bluuebunny/crossref_metadata_2025 huggingface dataset:
50 Reservoirs, 48 Well Slots & Two TLP's – Maximizing Recovery From the Deepwater Prolific Mars Field
Authors: Derek Newberry
Published: June 2014

The Mars B Development is by IPA definition an " Industrial Mega Project" that is within the execution phase. The development is focused on the addition of new infrastructure to the Mars Field located in the Mississippi Canyon protraction area of the Gulf of Mexico. The development operated by Shell (71.5%) with BP as a Working Interest Owner (28.5%) can be summarized into three major infrastructure components:The Olympus Tension Leg Platform (TLP)West Boreas/South Deimos Subsea Tie-backDedicated oil and gas export pipelines and the West Delta 143C Shallow Water Platform.

The Mars B Development is a first for Shell in the deepwater GOM, in that it represents the first occasion that a second significant production and drilling facility (Olympus TLP) has been installed to complement existing infrastructure (Mars TLP).

The Mars Field is a true deepwater giant with close to 4 billion boe hydrocarbons in place. The Mars TLP was brought on production in 1996 and to date (01.01.14) has produced over 700mln boe. The Mars TLP, a 24 well slot Tension Legged Platform with multiple subsea tie-backs, has a significant track record in developing the field. Constraints, such as the number of available well slots and capacity for future subsea tie-backs, limited its expansion. The structural limitation of the Mars TLP was a main driver for the need to install a second TLP, the Olympus TLP.

Once the Olympus TLP is brought on production in 2014, the Mars Field Depletion plan can be characterized by the following numbers and the unique challenges of integrating the following:One Deepwater Giant Field50+ discrete Hydrocarbon reservoirsTwo Tension Legged Platforms48 Platform well bores + 6 subsea wellsField life extended to 2050(+)

This presents the unique challenges of developing a holistic and evergreen Mars Field Depletion plan that captures the synergies provided by two production and drilling facilities on a single field; and further the ability to extend the Mars Field life to 2050(+) results in a depletion plan that will ensure that we maximize the recovery from a key GOM resource base.
Serpentina FPSO Mooring Integrity Issues and System Replacement: Unique Fast Track Approach
Authors: Bhattacharjee Subir , Majhi Sai , Smith David , Garrity Robert
Published: June 2014

This paper provides an overview of the first documented industry intervention involving replacement of a permanent mooring system due to seabed trenching near the suction piles. Another unique aspect of this intervention was the use of readily available hardware for installing a temporary mooring system to minimize operational risks. Brown-field interventions are often required to address mooring integrity issues or life extensions. These are more challenging than new (green-field) designs and installations due to existing infrastructure. This includes the Floating Production Storage and offloading System (FPSO) hull, risers and flowlines. Also, the production shutdown has to be minimized while maintaining operational safety. The present paper summarizes mooring integrity issues and the complete mooring system replacement of the Serpentina FPSO offshore Equatorial Guinea (EG) within ten years of service. A partial mooring replacement campaign was initially planned to address wire rope degradation and chain chafing damage on selected legs. However, seabed trenches near the suction piles, discovered at a late stage, required a complete change in the project plans. The revised scope included installation of a new set of anchors and off the shelf mooring hardware for all nine anchor legs, to address the risk of potential mooring failure in an expedient manner. Installation of new anchors and mooring lines for this project was executed in roughly 6 months from the discovery of the trenches. The planning and execution of this fast track project is discussed, along with the multiple challenges that needed to be addressed. Industry has limited experience in seabed-trenching related mooring issues and associated mitigation. The importance of seabed trench inspection for taut-mooring systems is discussed. Finally, lessons learned in planning and execution of the project in safe and expedient manner is summarized.
Flow Assurance Solutions and Control Systems for Long Step Out Subsea Production Systems
Authors: Gharaibah Emad , Parsons Robert
Published: June 2014

With the increasing need to operate Subsea Production Systems (SPS) in harsh environments, comes a need to produce with long distances (step out) from shore and in potentially deep water applications from the process plants, eliminating the need for manned offshore production units. This presents challenges for the flow assurance aspects to maintain high production regularity, asset integrity and thereby demands highly reliable control systems to ensure this happens. The Snøhvit project in the Barents Sea is a milestone in subsea oil and gas development, with a record breaking offset (147Km) and all subsea facilities tied-back to shore, without any surface-piercing structures such as platform or floating production facilities, with a consequent dramatic improvement in environmental impact. GE has further qualified the fibre optical control systems to 220Km. A similar control system is also now to be used for the Gorgon/Janz development. It is also envisaged that these systems can be utilised in offshore Tanzania.

The key flow assurance aspects to take into consideration for such a system are:Handling different operating regimes of transporting of multiphase fluids over the field lifeTransporting High viscous fluids at low pressure or temperature addressing Wax, Hydrates formations, mitigations and remediationStrategies to increase the operating envelope including shutdown or restart operations and the impact of operating modes on the production and system integrityFlow assurance challenges due to uneven seabed

In the recent years there has been increased focus on the aim for both standardisation and simplification, such that there has been new developments of new applications such as virtual flow meters. GE has developed this as part of the flow assurance aspect along with potential SMART system applications.

