bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of redox/Fyn/c‐Cbl pathway function by Cdc42 controls tumour initiation capacity and tamoxifen sensitivity in basal‐like breast cancer cells
Authors: Chen Hsing‐Yu , Yang Yin M. , Stevens Brett M. , Noble Mark
Published: April 2013

We found that basal‐like breast cancer (BLBC) cells use Cdc42 to inhibit function of the redox/Fyn/c‐Cbl (RFC) pathway, which normally functions to convert small increases in oxidative status into enhanced degradation of c‐Cbl target proteins. Restoration of RFC pathway function by genetic or pharmacological Cdc42 inhibition enabled harnessing of pro‐oxidant effects of low µM tamoxifen (TMX) concentrations – concentrations utilized in trials on multiple tumour types – to suppress division and induce death of BLBC cells in vitro and to confer TMX sensitivity in vivo through oestrogen receptor‐α‐independent mechanisms. Cdc42 knockdown also inhibited generation of mammospheres in vitro and tumours in vivo, demonstrating the additional importance of this pathway in tumour initiating cell (TIC) function. These findings provide a new regulatory pathway that is subverted in cancer cells, a novel means of attacking TIC and non‐TIC aspects of BLBCs, a lead molecule (ML141) that confers sensitivity to low µM TMX in vitro and in vivo and also appear to be novel in enhancing sensitivity to a non‐canonical mode of action of an established therapeutic agent.
R5 HIV‐1 envelope attracts dendritic cells to cross the human intestinal epithelium and sample luminal virions via engagement of the CCR5
Authors: Cavarelli Mariangela , Foglieni Chiara , Rescigno Maria , Scarlatti Gabriella
Published: April 2013

The gastrointestinal tract is a principal route of entry and site of persistence of human immunodeficiency virus type 1 (HIV‐1). The intestinal mucosa, being rich of cells that are the main target of the virus, represents a primary site of viral replication and CD4+ T‐cell depletion. Here, we show both in vitro and ex vivo that HIV‐1 of R5 but not X4 phenotype is capable of selectively triggering dendritic cells (DCs) to migrate within 30 min between intestinal epithelial cells to sample virions and transfer infection to target cells. The engagement of the chemokine receptor 5 on DCs and the viral envelope, regardless of the genetic subtype, drive DC migration. Viruses penetrating through transient opening of the tight junctions likely create a paracellular gradient to attract DCs. The formation of junctions with epithelial cells may initiate a haptotactic process of DCs and at the same time favour cell‐to‐cell viral transmission. Our findings indicate that HIV‐1 translocation across the intestinal mucosa occurs through the selective engagement of DCs by R5 viruses, and may guide the design of new prevention strategies.

→See accompanying article http://dx.doi.org/10.1002/emmm.201302763
Adaptive time series compensator for delay compensation of servo‐hydraulic actuator systems for real‐time hybrid simulation
Authors: Chae Yunbyeong , Kazemibidokhti Karim , Ricles James M.
Published: April 2013

Hydraulic actuators are typically used in a real‐time hybrid simulation to impose displacements to a test structure (also known as the experimental substructure). It is imperative that good actuator control is achieved in the real‐time hybrid simulation to minimize actuator delay that leads to incorrect simulation results. The inherent nonlinearity of an actuator as well as any nonlinear response of the experimental substructure can result in an amplitude‐dependent behavior of the servo‐hydraulic system, making it challenging to accurately control the actuator. To achieve improved control of a servo‐hydraulic system with nonlinearities, an adaptive actuator compensation scheme called the adaptive time series (ATS) compensator is developed. The ATS compensator continuously updates the coefficients of the system transfer function during a real‐time hybrid simulation using online real‐time linear regression analysis. Unlike most existing adaptive methods, the system identification procedure of the ATS compensator does not involve user‐defined adaptive gains. Through the online updating of the coefficients of the system transfer function, the ATS compensator can effectively account for the nonlinearity of the combined system, resulting in improved accuracy in actuator control. A comparison of the performance of the ATS compensator with existing linearized compensation methods shows superior results for the ATS compensator for cases involving actuator motions with predefined actuator displacement histories as well as real‐time hybrid simulations. Copyright © 2013 John Wiley & Sons, Ltd.
Alternative closed‐form solutions for the mean rate of exceedance of structural limit states
Authors: Romão Xavier , Delgado Raimundo , Costa Aníbal
Published: April 2013

Two new closed‐form expressions representing the mean rate of exceedance of a given limit state are presented herein. These proposals overcome limitations that were identified with the original formulation of the well‐known SAC/FEMA approach. The new expressions involve new parametric functions for the modeling of the seismic hazard data and for the demand evolution for increasing values of the earthquake intensity measure. Given the carefully selected parametric form of these functions, mathematical tractability is able to be maintained to establish two new closed‐form solutions representing the mean rate of exceedance of a given limit state. The function proposed for the hazard exhibits nonlinear behavior in log‐log space and is able to represent the actual hazard data over a wider range of earthquake intensity levels. The function proposed for the demand evolution addresses issues related to the inadequate performance of the SAC/FEMA approach when force‐based demand parameters such as the shear force are considered. To illustrate the applicability of the new closed‐form solutions, the probability of occurrence of several limit states is determined for a reinforced concrete structure. Copyright © 2013 John Wiley & Sons, Ltd.
Receiving while giving: The differential roles of receiving help and satisfaction with help on caregiver rewards among spouses and adult‐children
Authors: Savundranayagam Marie Y.
Published: April 2013

Objective

There is a growing body of literature on the rewards associated with caregiving and the utility of these rewards on buffering the negative consequences of caring for a family member with Alzheimer's disease. Many psychoeducational interventions aim to empower caregivers to seek and obtain help from their social support network, with the expectation that help will enable them to cope more effectively.

