bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Temperature Self-Supplied Isolated Driver Module for GaN Power Transistors
Authors: Baie Xavier , Dessard Vincent , Escoffier René , Laplace Fabien , Picun Gonzalo
Published: May 2016

In this paper, a compact isolated and self-supplied single channel driver module for operation at 200C (392F) is presented. It is aimed to drive a normally-on GaN device within a high voltage half bridge topology. The driver is implemented on a compact hybrid module. Two of such modules are then assembled on a dedicated half-bridge DBC with two GaN devices.
Development of BiAgX® HT Solder Paste for 200°C Application
Authors: Zhang Hongwen , Minter Jonathan , Lee Ning-Cheng
Published: May 2016

BiAgX® paste with the remelting temperature around 262°C has been tested and adopted successfully for die attach applications [1–5]. BiAgX® HT pastes with the enhanced remelting temperature above 265°C have been designed for the application of 200°C or even higher. The joint strength has been well maintained for most of the tested pastes after thermal aging @ 200°C for 1000hrs. The thermal cycling test (from −55°C to 200°C) degrades the bond shear strength but some of the tested pastes can still keep the joint strength well above IEC standard (IEC 60749-19) required. The melting temperature and the reliability have been observed to closely associate with the alloying elements Z%wt. The BiAgX® pastes have also been modified for board level assembly application. BiAgX® solder wire is under development too.
Silver Sintering Paste Rendering Low Porosity Joint for High Power Die Attach Application
Authors: Chen Sihai , LaBarbera Christine , Lee Ning-Cheng
Published: May 2016

Silver joints with ~10% porosity for die-attach have been achieved with specially engineered Ag sintering pastes, through combined pressureless sintering process plus thermal aging. The pastes developed in this work have the following advantages: 1) they can be used under pressure-less processing condition; 2) they are compatible with conventional reflow oven, resulting in a higher through-put as compared to that of stepwise heating oven; 3) they can be used under air reflow condition; 4) a highly reliable joint has been obtained as judged from the shear strength results from thermal aging and temperature cycling tests.

The silver sintering pastes are versatile in bonding different metallization surface including Au, Ag and Cu. It can also be used in bonding large area (10mm × 10mm) dies. Shear test results under varied temperatures implied that the maximum service temperature of Ag sintered joints can be as high as 470 – 530 °C, depending on the shear strength pass criteria, and this is more than 250°C higher than that of high-Pb joints.

Thermal aging test at 250°C for the joints generated on Ag-die/Au-DBC combination revealed that Ag continuously consolidates in the bulk phase resulting in the formation of larger pores with reduced numbers as compared to that of untreated samples. At the same time, it diffuses to sintered Ag/Au-DBC interface to form a dense Ag layer induced by alloying with Ni(Au) and Cu, which strengthened the bonding. A large bondline thickness is critical for obtaining highly reliable joints. The total porosity of the joint is found slightly decreased during the course of 3200h aging test. Temperature cycling at −55 °C to 200°C shows that the silver joints are stable for at least 1000 cycles.
Increased High-Temperature IC Packaging Reliability Using Die Extraction and Additive Manufacturing Assembly
Authors: Spory Erick M.
Published: May 2016

Semiconductor parts are most often specified for use in the “commercial” 0 to 70°C and, to a lesser extent, in the “industrial” −40 to 85°C operating temperature range. These operating temperature ratings generally satisfy the demands of the dominant semiconductor customers in the computer, telecommunications, and consumer electronic industries. There is also a demand for parts rated beyond the “industrial” temperature range, primarily from the aerospace, military, oil and gas exploration, and automotive industries (−55 to +125C, and even higher). However, the demand has not been large enough to attract or retain the interest of major semiconductor part manufacturers to make these parts. In fact, wide temperature range parts are becoming obsolete and functionally equivalent parts are not replacing them.

Today, for some applications, it is difficult to procure parts that meet engineering, economic, logistical, and technical integration requirements of product manufacturers, and that are rated for an extended temperature range (typically beyond 0 to 70°C). In some applications, the product is available only in the “commercial” temperature range, with commercial packaging. If the product application environment is outside the commercial range, steps must be taken to address this apparent incompatibility. For example, oil exploration and drilling applications require small, advanced communication electronics to work underground at high temperatures where cooling is not possible. This is where uprating comes into play.

Despite the fact that a part can be uprated relative to functional performance at higher than specified temperatures, the original packaging and connectivity may not be reliable with long term exposure to greater than 150C due to Kirkendall voiding and general plastic degradation. However, if the original die with gold wire and aluminum pad bond is extracted from the original plastic commercial package and reassembled into a new ceramic package body, excellent reliability at temperatures exceeding 200C can be achieved. The original gold/aluminum bond interface can be removed and replaced with an electroless nickel, electroless palladium, immersion gold (ENEPIG) process, or a much more economical, automated process can be used. This process is discussed in the accompanying paper and utilizes additive manufacturing to place an aerosol jet silver deposition over the existing gold ball, interfacing with the remaining exposed aluminum. In this manner, a high-reliability connection system can be achieved which is immune to Kirkendall voiding for the temperature range of interest.
Development of a High Temperature Interconnect Solution as an Alternative to High Lead or Gold Content Solders
Authors: Wickham Martin , Clayton Kate , Robador Ana , Hunt Chris , Pittson Robin , Statton Laura , Brown Tina , Lambert Fiona , Wotherspoon Tracy
Published: May 2016