The presentation focuses on the technical and logistical achievements in executing this ultra-long offset subsea-to-beach project and the interaction with flow assurance requirements.
On the Shape of the Wind Wave Spectrum of the Norwegian Continental Shelf
Authors: Houmb Ole Gunnar , Øian Torkel
Published: June 2014

The ultimate aim of this work is to contribute to the understanding of the North Sea wave spectral shape, with special emphasis on design conditions.

More than 6000 wave spectra from the North Sea have been analyzed. The JONSWAP 1 model is fitted to the spectra using a least squares technique with a varying number of free parameters.

We observe a systematic tendency for the JONSWAPI model to fit empirical spectra better than that by Pierson and Moskowitz2.

Methods are proposed for estimation of JONSWAP spectral parameters when the zeros order moment of the spectrum is known.

Introduction

Present knowledge of the shape of the wave spectrum can be summarized as follows:

Under idealized conditions the spectrum has a standard shape that can be described by a set of shape parameters.

The shape of the spectrum of a fully developed sea in deep water is given by the PiersonMoskowitz2 spectrum. It is therefore quite natural that this spectrum includes wind speed but not fetch as a scale parameter.

For growing sea states the spectral shape is given by the JONSWAp1 spectrum. Dimensionless fetch is therefore one of the scale parameters of this spectrum.

The JONSWAP model spectrum is recommended by the Norwegian Petroleum Directorate in computing the interactions between waves and marine structures. However, the values of the JONSWAP model parameters are subject to discussion and disagreements. The main purpose of the work described in this paper has been to estimate the JONSWAP model parameters on the basis of a large number of wind wave, samples.

Efforts are concentrated on design spectra of high sea states. As extreme design sea states are likely to occur during growing or fully developed wave conditions, the analyses were concentrated partly on growing sea states. It is assumed that results on spectral shape from growing seas can be extrapolated to the extreme design sea states.

Based on more than 6000 spectra the JONSWAP model has been parameterized in two slightly different ways that are both useful for engineering applications. Both methods are presented in this paper.

The Design Sea State

It is common practice to define the design sea state as an event having a return period of 50 or 100 years. In the North Sea this corresponds to Hs=15 m and individual waves of height from 30 to 33 m. The period corresponding to the spectral peak is estimated at 15 to 20 s.

Such high and long waves will most likely appear during or close to the peak of a generation phase with strong winds of long duration and fetch.

If swell is present it will most probably be mixed with the wind sea and therefore not appear as an independent spectral peak. The energy of swell present in a design sea state will be small compared to that of the wind sea. We therefore assume that the shape of a design wave spectrum is not influenced by swell, and we assume also that it is satisfactorily described by a model spectrum like the JONSWAP.
Hazard Management and Safety Management Systems: A Structured Approach
Authors: Bentley P.O. , Stockley J.D.
Published: June 2014

Description

The publication in November 1990 of the Public Inquiry Report by Lord Cullen into the events leading up to the Piper Alpha disaster in the UK North Sea on 6th July 1988 highlighted to the offshore industry that safety is "crucially dependent upon management and management systems". Lord Cullen proposed that oil companies should develop Safety Management Systems (SMS) that should "set out the safety objectives, the system by which these objectives are to be achieved, the performance standards which are to be met and the means by which adherence to these standards is to be monitored". SIPM (Shell Internationale Petroleum Mij. The Hague, Holland) fully accepts that the recommendations of the Cullen Report apply not only in local N. Sea application but in principle worldwide. This paper sets out the approach adopted by SIPM in the subsequent formalisation of their SMS guidelines). The approach is based upon a number of previous and existing safety and business improvement initiatives and is both compatible and complementary to activities already in progress within the Operating Companies.

Application

SIPM have to provide guidance to Operating Companies in very different technological environments, ranging from the N. Sea to the technically simpler and more clement S. China Sea as well as onshore in the deserts of Oman. The approach developed hence concentrated upon ensuring compatability with local conditions and upon the basic tenet that all hazards should be clearly understood by the "owner" or operator of the facility.

1) SIPM is a Shell Service Company which provides advice and services 00 Shell Operating Companies other than Shell Oil Company of the United States and its overseas subsiduaries.

The structure presented for hazard management is applicable for both new projects and existing facilities, and is aimed at control of safety critical operations. It maintains a strict focus upon the business introducing essential controls required for a safe operation on the basic fundamental criteria of necessity and sufficiency.

Results

Trials have been carried out in selected Shell Operating Companies and the SMS basis derived from this work is now being proven on a wider scale.

Significance

The development of SMS guidelines within SIPM for the use by Shell E&P Operating Companies has relevance not only to the onshore and offshore oil and gas industry but is equally applicable to all involved in the management of safety.