Methods

This study investigated the impact of changes in help and changes in satisfaction with help on positive aspects of caregiving for both spouse (N = 254) and adult‐child (N = 208) caregivers who attended a psychoeducational intervention.

Results

Analyses using structural equation modeling revealed that increases in amount of help and satisfaction with help were significantly linked with increases in caregiver rewards for adult‐children. However, only increases in satisfaction with help were significantly related to increases in caregiver rewards for spouses.

Conclusions

These group differences suggest that the quality of support is critical for spouses, whereas both quality and receiving extra help are useful for adult‐child caregivers. These findings are discussed in terms of the importance of understanding the differential needs of spouse and adult‐child caregivers in practice. Copyright © 2013 John Wiley & Sons, Ltd.
Multidisciplinary therapy including proton beam radiotherapy for a Ewing sarcoma family tumor of maxillary sinus in a 4‐year‐old girl
Authors: Yamaoka Masayoshi , Akiyama Masaharu , Yokokawa Yuichi , Terao Yoko , Yokoi Kentaro , Kato Takakuni , Fukushima Takashi , Sakurai Hideyuki , Ida Hiroyuki
Published: April 2013

Background

Although complete resection offers the best chance for controlling head and neck Ewing sarcoma family tumors (ESFTs), it is occasionally unfeasible because of possible functional and cosmetic side effects. Planning multidisciplinary treatment for head and neck ESFT is challenging.

Methods and Results

A 4‐year‐old girl had left‐sided excessive tearing, nasal obstruction, and exophthalmos for 4 months. A CT scan showed a mass filling the left maxillary sinus and extending to the left orbital wall. After a diagnosis of ESFT was established with biopsy, the patient was treated with vincristine, doxorubicin, cyclophosphamide/ifosfamide etoposide (VDC/IE) regimen over 50 weeks; partial maxillectomy was performed at week 15 and was followed by proton radiotherapy. The patient has remained tumor‐free for 16 months, with preservation of facial form and function.

Conclusion

Partial resection combined with proton radiotherapy may enable maximal tumor control and minimal functional and cosmetic side effects in children with head and neck ESFT. © 2013 Wiley Periodicals, Inc. Head Neck 35: E386–E390, 2013
Brief communication: The ecosystem perspective in ecotoxicology as a way forward for the ecological risk assessment of chemicals
Authors: De Laender Frederik , Janssen Colin R
Published: April 2013

One of the objectives of the European Union (EU) ecological risk assessment of chemicals (ERA) is to derive maximum environmental concentrations that are not expected to cause adverse ecological effects. To this end, related EU directives list protection goals as well as guidelines that should be used to reach these goals. It is generally accepted that the individual-level endpoints on which these guidelines are based do not correspond to the listed population- and ecosystem-level protection goals. In this article, we identify 5 research topics that are key to bridging this gap: 1) the refinement of population-level effects and recovery rates by explicitly taking into account competition and 2) predation, 3) the assessment of chemical effects on biodiversity, 4) the assessment of chemical stress on ecosystem functions and services, and 5) the quantification of the effects of chemical mixtures. In addition, we illustrate why an ecosystem perspective is needed to address these topics and to inform the risk assessment process. We propose the use of existing ecotoxicological community, food web, and ecosystem models to tackle these issues and discuss why new models are needed to predict chemical effects on biodiversity. Integr Environ Assess Manag 2013;9:e34–e38. © 2013 SETAC
Priorities to improve the ecological risk assessment and management for pesticides in surface water
Authors: Brock Theo CM
Published: April 2013

This article deals with prospective and retrospective ecological risk assessment (ERA) procedures for pesticides in surface waters as carried out under European legislation (Regulation 1107/2009/EC; Directive 2009/128/EC; Directive 2000/60/EC). Priorities to improve the aquatic risk assessment and management of pesticides are discussed on basis of the following 5 theses: 1) the management of the environmental risks of pesticides in surface water requires an appropriate implementation of feedback mechanisms between prospective and retrospective ERA, 2) an appropriate ERA cannot be carried out without well-defined specific protection goals, described in terms of focal vulnerable populations and related exposure assessment goals, 3) the interaction between the assessment of exposure and eco(toxico)logical effects in ERA is at a lower level of sophistication than either assessment of exposure or assessment of effects in the field, 4) there is insufficient experimental proof that, in prospective ERA, the chronic effect assessment procedures accurately predict long-term population- and community-level impacts, and 5) multiple stress by pesticides in aquatic ecosystems cannot be ignored in ERA, but in individual water bodies, toxicity usually is dominated by a limited number of substances. Integr Environ Assess Manag 2013;9:e64–e74. © 2013 SETAC
Positive regulation of osteogenesis by bile acid through FXR
Authors: Cho Sun Wook , An Jee Hyun , Park Hyojung , Yang Jae-Yeon , Choi Hyung Jin , Kim Sang Wan , Park Young Joo , Kim Seong Yeon , Yim Mijung , Baek Wook-Young , Kim Jung-Eun , Shin Chan Soo
Published: April 2013