A collaborative research programme between project partners Microsemi, the National Physical Laboratory (NPL) and Gwent Electronic Materials (GEM), has successfully developed innovative materials specifically designed to offer an alternative for high Pb or Au content materials to increase the operating temperature of electronic assemblies. Currently, for electronic assemblies to operate at high temperature, they must use a high lead solder or a very expensive gold based solder to withstand these temperatures. The ELCOSINT project has developed an inexpensive lead-free alternative for joining high temperature electronics suitable for operating at temperatures above 250°C utilising standard surface mount assembly processes. This paper summarises the work undertaken by the authors to develop and better understand this new family of electrical interconnection materials. The project brought together a materials supplier (GEM – Gwent Electronic Materials), an end-user (MSL - Microsemi) and an technology research organisation (NPL – National Physical Laboratory) to jointly develop, test and implement in production, the solution based on silver-loaded silicone materials. This paper focuses on the testing and materials evaluation undertaken at NPL to determine the long term performance of these alternative materials including high temperature ageing up to 300°C, thermal cycling and damp heat testing. Details of the shear strength and electrical performance of interconnects between the substrates and components during the test regimes are given. The manufacturing process is outlined including details of the test vehicles utilised. The processing temperature for the conductive adhesive is 250°C which offers additional advantages in potential improvements in component and substrate reliability compared to soldered solutions which would typically be processed at temperatures above 300°C.
Method to Determine Maximum Allowable Sinterable Silver Interconnect Size
Authors: Wereszczak A. A. , Modugno M. C. , Waters S. B. , DeVoto D. J. , Paret P. P.
Published: May 2016

The use of sintered-silver for large-area interconnection is attractive for some large-area bonding applications in power electronics such as the bonding of metal-clad, electrically-insulating substrates to heat sinks. Arrays of different pad sizes and pad shapes have been considered for such large area bonding; however, rather than arbitrarily choosing their size, it is desirable to use the largest size possible where the onset of interconnect delamination does not occur. If that is achieved, then sintered-silver's high thermal and electrical conductivities can be fully taken advantage of. Toward achieving this, a simple and inexpensive proof test is described to identify the largest achievable interconnect size with sinterable silver. The method's objective is to purposely initiate failure or delamination. Copper and invar (a ferrous-nickel alloy whose coefficient of thermal expansion (CTE) is similar to that of silicon or silicon carbide) disks were used in this study and sinterable silver was used to bond them. As a consequence of the method's execution, delamination occurred in some samples during cooling from the 250°C sintering temperature to room temperature and bonding temperature and from thermal cycling in others. These occurrences and their interpretations highlight the method's utility, and the herein described results are used to speculate how sintered-silver bonding will work with other material combinations.
Towards High Temperature Electronic Modules in which all Components would be attached using Silver Sintering
Authors: GEOFFROY Thomas , RIOU Jean-Christophe , BIENVENU Yves , PONS Corinne , MEILLE Sylvain , BAILLY Eric
Published: May 2016

This article points out the fact that conventional low temperature silver sintering processes do not seem to satisfy the needs for reliability when they are used to assemble passive components (such as multilayers ceramic capacitors) in electronic modules undergoing wide amplitude thermal cycles (−65°C / +200°C). These processes indeed lead to very porous microstructures of silver which favors rapid fatigue cracks propagation [1], [2], [3]. Even if these types of porous microstructures may be suitable for die attach, tests presented in this paper show they cannot resist to the levels of thermomechanical stress reached in attachment joints of multilayers ceramic capacitors (MLCCs). To find process parameters minimizing porosity in attachment joints of capacitors, measurements of the shrinkage of silver during sintering have been carried out by dilatometry. Then the impact of densification of attachment joints on the ageing behavior and on the mechanical behavior of assemblies has been assessed in this study.
Processing and Characterization of Thousand-Hour 500 °C Durable 4H-SiC JFET Integrated Circuits
Authors: Spry David J. , Neudeck Philip G. , Chen Liang-Yu , Lukco Dorothy , Chang Carl W. , Beheim Glenn M. , Krasowski Michael J. , Prokop Norman F.
Published: May 2016

This work reports fabrication and testing of integrated circuits (ICs) with two levels of interconnect that consistently achieve greater than 1000 hours of stable electrical operation at 500 °C in air ambient. These ICs are based on 4H-SiC junction field effect transistor (JFET) technology that integrates hafnium ohmic contacts with TaSi2 interconnects and SiO2 and Si3N4 dielectric layers over ~ 1-μm scale vertical topology. Following initial burn-in, important circuit parameters remain stable for more than 1000 hours of 500 °C operational testing. These results advance the technology foundation for realizing long-term durable 500 °C ICs with increased functional capability for sensing and control combustion engine, planetary, deep-well drilling, and other harsh-environment applications.
First-Order SPICE Modeling of Extreme-Temperature 4H-SiC JFET Integrated Circuits
Authors: Neudeck Philip G. , Spry David J. , Chen Liang-Yu
Published: May 2016