1. History of the Cullen Report and the development of Safety Management Systems

On 6th July 1988, an explosion occurred on the Piper Alpha production platform in the UK sector of the Northern North Sea which led to a course of events leading to the destruction of the platform and the loss of 167 lives. The UK government required Lord Cullen, a Senator of the Scottish College of Justice, to hold a Public Inquiry into the disaster.
Pile Load Tests In Dense Sand: Analysis Of Static Test Results
Authors: Al-Shafei K.A. , Cox W.R. , Helfrich S.C.
Published: June 2014

This paper describes test results from two tension tests and one compression test on 0.61 - m-diameter steel-pipe piles driven to 18-m depth in dense sand. This paper is a sequel to "Pile Load Tests in Dense Sand: Planning, Instrumentation, and Results, Paper 4847, OTC (1985)". The piles were fully instrumented with strain gages along the pile walls. Shaft frictions and pile movements from the test are analyzed. Results confirm that piles driven into dense sand of the Arabian Gulf can support loads that are up to six times the design capacities calculated by industry-accepted procedures.

INTRODUCTION

More than 1000 piles have been installed in the Arabian Gulf, Saudi Arabia. The piles vary in size up to 1.22 m in diameter. Design penetrations range up to 80 m, however most are between 20 m and 40 m. Design ultimate loads are usually less than 22 MN, but range up to 50 MN. Soil conditions vary significantly in the Arabian Gulf, but in general, the soils are strong enough so that pile installation is usually a difficult and uncertain task. A range of hammer sizes and types have been used to drive these piles. Most were single acting steam hammers with rated energies ranging from 54 KN-m to 700 KN-m. For a recent installation a hydraulic hammer with an energy of 1000 KN-m was used to drive the piles to design penetrations.

One common difficulty of driving piles in the Arabian Gulf arises when piles reach a penetration less than the design penetration and can not be advanced any farther (refusal) due to the presence of strong soil at the site. Another problem occurs when the pile is driven to the design penetration without developing a significant capacity.

In 1982, seventeen driven well conductors were pulled out of three platforms in the Safaniya Field, Arabian Gulf, Saudi Arabia. These conductors were removed by pulling with a 500 ton capacity crane on the jack-up barge, ARB-I. The conductors could be pulled only after driving downward with a hammer to reduce the soil friction along the pile wall. The ultimate tensile loads required to pull the conductors ranged from 1.5 to four times the computed tensile capacities using API RP2A(1982).

The unexpected hard driving, high resistance of the conductors to tensile loads and high cone tip resistance in these dense sands led to a full scale pile load test program.

This paper discusses the results of full scale tests on two piles. One pile was tested only in tension, and the second pile was tested in compression and then tension. Also presented are the measured load distribution and the corresponding unit skin friction for all the tested piles. Details of the test program were discussed in Helfrich et al (1985).
The Nordkapp Basin, Norway: Development Of Salt And Sediment Interplays For Hydrocarbon Exploration
Authors: Lerche I. , Tarudbakken B.O.
Published: June 2014

Investigation of a particular salt diapir in the Nordkapp Basin, Barents Sea has revealed the following sequence of events:salt started to rise when approximately 1.5 k 0.3 km ofsedimentary cover was present (Carboniferous/Permian time);salt reached the sediment surface when about 3.5 + 0.7 km of sediment had been deposited (Triassic time);the mushroom cap on the salt stock top developed over a period of about 75-100 Ma (i.e, during the time when about another km of sediment had been deposited) (Triassic through Base Cretaceous time);the mushroom cap started to dip down significantly (- I km) into the sediments around Cretaceous to Tertiary erosion time;oil generation started in the deep sediments of the Carboniferous around the time that salt reached the surface (Triassic time) and continues to the present day at sedimentary depths between about 4 to 7 km (currently Triassic and deeper sediments);gas generation started around mushroom cap development time and continues to the present day at sedimentary depths greater than about 6-7 km.

Introduction

The estimation of hydrocarbon reserves and their likely locations in the Nordkapp Basin poses special problems because of the presence of many salt diapirs, which have tops close to the seafloor and also widespread mushroom salt caps, making seismic identification of underlying sedimentary beds difficult. Apart from a few, generally shallow, wells there is little direct down hole information in the Nordkapp Basin on sub-surface conditions, or petro physical properties. Information available is generally restricted to:regional seismic reflection profiles;gravity surveys;regional geologic background information (e.g. Dalland et al., 1988; Gabrielsen et al., 1990; Johansen et al., 1992).

Physical models (see e.g. Koyi, 1991) suggest the likely development of the basin, while numerical models provide measures of sediment fill, compaction, fluid-flow, and salt evolution in relation to basinal tectonic evolution.

