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Using the Twentieth Century Reanalysis to assess climate variability for the European wind industry  [PDF]
Philip E. Bett,Hazel E. Thornton,Robin T. Clark
Physics , 2014, DOI: 10.1007/s00704-015-1591-y
Abstract: We characterise the long-term variability of European near-surface wind speeds using 142 years of data from the Twentieth Century Reanalysis (20CR), and consider the potential of such long-baseline climate data sets for wind energy applications. The low resolution of the 20CR would severely restrict its use on its own for wind farm site-screening. We therefore perform a simple statistical calibration to link it to the higher-resolution ERA-Interim data set (ERAI), such that the adjusted 20CR data has the same wind speed distribution at each location as ERAI during their common period. Using this corrected 20CR data set, wind speeds and variability are characterised in terms of the long-term mean, standard deviation, and corresponding trends. Many regions of interest show extremely weak trends on century timescales, but contain large multidecadal variability. Since reanalyses such as ERAI are often used to provide the background climatology for wind farm site assessments, but contain only a few decades of data, our results can be used as a way of incorporating decadal-scale wind climate variability into such studies, allowing investment risks for wind farms to be reduced.
PARTICLE ACCELERATION IN THE COLLIDING WIND BINARY WR 140
J. M. Pittard,S. M. Dougherty
Revista mexicana de astronomía y astrofísica , 2008,
Abstract: Los sistemas de estrellas masivas WR+O presentan un plasma a alta temperatura, calentado por shocks, en la regi′on donde el viento de la estrella WR colisiona con el de su compa nera binaria o regi′on de colisi′on de vientos (WCR). La WCR es una fuente de emisi′on t′ermica (por ejemplo, rayos X duros) y no-t′ermica (emisi′on sincrotr′on). Esta ′ultima surge de electrones y iones acelerados a energ′ as relativistas. Estas binarias de vientos en colisi′on constituyen un laboratorio excelente para estudiar la aceleraci′on de part′ culas a masas y densidades de energ′ a fot′onica y magn′etica mayores que las que existen en remanentes de supernovas. Los modelos recientes de emisi′on no-t′ermica en WR 140 han ayudado al entendimiento de este proceso.
Seasonal Variability of Wind Climate in Hungary
PéLINé NéMETH, Csilla,RADICS, Kornélia,BARTHOLY, Judit
Acta Silvatica & Lignaria Hungarica , 2011,
Abstract: One of the most important effects of climate variability and climate change may comefrom changes in the intensity and frequency of climatic extremes. Responding to the need of newclimatologic analyses, complex wind field research was carried out to study and provide reliableinformation about the state and variability of wind climate in Hungary. First of all, special attentionwas paid on creation of a high quality, homogeneous data series. The research is based on 36-yearlong(1975–2010) wind data series of 36 Hungarian synoptic meteorological stations. The means andextremes of near-surface wind conditions assist in estimating the regional effects of climate change,therefore a complex wind climate analysis was carried out. Spatial and temporal distribution of meanand extreme wind characteristics were estimated; wind extremes and trends were interpolated andmapped over the country. Furthermore, measured and ERA Interim reanalysis data were compared inorder to estimate the effects of regional climate change.
Proper motions of new dust in the colliding-wind binary WR 140  [PDF]
J. D. Monnier,P. G. Tuthill,W. C. Danchi
Physics , 2002, DOI: 10.1086/340005
Abstract: The eccentric WR+O binary system WR 140 produces dust for a few months at intervals of 7.94 yrs coincident with periastron passage. We present the first resolved images of this dust shell, at binary phases ~0.039 and ~0.055, using aperture masking techniques on the Keck-I telescope to achieve diffraction-limited resolution. Proper motions of approximately 1.1 milliarcsecond per day were detected, implying a distance ~1.5 kpc from the known wind speed. The dust plume observed is not as simple as the ``pinwheel'' nebulae seen around other WR colliding wind binaries, indicating the orbital plane is highly inclined to our line-of-sight and/or the dust formation is very clumpy. Follow-up imaging in the mid-infrared and with adaptive optics is urgently required to track the dust motion further, necessary for unambiguously determining the orbital geometry which we only partially constrain here. With full knowledge of the orbital elements, these infrared images can be used to reconstruct the dust distribution along the colliding wind interface, providing a unique tool for probing the post-shock physical conditions of violent astrophysical flows.
