bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre-Drilled Geomechanical Modeling Reduces Risks in Drilling a Wildcat High-Pressure/High-Temperature Exploratory Well - A Case Study from Asia Pacific
Authors: Ghosh Amitava , Chatterjee Avirup , Ong See Hong
Published: March 2018

Pore pressure prediction and geomechanical modelling play a very important role in well planning. The exploration focus worldwide is moving more and more into the challenging environments. Well planning and design in high pressure high temperature (HPHT) environments comprise numerous challenges such as play identification and prospect de-risking to drillability and development to production. Overpressure prediction is one of the principal challenges facing the oil industry today, as exploration focus worldwide moves further into the HPHT environments. Pressure related problems in HPHT wells include well control incidents, lost circulation, formation breathing, differential sticking, reduced rates of penetration, and reservoir damage, many which can potentially lead to expensive sidetracks, well abandonments and underground blowouts. A better understanding of the prevalent pore pressure regimes including generating mechanisms, pressure maintenance and dissipation through geologic time enables invaluable insight into these challenges and the ability to mitigate or minimize them. It is important to analyse the challenges prior to drilling so that various plans and systems can be established. Once the pore pressure regime is well understood, the next step is to understand the stress regime. Thus building a geomechanical model is the next key element for well design. The stress model can be used for wellbore stability analysis to understand wellbore failures and help in thedesignof optimum mud weights. Additionally in HPHT environments, thermal-induced stresses and their impacts on stability must also be considered. This understanding helps in modelling wellbore failures due to heating and cooling arising from mud circulation. Other considerations including drilling through faults can set another aspect of wellbore failure which could further complicate the already difficult drilling situation.

This paper presents a case study on using geomechanical evaluations to reduce drilling risks and costs in a high-pressure/high-temperature (HP/HT) well located in offshore Asia Pacific. The major risk anticipated for this well, which was drilled to explore a deep-play (>3.5 Km), was high-pressure (>10,000 psi) and high-temperature (>2000C) with narrow margin drilling conditions. The geomechanical study provided inputs for an effective well design.
Comparing Results of Time Domain Fatigue Design of Steel Catenary Risers Using Linear and Nonlinear Riser Soil Interaction Models Under Random Waves
Authors: Muraleedharan Atmaram , Kimiae Mehrdad
Published: March 2018

Steel Catenary Risers (SCRs) are still among the most popular types of riser systems and are widely adopted across deep water oil and gas projects globally. Fatigue design of SCRs are associated with high nonlinearity and it remains a challenge for riser engineers and researchers. In the Touch Down Zone (TDZ), the soil structure interaction model plays a vital role in the fatigue design and it becomes more complex when dealing with irregular waves and a nonlinear soil structure interaction model.

In this paper the effect of nonlinear and linear soil structure interaction models under randomly generated waves for a wide range of seastates are analyzed in time domain. Fatigue damage results under randomly generated waves are calculated in time-domain analysis. Sensitivity of the results to various parameters like the soil type model, the severity of seastates and the duration of dynamic simulations are discussed in detail. Results of this study give a better insight into the fatigue design of SCRs in TDZ.
OCTG Standardization and Surplus Reutilization Bring Cost Reduction Efforts to Fruition
Authors: Ong Gary S. H. , Abdullah Malik Faisal , Razak M. Zahin A. , Ghani Athiyatul Shakirah Abdul , Bong David , Thanaraju Andrew , Low Jun Leon
Published: March 2018

The ongoing low oil price environment underscores the need to be constantly prudent. Long term sustainable changes implementation are necessary in all areas to preserve profitability including that of effective drilling materials and surplus management with OCTG (Oil Country Tubular Goods) being the prime issue from both quantity and price perspectives. Drilling operators especially those with large scale and diversely complex well programs have to manage excessive surplus mess uncontrollably amassed when oil prices were high. Some opted to dispose while others chose surplus reutilization. Disposal seems to be an easier way out as it frees up yard space and reduces preservation cost but it incurs value leakages as it often fetches unreasonably low scrap prices. PETRONAS took on a bold strategy to overcome the issue by channeling efforts on producing a robust OCTG standardization program as well as enhancing reutilization through reverse engineering which involves meticulously designing wells casing programs based on available surplus. These initiatives aim to take materials management to a higher level of efficiency and avoid future excessive surplus accumulations.