Farnesoid X receptor (FXR) is a nuclear receptor that functions as a bile acid sensor controlling bile acid homeostasis. We investigated the role of FXR in regulating bone metabolism. We identified the expression of FXR in calvaria and bone marrow cells, which gradually increased during osteoblastic differentiation in vitro. In male mice, deletion of FXR (FXR−/−) in vivo resulted in a significant reduction in bone mineral density by 4.3% to 6.6% in mice 8 to 20 weeks of age compared with FXR+/+ mice. Histological analysis of the lumbar spine showed that FXR deficiency reduced the bone formation rate as well as the trabecular bone volume and thickness. Moreover, tartrate-resistant acid phosphatase (TRACP) staining of the femurs revealed that both the osteoclast number and osteoclast surface were significantly increased in FXR−/− mice compared with FXR+/+ mice. At the cellular level, induction of alkaline phosphatase (ALP) activities was blunted in primary calvarial cells in FXR−/− mice compared with FXR+/+ mice in concert with a significant reduction in type I collagen a1(Col1a1), ALP, and runt-related transcription factor 2 (Runx2) gene expressions. Cultures of bone marrow–derived macrophages from FXR−/− mice exhibited an increased number of osteoclast formations and protein expression of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1). In female FXR−/− mice, although bone mineral density (BMD) was not significantly different from that in FXR+/+ mice, bone loss was accelerated after an ovariectomy compared with FXR+/+ mice. In vitro, activation of FXR by bile acids (chenodeoxycholic acid [CDCA] or 6-ECDCA) or FXR agonists (GW4064 or Fexaramine) significantly enhanced osteoblastic differentiation through the upregulation of Runx2 and enhanced extracellular signal-regulated kinase (ERK) and β-catenin signaling. FXR agonists also suppressed osteoclast differentiation from bone marrow macrophages. Finally, administration of a farnesol (FOH 1%) diet marginally prevented ovariectomy (OVX)-induced bone loss and enhanced bone mass gain in growing C57BL/6J mice. Taken together, these results suggest that FXR positively regulates bone metabolism through both arms of the bone remodeling pathways; ie, bone formation and resorption. © 2013 American Society for Bone and Mineral Research.
Prospective observational study of physical functioning, physical activity, and time outdoors and the risk of hip fracture: A population-based cohort study of 158,057 older adults in the 45 and up study
Authors: Lai Jeffrey K C , Lucas Robyn M , Armstrong Miranda , Banks Emily
Published: April 2013

Low levels of physical activity or sun exposure and limitations to physical functioning (or disability) have been identified as possible risk factors for hip fracture. However, these factors are closely related, and data on their independent and joint association with risk of hip fracture are limited. A total of 158,057 individuals aged ≥45 years sampled from the general population of New South Wales, Australia, from the prospective 45 and Up Study completed a baseline postal questionnaire in 2006 to 2009 including data on physical activity (Active Australia questionnaire); sun exposure (usual time outdoors); and physical functioning (Medical Outcomes Score-Physical Functioning; scored 0 to 100). Incident first hip fractures were ascertained by linkage to administrative hospital data (n = 293; average follow-up 2.3 years). The relative risk (RR) of hip fracture was estimated using Cox proportional hazards. Poorer physical functioning, lower physical activity, and less time outdoors were positively related to each other at baseline and individually associated with significantly increased hip fracture risk. However, physical activity and time outdoors were not significantly related to hip fracture risk after adjustment for baseline physical functioning or when analysis was restricted to those with no or mild baseline physical limitation. In contrast, physical functioning remained strongly related to hip fracture risk after adjustment for the other two factors; compared with the group without limitation (100), the RR of hip fracture among those with mild (75–95), moderate (50–70), severe (25–45), and greatest (0–20) level of physical limitation was 1.38 (95% confidence interval [CI] 0.88–2.14), 2.14 (1.29–3.53), 3.87 (2.31–6.44), and 5.61 (3.33–9.42), respectively. The findings suggest that limitation in physical functioning, but not physical activity or time outdoors, is strongly related to hip fracture risk. The apparent increased risk of hip fracture previously described for low physical activity or sun exposure may be, at least in part due to uncontrolled confounding. © 2013 American Society for Bone and Mineral Research.
Existence of dynamic tautomerism and divalent N(I) character inN‐(pyridin‐2‐yl)thiazol‐2‐amine
Authors: Bhatia Sonam , Malkhede Yogesh J. , Bharatam Prasad V.
Published: April 2013