Background Geological Information

Development of the Nordkapp Basin in relation to the largerBarents Sea picture has been addressed (e.g. Rannevik et al., 1982; Faleide et al., 1984; Jensen and Sorensen, 1988, 1992; Gabrielsen et al., 1990; Johansen et al., 1992; P. van Veen et al., 1992; Talbot et al., 1992; Richardson et al., 1992). The basin formed due to crustal extension during the Late Devonian (?) to Early Carboniferous and contains numerous diapirs of Carboniferous salt. Evaporite deposition in the Early Permian has also been suggested by Faleide et al. (1984), After formation, the basin and surrounding areas became tectonically stable and a carbonate platform developed regionally in the Late Carboniferous - Early Permian. From the Late Permian until the end of the Triassic large amounts of dominating tine-grained clastic sediments were deposited in the Nordkapp Basin.
Improvement in UOE Pipe Collapse Resistance by Thermal Aging
Authors: Al-Sharif A.M. , Preston R.
Published: June 2014

A recent investigation has shown that the UOE pipe manufacturing process significantly degrades the collapse resistance of high strength line pipe. This paper assesses the degree of strength recovery that can be achieved by aging the pipe. An experimental investigation was performed in order to develop a quantitative relationship between time andtemperature of aging, which produces an increase in compressive yield strength with consequent increase in collapse resistance to external pressure loading.

Introduction

The mechanical properties of high strength large diameter, submerged-arc welded line pipe depend on its chemical composition and thermo-mechanical history, with the latter including the plate mill rolling practice and the cold deformation that occurs during the pipe forming and expansion operations. Pipe forming and expansion tend to induce material anisotropy which is a measure of the same property in different directions. Anisotropy is usually more pronounced in the plastic. The anisotropy is evident from the reduction in compressive yield strength in the hoop direction when the axial strength which is less affected by the pipe forming process. As can be seen Figure 1, the degree of anisotropy varies across the thickness, being more pronounced at the outside of the pipe wall. The differences shape between hoop and axial stress curves is also significant. For pipelines which buckle in the plastic range, such an anisotropy directly affects the collapse pressure.

A fill scale test program was completed in 1994 which investigated the collapse strength of UOE pipe. This test program was necessary because of the absence of previous experimental results for pipe of the size required for the Oman India Pipeline which will cross the Arabian Sea at depths if up to 3500 meters. This test program successfully evaluated the reduction in collapse strength manufacturing process and showed resulting the UOE that the loss of material compressive strength can be substantially after stress relieving the pipe by furnace heat treatment (typically 560°CA 10° C for one hour per inch thickness). However, this process is highly energy and time demanding and can produce detrimental effects on weld fracture toughness properties.

A thermal aging process was suggested by a leading pipe manufacturer as a possible alternative to full stress relief. This process requires far less time and energy than stress relief and offers the possibility of application into a continuous pipe manufacturing production line. The Oman India Pipeline project team decided to investigate the effective of thermal aging and therefore performed a study of the phenomenon which included a series of scale tests and small scale experiments.

A literature search revealed a good number of previous research efforts directed at material aging. However, generally these investigations into aging behavior have mainly been concerned with the negative impact that such aging has on the material mechanical properties, especially fracture toughness.
Basic Features of the Submerged Turret Production (STP) Concept
Authors: Aanesland V. , Skjåstad O. , Vinje T. , Major F.
Published: June 2014

The Submerged Turret Production (STP) system is a standardized and compact mooring and production system for FPSO applications. The system is applied in the development of the Lufeng oil field in the South China Sea. The system consists of a complete spread mooring system integrated with a STP Buoy, two risers and two umbilicals. When the Buoy is pulled into and locked to the mating cone the vessel is free to weather-vane. The STP Buoy can be disconnected from the FPSO and will then sink to an idle position of about 40 m below the water surface and the FPSO is free to leave the site.

Introduction

The Lufeng 22-1 oil field is being developed by Statoil as Operator, in partnership with the China National Offshore Oil Corporation, through its subsidiary, Nan Hai East Oil Corporation. The field is located in the South China Sea about 3 10 krn East-Southeast of Chivan in the People's Republic of China (PRC). The water depth in the area is about 330 m.

The economic life time of the field is stipulated to be 5 years. The STP Buoy is designed for a life of 15 years, where as the STP Mooring is designed for a life time of 7 years. The relative short life time of the Lufeng field motivates for a development based on a Subsea Production System (SPS) and a Floating Production, Storage and Offloading Vessel (FPSO). Off-loading shall be to Shuttle Tankers, Fig. I.

The field will have five horizontally completed subsea production wells. The reservoir requires artificial lift to produce fluids to the surface production facilities, and a booster pump system will be used. The crude oil will be lifted through two 7" (ID) flexible risers from the manifold to the STP Buoy. The power and control umbilicals for the booster pumps will be hanged off in the STP Buoy Turret.