A separate submission to this conference reports that 4H-SiC Junction Field Effect Transistor (JFET) digital and analog Integrated Circuits (ICs) with two levels of metal interconnect have reproducibly demonstrated electrical operation at 500 °C in excess of 1000 hours. While this progress expands the complexity and durability envelope of high temperature ICs, one important area for further technology maturation is the development of reasonably accurate and accessible computer-aided modeling and simulation tools for circuit design of these ICs. Towards this end, we report on development and verification of 25 °C to 500 °C SPICE simulation models of first-order accuracy for this extreme-temperature durable 4H-SiC JFET IC technology. For maximum availability, the JFET IC modeling is implemented using the baseline-version SPICE NMOS LEVEL 1 model that is common to other variations of SPICE software and importantly includes the body-bias effect. The first-order accuracy of these device models is verified by direct comparison with measured experimental device characteristics.
C0G and X7R Ceramic Capacitors for High Temperature Applications
Authors: Gurav Abhijit , Magee Jim , Phillips Reggie , Carson Scott
Published: May 2016

For applications such as electronics for down-hole drilling and exploration, geothermal energy generation and power electronics, there is a growing need for capacitors that have robust reliability at temperatures of 150°C or above. Conventional X7R and X8R type ceramic capacitors are designed for applications up to 125°C and 150°C, respectively. At temperatures above 150°C, these types of capacitors typically suffer from degradation of reliability performance and severe reduction in capacitance, especially under DC bias conditions. A Class-I C0G dielectric has been developed using Nickel electrodes for high temperature application up to 200°C and beyond. Due to its linear dielectric nature, this material exhibits highly stable capacitance as a function of temperature and voltage. Multi-layer ceramic capacitors (MLCC) made from this material can be qualified as X9G with robust reliability. These C0G capacitors are showing robust reliability at extreme temperature of 260°C (500 degrees Fahrenheit). We have also developed a modified-X7R dielectric composition with nickel internal electrodes showing high reliability in this Class-II dielectric at 175°C. This paper will report electrical properties and reliability test data on these Class-I C0G and Class-II ceramic capacitors at high temperatures of 150–200°C and above.
High temperature / radiation hardened capable ARM® Cortex®-M0 microcontrollers
Authors: Bannatyne R. , Gifford D. , Klein K. , Merritt C.
Published: May 2016

VORAGO Technologies has developed a pair of ARM Cortex M0 MCUs designed from the ground up to be high temperature capable. One of these devices is specifically developed for high temperature applications, the other adds capabilities that make it suitable for use in high radiation environments as well. These devices are fabricated using a modified version of commercial bulk 130nm CMOS technology utilizing our HARDSIL® technology, which provides immunity to the increased effects of latchup and EOS encountered at higher application temperatures. In addition to the processor these devices include features more typical of low temperature SoCs including on-chip memory, timers, and communications peripherals. In addition to the ceramic package and die format typically utilized at high temperature, a new lower-cost plastic package is available that has been characterized at higher temperatures. These devices have been characterized at temperatures up to 200C and results showing the latchup behavior and device performance are provided. Some of the tradeoffs involved in creating such devices are discussed, as well as some of the similarities and tradeoffs in creating a radiation hardened devices vs. a high temperature device.
High Temperature Potting Materials for Wire Bond Encapsulation
Authors: Shaddock David , Yin Liang
Published: May 2016

Test results for a range of potting materials for encapsulation of wire bonds for a high temperature multi-chip module is presented. The potting materials include gels and more rigid epoxies, silicone, and silicone-ceramic materials. The materials were initially screened based on ease of processing, cracking, and weight loss at 200, 225, and 250°C. Materials that performed well after this initial screening were tested for insulation resistance at 200, 225, and 250°C and wire bonds were encapsulated for thermal cycled at −55 to 200°C and −55 to 250°C.
Encapsulation Method for Small Wireless Measurement Systems in High Temperature Environments
Authors: Johansson J. , Borg J.
Published: May 2016

This paper presents an encapsulation concept that enables the construction of small wireless measurement systems that can operate in industrial environments with ambient temperatures of up to 1200°C. To maximize operational time and minimize size, a layer of thermal insulation is combined with water absorbed in a porous material in the core of the device. The simulated operating time before all of the frozen water at 0°C has transformed into steam at 100°C when the ambient temperature of the device was 1200°C is 21 minutes for a sphere with an outer radius of 4 cm. If the outer radius is increased to 10 cm the simulated operating time increases to 125 minutes. Measurements were performed to validate the design. When a sphere with a radius of 4 cm was subjected to an oven temperature of 1200°C the device held the core temperature at or below 101°C for a total of 25 minutes. The time to reach the boiling point of the water was 9 minutes. Thereafter, the temperature was held constant at 100 +/− 1°C for an additional 16 minutes whereafter a rapid rise in temperature took place once all water had evaporated.
Is a 10-sow unit economically sustainable? A profitability assessment of productivity amongst small-holder pig farmers, Mpumalanga, South Africa
Authors: Munzhelele Priscilla , Oguttu James W. , Fasina Folorunso O.
Published: May 2016