N‐(Pyridin‐2‐yl)thiazol‐2‐amine is a versatile chemical functional unit present in many therapeutically important species. Quantum chemical analysis shows that there are six competitive isomeric structures possible for this class of compounds within a relative energy difference of ∼4 kcal/mol. Some of the isomeric structures possess divalent N(I) character. There appears to be a competition between the thiazole and pyridine groups to accommodate the tautomeric hydrogen, and consequently show electron donating property in the structure with R‐N←L representation. Details of electron distribution, tautomeric preferences, protonation energy, and divalent N(I) character, and so on, of this class of compounds are presented in this article. Subsequently, upon protonation, (L→N←L)⊕character is clearly evident in these moieties as molecular orbital analysis clearly shows two lone pairs of electrons on the central nitrogen, in this system. © 2013 Wiley Periodicals, Inc.
An efficient fluctuating charge model for transition metal complexes
Authors: Comba Peter , Martin Bodo , Sanyal Avik
Published: April 2013

A fluctuating charge model for transition metal complexes, based on the Hirshfeld partitioning scheme, spectroscopic energy data from the NIST Atomic Spectroscopy Database and the electronegativity equalization approach, has been developed and parameterized for organic ligands and their high‐ and low‐spin FeIIand FeIII, low‐spin CoIIIand CuIIcomplexes, using atom types defined in the Momec force field. Based on large training sets comprising a variety of transition metal complexes, a general parameter set has been developed and independently validated which allows the efficient computation of geometry‐dependent charge distributions in the field of transition metal coordination compounds. © 2013 Wiley Periodicals, Inc.
Structure of Titan's induced magnetosphere under varying background magnetic field conditions: Survey of Cassini magnetometer data from flybys TA–T85
Authors: Simon Sven , van Treeck Shari C. , Wennmacher Alexandre , Saur Joachim , Neubauer Fritz M. , Bertucci Cesar L. , Dougherty Michele K.
Published: April 2013

Cassini magnetic field observations between 2004 and 2012 suggest the ambient field conditions near Titan's orbit to differ significantly from the frequently applied pre‐Cassini picture (background magnetic field homogeneous and perpendicular to Titan's orbital plane, stationary upstream conditions). In this study, we analyze the impact of these varying background field conditions on the structure of Titan's induced magnetosphere by conducting a systematic survey of Cassini magnetic field observations in the interaction region during flybys TA–T85 (July 2004–July 2012). We introduce a set of criteria that allow to identify deviations in the structure of Titan's induced magnetosphere—as seen by the Cassini magnetometer (MAG)—from the picture of steady‐state field line draping. These disruptions are classified as “weak”, “moderate”, or “strong”. After applying this classification scheme to all available Titan encounters, we survey the data for a possible correlation between the disruptions of the draping pattern and the ambient magnetospheric field conditions, as characterized by Simon et al. [2010a]. Our major findings are: (1) When Cassini is embedded in the northern or southern lobe of Saturn's magnetodisk within a ± 3 h interval around closest approach, Titan's induced magnetosphere shows little or no deviations at all from the steady‐state draping picture. (2) Even when Titan is embedded in perturbed current sheet fields during an encounter, the notion of draping the average background field around the moon's ionosphere is still applicable to explain MAG observations from numerous Titan flybys. (3) Only when Titan is exposed to intense north‐south oscillations of Saturn's current sheet at the time of an encounter, the signatures of the moon's induced magnetosphere may be completely obscured by the ambient field perturbations. (4) So far, T70 is the only flyby that fully meets the idealized pre‐Cassini picture of the Titan interaction (steady background field perpendicular to Titan's orbital plane, steady upstream flow, unperturbed induced magnetosphere).
Acoustic‐gravity waves from the source region of the 2011 great Tohoku earthquake (Mw = 9.0)
Authors: Mikumo Takeshi , Garces Milton , Shibutani Takuo , Morii Wataru , Okawa Takashi , Ishihara Yasushi
Published: April 2013

Atmospheric pressure waves were recorded within 5 h after the 2011 great Tohoku earthquake (Mw = 9.0) by sensitive microbarographs at four regional stations and eight International Monitoring System stations at distances up to 6700 km. While its apparent phase velocity between the regional stations is 341 m/s, the global stations indicate weak dispersive wave trains with low frequencies between 1.6 and 4.8 mHz, propagating with an average phase velocity around 364 m/s. The low‐frequency waves may be interpreted as acoustic‐gravity waves excited by upheaval and depression of the sea surface in the source region due to coseismic uplift and subsidence of the sea bottom during this great thrust earthquake. Assuming the source dimension and the average coseismic vertical displacements of the sea surface, with reference to tsunami observations, we calculate synthetic waveforms for some of the far‐field stations by incorporating a standard sound velocity structure in the atmosphere up to an altitude of 220 km. The synthetics provide reasonable explanations for the general features of the observed waveforms, suggesting possible ranges for the source parameters generating these acoustic‐gravity waves. Our analysis suggests that the average initial upheaval of the sea surface in the central zones of the source region may exceed 4–6 m and that the risetime of the coseismic deformation may be in the range between 3 and 4 min. In the eastern narrow zone adjacent to the Japan Trench, the deformation has significantly higher initial amplitude and shorter risetime.
Spatio‐temporal distribution of fault slip and high‐frequency radiation of the 2010 El Mayor‐Cucapah, Mexico earthquake
Authors: Uchide Takahiko , Yao Huajian , Shearer Peter M.
Published: April 2013

