice, sea-surface temperature, vegetation, soils and lakes. Our retrodicted palaeogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project, Phase 2 (PlioMIP2) experiments.
Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation
Authors: Livingstone Stephen J. , Clark Chris D.
Published: March 2016

Abstract. Tunnel valleys have been widely reported on the bed of former ice sheets and are considered an important expression of subglacial meltwater drainage. Although known to have been cut by erosive meltwater flow, the water source and development of channels has been widely debated; ranging between outburst flood events through to gradually occurring channel propagation. We have mapped and analysed the spatial pattern and morphometry of tunnel valleys and associated glacial bedforms along the southern sector of the former Laurentide Ice Sheet from high-resolution digital elevation models. Around 2000 tunnel valleys have been mapped, revealing a well-organised pattern of sub-parallel, semi-regularly spaced valleys that cluster together in distinctive networks. The tunnel valleys are typically < 20 km long, and 0.5–3 km wide and preferentially terminate at moraines. They tend to be associated with outwash fans, eskers, giant current ripples, and hill-hole-pairs. At the ice-sheet scale, we find most tunnel valleys occur on the flat portions of palaeo-ice sheet beds, where subglacial water flow would have been largely unconstrained by topography, while tunnel valley morphology is strongly modulated by local variations in basal conditions (e.g. thermal regime and topography) and hydrology (i.e. whether conduit erosion is up into the ice or down into the sediments). Analysis of cross-cutting relationships between tunnel valleys, moraines and outwash fans permits reconstruction of channel development in relation to the retreating ice margin. The reconstruction demonstrates incremental growth of valleys, with some used repeatedly, or for long periods, during deglaciation, while others were abandoned shortly after their formation. Our data and interpretation supports gradual (rather than a single-event) tunnel valley formation, with secondary contributions from flood drainage of subglacial and/or supraglacially stored water.
Creating long-term gridded fields of reference evapotranspiration in Alpine terrain based on a recalibrated Hargreaves method
Authors: Haslinger Klaus , Bartsch Annett
Published: March 2016

Abstract. A new approach for the construction of high-resolution gridded fields of reference evapotranspiration for the Austrian domain on a daily time step is presented. Gridded data of minimum and maximum temperatures are used to estimate reference evapotranspiration based on the formulation of Hargreaves. The calibration constant in the Hargreaves equation is recalibrated to the Penman–Monteith equation in a monthly and station-wise assessment. This ensures, on one hand, eliminated biases of the Hargreaves approach compared to the formulation of Penman–Monteith and, on the other hand, also reduced root mean square errors and relative errors on a daily timescale. The resulting new calibration parameters are interpolated over time to a daily temporal resolution for a standard year of 365 days. The overall novelty of the approach is the use of surface elevation as the only predictor to estimate the recalibrated Hargreaves parameter in space. A third-order polynomial is fitted to the recalibrated parameters against elevation at every station which yields a statistical model for assessing these new parameters in space by using the underlying digital elevation model of the temperature fields. With these newly calibrated parameters for every day of year and every grid point, the Hargreaves method is applied to the temperature fields, yielding reference evapotranspiration for the entire grid and time period from 1961–2013. This approach is opening opportunities to create high-resolution reference evapotranspiration fields based only temperature observations, but being as close as possible to the estimates of the Penman–Monteith approach.