The majority of small-holder pig farmers in Mpumalanga had between 1- and 10-sow herds. The main aim of this study is to evaluate the current government agricultural intervention (supply of 10 sows and a boar) in terms of technical and economic feasibilities and ascertain whether the small-scale pig value chain system alleviates poverty. Data were obtained from 220 randomly selected small-holder pig farmers using a semi-structured questionnaire. The results showed that 58% farrowed ≤ 10 piglets/born/sow/litter, 44.2% practiced no weaning method and many fed swill and leftovers alone (41.6%). Pair-wise association revealed that the feeding of commercial feeds had a relationship with pigs in relatively good to very good body condition. Pigs in poor body condition were positively correlated with the feeding of swill alone. The economic models for the 10-sow unit proved that pig farming is unprofitable if the current management and feeding systems that operate in the commercial industry are utilised. However, only through a combination of cooperative systems, benefits of economies of scale, reduction of preweaning mortalities and structured government inputs can pig production be profitable at this scale of production.Keywords: piglets; market; profit; economics; feeds
Anaesthetic management of vein of Galen malformation in a very low birth weight preterm baby for endovascular embolisation
Authors: Ramakrishnan Rajani , Goraksha Shwetal , Thakore Bhoomika , Monteiro Joseph , Butani Manju
Published: May 2016

Extra-cardiac arteriovenous malformations are rare causes of severe cardiac failure in the neonatal period. Aneurysmal malformation of the vein of Galen may lead to a diagnostic confusion because the presenting signs point to a cardiac cause of failure. Endovascular therapy is found to be an effective and safe therapeutic modality available to treat these lesions. Intervention in the newborn is difficult and is preferably postponed until about 5 months. We present the anaesthetic management of a very low birth weight preterm neonate with a vein of Galen malformation who needed intervention within the first week of life.
An unusual case of osmotic demyelination syndrome without electrolyte changes in a patient with diabetes
Authors: Kote Shrikant , Khandelwal Ankur , Pathak Deba , Nath Rupankar
Published: May 2016

Central pontine myelinolysis (CPM) is a demyelinating disease of the pons which is also associated with the demyelination of extrapontine areas of the central nervous system. Although the aetiology and pathogenesis are unclear, CPM is usually associated with hyponatremia or its rapid correction. Malnutrition and chronic alcoholism are also the common underlying conditions. Herein, we report a rare presentation of ODS, secondary to hyperosmolar hyperglycaemic state. We observed a 37-year-old female with diabetes type 1 and hypertension who presented with ataxia, dysarthria and pseudobulbar effect which evolved over a duration of few weeks at home with no evidence of hyponatremia or its rapid correction and no history of alcohol abuse or malnutrition.
Anaesthetic management and perioperative complications during deep brain stimulation surgery: Our institutional experience
Authors: Bala Renu , Chaturvedi Arvind , Pandia Mihir , Bithal Parmod
Published: May 2016

Background: Deep brain stimulation (DBS) surgery is an established therapeutic option for alleviating movement disorders. It represents unique challenges for anaesthesiologists. We retrospectively reviewed the patients, who underwent this surgery at our institution, to study anaesthetic management and perioperative complications. Materials and Methods: After taking approval from the Institutional Ethics Committee, medical, surgical and anaesthesia records of 67 patients who were admitted to undergo DBS surgery during 11 years period (January 2001 to December 2011) were retrieved and reviewed. Sixty-five patients underwent the procedure. Various anaesthetic events and perioperative complications were noted and appropriate statistical analysis was carried out to analyse the data. Results: Electrode placement under monitored anaesthesia care (MAC) was the most commonly used technique (86% of patients). Intra-operative complications occurred in 16 patients (24%) whereas post-operative complication occurred in 10 patients (15.4%). There was one mortality. Though age >60 years and American Society of Anesthesiologists status >II were found to be the risk factors for post-operative complications in the bivariate analysis; they were not significant in multivariate analysis. Conclusions: We report our experience of DBS surgery, which was performed using MAC in majority of patients, though general anaesthesia is also feasible. Further prospective randomised studies comprising large number of patients are warranted to corroborate our finding and to find out the most suitable sedative agent.
Intensive care management of status epilepticus
Authors: Gupta Nidhi
Published: May 2016

