The Phoenix Evening Transition Flow Experiment (TRANSFLEX)     

Harindra J. S. Fernando  Brett Verhoef  Silvana Di Sabatino  Laura S. Leo  Seoyeon Park 《Boundary-Layer Meteorology》2013,147(3):443-468

Motivated by air quality and numerical modelling applications as well as recent theoretical advancements in the topic, a field experiment, dubbed transition flow experiment, was conducted in Phoenix, Arizona to study the evening transition in complex terrain (shift of winds from upslope to downslope). Two scenarios were considered: (i) the flow reversal due to a change of buoyancy of a cooled slab of air near the ground, and (ii) the formation of a transition front. A suite of in-situ flow, turbulence and particulate matter (PM) concentration sensors, vertically profiling tethered balloons and remote sensors were deployed, and a mesoscale numerical model provided guidance for interpreting observations. The results were consistent with the front formation mechanism, where it was also found that enhanced turbulence associated with the front increases the local PM concentration. During the transition period the flow adjustment was complex, involving the arrival of multiple fronts from different slopes, directional shear between fronts and episodic turbulent mixing events. The upward momentum diffusion from the incipient downslope flow was small because of stable stratification near the ground, and full establishment of downslope flow occurred over several hours following sunset. Episodic frontal events pose challenges to the modelling of the evening transition in complex terrain, requiring conditional parametrizations for subgrid scales. The observed increase of PM concentration during the evening transition has significant implications for the regulatory enforcement of PM standards for the area.  相似文献   

Functional clustering for Italian climate zones identification     

E. Di Giuseppe  G. Jona Lasinio  S. Esposito  M. Pasqui 《Theoretical and Applied Climatology》2013,114(1-2):39-54

This work presents a functional clustering procedure applied to meteorological time series. Our proposal combines time series interpolation with smoothing penalized B-spline and the partitioning around medoids clustering algorithm. Our final goal is to obtain homogeneous climate zones of Italy. We compare this approach to standard methods based on a combination of principal component analysis and Cluster Analysis (CA) and we discuss it in relation to other functional clustering approaches based on Fourier analysis and CA. We show that a functional approach is simpler than the standard methods from a methodological and interpretability point of view. Indeed, it becomes natural to find a clear connection between mathematical results and physical variability mechanisms. We discuss how the choice of the basis expansion (splines, Fourier) affects the analysis and propose some comments on their use. The basis for classification is formed by monthly values of temperature and precipitation recorded during the period 1971–2000 over 95 and 94 Italian monitoring stations, respectively. An assessment based on climatic patterns is presented to prove the consistency of the clustering and a comparison of results obtained with different methods is used to judge the functional data approach.  相似文献   

Impact assessment and protection of outstanding landscape integrity in a natural heritage site: Fairy valley, Kanas Nature Reserve, Xinjiang, China   总被引：1，自引：0，他引：1  

Fang Han  Zhaoping Yang  Xinyu Liu  Feng Di 《山地科学学报》2011,8(1):46-52

The essential purpose of the Convention Concerning the Protection of World Cultural and Natural Heritage is to protect the integrity of heritage values. Outstanding landscape is the core embodiment of the aesthetic value of a natural heritage site. This paper proposes a new assessment method from the point of view of the protection of heritage values. It is used to measure the degree of outstanding landscape integrity under the human and natural impact in natural heritage sites. This paper employ three indices, a visual index of outstanding landscape, a harmony index of the artificial landscape and a disturbance index of damaged landscape, to measure the impact of landscape integrity. The impact assessment model is based on a weighted combination of the three indices. The study site is the Fairy Valley, Kanas Nature Reserve, Xinjiang Uygur Autonomous Region in northwest China. The information employed is derived from field investigation and a Digital Elevation Model (DEM). A comprehensive evaluation of the Fairy valley was undertaken and it was determined that the outstanding landscape values are being compromised. Three protection methods are proposed to reduce the adverse effects and maintain landscape quality, thereby providing site managers with suggestions for the protection of natural heritage values. More broadly, the paper contributes novel methods of landscape assessment applicable to natural protected areas.  相似文献   