Submerged Turret Production, STP

The Submerged Turret Production system, which is delivered by APL, comprises:One integrated Buoy hull and Turret structureA spread mooring system including buoyancy elementsand suction anchor

The STP Buoy is designed to ensure sufficient buoyancy to the disconnected system so that the Buoy will float at an idle position of about 40 m below the water surface, Fig.2. When connected to the mating cone of the FPSO, the Buoy will transfer the mooring forces from the turret to the FPSO, Fig.3. The Buoy will be tightly locked to the vessel and follow all the vessel motions. The cylindrical turret is free to rotate inside the Buoy hull and the mooring lines, risers and umbilicals are connected to the turret. Hence the FPSO is free to weather-vane depending on the environmental forces acting on the vessel and the mooring system.

STP Buoy

The buoyancy cone is divided into several independent buoyancy compartments, Fig 4. The compartments in the turret and buoy are made in order to reduce the risk for a critical loss of buoyancy in case of accidental impact on the buoy.
Integration of oral health into primary health care system: views of primary health care workers in Lagos State, Nigeria
Authors: Braimoh Matilda , Ogunbodede Eyitope , Adeniyi Abiola
Published: June 2014

The limited access to oral health care in developing countries can be greatly improved by integrating oral health into the Primary Health Care (PHC) system. This study was designed to assess the views of PHC workers on integrating oral health care into the PHC system. A self-administered questionnaire survey was conducted in two selected local government areas of Lagos State. The instrument contained three sections assessing sociodemographic features, knowledge of common oral diseases and views on integration of oral health into PHC respectively. The mean knowledge score was 7.75 (SD=±1.81), while 60.4% of the respondents had average knowledge scores. Educational status (P=0.018) and designation (P=0.033) were significantly related to the mean knowledge scores. There was no significant difference in the oral health knowledge of the various cadres (P=0.393). Majority (85.4%) of the respondents were willing to include oral health education in their job schedule and 82% believed they needed more training on oral health. The knowledge of the respondents on the causes of the common oral diseases was deficient. Oral health education should be included in the future curriculum of these personnel.
A comparison of competitive intelligence activities in Brazil, Malaysia, Morocco and South Africa
Authors: Du Toit Adeline S.A. , Sewdass Nisha
Published: June 2014

Orientation: This article compared competitive intelligence activities in Brazil, Malaysia, Morocco and South Africa.Research purpose: The purpose was to determine how these countries can use competitive intelligence to increase their competitiveness in the global economy.Motivation for the study: Competitive intelligence is a challenge in developing economies.Research design, approach and method: A questionnaire survey was sent to competitive intelligence professionals in the four study countries.Main findings: The most important primary information source used in all four countries is direct customer feedback and the most important secondary information source used is corporate websites. Companies in all four countries did not use advanced analysis techniques.Practical/managerial implications: It is recommended that all four countries should develop a competitive intelligence culture by creating awareness of competitive intelligence amongst their employees.Contribution/value added: It is crucial to apply competitive intelligence in the four countries in order to become more competitive in the global economy.
Zoonotic Ancylostoma ceylanicum Infection Detected by Endoscopy
Authors: Ngui Romano , Lim Yvonne A. L. , Ismail Wan Hafiz Wan , Lim Kie Nyok , Mahmud Rohela
Published: June 2014

We report a case of Ancylostoma ceylanicum infection detected by endoscopy. It was diagnosed and confirmed using polymerase chain reaction (PCR) and DNA sequencing. The patient is a 58-year-old Malaysian woman who lives in a rural area, where uncontrolled populations of stray and semidomesticated dogs live in close proximity with humans.
Awareness of Meningococcal Disease among Travelers from the United Kingdom to the Meningitis Belt in Africa
Authors: Goodman Anna L. , Masuet-Aumatell Cristina , Halbert Jay , Zuckerman Jane N.
Published: June 2014

Meningococcal disease causes considerable morbidity and has a high case-fatality rate. In the United Kingdom, the meningococcal quadrivalent vaccine is recommended for travelers visiting the meningitis belt of Africa. We analyzed 302 responses to a cross-sectional study conducted in 2010 of travelers who had visited the meningitis belt recently or were shortly due to travel there. Using the results of an online questionnaire, we assessed knowledge and understanding of meningococcal disease and likelihood of uptake of meningococcal immunization before travel. Meningococcal vaccine uptake was 30.1%. Although global scores in the questionnaire did not correlate with vaccine uptake, knowledge of the meningitis belt and knowledge of certain key symptoms or signs were statistically associated with high vaccine uptake. We conclude that improved education of travelers may improve vaccine uptake before travel to the meningitis belt in Africa.
Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)
Authors: Pereira K. L. , Hamilton J. F. , Rickard A. R. , Bloss W. J. , Alam M. S. , Camredon M. , Muñoz A. , Vázquez M. , Borrás E. , Ródenas M.
Published: June 2014