Status epilepticus (SE) is a life-threatening neurological emergency that requires prompt diagnosis and treatment. SE may be classified into convulsive and non-convulsive types, based on the presence of rhythmic jerking of the extremities. Clinically, tonic-clonic convulsive SE (CSE) is divided into four subsequent stages: Early, established, refractory and super-refractory. Initial elements of resuscitation include airway protection, haemodynamic resuscitation and seizure control. Further treatment should then be guided by the diagnostic workup. Rapid treatment of early SE is achieved with intravenous (IV) lorazepam or intramuscular midazolam. In established SE, IV antiepileptic drugs (AEDs) (phenytoin/fosphenytoin, valproate, levetiracetam, phenobarbital) are most commonly used, but there is no Class I evidence for choosing one over the other. Considered overall, cumulative data from the literature are consistent with valproate and levetiracetam, being a safe and effective therapeutic alternative to phenobarbital and phenytoin for treatment of established SE. Refractory SE (RSE) and super-RSE are treated with anaesthetic medications (propofol, midazolam, thiopental/pentobarbital, ketamine), non-anaesthetic drugs (lidocaine, magnesium, pyridoxine), AEDs (levetiracetam, lacosamide, topiramate, lacosamide, pregabalin, gabapentin) and other cause-directed treatments with low success rates. Potential non-pharmacologic interventions to be considered in super-RSE include hypothermia, electroconvulsive therapy, ketogenic diet, immunomodulatory treatments, emergency resective epilepsy surgery, cerebrospinal fluid drainage and vagal nerve or deep brain stimulation or transcranial magnetic stimulation. Diagnosis of non-CSE requires continuous electroencephalography and involves a high index of suspicion in all patients with an altered mental status of unclear cause or with a prolonged postictal state. Treatment options include addressing underlying causes and aggressive pharmacologic interventions with a benzodiazepine, phenytoin and valproate.
Real Hypersurfaces in Complex Two-plane Grassmannians with Reeb Parallel Ricci Tensor in the GTW Connection
Authors: de Dios Pérez Juan , Lee Hyunjin , Jin Suh Young , Woo Changhwa
Published: May 2016

There are several kinds of classification problems for real hypersurfaces in complex two-plane GrassmanniansG2(ℂm+2). Among them, Suh classified Hopf hypersurfaces inG2(ℂm+2) with Reeb parallel Ricci tensor in Levi–Civita connection. In this paper, we introduce the notion of generalized Tanaka–Webster (GTW) Reeb parallel Ricci tensor for Hopf hypersurfaces inG2(ℂm+2). Next, we give a complete classification of Hopf hypersurfaces inG2(ℂm+2) with GTW Reeb parallel Ricci tensor.
Atmospheric changes caused by galactic cosmic rays over the period 1960–2010
Authors: Jackman Charles H. , Marsh Daniel R. , Kinnison Douglas E. , Mertens Christopher J. , Fleming Eric L.
Published: May 2016

Abstract. The Specified Dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM) and the Goddard Space Flight Center two-dimensional (GSFC 2-D) models are used to investigate the effect of galactic cosmic rays (GCRs) on the atmosphere over the 1960–2010 time period. The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) computation of the GCR-caused ionization rates are used in these simulations. GCR-caused maximum NOx increases of 4–15 % are computed in the Southern polar troposphere with associated ozone increases of 1–2 %. NOx increases of  ∼ 1–6 % are calculated for the lower stratosphere with associated ozone decreases of 0.2–1 %. The primary impact of GCRs on ozone was due to their production of NOx. The impact of GCRs varies with the atmospheric chlorine loading, sulfate aerosol loading, and solar cycle variation. Because of the interference between the NOx and ClOx ozone loss cycles (e.g., the ClO + NO2+ M  →  ClONO2+ M reaction) and the change in the importance of ClOx in the ozone budget, GCRs cause larger atmospheric impacts with less chlorine loading. GCRs also cause larger atmospheric impacts with less sulfate aerosol loading and for years closer to solar minimum. GCR-caused decreases of annual average global total ozone (AAGTO) were computed to be 0.2 % or less with GCR-caused column ozone increases between 1000 and 100 hPa of 0.08 % or less and GCR-caused column ozone decreases between 100 and 1 hPa of 0.23 % or less. Although these computed ozone impacts are small, GCRs provide a natural influence on ozone and need to be quantified over long time periods. This result serves as a lower limit because of the use of the ionization model NAIRAS/HZETRN which underestimates the ion production by neglecting electromagnetic and muon branches of the cosmic ray induced cascade. This will be corrected in future works.
Modeling lightning-NOx chemistry on a sub-grid scale in a global chemical transport model
Authors: Gressent Alicia , Sauvage Bastien , Cariolle Daniel , Evans Mathew , Leriche Maud , Mari Céline , Thouret Valérie
Published: May 2016

Abstract. For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the nonlinear reactions occurring within high concentrated NOx plumes from lightning NOx emissions (LNOx) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NOx–O3 chemical interactions, and the fractions of NOx conversion into HNO3 within the plume. Parameter estimates were made using the Dynamical Simple Model of Atmospheric Chemical Complexity (DSMACC) box model, simple plume dispersion simulations, and the 3-D Meso-NH (non-hydrostatic mesoscale atmospheric model). In order to assess the impact of the LNOx plume approach on the NOx and O3 distributions on a large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNOx parameterization implies an NOx and O3 decrease on a large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over central Africa in July) and a relative increase downwind of LNOx emissions (up to 18 and 2 % for NOx and O3, respectively, in July). The calculated variability in NOx and O3 mixing ratios around the mean value according to the known uncertainties in the parameter estimates is at a maximum over continental tropical regions with ΔNOx [−33.1, +29.7] ppt and ΔO3 [−1.56, +2.16] ppb, in January, and ΔNOx [−14.3, +21] ppt and ΔO3 [−1.18, +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows us (i) to reproduce a more realistic lightning NOx chemistry leading to better NOx and O3 distributions on the large scale and (ii) to focus on other improvements to reduce remaining uncertainties from processes related to NOx chemistry in CTM.
Properties of aerosols and formation mechanisms over southern China during the monsoon season
Authors: Chen Weihua , Wang Xuemei , Cohen Jason Blake , Zhou Shengzhen , Zhang Zhisheng , Chang Ming , Chan Chuen Yu
Published: May 2016