This paper will walk through the various hurdles and solutions in the course of delineating Fit-For-Purpose (FFP) configurations and minimum technical criteria for OCTG material and connections specifications to satisfy PETRONAS’ application requirements for all well types ranging from conventional to High Pressure High Temperature (HPHT) and Deepwater. It also describes various operational challenges from onshore machine shop support to offshore tubular running equipment and services which were critical pieces in putting together the standardization puzzle. It will further provide a lowdown on the misperception of having the lowermost specifications and lowest prices as the primary drivers in realizing the greatest value for money for OCTG applications especially for operators with wide ranging application needs.
Quantitative Ranking and Development of Hydrate Anti-Agglomerants
Authors: Morrissy Shane A. , Kuteyi Temiloluwa O. , Johns Mike L. , May Eric F. , Aman Zachary M. , McKay Stuart. F.
Published: March 2018

During the production of offshore oil and gas, production fluids will cool toward seafloor temperatures which will place the flowline into the natural gas hydrate stability region. Small particles of hydrate can form, which can aggregate and result in blockage of the flowline. The most common hydrate management strategy involves using large volumes of thermodynamic inhibitor (THI) to operate outside the hydrate stability region. The THI hydrate management strategy represents a significant CAPEX and OPEX investment, rendering some deepwater fields economically unviable to develop. Low dosage hydrate inhibitors (LDHIs), in the form of kinetic hydrate inhibitors (KHIs) and anti-agglomerants (AAs), present an alternative to THIs. AAs allow hydrates to form, but limit hydrate agglomeration and enable the transport of a stable hydrate-in-oil slurry. AAs have traditionally been qualified for field deployment on black oils using high-pressure rocking cells and autoclaves. These tools provide qualitative assessments of AA performance, but are unable to resolve structure-function relationships at the interfacial length scale. In this study, a quantitative micromechanical force (MMF) has been deployed to study the performance of seven industry AAs. Four of these AAs are current generation AAs being deployed today and the remainder represent successive generations of AA products. The results illustrate that an effective AA must be one that lowers the cohesive forces between hydrate particles. For the four generations of AA chemistry an improvement in the maximum hydrate cohesive force reduction for the current generation chemistry (80%> force reduction) relative to the previous ones (40-50% force reduction) we observed. All current generation AA chemistries lower hydrate cohesive force by more than >80% indicating a high likelihood of successfully dispersing hydrates. To assess this likelihood each chemistry was then validated in high pressure sapphire autoclave under high shear; in this technique, which is analogous to more traditional qualification methods, performance may be quantified in terms of the maximum relative torque, defined as the ratio of the maximum torque required to maintain a set shear rate in the presence of hydrates to the torque required before hydrate formation. Consistent with the observations in the MMF, all current generation AAs kept the relative torque < 2, while systems with no AA experienced a maximum relative torque of ~20. The MMF results are consistent with the more traditional autoclave qualification but provides a more quantitative insight into hydrate cohesion which is a key aspect of AA performance.
Improved Understanding of Reservoir Performance Behaviors from 4D Seismic Data – A Case Study from Malaysian Basin
Authors: Pathak Ravi , Ranjan Rakesh , Masoudi Rahim
Published: March 2018

Improved understanding of reservoir performance and behavior are critical for developing sound reservoir management strategy for optimized field development. The reservoir surveillance information gathered over different stages of depletion provide hard data for validating the predicted reservoir performance and trigger suitable course correction in development strategy. Majority of surveillance information gathered is at the well level and flow inside the reservoir is interpreted using reservoir simulation models and/or other analytical methods. Non-uniqueness of these models create uncertainty in understanding of flow patterns inside the reservoir driving the observed reservoir performance.

The paper illustrates an example from Malaysian basin where 4D seismic information was used for optimizing reservoir management and future development strategies.
Optimal Sand Control Design & Technique Selection: A Simplified Practical Guidance Tool
Authors: Reyes Raymond , Sipi Aluyah
Published: March 2018

Objectives

The primary aim of this study was to design a guideline in the form of a flow chart that can potentially be used in practice when optimal sand control methods and implementation of completion techniques are considered in sand producing wells. The flow chart could also serve as a tool during the decision-making process where sand control is deemed necessary. Distinct reservoir data and key parameters were incorporated into the designing of the flow chart. This paper predominantly focused on two of the most common techniques used currently in practice; sand screens and gravel pack.

Methodology

A retrospective analytical review was carried out. A systematic search was undertaken to analyze sand control methodologies used in recent studies to ascertain key considerations undertaken when choosing gravel pack and/or sand screen. Studies selected were based on a predetermined set of inclusion and exclusion criteria. Recurrent pattern that existed when choice of a specific technique was identified; a list of criteria that was considered when selecting gravel pack and/or sand screen techniques was developed. Information and data obtained were then eventually integrated in stages into designing a concise flowchart.