One decade of parallel fine (PM2.5) and coarse (PM10–PM2.5) particulate matter measurements in Europe: trends and variability
I. Barmpadimos, J. Keller, D. Oderbolz, C. Hueglin,A. S. H. Prév t
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: The trends and variability of PM10, PM2.5 and PMcoarse concentrations at seven urban and rural background stations in five European countries for the period between 1998 and 2010 were investigated. Collocated or nearby PM measurements and meteorological observations were used in order to construct Generalized Additive Models, which model the effect of each meteorological variable on PM concentrations. In agreement with previous findings, the most important meteorological variables affecting PM concentrations were wind speed, wind direction, boundary layer depth, precipitation, temperature and number of consecutive days with synoptic weather patterns that favor high PM concentrations. Temperature has a negative relationship to PM2.5 concentrations for low temperatures and a positive relationship for high temperatures. The stationary point of this relationship varies between 5 and 15 °C depending on the station. PMcoarse concentrations increase for increasing temperatures almost throughout the temperature range. Wind speed has a monotonic relationship to PM2.5 except for one station, which exhibits a stationary point. Considering PMcoarse, concentrations tend to increase or stabilize for large wind speeds at most stations. It was also observed that at all stations except one, higher PM2.5 concentrations occurred for east wind direction, compared to west wind direction. Meteorologically adjusted PM time series were produced by removing most of the PM variability due to meteorology. It was found that PM10 and PM2.5 concentrations decrease at most stations. The average trends of the raw and meteorologically adjusted data are 0.4 μg m 3 yr 1 for PM10 and PM2.5 size fractions. PMcoarse have much smaller trends and after averaging over all stations, no significant trend was detected at the 95% level of confidence. It is suggested that decreasing PMcoarse in addition to PM2.5 can result in a faster decrease of PM10 in the future. The trends of the 90th quantile of PM10 and PM2.5 concentrations were examined by quantile regression in order to detect long term changes in the occurrence of very large PM concentrations. The meteorologically adjusted trends of the 90th quantile were significantly larger (as an absolute value) on average over all stations ( 0.6 μg m 3 yr 1).
Wind Variability in BZ Camelopardalis  [PDF]
Kent Honeycutt,Stella Kafka,Jeff Robertson
Physics , 2013,
Abstract: (Shortened) Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on 9 nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm past results that the P-Cygni absorption components of the lines mostly evolve from a higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the Halpha line profile, whose velocities and durations strongly suggest that they are also due to the wind. We suggest that the progression from larger to smaller expansion velocities is due the higher velocity portions of a wind concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We also derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the HeI 5876AA line, finding P = 0.15353(4). Using this period the wind episodes in BZ Cam are found to be concentrated near inferior conjuction of the emission line source. This result confirms that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering time scales onto the wind events, as well as leading to an orbital modulation of the wind due to the non-axisymmetric nature of the stream/disk interaction.
Condition and development of wind energy in European Union
Roman Kisiel,Aleksander Wasiuta
Journal of Agribusiness and Rural Development , 2009,
Abstract: On conventional background of both Polish and European Union development of energy policy, an analysis was carried out of condition and perspectives of wind energy development in the context of renewable energetics, which as well as water energy is the fastest growing renewable energy field in industrialized countries all over the world. Based on different international and national sources, with taking into consideration statistical data and scientific literature, authors revealed upward trends in wind energetics as characteristic economic trend, irrefutable in modern European geopolitical conditions, current for Polish economy development and energy policy in context of overall approach to European Union energy policy. In the paper the role of wind energy development is presented as inherent Polish and European strategy of regional development, permanent and sustainable development, diversification of energy supply, gaining independence from manning the domain political.