Abstract. The increasing demand for palm oil for uses in biofuel and food products is leading to rapid expansion of oil palm agriculture. Methyl chavicol (also known as estragole and 1-allyl-4-methoxybenzene) is an oxygenated biogenic volatile organic compound (VOC) that was recently identified as the main floral emission from an oil palm plantation in Malaysian Borneo. The emissions of methyl chavicol observed may impact regional atmospheric chemistry, but little is known of its ability to form secondary organic aerosol (SOA). The photo-oxidation of methyl chavicol was investigated at the European Photoreactor chamber as a part of the atmospheric chemistry of methyl chavicol (ATMECH) project. Aerosol samples were collected using a particle into liquid sampler (PILS) and analysed offline using an extensive range of instruments including; high-performance liquid chromatography mass spectrometry (HPLC-ITMS), high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The SOA yield was determined as 18 and 29% for an initial VOC mixing ratio of 212 and 460 ppbv (parts per billion by volume) respectively; using a VOC:NOx ratio of ~5:1. In total, 59 SOA compounds were observed and the structures of 10 compounds have been identified using high-resolution tandem mass spectrometry. The addition of hydroxyl and/or nitro-functional groups to the aromatic ring appears to be an important mechanistic pathway for aerosol formation. This results in the formation of compounds with both low volatility and high O:C ratios, where functionalisation rather than fragmentation is mainly observed as a result of the stability of the ring. The SOA species observed can be characterised as semi-volatile to low-volatility oxygenated organic aerosol (SVOOA and LVOOA) components and therefore may be important in aerosol formation and growth.
Acetaldehyde exchange above a managed temperate mountain grassland
Authors: Hörtnagl L. , Bamberger I. , Graus M. , Ruuskanen T. M. , Schnitzhofer R. , Walser M. , Unterberger A. , Hansel A. , Wohlfahrt G.
Published: June 2014

Abstract. An overview of acetaldehyde exchange above a managed temperate mountain grassland in Austria over four growing seasons is presented. The meadow acted as a net source of acetaldehyde in all 4 years, emitting between 7 and 28 mg C m−2 over the whole growing period. The cutting of the meadow resulted in huge acetaldehyde emission bursts of up to 16.5 nmol m−2 s−1 on the day of harvesting or 1 day later. During undisturbed conditions both periods with net uptake and net emissions of acetaldehyde were observed. The bidirectional nature of acetaldehyde fluxes was also reflected by clear diurnal cycles during certain time periods, indicating strong deposition processes before the first cut and emission towards the end of the growing season. The analysis of acetaldehyde compensation points revealed a complex relationship between ambient acetaldehyde mixing ratios and respective fluxes, significantly influenced by multiple environmental parameters and variable throughout the year. As a major finding of this study, we identified both a positive and negative correlation between concentration and flux on a daily scale, where soil temperature and soil water content were the most significant factors in determining the direction of the slope. In turn, this bidirectional relationship on a daily scale resulted in compensation points between 0.40 and 0.54 ppbv, which could be well explained by collected ancillary data. We conclude that in order to model acetaldehyde fluxes at the site in Neustift on a daily scale over longer time periods, it is crucial to know the type of relationship, i.e., the direction of the slope, between mixing ratios and fluxes on a given day.
Emissions of terpenoids, benzenoids, and other biogenic gas-phase organic compounds from agricultural crops and their potential implications for air quality
Authors: Gentner D. R. , Ormeño E. , Fares S. , Ford T. B. , Weber R. , Park J.-H. , Brioude J. , Angevine W. M. , Karlik J. F. , Goldstein A. H.
Published: June 2014

Abstract. Agriculture comprises a substantial, and increasing, fraction of land use in many regions of the world. Emissions from agricultural vegetation and other biogenic and anthropogenic sources react in the atmosphere to produce ozone and secondary organic aerosol, which comprises a substantial fraction of particulate matter (PM2.5). Using data from three measurement campaigns, we examine the magnitude and composition of reactive gas-phase organic carbon emissions from agricultural crops and their potential to impact regional air quality relative to anthropogenic emissions from motor vehicles in California's San Joaquin Valley, which is out of compliance with state and federal standards for tropospheric ozone PM2.5. Emission rates for a suite of terpenoid compounds were measured in a greenhouse for 25 representative crops from California in 2008. Ambient measurements of terpenoids and other biogenic compounds in the volatile and intermediate-volatility organic compound ranges were made in the urban area of Bakersfield and over an orange orchard in a rural area of the San Joaquin Valley during two 2010 seasons: summer and spring flowering. We combined measurements from the orchard site with ozone modeling methods to assess the net effect of the orange trees on regional ozone. When accounting for both emissions of reactive precursors and the deposition of ozone to the orchard, the orange trees are a net source of ozone in the springtime during flowering, and relatively neutral for most of the summer until the fall, when it becomes a sink. Flowering was a major emission event and caused a large increase in emissions including a suite of compounds that had not been measured in the atmosphere before. Such biogenic emission events need to be better parameterized in models as they have significant potential to impact regional air quality since emissions increase by several factors to over an order of magnitude. In regions like the San Joaquin Valley, the mass of biogenic emissions from agricultural crops during the summer (without flowering) and the potential ozone and secondary organic aerosol formation from these emissions are on the same order as anthropogenic emissions from motor vehicles and must be considered in air quality models and secondary pollution control strategies.
Comparison of in-situ FISH measurements of water vapor in the UTLS with ECMWF (re)analysis data
Authors: Kunz A. , Spelten N. , Konopka P. , Müller R. , Forbes R. M. , Wernli H.
Published: June 2014