Abstract. Measurements of size-resolved aerosols from 0.25 to 18 μm were conducted at three sites (urban, suburban and background sites) and used in tandem with an atmospheric transport model to study the size distribution and formation of atmospheric aerosols in southern China during the monsoon season (May–June) in 2010. The mass distribution showed the majority of chemical components were found in the smaller size bins (< 2.5 μm). Sulfate, was found to be strongly correlated with aerosol water, and anti-correlated with atmospheric SO2, hinting at aqueous-phase reactions being the main formation pathway. Nitrate was the only major species that showed a bi-modal distribution at the urban site, and was dominated by the coarse mode in the other two sites, suggesting that an important component of nitrate formation is chloride depletion of sea salt transported from the South China Sea. In addition to these aqueous-phase reactions and interactions with sea salt aerosols, new particle formation, chemical aging, and long-range transport from upwind urban or biomass burning regions were also found to be important in at least some of the sights on some of the days. This work therefore summarizes the different mechanisms that significantly impact the aerosol chemical composition during the Monsoon over southern China.
Quantification and parametrization of non-linearity effects by higher-order sensitivity terms in scattered light differential optical absorption spectroscopy
Authors: Puķīte Jānis , Wagner Thomas
Published: May 2016

Abstract. We address the application of differential optical absorption spectroscopy (DOAS) of scattered light observations in the presence of strong absorbers (in particular ozone), for which the absorption optical depth is a non-linear function of the trace gas concentration. This is the case because Beer–Lambert law generally does not hold for scattered light measurements due to many light paths contributing to the measurement. While in many cases linear approximation can be made, for scenarios with strong absorptions non-linear effects cannot always be neglected. This is especially the case for observation geometries, for which the light contributing to the measurement is crossing the atmosphere under spatially well-separated paths differing strongly in length and location, like in limb geometry. In these cases, often full retrieval algorithms are applied to address the non-linearities, requiring iterative forward modelling of absorption spectra involving time-consuming wavelength-by-wavelength radiative transfer modelling. In this study, we propose to describe the non-linear effects by additional sensitivity parameters that can be used e.g. to build up a lookup table. Together with widely used box air mass factors (effective light paths) describing the linear response to the increase in the trace gas amount, the higher-order sensitivity parameters eliminate the need for repeating the radiative transfer modelling when modifying the absorption scenario even in the presence of a strong absorption background. While the higher-order absorption structures can be described as separate fit parameters in the spectral analysis (so-called DOAS fit), in practice their quantitative evaluation requires good measurement quality (typically better than that available from current measurements). Therefore, we introduce an iterative retrieval algorithm correcting for the higher-order absorption structures not yet considered in the DOAS fit as well as the absorption dependence on temperature and scattering processes.
Equatorward phytoplankton migration during a cold spell within the Late Cretaceous super-greenhouse
Authors: van Helmond Niels A. G. M. , Sluijs Appy , Papadomanolaki Nina M. , Plint A. Guy , Gröcke Darren R. , Pearce Martin A. , Eldrett James S. , Trabucho-Alexandre João , Walaszczyk Ireneusz , van de Schootbrugge Bas , Brinkhuis Henk
Published: May 2016

Abstract. Oceanic Anoxic Event 2 (OAE2), a  ∼  600 kyr episode close to the Cenomanian–Turonian boundary (ca. 94 Ma), is characterized by relatively widespread marine anoxia and ranks amongst the warmest intervals of the Phanerozoic. The early stages of OAE2 are, however, marked by an episode of widespread transient cooling and bottom water oxygenation: the Plenus Cold Event. This cold spell has been linked to a decline in atmospheric pCO2, resulting from enhanced global organic carbon burial. To investigate the response of phytoplankton to this marked and rapid climate shift we examined the biogeographical response of dinoflagellates to the Plenus Cold Event. Our study is based on a newly generated geochemical and palynological data set from a high-latitude Northern Hemisphere site, Pratts Landing (western Alberta, Canada). We combine these data with a semi-quantitative global compilation of the stratigraphic distribution of dinoflagellate cyst taxa. The data show that dinoflagellate cysts grouped in the Cyclonephelium compactum–membraniphorum morphological plexus migrated from high to mid-latitudes during the Plenus Cold Event, making it the sole widely found (micro)fossil to mark this cold spell. In addition to earlier reports from regional metazoan migrations during the Plenus Cold Event, our findings illustrate the effect of rapid climate change on the global biogeographical dispersion of phytoplankton.
Response of dissolved and particulate organic carbon and nitrogen in runoff to monsoon storm events in two watersheds of different tree species composition
Authors: Lee Mi-Hee , Payeur-Poirier Jean-Lionel , Park Ji-Hyung , Matzner Egbert
Published: May 2016