Earthquake slip history and moment release are best resolved using long period seismic waves, but details in the rupture process, such as sharp changes in rupture velocity or direction, can be imaged more clearly using higher frequency waves. Here, we investigate the slip and the high‐frequency radiation histories of the 2010 El Mayor‐Cucapah, Baja California, Mexico earthquake (Mw7.2). The slip distribution inferred from inversion of strong motion data between 0.02 and 0.25 Hz indicates northwest propagating rupture, followed by bilateral rupture for 40 s. The sources of high‐frequency radiation between 0.3 and 2 Hz inferred from back‐projection analysis using teleseismic data are adjacent to, but not within, the high‐slip patches from the finite slip model in time and space. This implies relatively smooth rupture during the times and regions of maximum moment release. As theoretical models have predicted, high‐frequency radiation seems mostly associated with changes in rupture velocity or slip magnitude. Strong high‐frequency radiation is also found where the rupture propagated to a branch fault 50‐km northwest of the hypocenter. Complementary constraints on both fault slip and high‐frequency radiation provide increased understanding of earthquake rupture mechanics and may help improve strong motion evaluation at high frequencies.
Global surface eddy diffusivities derived from satellite altimetry
Authors: Abernathey R. P. , Marshall J.
Published: April 2013

Velocities derived from AVISO sea‐surface height observations, adjusted to be nondivergent, are used to simulate the evolution of passive tracers at the ocean surface. Eddy mixing rates are derived from the tracer fields in two ways. First, the method of Nakamura is applied to a sector in the East Pacific. Second, the Osborn‐Cox diffusivity is calculated globally to yield estimates of diffusivity in two dimensions. The results from the East Pacific show weak meridional mixing at the surface in the Southern Ocean (<1000 m2 s−1, consistent with previous results) but higher mixing rates (~3000–5000 m2 s−1) in the tropical ocean. The Osborn‐Cox diagnostic provides a global picture of mixing rates and agrees reasonably well with the results from the East Pacific. It also shows extremely high mixing rates (~104 m2 s−1) in western boundary current regions. The Osborn‐Cox diffusivity is sensitive to the tracer initialization, which we attribute to the presence of anisotropic mixing processes. The mixing rates are strongly influenced by the presence of a mean flow nearly everywhere, as shown by comparison with an eddy‐only calculation, with the mean flow absent. Finally, results are compared with other recent estimates of mixing rates using Lagrangian and inverse methods.
Ground/satellite observations and atmospheric modeling of dust storms originating in the high Puna‐Altiplano deserts (South America): Implications for the interpretation of paleo‐climatic archives
Authors: Gaiero D.M. , Simonella L. , Gassó S. , Gili S. , Stein A.F. , Sosa P. , Becchio R. , Arce J. , Marelli H.
Published: April 2013

This study provides a detailed description of the sources, transport, dispersion, and deposition of two major dust events originating from the high‐altitude subtropical Puna‐Altiplano Plateau (15–26°S; 65–69°W) in South America. A long and severe drought provided the right conditions for the onset of both events in July 2009 and 2010. Dust was transported SE and deposited over the Pampas region and was observed to continue to the Atlantic Ocean. Dust monitoring stations located downwind recorded both events, and samples were characterized through chemical and textural analysis. Through a combination of meteorological data and satellite observations (CALIPSO and MODIS detectors), we estimate the emission flux for the 2010 event. This estimate was used to constrain the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) transport model and simulate the dust event. Both satellite imagery and model results agree in the location and extension of the dust cloud. CALIPSO detected dust between ~6000 and ~8500 m a.s.l., which remained at this height during most of its trajectory. The dust cloud mixed with a strong convective system in the region, and the associated precipitation brought down significant amounts of dust to the ground. Dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12.4–14.1 µm, similar to modes observed 1300 km away. Chemical composition of sediments from potential dust sources shows distinct signatures within the Puna‐Altiplano Plateau, the Puna sector being clearly different from the Altiplano area. In addition, both sources are markedly different from the Patagonian chemical fingerprint. These results have important implications to improve the interpretation of paleo‐environmental archives preserved on the Argentine loess, Antarctic ice cores, and Southern Ocean marine sediments.
The response of the North American Monsoon to increased greenhouse gas forcing
Authors: Cook B. I. , Seager R.
Published: April 2013

We analyze the response of the North American Monsoon (NAM) to increased greenhouse gas (GHG) forcing (emissions scenario RCP 8.5) using new simulations available through the Coupled Model Intercomparison Project version 5 (CMIP5). Changes in total monsoon season rainfall with GHG warming are small and insignificant. The models do, however, show significant declines in early monsoon season precipitation (June‐July) and increases in late monsoon season (September‐October) precipitation, indicating a shift in seasonality toward delayed onset and withdrawal of the monsoon. Early in the monsoon season, tropospheric warming increases vertical stability, reinforced by reductions in available surface moisture, inhibiting precipitation and delaying the onset of the monsoon. By the end of the monsoon season, moisture convergence is sufficient to overcome the warming induced stability increases, and precipitation is enhanced. Even with no change in total NAM rainfall, shifts in the seasonal distribution of precipitation within the NAM region are still likely to have significant societal and ecological consequences, reinforcing the need to not only understand the magnitude, but also the timing, of future precipitation changes.
Radiative heating of the ISCCP upper level cloud regimes and its impact on the large‐scale tropical circulation
Authors: Li Wei , Schumacher Courtney , McFarlane Sally A.
Published: April 2013

Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% to 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(day∙km), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25‐year ISCCP data set, the tropics‐wide average profile has a radiative heating maximum of 0.45 K day‐1 near 250 hPa. Column‐integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics‐wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large‐scale tropical circulation variations because of convective feedbacks rather than direct forcing by the cloud radiative heating profiles. However, the height of the radiative heating maxima and gradient of the heating profiles are important to determine the sign and patterns of the horizontal circulation anomaly driven by radiative heating at upper levels.
Evaluation of cloud microphysics schemes in simulations of a winter storm using radar and radiometer measurements
Authors: Han Mei , Braun Scott A. , Matsui Toshihisa , Williams Christopher R.
Published: April 2013

Using observations from a space‐borne radiometer and a ground‐based precipitation profiling radar, the impact of cloud microphysics schemes in the WRF model on the simulation of microwave brightness temperature (Tb), radar reflectivity, and Doppler velocity (Vdop) is studied for a winter storm in California. The unique assumptions of particles size distributions, number concentrations, shapes, and fall speeds in different microphysics schemes are implemented into a satellite simulator and customized calculations for the radar are performed to ensure consistent representation of precipitation properties between the microphysics schemes and the radiative transfer models.

Simulations with four different schemes in the WRF model, including the Goddard scheme (GSFC), the WRF single‐moment 6‐class scheme (WSM6), the Thompson scheme (THOM), and the Morrison double‐moment scheme (MORR), are compared directly with measurements from the sensors. Results show large variations in the simulated radiative properties. General biases of ~20 K or larger are found in (polarization‐corrected) Tb, which is linked to an overestimate of the precipitating ice aloft. The simulated reflectivity with THOM appears to agree well with the observations, while high biases of ~5−10 dBZ are found in GSFC, WSM6 and MORR. Peak reflectivity in MORR exceeds other schemes. These biases are attributable to the snow intercept parameters or the snow number concentrations. Simulated Vdop values based on GSFC agree with the observations well, while other schemes appear to have a ~1 m s‐1 high bias in the ice layer. In the rain layer, the model representations of Doppler velocity vary at different sites.
Eruption of the Eyjafjallajökull Volcano in spring 2010: Multiwavelength Raman lidar measurements of sulphate particles in the lower troposphere
Authors: Navas‐Guzmán F. , Müller D. , Bravo‐Aranda J. A. , Guerrero‐Rascado J. L. , Granados‐Muñoz M. J. , Pérez‐Ramírez D. , Olmo F. J. , Alados‐Arboledas L.
Published: April 2013

A fraction of the volcanic plume that originated from the Eyjafjallajökull volcanic eruption on Iceland in 2010 reached the southern Iberian Peninsula in May 2010. The plume was monitored and characterized in terms of optical and microphysical properties with a combination of Raman lidar and star‐ and Sun‐photometers. Our observations showed that the plume arriving at the Iberian Peninsula was mainly composed of sulphate and sulphuric‐acid particles. To our knowledge, this is the first study of optical properties and inverted microphysical properties of volcanic sulphate particles in the lower troposphere/boundary layer based on multiwavelength Raman lidar measurements. A remarkable increase in the particle number concentration in the accumulation mode was determined from the inversion of the aerosol optical properties. The large Ångström exponents and low linear particle depolarization ratios (4–7%) indicated the presence of small and spherical particles. The particle effective radii ranged between 0.30 and 0.55 µm. In situ instrumentation confirmed an increase of sulphate particles at ground level during this period.
View‐angle‐dependent AIRS cloudiness and radiance variance: Analysis and interpretation
Authors: Gong Jie , Wu Dong L.
Published: April 2013

Upper tropospheric clouds play an important role in the global energy budget and hydrological cycle. Significant view‐angle asymmetry has been observed in upper‐level tropical clouds derived from 8 years of Atmospheric Infrared Sounder (AIRS) 15 µm radiances. Here we find that the asymmetry also exists in the extratropics. It is larger during day than that during night, more prominent near elevated terrain, and closely associated with deep convection and wind shear. The cloud radiance variance, a proxy for cloud inhomogeneity, has consistent characteristics of the asymmetry to those in the AIRS cloudiness. The leading causes of the view‐dependent cloudiness asymmetry are the local time difference and small‐scale organized cloud structures. The local time difference (1–1.5 h) of upper‐level clouds between two AIRS outermost views can create parts of the observed asymmetry. On the other hand, small‐scale tilted and banded structures of the upper‐level clouds can induce about half of the observed view‐angle‐dependent differences in the AIRS cloud radiances and their variances. This estimate is inferred from analogous study using microwave humidity sounder radiances observed during the period of time when there were simultaneous measurements at two different view‐angles from NOAA‐18 and NOAA‐19 satellites. The existence of tilted cloud structures and asymmetric 15 µm and 6.7 µm cloud radiances implies that cloud statistics would be view‐angle‐dependent, and should be taken into account in radiative transfer calculations, measurement uncertainty evaluations and cloud climatology investigations. In addition, the momentum forcing in the upper troposphere from tilted clouds is also likely asymmetric, which can affect atmospheric circulation anisotropically.
Carbon flux estimation for Siberia by inverse modeling constrained by aircraft and tower CO2 measurements
Authors: Saeki T. , Maksyutov S. , Sasakawa M. , Machida T. , Arshinov M. , Tans P. , Conway T. J. , Saito M. , Valsala V. , Oda T. , Andres R. J. , Belikov D.
Published: April 2013