Results, Discussion, Conclusion

List of criteria developed when contemplating sand control and completion methods were as follows, 1. Determine rock mechanics, 2. Study individual reservoir conditions, 3. Note lithological changes, 4. Obtain well data, 5. Characterize formation sand, 6. Select gravel size, 7. Select screen and size, 8. Select completion method and 9. Evaluate the potential cost and economical outcome. The development of flow chart then began with the categorisation of key information into four significant stages as follows, sand prediction, sand analysis, sand control and completion method. Looking at the step 1 to 9 of the list of criteria and the four phases of the flow chart together, a more structured and integrated thought process took place. When the sand analysis stage was referred to, criteria 1 to 5 were determined simultaneously. Then, the sand prediction stage was referred to in the flow chart where upon obtaining the sand production rate it could be determined if the sand produced was low/manageable. A choice to live with the sand produced is made if so. If the rate was high, then the rest of criteria 6 to 9 as per the list above were determined and advancement is made to the next stage flow chart according to the sections. Both, the criteria list and flow chart can be used in parallel as guidance when implementing respective techniques in an individual sand-producing well.
Application of Integrated Compositional Gas Ratio Analysis to Understand Reservoir Hydrocarbon Potential and Enhance Confidence of Testing and Reservoir Lateral Drilling: With Examples from Krishna Godavari Basin, India
Authors: Sahu Arijit
Published: March 2018

The subsurface geological complexities in Krishna Godavari Basin, India often result into discrete and challenging reservoirs. Limited geological correlation plus HP-HT regime down-hole further add up to the challenge to understand reservoir HC potential. In this context, application and meaningful interpretation of gas ratio analyses are discussed in reservoir sections of two exploratory wells (A & B of L. Cretaceous and L. Eocene) from KG Basin.

Formation Gas data obtained during drilling are commonly analyzed as well-known ratios of ‘Dryness’, ‘Wetness’, ‘Balance’, ‘Character’ & ‘Pixler ratios’ which are simple, quick and field based. It is a proxy that can save time and resource; by aiding in identification of reservoir fluids, fluid contacts & choosing testing intervals, thus enhancing confidence about reservoir. It can be practiced especially where log quality is poor and in cases where logging scope is limited due to complications or high thermal regime.

It is found that gas ratio studies indicate gas-condensate in Well-A while gas with light crude oil in Well-B reservoirs. Moreover it is capable of picking up top of reservoir facies, gas-water & gas-oil contacts and variation in reservoir tightness across reservoir sections as found in Well-A & B. The comparative approach of ratios also interprets about presence of several discrete yet closely spaced HC pools across the reservoir section of Well-B. These findings simply enhance understanding of otherwise complex reservoirs. Along with petrophysical analysis it adds confidence to propose precise testing intervals against HC fluid of interest.

Since gas-ratios are proxy of fluid contacts, their utility can be extended to drilling reservoir lateral wells, if compositional gas data can be obtained fast- in which case gas-ratio analysis can guide drilling effectively to avoid deviation to unwanted fluid zone although reservoir litho-facies variation is less. Gas ratios and electrologs are integrated to introduce to a practical concept of Oil Potential Parameter (OPP) to evaluate effective extent of arenaceous reservoir and reduce qualitative geological risk while planning wells to develop an oil field, as shown with a KG basin example.
Gas Centrifugal Compressor: Pushing its Capacity Limit via Surge Control & Polytrophic Efficiency Operating Point Optimization, Driven Gas Turbine Fuel Savings
Authors: Ir. Siva Kumaran C.
Published: March 2018

In many offshore oil and gas installations, the gas compressors are directly driven by the gas turbines which uses fuel gas that can be monetized if the gas turbines fuel gas consumption is reduced; both from operating the compressors at higher efficiency and optimized compressor operating envelope to operate as close to surge region, thus avoiding gas recycling at the compressor. This paper shows every molecule savings on the fuel gas consumption can derive substantial commercial value for the end users.

The presenter list prerequisites for the gas compressor operating points optimization and surge control optimization. The methods used will guide end users to operate multiple gas compressors by taking advantage of their best efficiency operating points based on either polytrophic or isentrophic efficiency calculated. Simple algorithm and easy to measure parameters from the field to derive the monetized values of the fuel savings to see if it is worth to adjust the operating points can be determined. The incipient surge test can be conducted to determine the surge region to ensure we operate the compressors without gas recycling which is waste of energy during capacity turndown for the compressor, thus this also yields return on investment.

By operating the compressor at better efficiency points, the compressor absorbs lesser brake horsepower (bhp) or shaft power, in turn, the gas turbines fuel is consumed at optimized flowrate, resulting in reduction of fuel gas that can be monetized instead of being burned in combustion chamber of the gas turbine and emitted as Green House Gas (GHG) from the gas turbine exhaust stacks. Operating the gas turbine efficiently means we are truly embarking on GREENER environment, not just by words but this is also a practical way to embrace Paris climate change initiatives. The Paris Agreement, Paris climate accord or Paris climate agreement is an agreement within the United Nations Framework Convention on Climate Change dealing with greenhouse gas emissions mitigation.