Abstract. Heavy storm events may increase the amount of organic matter in runoff from forested watersheds as well as the relation of dissolved to particulate organic matter. Little is known about the behaviour of dissolved and particulate organic N and its relations to C. This study evaluated the effects of monsoon storm events on the runoff fluxes and on the quality of dissolved (< 0.45 µm) and particulate (0.7 µm to 1 mm) organic carbon and nitrogen (DOC, DON, POC, PON) in a mixed coniferous/deciduous (mixed watershed) and a deciduous forested watershed (deciduous watershed) in South Korea. During storm events, DOC concentrations in runoff increased with discharge, while DON concentrations were stable. DOC, DON and NO3-N fluxes in runoff increased linearly with discharge, whereas nonlinear responses of POC and PON fluxes were observed. The cumulative C and N fluxes in runoff were in the order; DOC > POC and NO3-N > DON > PON. The cumulative DOC fluxes in runoff during the 2 months study period were much larger at the deciduous watershed (16 kg C ha−1) than at the mixed watershed (7 kg C ha−1), while the cumulative NO3-N fluxes were higher at the mixed watershed (5.2 kg N ha−1) than at the deciduous watershed (2.9 kg N ha−1). Cumulative fluxes of POC and PON were similar at both watersheds. Quality parameters of organic matter in soils and runoff suggested that the contribution of near surface flow to runoff was larger at the deciduous than at the mixed watershed. Our results demonstrate different responses of dissolved C and N in runoff to storm events as a combined effect of tree species composition and watershed-specific flowpaths.
How does grid-resolution modulate the topographic expression of geomorphic processes?
Authors: Grieve Stuart W. D. , Mudd Simon M. , Milodowski David T. , Clubb Fiona J. , Furbish David J.
Published: May 2016

Abstract. In many locations, our ability to study the processes which shape the Earth are greatly enhanced through the use of high resolution digital topographic data. However, although the availability of such datasets has markedly increased in recent years, many locations of significant geomorphic interest still do not have high resolution topographic data available. Here, we aim to constrain how well we can understand surface processes through topographic analysis performed on lower resolution data. We generate digital elevation models from point clouds at a range of grid sizes from 1 to 30 m, which covers the range of widely used data resolutions available globally, at three locations in the United States. Using this data, the relationship between curvature and grid resolution is explored, alongside the estimation of the hillslope sediment transport coefficient (D, in m2 yr−1) for each landscape. Curvature, and consequently D, values are shown to be generally insensitive to grid resolution, particularly in landscapes with broad hilltops and valleys. Curvature distributions, however, become increasingly condensed around the mean, and theoretical considerations suggest caution should be used when extracting curvature from landscapes with sharp ridges. Two methods of extracting channels from topographic data are tested. A geometric method of channel extraction that finds channels by detecting threshold values of planform curvature is shown to perform well at resolutions up to 30 m in all three landscapes. The landscape parameters of hillslope length and relief are both successfully extracted at the same range of resolutions. These parameters can be used to detect landscape transience and our results suggest that such work need not be confined to high resolution topographic data. A synthesis of the results presented in this work indicate that although high resolution (e.g., 1 m) topographic data does yield exciting possibilities for geomorphic research, many key parameters can be understood in lower resolution data, given careful consideration of how analyses are performed.
Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models
Authors: Christensen Nikolaj Kruse , Christensen Steen , Ferre Ty Paul A.
Published: May 2016

Abstract. In spite of geophysics being used increasingly, it is often unclear how and when the integration of geophysical data and models can best improve the construction and predictive capability of groundwater models. This paper uses a newly developed HYdrogeophysical TEst-Bench (HYTEB) that is a collection of geological, groundwater and geophysical modeling and inversion software to demonstrate alternative uses of electromagnetic (EM) data for groundwater modeling in a hydrogeological environment consisting of various types of glacial deposits with typical hydraulic conductivities and electrical resistivities covering impermeable bedrock with low resistivity (clay). The synthetic 3-D reference system is designed so that there is a perfect relationship between hydraulic conductivity and electrical resistivity. For this system it is investigated to what extent groundwater model calibration and, often more importantly, model predictions can be improved by including in the calibration process electrical resistivity estimates obtained from TEM data. In all calibration cases, the hydraulic conductivity field is highly parameterized and the estimation is stabilized by (in most cases) geophysics-based regularization. For the studied system and inversion approaches it is found that resistivities estimated by sequential hydrogeophysical inversion (SHI) or joint hydrogeophysical inversion (JHI) should be used with caution as estimators of hydraulic conductivity or as regularization means for subsequent hydrological inversion. The limited groundwater model improvement obtained by using the geophysical data probably mainly arises from the way these data are used here: the alternative inversion approaches propagate geophysical estimation errors into the hydrologic model parameters. It was expected that JHI would compensate for this, but the hydrologic data were apparently insufficient to secure such compensation. With respect to reducing model prediction error, it depends on the type of prediction whether it has value to include geophysics in a joint or sequential hydrogeophysical model calibration. It is found that all calibrated models are good predictors of hydraulic head. When the stress situation is changed from that of the hydrologic calibration data, then all models make biased predictions of head change. All calibrated models turn out to be very poor predictors of the pumping well's recharge area and groundwater age. The reason for this is that distributed recharge is parameterized as depending on estimated hydraulic conductivity of the upper model layer, which tends to be underestimated. Another important insight from our analysis is thus that either recharge should be parameterized and estimated in a different way, or other types of data should be added to better constrain the recharge estimates.
Short-term volcano-tectonic earthquake forecasts based on a moving mean recurrence time algorithm: the El Hierro seismo-volcanic crisis experience
Authors: García Alicia , De la Cruz-Reyna Servando , Marrero José M. , Ortiz Ramón
Published: May 2016