Abstract. An evaluation of water vapor in the UTLS in the atmospheric ERA-Interim reanalysis data set is presented by using in-situ measurements from a large set of airborne measurement campaigns from 2001 to 2011 in the tropics, midlatitudes and polar regions. Water vapor measurements are derived from the Fast In-situ Stratospheric Hygrometer (FISH) and cover isentropic layers from 300–400 K (5–18 km). At the same time, the improvement of the ECMWF assimilation scheme representation of water vapor is addressed for time periods representing different cycles of the Integrated Forecast System (IFS). The ratio Δ(H2O) = H2OERA / H2OFISH is used as a simple measure for the difference between observations and the reanalyses. Overall, the reanalysis data reproduce around 87% of all FISH measurements within Δ(H2O) = 0.5–2, and 30% are within Δ(H2O) = 1.0 ± 0.1. Nevertheless, also strong over- and underestimations occur both in the troposphere and in the stratosphere. Δ(H2O) values indicate deviations of factors up to 10, with lower deviations in the stratosphere (Δ(H2O) = 0.5–4) than in the troposphere (Δ(H2O) = 0.5–10). In the tropical stratosphere the ratio is closer to 1 (Δ(H2O) = 0.5–2) than in the extratropical stratosphere where strong deviations occur (Δ(H2O) = 0.1–4). When considering operational analysis data, the agreement with FISH improves over the time, in particular when comparing water vapor fields for time periods before 2004 and after 2010. It appears that influences of tropical tropospheric and extratropical lower stratospheric processes on the water vapor distribution in the UTLS are particularly challenging, resulting in an overestimation of low and underestimation of high water vapor mixing ratios.
Satellite observations of peroxyacetyl nitrate from the Aura Tropospheric Emission Spectrometer
Authors: Payne V. H. , Alvarado M. J. , Cady-Pereira K. E. , Worden J. R. , Kulawik S. S. , Fischer E. V.
Published: June 2014

Abstract. We present a description of the algorithm used to retrieve peroxyacetyl nitrate (PAN) concentrations from the Aura Tropospheric Emission Spectrometer (TES). We describe the spectral microwindows, error analysis and the utilization of a priori and initial guess information provided by the GEOS-Chem global chemical transport model. The TES PAN retrievals contain up to one degree of freedom for signal. Estimated single-measurement uncertainties are 30 to 50%. The detection limit for a single TES measurement is dependent on the atmospheric and surface conditions as well as on the instrument noise. For observations where the cloud optical depth is less than 0.5, we find that the TES detection limit for PAN is in the region of 200 to 300 pptv. We show that PAN retrievals over the Northern Hemisphere Pacific in springtime show spatial features that are qualitatively consistent with the expected distribution of PAN in outflow of Asian pollution.
Determination of car on-road black carbon and particle number emission factors and comparison between mobile and stationary measurements
Authors: Ježek I. , Drinovec L. , Ferrero L. , Carriero M. , Močnik G.
Published: June 2014

Abstract. We have used two methods for measuring emission factors (EF) in real driving conditions on five cars in a controlled environment: the stationary method, where the investigated vehicle drives by the stationary measurement platform and the composition of the plume is measured; and the chasing method, where a mobile measurement platform drives behind the investigated vehicle. We measured EF of black carbon and particle number concentration. The stationary method was tested for repeatability at different speeds and on a slope. The chasing method was tested on a test track and compared to the portable emission measurement system. We further developed the data processing algorithm for both methods, trying to improve consistency, determine the plume duration, limit the background influence and facilitate automatic processing of measurements. The comparison of emission factors determined by the two methods showed good agreement. EFs of a single car measured with either method have a specific distribution with a characteristic value and a long tail of super emissions. Measuring EFs at different speeds or slopes did not significantly influence the EFs of different cars, hence we propose a new description of vehicle emissions that is not related to kinematic or engine parameters, rather we describe the vehicle EF with a characteristic value and a "super emission" tail.
Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region
Authors: Parsons S. A. , Valdez-Ramirez V. , Congdon R. A. , Williams S. E.
Published: June 2014