It is also common that we recycle gas to avoid surging the compressors for low flowrate scenarios in our compression operations which is an inefficient way of compression as recycling gas means energy is wasted by compressing gas then its pressure is killed via capacity recycle or anti surge control valve which in turn dissipates as heat and noise during gas recycling. Therefore, one of the desired solution is to push compressors closest to the surge region by conducting incipient surge test at site conditions to define the actual surge boundary, allowing the compressor to operate without recycling at lower flowrates, thus recycling is minimized or/and some cases avoided. This paper presents the incipient surge test done offshore with risk mitigated whilst some OEM's do not recommend this test. The author has personally conducted such test offshore, and presents risks and values proposition for end users.
Measures to Overcome Subsea Installation Challenges from High Currents Offshore East Coast of India
Authors: Gupta Ashish , Paul Eldho
Published: March 2018

Subsea installation across the globe comes with associated challenges and offshore East Coast of India is no exception considering the limited installation window available due to the annual monsoon season. The months of December to March are normally considered as the most suitable period for offshore installation. However, McDermott International, Inc as a contractor, faced a number of challenges due to persistent high currents during one of its recent offshore installation campaigns. The surface currents were recorded as high as 3.0 knots during the campaign which persisted for several days.

This paper details novel ideas adopted by McDermott to improve operability and mitigate the risks involved with working in high currents.
Lessons Learned from Using a Drilling Connection in Extreme Conditions
Authors: Marta Lafuente , Fabien Carrois
Published: March 2018

Objectives/Scope

This paper presents a comprehensive summary of the different techniques for increasing the available torque of existing drilling products, the limitations of these techniques and the best practices that can be implemented to reduce risks when using drilling tubulars beyond the API recommended make-up torques.

Methods, Procedures, Process

The torsional strength and make-up torque of a threaded connection are traditionally calculated by only using inherent attributes of the connection, such as the thread design, the yield strength of the connector's material, and the cross critical section of the connector. However, the design of a connector is not the only option to increase its operational torque. Stress balancing considerations and the thread compound friction factor can also help increase operational torque. The recommended make-up torque for rotary shouldered connections is typically defined by stressing those connections to 60% of their torsional strength, thus leaving a margin for using a higher make-up torque‒and hence reaching a higher operational torque. Another option to increase the available operational torque is to use a thread compound with an increased friction factor. API thread compounds are designed with a friction factor of 1. Because of this, when using a thread compound with a higher friction factor, the applicable make-up torque has to be corrected.

Results, Observations, Conclusions

Although stress balancing and the thread compound friction factor considerations can easily and economically increase the available torque of a connector during drilling and allow having more versatile products on the rig, these practices can also carry some risks.

Novel/Additive Information

Compilation of lessons learned from torque-increasing techniques for rotary shouldered connections and compatibility considerations with rig equipment when using them.
Impact of Real-Time Optimisation and Geomechanics to Enhance Performance and Optimise Cost
Authors: Dabyah Ali A. Al , Elsherbeny W. I. , Taylor R. H.
Published: March 2018

Poor drilling performance can lead to increased costs when enhanced drilling performance and extended reach are the main goals for oil operators. Service companies and operators can use the latest technology and several pre-well planning processes and methods to enhance drilling operations effectively and attain these goals. These processes include developing a thorough understanding and application of the geological structure and conducting a formal planning process that incorporates all aspects of drilling, well design, formation evaluation, bit selection and bottomhole assembly.

In this dynamic market where companies are trying to minimize the cost and attain the objective, basic planning and execution using the latest advanced technology are not enough to provide significant performance improvements.

Extensive job planning, including sensitivity analysis, is essential. During the execution phase, close monitoring of drilling parameters and continual testing against modeled data help identify hazards early.

Enabling quick and informed decisions to ensure safe and efficient drilling in a challenging environment will be one of the main factors to improve performance.

Using the right downhole optimization tool with highly experienced engineers enable the interaction with real-time parameters. That's the key factor to overcome extended-reach challenges such as Steering in different environmentsVibrationsTransfer of usable energyHole cleaning and quality indications

Supporting downhole optimization with real-time geomechanics will influence the success rate to deliver the expected performance. The involvement of geomechanics in the planning stage and during execution enables faster and safer drilling and resolves many challenges in extend-reach wells such as Wellbore stabilityHole qualityHole cleaningPressure managementTorque and dragMud system and properties

This paper highlights the importance of utilizing a downhole optimization tool and real-time geomechanics by describing a case study from the Middle East.
Official controls according to Integrated Regional Plan in Campania Region 2011/2014
Authors: Mandato Diletta , Colarusso Germana , Pellicanò Roberta , Baldi Loredana , Guarino Achille , Sarnelli Paolo
Published: March 2018

Due to EU law, European citizens enjoy one of the highest worldwide food safety standards. Along the entire food supply chain, mandatory controls are made to ensure that plant and animal products healthiness and food and feed safety are properly labeled and comply with the strictly EU rules. The process of review of European legislation began with the promulgation of the Regulation 178/2002/EC (Official Journal of the EC no. L31 of 01/02/2002) and was completed with the hygiene package. Regulation No. 178/2002/EC (the General Food Law) laying down the general principles and requirements of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety.
Food safety in food services in Lombardy: proposal for an inspection-scoring model
Authors: Balzaretti Claudia M. , Razzini Katia , Ziviani Silvia , Ratti Sabrina , Milicevic Vesna , Chiesa Luca M. , Panseri Sara , Castrica Marta
Published: March 2018