Being one of the largest carbon reservoirs in the world, the Siberian carbon sink however remains poorly understood due to the limited numbers of observation. We present the first results of atmospheric CO2 inversions utilizing measurements from a Siberian tower network (Japan‐Russia Siberian Tall Tower Inland Observation Network; JR‐STATION) and four aircraft sites, in addition to surface background flask measurements by the National Oceanic and Atmospheric Administration (NOAA). Our inversion with only the NOAA data yielded a boreal Eurasian CO2 flux of −0.56 ± 0.79 GtC yr−1, whereas we obtained a weaker uptake of −0.35 ± 0.61 GtC yr−1 when the Siberian data were also included. This difference is mainly explained by a weakened summer uptake, especially in East Siberia. We also found the inclusion of the Siberian data had significant impacts on inversion results over northeastern Europe as well as boreal Eurasia. The inversion with the Siberian data reduced the regional uncertainty by 22% on average in boreal Eurasia, and further uncertainty reductions up to 80% were found in eastern and western Siberia. Larger interannual variability was clearly seen in the inversion which includes the Siberia data than the inversion without the Siberia data. In the inversion with NOAA plus Siberia data, east Siberia showed a larger interannual variability than that in west and central Siberia. Finally, we conducted forward simulations using estimated fluxes and confirmed that the fit to independent measurements over central Siberia, which were not included in inversions, was greatly improved.
13C‐ and 14C‐based study of sources and atmospheric processing of water‐soluble organic carbon (WSOC) in South Asian aerosols
Authors: Kirillova Elena N. , Andersson August , Sheesley Rebecca J. , Kruså Martin , Praveen P. S. , Budhavant Krishnakant , Safai P. D. , Rao P. S. P. , Gustafsson Örjan
Published: April 2013

Water‐soluble organic carbon (WSOC) is typically a large component of carbonaceous aerosols with a high propensity for inducing cloud formation. The sources of WSOC, which may be both of primary and secondary origins, are in general poorly constrained. This study assesses the concentrations and dual‐carbon isotope (14C and 13C) signatures of South Asian WSOC during a 15‐month continuous campaign in 2008–2009. Total suspended particulate matter samples were collected at Sinhagad (SINH) India and at the Maldives Climate Observatory at Hanimaadhoo (MCOH). Monsoon‐driven meteorology yields significant WSOC concentration differences between the dry winter season (0.94 ± 0.43 µg m−3 MCOH and 3.6 ± 2.3 µg m−3 SINH) and the summer monsoon season (0.10 ± 0.04 µg m−3 MCOH and 0.35 ± 0.21 µg m−3 SINH). Radiocarbon‐based source apportionment of WSOC not only shows the dominance of biogenic/biomass combustion sources but also a substantial anthropogenic fossil‐fuel contribution (17 ± 4% MCOH and 23 ± 4% SINH). Aerosols reaching MCOH after long‐range over‐ocean transport were enriched by 3–4‰ in δ13C‐WSOC relative to SINH. This is consistent with particle‐phase aging processes influencing the δ13C‐WSOC signal in the South Asian regional receptor atmosphere.
Are climate model simulations of clouds improving? An evaluation using the ISCCP simulator
Authors: Klein Stephen A. , Zhang Yuying , Zelinka Mark D. , Pincus Robert , Boyle James , Gleckler Peter J.
Published: April 2013

The annual cycle climatology of cloud amount, cloud‐top pressure, and optical thickness in two generations of climate models is compared to satellite observations to identify changes over time in the fidelity of simulated clouds. In more recent models, there is widespread reduction of a bias associated with too many highly reflective clouds, with the best models having eliminated this bias. With increased amounts of clouds with lesser reflectivity, the compensating errors that permit models to simulate the time‐mean radiation balance have been reduced. Errors in cloud amount as a function of height or climate regime on average show little or no improvement, although greater improvement can be found in individual models.
Northern Hemisphere blocking frequency and duration in the CMIP5 models
Authors: Dunn‐Sigouin Etienne , Son Seok‐Woo
Published: April 2013