Hawking radiation from rotating AdS black holes in conformal gravity     

Shuang-Qing Wu  Gao-Ming Deng  Di Wu 《Astrophysics and Space Science》2014,352(2):751-762

We extend to study Hawking radiation via tunneling in conformal gravity. We adopt Parikh-Wilczek’s semi-classical tunneling method and the method of complex-path integral to investigate Hawking radiation from new rotating AdS black holes in conformal gravity. In this paper, the research on Hawking radiation from the rotating black holes is done in a general system, not limited in dragging coordinate systems any longer. Moreover, there existed some shortcomings in the previous derivation of geodesic equations. Different from the massless case, they used a different approach to derive the geodesic equation of the massive particles. Even the treatment was inconsistent with the variation principle of action. To remedy the shortcoming, we improve treatment to deduce the geodesic equations of massive and massless particles in a unified and self-consistent way. In addition, we also recover the Hawking temperature resorting to the complex-path integral method.  相似文献   

云南天文台太阳射电望远镜跟踪精度和定标精度     

纪树臣  陈国强  胡笛  黄占奎 《天文研究与技术》1992,(4)

本文采用天线方向图半功率宽度和曲线偏离度两种方法,测得自动跟踪精度为8小时偏差不超过0.°01。同时改进了定标精度的计算公式,并从理论上寻找误差原理后,再计算自动定标系统的检验值,从而大大地提高了观测精度。  相似文献   

Neutrino-Astronomy with the Macro Experiment at Gran Sasso     

A. Di Credico 《Astrophysics and Space Science》1997,258(1-2):99-104

The MACRO experiment at Gran Sasso is collecting muons since February 1989. These muons are induced by charged current interactions of atmospheric and, possibly, astrophysical muon neutrinos below the apparatus. A search has been made for discrete astrophysical sources of VHE and UHE neutrinos using the upward going muons direction information. Given the large area and the long period of data taking MACRO is, at the moment, able to set very competitive upper limits to the flux of neutrinos from most of the sources considered in the search. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

双点后方交会解算方法探讨     

金其坤  狄方贤  石锦昌 《地球科学与环境学报》1991,(4)

双点后方交会问题,中外专家学者已研究多年,发表了不少有关论文。本文利用坐标交换原理,提出了一种新的解算方法,并设计了计算表格,作了实例计算,推理简明,计算方便。  相似文献   

In memoriam—Giuseppe Martelli (1923–1994)     

Mario Di Martino  Paolo Paolicchi 《Planetary and Space Science》1994,42(12):1011-1012

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Simulation of hypervelocity impacts using a contact charge     

I. Giblin  G. Martelli  P.N. Smith  M. Di Martino 《Planetary and Space Science》1994,42(12):1027-1030

Two sets of hypervelocity impact experiments have been performed in the open using a contact charge technique and recorded using fast-framing cameras. It has been possible to record the uninterrupted ballistic trajectories of fragments from the catastrophically disrupted targets, together with their velocity and rotational properties directly after the impact, as well as their size. By performing these experiments in the open and on fairly soft ground, secondary fragmentation normally caused by impact onto the walls or floor of a test chamber has been minimised. A total of 10 experiments have been performed using targets of artificial rock which were either homogeneous, cored or carefully pre-fractured. We report here on the analysis of some of these data using a computer and special software written and developed by our group, with an indication of the results obtained.  相似文献   

Non-Spherical Sources of Strong Gravitational Fields Out of Hydrostatic Equilibrium     

L. Herrera  A. Di Prisco  J. Martínez 《Astrophysics and Space Science》2001,277(3):447-459

We describe the departure from equilibrium of matter distributions representing sources for a class of Weyl metric. It is shown that, for extremely high gravitational fields, slight deviations from spherical symmetry may weaken its tendency to a catastrophic collapse. For critical values of surface gravitational potential, in contrast with the exactly spherically symmetric case, the speed of entering the collapse regime decreases substantially, at least for specific cases. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献