The purpose of this study was to elaborate a checklist with an inspection scoring system at national level in order to assess compliance with sanitary hygiene requirements of food services. The inspection scoring system was elaborated taking into account the guidelines drawn up by NYC Department of Food Safety and Mental Hygiene. Moreover the checklist was used simultaneously with the standard inspection protocol adopted by Servizio Igiene Alimenti Nutrizione (Servizio Igiene Alimenti Nutrizione - Ss. I.A.N) and defined by D.G.R 6 March 2017 – n. X/6299 Lombardy Region. Ss. I.A.N protocol consists of a qualitative response according to which we have generated a new protocol with three different grading: A, B and C. The designed checklist was divided into 17 sections. Each section corresponds to prerequisites to be verified during the inspection. Every section includes the type of conformity to check and the type of violation: critical or general. Moreover, the failure to respect the expected compliance generates 4 severity levels that correspond to score classes. A total of 7 food services were checked with the two different inspection methods. The checklist results generated a food safety score for each food service that ranged from 0.0 (no flaws observed) to 187.2, and generates three grading class: A (0.0-28.0); B (29.0 - 70.0) and C (>71.00). The results from the Ss. I. A. N grading method and the checklist show positive correlation (r=0.94, P>0.01) suggesting that the methods are comparable. Moreover, our scoring checklist is an easy and unique method compared to standard and allows also managers to perform effective surveillance programs in food service.
Patellofemoral pain syndrome in female athletes: A review of diagnoses, etiology and treatment options
Authors: Vora Molly , Curry Emily , Chipman Amanda , Matzkin Elizabeth , Li Xinning
Published: March 2018

Patellofemoral pain syndrome (PFPS) is one of the most common causes of knee pain and is present in females disproportionately more relative to males. PFPS causes tend to be multifactorial in nature and are described in this review. From a review of the current literature, it is clear that there needs to be further research on PFPS in order to better understand the complex etiology of this disorder in both males and females. It is known that females with patellofemoral pain syndrome demonstrate a decrease in abduction, external rotation and extension strength of the affected side compared with healthy patients. Conservative management, including optimizing muscle balance between the vastus medialis and lateralis around the patella along with formal therapy should be the first line of treatment in patients presenting with PFPS. Surgery should be reserved for patients in which all conservative management options have failed. This review aims to guide physicians in accurate clinicaldecision making regarding conservative and surgical treatment options when specifically faced with PFPS in a female athlete. Furthermore, we will discuss the anatomic variants, incidence and prevalence, etiology, diagnosis and treatment of PFPS.
Valoraciones actualizadas de las competencias profesionales en la práctica laboral de los periodistas españoles
Authors: Schena Jucinara , Besalú Reinald , Singla Casellas Carles
Published: March 2018

El punto de partida del presente artículo es poner en cuestión cuáles son actualmente las competencias más importantes para el ejercicio de la profesión periodística. La investigación se basa en la aplicación de un cuestionario online como instrumento de recogida de datos sobre una muestra compuesta por profesionales, profesorado, alumnado y gestores académicos (N=103) complementada por entrevistas a profesionales del ámbito periodístico en España. El artículo presenta la evaluación por parte de esta muestra de la valoración de importancia y la utilidad de conocimientos disciplinares (saber), competencias profesionales (saber hacer), competencias académicas y otras competencias específicas propuestas en el Libro Blanco de la ANECA. Los datos de la encuesta han sido analizados mediante el software estadístico SPSS. Los resultados principales permiten observar que se mantiene una consideración relevante hacia competencias tradicionales del perfil del periodista y que a estas se añaden otras que están en sintonía con los desafíos propuestos por los cambios tecnológicos y sociales.
Emissions of trace gases from Australian temperate forest fires: emission factors and dependence on modified combustion efficiency
Authors: Guérette Elise-Andrée , Paton-Walsh Clare , Desservettaz Maximilien , Smith Thomas E. L. , Volkova Liubov , Weston Christopher J. , Meyer Carl P.
Published: March 2018