First visual orbit for the prototypical colliding-wind binary WR 140  [PDF]
J. D. Monnier,Ming Zhao,E. Pedretti,R. Millan-Gabet,J. P. Berger,W. Traub,F. P. Schloerb,T. ten Brummelaar,H. McAlister,S. Ridgway,L. Sturmann,J. Sturmann,N. Turner,F. Baron,S. Kraus,A. Tannirkulam,P. M. Williams
Physics , 2011, DOI: 10.1088/2041-8205/742/1/L1
Abstract: Wolf-Rayet stars represent one of the final stages of massive stellar evolution. Relatively little is known about this short-lived phase and we currently lack reliable mass, distance, and binarity determinations for a representative sample. Here we report the first visual orbit for WR 140(=HD193793), a WC7+O5 binary system known for its periodic dust production episodes triggered by intense colliding winds near periastron passage. The IOTA and CHARA interferometers resolved the pair of stars in each year from 2003--2009, covering most of the highly-eccentric, 7.9 year orbit. Combining our results with the recent improved double-line spectroscopic orbit of Fahed et al. (2011), we find the WR 140 system is located at a distance of 1.67 +/- 0.03 kpc, composed of a WR star with M_WR = 14.9 +/- 0.5 Msun and an O star with M_O = 35.9 +/- 1.3 Msun. Our precision orbit yields key parameters with uncertainties times 6 smaller than previous work and paves the way for detailed modeling of the system. Our newly measured flux ratios at the near-infrared H and Ks bands allow an SED decomposition and analysis of the component evolutionary states.
Suzaku monitoring of the Wolf-Rayet binary WR140 around periastron passage: An approach for quantifying the wind parameters  [PDF]
Yasuharu Sugawara,Yoshitomo Maeda,Yohko Tsuboi,Kenji Hamaguchi,Michael Corcoran,A. M. T. Pollock,Anthony F. J. Moffat,Peredur M. Williams,Sean Dougherty,Julian Pittard
Physics , 2015, DOI: 10.1093/pasj/psv099
Abstract: Suzaku observations of the Wolf-Rayet binary WR 140 (WC7pd+O5.5fc) were made at four different times around periastron passage in 2009 January. The spectra changed in shape and flux with the phase. As periastron approached, the column density of the low-energy absorption increased, which indicates that the emission from the wind-wind collision plasma was absorbed by the dense W-R wind. The spectra can be mostly fitted with two different components: a warm component with kT=0.3--0.6 keV and a dominant hot component with kT~3 keV. The emission measure of the dominant, hot component is not inversely proportional to the distance between the two stars. This can be explained by the O star wind colliding before it has reached its terminal velocity, leading to a reduction in its wind momentum flux. At phases closer to periastron, we discovered a cool plasma component in a recombining phase, which is less absorbed. This component may be a relic of the wind-wind collision plasma, which was cooled down by radiation, and may represent a transitional stage in dust formation.
Causes of Greenland temperature variability over the past 4000 yr: implications for northern hemispheric temperature change  [PDF]
T. Kobashi,K. Kawamura,K. Goto-Azuma,J. E. Box
Climate of the Past Discussions , 2012, DOI: 10.5194/cpd-8-4817-2012
Abstract: A new Greenland temperature record reconstructed from argon and nitrogen isotopes from trapped air in a GISP2 ice core, provides high-resolution (<20 yr) and precise annual average temperature estimates for the past 4000 yr. Due to tight age-controls and abundant paleoclimatic information from the ice core, the temperature record provides an exceptional opportunity to investigate the late Holocene climate in a multi-decadal to millennial time scale. To investigate causes of Greenland temperature variability over the past 4000 yr, we calculated high latitude (70–80° N) temperature change using a one-dimensional energy balance model with reconstructed climate forcings including orbital, solar, volcanic, and greenhouse gas forcings. Greenland temperature was calculated from the high latitude temperature, considering Greenland's negative temperature responses to solar variability due to associated changes in atmospheric and oceanic circulations. The calculated Greenland temperature was significantly correlated with the ice-core-derived Greenland temperatures with the 97% confidence level. Therefore, the past variability of climate forcings can explain at least 10% of the multi-decadal to millennial variability in Greenland temperature over the past 4000 yr. An average temperature trend for the Northern Hemisphere (NH) over the past 4000 yr was also inferred from the ice-core derived Greenland temperatures. Lines of evidence indicate that the current decadal average temperature of NH is likely warmer than at any time over the past 4000 yr. Sequential cooling events starting around 800 B.C.E. (the 2.8 ka event), which were induced by several large volcanic eruptions as well as low solar activity, had similar magnitude with the Little Ice Age cooling.
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