Northern Hemisphere (NH) blocking climatology is examined using a subset of climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5). Both historical and Representative Concentration Pathway (RCP) 8.5 integrations are analyzed to evaluate the performance of the CMIP5 models and to identify possible changes in NH blocking frequency and duration in a warmer climate. Comparison with reanalysis data reveals that CMIP5 models can reproduce the NH blocking climatology reasonably well, although the frequency of Euro‐Atlantic blockings, particularly those with relatively short duration, is significantly underestimated during the cold season. In most models, overestimation of the Pacific blocking frequency is also evident for all durations throughout the year. In comparison to historical integrations, RCP 8.5 integrations show significant decreases in blocking frequency over both the North Pacific and north Atlantic regions, with a hint of increasing blocking frequency over western Russia. However, there is no noticeable change in the duration of individual blocking events for all durations.
Wind extremes in the North Sea Basin under climate change: An ensemble study of 12 CMIP5 GCMs
Authors: de Winter R. C. , Sterl A. , Ruessink B. G.
Published: April 2013

Coastal safety may be influenced by climate change, as changes in extreme surge levels and wave extremes may increase the vulnerability of dunes and other coastal defenses. In the North Sea, an area already prone to severe flooding, these high surge levels and waves are generated by low atmospheric pressure and severe wind speeds during storm events. As a result of the geometry of the North Sea, not only the maximum wind speed is relevant, but also wind direction. Climate change could change maximum wind conditions, with potentially negative effects for coastal safety. Here, we use an ensemble of 12 Coupled Model Intercomparison Project Phase 5 (CMIP5) General Circulation Models (GCMs) and diagnose the effect of two climate scenarios (rcp4.5 and rcp8.5) on annual maximum wind speed, wind speeds with lower return frequencies, and the direction of these annual maximum wind speeds. The 12 selected CMIP5 models do not project changes in annual maximum wind speed and in wind speeds with lower return frequencies; however, we do find an indication that the annual extreme wind events are coming more often from western directions. Our results are in line with the studies based on CMIP3 models and do not confirm the statement based on some reanalysis studies that there is a climate‐change‐related upward trend in storminess in the North Sea area.
The role of snow‐surface coupling, radiation, and turbulent mixing in modeling a stable boundary layer over Arctic sea ice
Authors: Sterk H. A. M. , Steeneveld G. J. , Holtslag A. A. M.
Published: April 2013

To enhance the understanding of the impact of small‐scale processes in the polar climate, this study focuses on the relative role of snow‐surface coupling, radiation and turbulent mixing in an Arctic stable boundary layer. We extend the GABLS1 (GEWEX Atmospheric Boundary‐Layer Study 1) model intercomparison for turbulent mixing with the other relevant physical processes in the stable boundary layer over sea ice. We use the Single Column Model (SCM) version of the Weather Research and Forecasting (WRF) mesoscale meteorological model and run different combinations of boundary layer and radiation schemes, using a state‐of‐the art land surface scheme. With this intercomparison of schemes, we confirm a wide variety in the state of the atmosphere and the surface variables for the selected parameterization schemes. To understand this variety, a sensitivity analysis for one particular combination of parameterization schemes is performed, using a novel analysis method of process diagrams. The variation between the sensitivity runs indicates a relative orientation of model sensitivities to variations in each of the governing processes and these can explain the variety of model results obtained in the intercomparison of different parameterization schemes. Moreover, we apply the same method for several geostrophic wind speeds to represent a large range of synoptic conditions. Results indicate a shift in process significance for different wind regimes. For low wind regimes, the model sensitivity is larger for surface coupling and radiation, while for high wind speeds, the largest sensitivity is found for the turbulent mixing process. An interesting non‐linear feature was found for turbulent mixing for frequently occurring wind speeds and low wind speed cases, where the 2 m temperature increases for decreased amounts of mixing.
Applicability of the Rayleigh‐Gans approximation for scattering by snowflakes at microwave frequencies in vertical incidence
Authors: Tyynelä J. , Leinonen J. , Westbrook C. D. , Moisseev D. , Nousiainen T.
Published: April 2013

The applicability of the Rayleigh‐Gans approximation (RGA) for scattering by snowflakes is studied in the microwave region of the electromagnetic spectrum. Both the shapes of the single ice crystals, or monomers, and their amounts in the modeled snowflakes are varied. For reference, the discrete‐dipole approximation (DDA) is used to produce numerically accurate solutions to the single‐scattering properties, such as the backscattering and extinction cross‐sections, single‐scattering albedo, and the asymmetry parameter. We find that the single‐scattering albedo is the most accurate with only about 10% relative bias at maximum. The asymmetry parameter has about 0.12 absolute bias at maximum. The backscattering and extinction cross‐sections show about − 65% relative biases at maximum, corresponding to about − 4.6 dB difference. Overall, the RGA agrees well with the DDA computations for all the cases studied and is more accurate for the integrated quantities, such as the single‐scattering albedo and the asymmetry parameter than the cross‐sections for the same snowflakes. The accuracy of the RGA seems to improve, when the number of monomers is increased in an aggregate, and decrease, when the frequency increases. It is also more accurate for less dense monomer shapes, such as stellar dendrites. The DDA and RGA results are well correlated; the sample correlation coefficients of those are close to unity throughout the study. Therefore, the accuracy of the RGA could be improved by applying appropriate correction factors.