Abstract. We characterised trace gas emissions from Australian temperate forest fires
through a mixture of open-path Fourier transform infrared (OP-FTIR) measurements and selective ion flow tube
mass spectrometry (SIFT-MS) and White cell FTIR analysis of grab samples. We
report emission factors for a total of 25 trace gas species measured in smoke
from nine prescribed fires. We find significant dependence on modified
combustion efficiency (MCE) for some species, although regional differences
indicate that the use of MCE as a proxy may be limited. We also find that the
fire-integrated MCE values derived from our in situ on-the-ground open-path
measurements are not significantly different from those reported for airborne
measurements of smoke from fires in the same ecosystem. We then compare our
average emission factors to those measured for temperate forest fires
elsewhere (North America) and for fires in another dominant Australian
ecosystem (savanna) and find significant differences in both cases. Indeed,
we find that although the emission factors of some species agree within
20 %, including those of hydrogen cyanide, ethene, methanol, formaldehyde
and 1,3-butadiene, others, such as acetic acid, ethanol, monoterpenes,
ammonia, acetonitrile and pyrrole, differ by a factor of 2 or more. This
indicates that the use of ecosystem-specific emission factors is warranted
for applications involving emissions from Australian forest fires.
Greenhouse gas measurements from a UK network of tall towers: technical description and first results
Authors: Stanley Kieran M. , Grant Aoife , O'Doherty Simon , Young Dickon , Manning Alistair J. , Stavert Ann R. , Spain T. Gerard , Salameh Peter K. , Harth Christina M. , Simmonds Peter G. , Sturges William T. , Oram David E. , Derwent Richard G.
Published: March 2018

Abstract. A network of three tall tower measurement stations was set up in 2012 across the United Kingdom to expand measurements made at the long-term background northern hemispheric site, Mace Head, Ireland. Reliable and precise in situ greenhouse gas (GHG) analysis systems were developed and deployed at three sites in the UK with automated instrumentation measuring a suite of GHGs. The UK Deriving Emissions linked to Climate Change (UK DECC) network uses tall (165–230 m) open-lattice telecommunications towers, which provide a convenient platform for boundary layer trace gas sampling. In this paper we describe the automated measurement system and first results from the UK DECC network for CO2, CH4, N2O, SF6, CO and H2. CO2 and CH4 are measured at all of the UK DECC sites by cavity ring-down spectroscopy (CRDS) with multiple inlet heights at two of the three tall tower sites to assess for boundary layer stratification. The short-term precisions (1σ on 1 min means) of CRDS measurements at background mole fractions for January 2012 to September 2015 is < 0.05 µmol mol−1 for CO2 and < 0.3 nmol mol−1 for CH4. Repeatability of standard injections (1σ) is < 0.03 µmol mol−1 for CO2 and < 0.3 nmol mol−1 for CH4 for the same time period. N2O and SF6 are measured at three of the sites, and CO and H2 measurements are made at two of the sites, from a single inlet height using gas chromatography (GC) with an electron capture detector (ECD), flame ionisation detector (FID) or reduction gas analyser (RGA). Repeatability of individual injections (1σ) on GC and RGA instruments between January 2012 and September 2015 for CH4, N2O, SF6, CO and H2 measurements were < 2.8 nmol mol−1, < 0.4 nmol mol−1, < 0.07 pmol mol−1, < 2 nmol mol−1 and < 3 nmol mol−1, respectively. Instrumentation in the network is fully automated and includes sensors for measuring a variety of instrumental parameters such as flow, pressures, and sampling temperatures. Automated alerts are generated and emailed to site operators when instrumental parameters are not within defined set ranges. Automated instrument shutdowns occur for critical errors such as carrier gas flow rate deviations. Results from the network give good spatial and temporal coverage of atmospheric mixing ratios within the UK since early 2012. Results also show that all measured GHGs are increasing in mole fraction over the selected reporting period and, except for SF6, exhibit a seasonal trend. CO2 and CH4 also show strong diurnal cycles, with night-time maxima and daytime minima in mole fractions.
Ionospheric anomalies detected by ionosonde and possibly related to crustal earthquakes in Greece
Authors: Perrone Loredana , De Santis Angelo , Abbattista Cristoforo , Alfonsi Lucilla , Amoruso Leonardo , Carbone Marianna , Cesaroni Claudio , Cianchini Gianfranco , De Franceschi Giorgiana , De Santis Anna , Di Giovambattista Rita , Marchetti Dedalo , Pavòn-Carrasco Francisco J. , Piscini Alessandro , Spogli Luca , Santoro Francesca
Published: March 2018

Abstract. Ionosonde data and crustal earthquakes with magnitude M≥6.0 observed in Greece during the 2003–2015 period were examined to check if the relationships obtained earlier between precursory ionospheric anomalies and earthquakes in Japan and central Italy are also valid for Greek earthquakes. The ionospheric anomalies are identified on the observed variations of the sporadic E-layer parameters (h′Es, foEs) and foF2 at the ionospheric station of Athens. The corresponding empirical relationships between the seismo-ionospheric disturbances and the earthquake magnitude and the epicentral distance are obtained and found to be similar to those previously published for other case studies. The large lead times found for the ionospheric anomalies occurrence may confirm a rather long earthquake preparation period. The possibility of using the relationships obtained for earthquake prediction is finally discussed. Keywords. Ionosphere (Ionospheric disturbances)
Over-calcified forms of the coccolithophore Emiliania huxleyi in high-CO2 waters are not preadapted to ocean acidification
Authors: von Dassow Peter , Díaz-Rosas Francisco , Bendif El Mahdi , Gaitán-Espitia Juan-Diego , Mella-Flores Daniella , Rokitta Sebastian , John Uwe , Torres Rodrigo
Published: March 2018

