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Ü. Rannik T. Markkanen J. Raittila P. Hari T. Vesala 《Boundary-Layer Meteorology》2003,109(2):163-189
Observations of wind statistics within and above a Scots pine forest are comparedwith those predicted from an analytical second-order closure model. The roughnesssublayer (RSL) effects, and the influence of stability on similarity functions, arestudied using observations. The commonly accepted forms of similarity functionsdescribe the influence of diabatic effects above the RSL well. According to earlierstudies they are expected also to apply within the RSL. As an exception, the averagewind speed normalised with friction velocity was found to be invariant with stabilityclose to the canopy top under unstable conditions. Lagrangian stochastic trajectorysimulations were used to evaluate the influence of canopy turbulence profiles onfootprint prediction. The main uncertainty was found to arise from parameterisationof the random forcing term in the Lagrangian velocity equation. The influence ofdiabatic conditions was studied, and it was found that thermal stability affectssignificantly the footprint function above the forest canopy, but significantuncertainty exists because of uncertainties in the formulation of stability functions. 相似文献
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The Niger River is the third largest river in the African continent. Nine riparian countries share its basin, which rank all among the world’s thirty poorest. Existing challenges in West Africa, including endemic poverty, inadequate infrastructure and weak adaptive capacity to climate variability, make the region vulnerable to climate change. In this study, a risk-based methodology is introduced and demonstrated for the analysis of climate change impacts on planned infrastructure investments in water resources systems in the Upper and Middle Niger River Basin. The methodology focuses on identifying the vulnerability of the Basin’s socio-economic system to climate change, and subsequently assessing the likelihood of climate risks by using climate information from a multi-run, multi-GCM ensemble of climate projections. System vulnerabilities are analyzed in terms of performance metrics of hydroelectricity production, navigation, dry and rainy season irrigated agriculture, flooding in the Inner Delta of the Niger and the sustenance of environmental flows. The study reveals low to moderate risks in terms of stakeholder-defined threshold levels for most metrics in the 21st Century. The highest risk levels were observed for environmental flow targets. The findings indicate that the range of projected changes in an ensemble of CMIP3 GCM projections imply only relatively low risks of unacceptable climate change impacts on the present large-scale infrastructure investment plan for the Basin. 相似文献
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Ü. Ertan M. A. Alpar M. H. Erkut K. Y. Ekşi Ş. Çalışkan 《Astrophysics and Space Science》2007,308(1-4):73-77
The anomalous X-ray pulsar 4U 0142+61 was recently detected in the mid infrared bands with the SPITZER Observatory (Wang, Chakrabarty and Kaplan: Nature 440, 772 (2006)). This observation is the first instance for a disk around an AXP. From a reanalysis of optical and infrared data, we show that the observations indicate that the disk is likely to be an active disk rather than a passive dust disk beyond the light cylinder, as proposed in the discovering paper. Furthermore, we show that the irradiated accretion disk model can also account for all the optical and infrared observations of the anomalous X-ray pulsars in the persistent state. 相似文献
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Doğan Bülent Aşci Metin Karakaş Ahmet Pekşen Ertan Erener Arzu Çepni Murat Selim Yavuzyilmaz Selin Alahmad Mohammad Sertçelik Fadime Sertçelik İbrahim Kurtuluş Cengiz 《Natural Hazards》2021,109(2):1675-1716
Natural Hazards - The Northern Branch of the North Anatolian Fault System controls and deforms the Izmit Basin and the Sapanca Lake Basin in the study area. Unlike the Sapanca Lake Basin, the... 相似文献
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A. Y. Ertan O. Tumer Z. Tunca C. Ibanoĝlu M. Kurutac S. Evren 《Astrophysics and Space Science》1982,87(1-2):255-268
The eclípsing binary AR Lac has been observed in two colours,B andV, in 1980 and 1981. The new times of minimal obtained during the observatons indicate that the period of the system is still continuing its decrease. The wave-like distortions outside eclipses have two maxima and are very similar in shape in successive two years. 相似文献
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C. Ibanoĝlu S. Evren O. Tümer A. Y. Ertan Z. Tunca 《Astrophysics and Space Science》1983,95(2):409-416
Two-colour photoelectric observations of LX Per carried out at Ege University Observatory in 1981 and 1982 observing seasons are presented. The light curve of the system has a wave-like distortion which migrates towards the decreasing orbital phase. The period of the retrograde migration of the wave-like distortion has been determined as 475 days. The amplitude of the wave appears to change with time periodically. 相似文献
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S. Evren C. Ibanoglu O. Tümer Z. Tunca A. Y. Ertan 《Astrophysics and Space Science》1983,95(2):401-408
In this paper we present the observations of AR Lac, which were obtained in 1982. The variations in the light curves, occurred in the time interval as short as two months, indicated that the system was very active in 1982 like in 1979. The times of the minima obtained in this study indicate that the orbital period of the system continues to decrease. The decrease in the period was recalculated using all the times of minima obtained photoelectrically between 1961 and 1982 and found to be 17.0±1.4 s century?1. 相似文献
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