Abstract. The seasonality of litter inputs in forests has important implications for understanding ecosystem processes and biogeochemical cycles. We quantified the drivers of seasonality in litterfall and leaf decomposability, using plots throughout the Australian wet tropical region. Litter fell mostly in the summer (wet, warm) months in the region, but other peaks occurred throughout the year. Litterfall seasonality was modelled well with the level of deciduousness of the site (plots with more deciduous species had lower seasonality than evergreen plots), temperature (higher seasonality in the uplands), disturbance (lower seasonality with more early secondary species) and soil fertility (higher seasonality with higher N : P/P limitation) (SL total litterfall model 1 = deciduousness + soil N : P + early secondary sp: r2 = 0.63, n = 30 plots; model 2 = temperature + early secondary sp. + soil N : P: r2 = 0.54, n = 30; SL leaf = temperature + early secondary sp. + rainfall seasonality: r2 = 0.39, n = 30). Leaf litter decomposability was lower in the dry season than in the wet season, driven by higher phenolic concentrations in the dry, with the difference exacerbated particularly by lower dry season moisture. Our results are contrary to the global trend for tropical rainforests; in that seasonality of litterfall inputs were generally higher in wetter, cooler, evergreen forests, compared to generally drier, warmer, semi-deciduous sites that had more uniform monthly inputs. We consider this due to more diverse litter shedding patterns in semi-deciduous and raingreen rainforest sites, and an important consideration for ecosystem modellers. Seasonal changes in litter quality are likely to have impacts on decomposition and biogeochemical cycles in these forests due to the litter that falls in the dry being more recalcitrant to decay.
Does soil moisture overrule temperature dependency of soil respiration in Mediterranean riparian forests?
Authors: Chang C.-T. , Sabaté S. , Sperlich D. , Poblador S. , Sabater F. , Gracia C.
Published: June 2014

Abstract. Soil respiration (SR) is a major component of ecosystem's carbon cycle and represents the second largest CO2 flux of the terrestrial biosphere. Soil temperature is considered to be the primary control on SR whereas soil moisture as the secondary control factor. However, soil moisture can become the dominant control on SR in very wet or dry conditions. Determining the trigger that switches-on soil moisture as the primary control factor of SR will provide a deeper understanding on how SR changes under projected future increased droughts. Specific objectives of this study were (1) to investigate the seasonal variations and the relationship between SR and both soil temperature and moisture in a Mediterranean riparian forest along a groundwater level gradient; (2) to determine soil moisture thresholds at which SR is rather controlled by soil moisture than by temperature; (3) to compare SR responses under different tree species present in a Mediterranean riparian forest (Alnus, glutinosa, Populus nigra and Fraxinus excelsior). Results showed that the heterotrophic soil respiration rate, groundwater level and 30 cm integral soil moisture (SM30) decreased significantly from riverside to uphill and showed a pronounced seasonality. SR rates showed significant differences among tree species, with higher SR for P. nigra and lower SR for A. glutinosa. The lower threshold of soil moisture was 20 and 17% for heterotrophic and total SR respectively. Daily mean SR rate was positively correlated with soil temperature when soil moisture exceeded the threshold, with Q10 values ranging from 1.19 to 2.14; nevertheless, SR became decoupled from soil temperature when soil moisture dropped below these thresholds.
Coastal vulnerability of a pinned, soft-cliff coastline – Part I: Assessing the natural sensitivity to wave climate
Authors: Barkwith A. , Thomas C. W. , Limber P. W. , Ellis M. A. , Murray A. B.
Published: June 2014

Abstract. The impact of future sea-level rise on coastal erosion as a result of a changing climate has been studied in detail over the past decade. The potential impact of a changing wave climate on erosion rates, however, is not typically considered. We explore the effect of changing wave climates on a pinned, soft-cliff, sandy coastline, using as an example the Holderness coast of East Yorkshire, UK. The initial phase of the study concentrates on calibrating a numerical model to recently measured erosion rates for the Holderness coast using an ensemble of geomorphological and shoreface parameters under an observed offshore wave climate. In the main phase of the study, wave climate data are perturbed gradually to assess their impact on coastal morphology. Forward-modelled simulations constrain the nature of the morphological response of the coast to changes in wave climate over the next century. Results indicate that changes to erosion rates over the next century will be spatially and temporally heterogeneous, with a variability of up to ±25% in the erosion rate relative to projections under constant wave climate. The heterogeneity results from the current coastal morphology and the sediment transport dynamics consequent on differing wave climate regimes.
Comparison between experimental and numerical stratigraphy emplaced by a prograding delta
Authors: Viparelli E. , Blom A. , Ferrer-Boix C. , Kuprenas R.
Published: June 2014

Abstract. A one-dimensional model that is able to store the stratigraphy emplaced by a prograding delta is validated against experimental results. The laboratory experiment describes the migration of a Gilbert delta on a sloping basement into standing water, i.e., a condition in which the stratigraphy emplaced by the delta front is entirely stored in the deposit. The migration of the delta front and the deposition on the delta top are modeled with total and grain-size-based mass conservation models. The vertical sorting on the delta front is modeled with a lee-face-sorting model as a function of the grain size distribution of the sediment deposited at the brinkpoint, i.e., at the downstream end of the delta top. Notwithstanding the errors associated with the grain-size-specific bedload transport formulation, the comparison between numerical and experimental results shows that the model is able to reasonably describe the progradation of the delta front, the frictional resistances on the delta top, and the overall grain size distribution of the delta top and delta front deposits. Further validation of the model in the case of variable base level is currently in progress to allow for future studies, at field and laboratory scale, on how the delta stratigraphy is affected by different changes of relative base level.