Abstract. Marine multicellular organisms inhabiting waters with natural high fluctuations in pH appear more tolerant to acidification than conspecifics occurring in nearby stable waters, suggesting that environments of fluctuating pH hold genetic reservoirs for adaptation of key groups to ocean acidification (OA). The abundant and cosmopolitan calcifying phytoplankton Emiliania huxleyi exhibits a range of morphotypes with varying degrees of coccolith mineralization. We show that E. huxleyi populations in the naturally acidified upwelling waters of the eastern South Pacific, where pH drops below 7.8 as is predicted for the global surface ocean by the year 2100, are dominated by exceptionally over-calcified morphotypes whose distal coccolith shield can be almost solid calcite. Shifts in morphotype composition of E. huxleyi populations correlate with changes in carbonate system parameters. We tested if these correlations indicate that the hyper-calcified morphotype is adapted to OA. In experimental exposures to present-day vs. future pCO2 (400 vs. 1200 µatm), the over-calcified morphotypes showed the same growth inhibition (−29.1±6.3 %) as moderately calcified morphotypes isolated from non-acidified water (−30.7±8.8 %). Under the high-CO2–low-pH condition, production rates of particulate organic carbon (POC) increased, while production rates of particulate inorganic carbon (PIC) were maintained or decreased slightly (but not significantly), leading to lowered PIC ∕ POC ratios in all strains. There were no consistent correlations of response intensity with strain origin. The high-CO2–low-pH condition affected coccolith morphology equally or more strongly in over-calcified strains compared to moderately calcified strains. High-CO2–low-pH conditions appear not to directly select for exceptionally over-calcified morphotypes over other morphotypes, but perhaps indirectly by ecologically correlated factors. More generally, these results suggest that oceanic planktonic microorganisms, despite their rapid turnover and large population sizes, do not necessarily exhibit adaptations to naturally high-CO2 upwellings, and this ubiquitous coccolithophore may be near the limit of its capacity to adapt to ongoing ocean acidification.
Ammonia emission measurements of an intensively grazed pasture
Authors: Voglmeier Karl , Jocher Markus , Häni Christoph , Ammann Christof
Published: March 2018

Abstract. The quantification of ammonia (NH3) emissions in ambient air conditions is still a challenge and the corresponding emission factor for grazed pastures have therefore a large uncertainty. This study presents NH3 emission measurements of two pasture systems in western Switzerland over the entire grazing season 2016. During the measurement campaign, each pasture system was grazed by 12 dairy cows in an intensive rotational management. The cow herds on the two pastures differed in the energy to protein balance of the diet. NH3 concentrations were measured upwind and downwind of a grazed sub plot with line integrating open path instruments that were able to retrieve small horizontal concentration differences (
Historical drought patterns over Canada and their relation to teleconnections
Authors: Asong Zilefac Elvis , Wheater Howard Simon , Bonsal Barrie , Razavi Saman , Kurkute Sopan
Published: March 2018

Abstract. Drought is a recurring extreme climate event and among the most costly natural disasters in the world. This is particularly true over Canada, where drought is both a frequent and damaging phenomenon with impacts on regional water resources, agriculture, industry, aquatic ecosystems and health. However, nation-wide drought assessments are currently lacking and impacted by limited ground-based observations. This study provides a comprehensive analysis of historical droughts over the whole of Canada, including the role of large-scale teleconnections. Drought events are characterized by the Standardized Precipitation-Evapotranspiration Index (SPEI) over various temporal scales (1, 3, 6, and 12 consecutive months, 6 months from April to September, and 12 months from October to September) applied to different gridded monthly data sets for the period 1950–2013. The Mann Kendall test, Rotated Empirical Orthogonal Function, Continuous Wavelet Transform, and Wavelet Coherence analyses are used, respectively, to investigate the trend, spatiotemporal patterns, periodicity, and teleconnectivity of drought events. Results indicate that southern (northern) parts of the country experienced significant trends towards drier (wetter) conditions although substantial variability exists. Two spatially well-defined regions with different temporal evolution of droughts were identified―the Canadian Prairies and Northern-central Canada. The analyses also revealed the presence of a dominant periodicity of between 8–32 months in the Prairie region, and 8–40 months in the Northern central region. These cycles of low-frequency variability are found to be associated principally to the Pacific-North American (PNA) and Multivariate El Niño/Southern Oscillation Index (MEI) relative to other considered large-scale climate indices. This study is the first of its kind to identify dominant periodicities in drought variability over the whole of Canada in terms of when the drought events occur, the duration, and how often they do so.
Near-surface temperature inversion during summer at Summit, Greenland, and its relation to MODIS-derived surface temperatures
Authors: Adolph Alden C. , Albert Mary R. , Hall Dorothy K.
Published: March 2018