Abstract. Under certain conditions, volcano-tectonic (VT) earthquakes may pose significant hazards to people living in or near active volcanic regions, especially on volcanic islands; however, hazard arising from VT activity caused by localized volcanic sources is rarely addressed in the literature. The evolution of VT earthquakes resulting from a magmatic intrusion shows some orderly behaviour that may allow the occurrence and magnitude of major events to be forecast. Thus governmental decision makers can be supplied with warnings of the increased probability of larger-magnitude earthquakes on the short-term timescale. We present here a methodology for forecasting the occurrence of large-magnitude VT events during volcanic crises; it is based on a mean recurrence time (MRT) algorithm that translates the Gutenberg-Richter distribution parameter fluctuations into time windows of increased probability of a major VT earthquake. The MRT forecasting algorithm was developed after observing a repetitive pattern in the seismic swarm episodes occurring between July and November 2011 at El Hierro (Canary Islands). From then on, this methodology has been applied to the consecutive seismic crises registered at El Hierro, achieving a high success rate in the real-time forecasting, within 10-day time windows, of volcano-tectonic earthquakes.
Using spatial Markovian chain for the statistical analysis of seismic occurrences in the Azores Region
Authors: Rodrigues Maria Cecília M. , Oliveira Carlos S.
Published: May 2016

Abstract. The objective of this paper is to study the spatial sequence of the epicentral locations of seismic occurrences (Space variable) in the Azores region. In a previous investigation based on geological considerations and statistical criteria that addresses the existing historical and instrumental information, the epicentral locations were assigned to seven seismic zones. This paper focuses on the analysis of occurrences in the seven seismic zones using Markovian chains. The probability of occurrence of an earthquake in one of the seven adopted zones is estimated, revealing great differences among the seismic zones. Additionally, the one-step transitions of this variable (seismic zone for the next occurrence in time) are explored and show an evident dependence between consecutive earthquake locations. Assuming that the process is stationary, N-step transitions are also discussed. Based on the developed Markovian model, this study also simulates the sequence of epicentral zones where occurrences can take place, which is an important component of modelling the entire process of seismic occurrences in the Azores region.
Occurrence and characteristics of mesoscale eddies in the tropical northeastern Atlantic Ocean
Authors: Schütte Florian , Brandt Peter , Karstensen Johannes
Published: May 2016

Abstract. Coherent mesoscale features (referred to here as eddies) in the tropical northeastern Atlantic Ocean (between 12–22° N and 15–26° W) are examined and characterized. The eddies' surface signatures are investigated using 19 years of satellite-derived sea level anomaly (SLA) data. Two automated detection methods are applied, the geometrical method based on closed streamlines around eddy cores, and the Okubo–Weiß method based on the relation between vorticity and strain. Both methods give similar results. Mean eddy surface signatures of SLA, sea surface temperature (SST) and sea surface salinity (SSS) anomalies are obtained from composites of all snapshots around identified eddy cores. Anticyclones/cyclones are identified by an elevation/depression of SLA and enhanced/reduced SST and SSS in their cores. However, about 20 % of all anticyclonically rotating eddies show reduced SST and reduced SSS instead. These kind of eddies are classified as anticyclonic mode-water eddies (ACMEs). About 146 ± 4 eddies per year with a minimum lifetime of 7 days are identified (52 % cyclones, 39 % anticyclones, 9 % ACMEs) with rather similar mean radii of about 56 ± 12 km. Based on concurrent in situ temperature and salinity profiles (from Argo float, shipboard, and mooring data) taken inside of eddies, distinct mean vertical structures of the three eddy types are determined. Most eddies are generated preferentially in boreal summer and along the West African coast at three distinct coastal headland regions and carry South Atlantic Central Water supplied by the northward flow within the Mauretanian coastal current system. Westward eddy propagation (on average about 3.00 ± 2.15 km d−1) is confined to distinct zonal corridors with a small meridional deflection dependent on the eddy type (anticyclones – equatorward, cyclones – poleward, ACMEs – no deflection). Heat and salt fluxes out of the coastal region and across the Cape Verde Frontal Zone, which separates the shadow zone from the ventilated subtropical gyre, are calculated.