Abstract. As rapid warming of the Arctic occurs, it is imperative that climate
indicators such as temperature be monitored over large areas to understand
and predict the effects of climate changes. Temperatures are traditionally
tracked using in situ 2 m air temperatures and can also be assessed using
remote sensing techniques. Remote sensing is especially valuable over the
Greenland Ice Sheet, where few ground-based air temperature measurements
exist. Because of the presence of surface-based temperature inversions in
ice-covered areas, differences between 2 m air temperature and the
temperature of the actual snow surface (referred to as “skin” temperature)
can be significant and are particularly relevant when considering validation
and application of remote sensing temperature data. We present results from
a field campaign extending from 8 June to 18 July 2015, near Summit
Station in Greenland, to study surface temperature using the following
measurements: skin temperature measured by an infrared (IR) sensor, 2 m air
temperature measured by a National Oceanic and Atmospheric Administration
(NOAA) meteorological station, and a Moderate Resolution Imaging Spectroradiometer (MODIS) surface temperature product. Our data indicate
that 2 m air temperature is often significantly higher than snow skin
temperature measured in situ, and this finding may account for apparent
biases in previous studies of MODIS products that used 2 m air temperature
for validation. This inversion is present during our study period when
incoming solar radiation and wind speed are both low. As compared to our in
situ IR skin temperature measurements, after additional cloud masking, the
MOD/MYD11 Collection 6 surface temperature standard product has an RMSE of
1.0 ∘C and a mean bias of −0.4 ∘C, spanning a range of
temperatures from −35 to −5 ∘C (RMSE =
1.6 ∘C and mean bias = −0.7 ∘C prior to cloud
masking). For our study area and time series, MODIS surface temperature
products agree with skin surface temperatures better than previous studies
indicated, especially at temperatures below −20 ∘C, where other
studies found a significant cold bias. We show that the apparent cold
bias present in other comparisons of 2 m air temperature and MODIS surface
temperature may be a result of the near-surface temperature inversion.
Further investigation of how in situ IR skin temperatures compare to MODIS
surface temperature at lower temperatures (below −35 ∘C) is
warranted to determine whether a cold bias exists for those temperatures.
Arctic sea ice signatures: L-band brightness temperature sensitivity comparison using two radiation transfer models
Authors: Richter Friedrich , Drusch Matthias , Kaleschke Lars , Maaß Nina , Tian-Kunze Xiangshan , Mecklenburg Susanne
Published: March 2018

Abstract. Sea ice is a crucial component for short-, medium- and long-term numerical weather predictions. Most importantly, changes of sea ice coverage and areas covered by thin sea ice have a large impact on heat fluxes between the ocean and the atmosphere. L-band brightness temperatures from ESA's Earth Explorer SMOS (Soil Moisture and Ocean Salinity) have been proven to be a valuable tool to derive thin sea ice thickness. These retrieved estimates were already successfully assimilated in forecasting models to constrain the ice analysis, leading to more accurate initial conditions and subsequently more accurate forecasts. However, the brightness temperature measurements can potentially be assimilated directly in forecasting systems, reducing the data latency and providing a more consistent first guess. As a first step towards such a data assimilation system we studied the forward operator that translates geophysical parameters provided by a model into brightness temperatures. We use two different radiative transfer models to generate top of atmosphere brightness temperatures based on ORAP5 model output for the 2012/2013 winter season. The simulations are then compared against actual SMOS measurements. The results indicate that both models are able to capture the general variability of measured brightness temperatures over sea ice. The simulated brightness temperatures are dominated by sea ice coverage and thickness changes are most pronounced in the marginal ice zone where new sea ice is formed. There we observe the largest differences of more than 20 K over sea ice between simulated and observed brightness temperatures. We conclude that the assimilation of SMOS brightness temperatures yields high potential for forecasting models to correct for uncertainties in thin sea ice areas and suggest that information on sea ice fractional coverage from higher-frequency brightness temperatures should be used simultaneously.
Local topography increasingly influences the mass balance of a
retreating cirque glacier
Authors: Florentine Caitlyn , Harper Joel , Fagre Daniel , Moore Johnnie , Peitzsch Erich
Published: March 2018

Abstract. Local topographically driven processes such as wind drifting, avalanching, and shading, are known to alter the relationship between the mass balance of small cirque glaciers and regional climate. Yet partitioning such local effects apart from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA using field-measured surface mass balance, geodetic constraints on mass balance, and regional climate data recorded at a network of meteorological stations. Geodetically derived mass changes between 1950–1960, 1960–2005, and 2005–2014 document average mass loss rates during each period at −0.22±0.12 m w.e. yr−1, −0.18±0.05 m w.e. yr−1, and −0.10±0.03 m w.e. yr−1. A correlation of field-measured mass balance and regional climate variables closely predicts the geodetically measured mass loss from 2005–2014. However, this correlation overestimates glacier mass balance for 1950–1960 by +1.18±0.92 m w.e. yr−1. This suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net mass balance as the glacier lost 0.50 km2 and retreated further into its cirque.