近40年来甘肃省降水的变化特征   总被引：34，自引：10，他引：24  

林纾  陆登荣 《高原气象》2004,23(6):898-904

利用1960—2003年甘肃省59个测站逐日降水资料,研究了甘肃省四季和年降水量及雨日的气候变化特征。结果表明,平均年降水量和雨日的空间分布非常相似。河西和白银市的年降水量的趋势系数为正,省内其它地区为负;河西大部和甘南部分地区的年雨日的趋势系数为正,省内其它地区为负。线性倾向估计的结果表明,年降水量线性倾向值的零线基本以黄河为界,河西在增加,河东在减少,减少最明显的区域在徽县和康县盆地;雨日增加主要在河西西部偏南地区、沿祁连山的大部分地区及临夏以及甘南等海拔相对较高的地区,中部和陇东南的雨日在减少。雨日增多的地方降水量也在增加,反之亦然。全省年降水量和年雨日在1990年代均为低谷,而在21世纪初又都有上升趋势。降水量突变在1990年代中期;雨日突变河西在1960年代后期,河东在1970年代后期和1990年代中期。冬季降水量及雨日表现全省性大范围的增加趋势,秋季降水量及雨日亦呈全省性减少趋势;而春、夏季的降水量及雨日变化趋势则是地区性的。  相似文献   

青藏高原及邻近地区的气候特征   总被引：21，自引：5，他引：16  

白虎志  董文杰  马振锋 《高原气象》2004,23(6):890-897

利用中国710个站(青藏高原72个站)的气温和降水资料,分析了青藏高原的气候特征及与中国区域气候异常的联系。结果表明：中国多雨日区域随季节分布大致可以分为华南区、华南一青藏高原东南部区、青藏高原区以及华西区共5个区域,多雨日区自东向西移动。青藏高原东南地区降水特征呈双峰型,西北呈单峰型;西南部存在明显的“高原梅雨”、伏旱和秋雨。林芝地区的遥相关分析表明：冬季温度与青藏高原同期温度为正相关,与我国其它大部分地方为负相关;夏季降水与青藏高原南部和长江中下游地区同期降水为正相关,与高原北部同期降水呈反相关关系;冬季温度与黄河到长江流域之间区域夏季降水呈反相关关系。  相似文献   

EM Cygni: A study of its eclipse timings     

Sz. Csizmadia  Zs. Nagy  T. Borkovits  T. Hegedüs  I.B. Bír  Z.T. Kiss 《Astronomische Nachrichten》2008,329(1):39-43

EM Cygni is a Z Cam‐subtype eclipsing dwarf nova. Its orbital period variations were reported in the past but the results were in conflict to each other while other studies allowed the possibility of no period variation. In this study we report accurate new times of minima of this eclipsing binary and update itsO –C diagram.We also estimate the mass transfer rate in EM Cygni system and conclude that the mass transfer is far from the critical value. The mass transfer rate determined from the eclipse timings is in agreement with the spectroscopically determined value. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Molecular lines from protoplanetary nebulae: observations with ALMA     

Valentín Bujarrabal 《Astrophysics and Space Science》2008,313(1-3):209-214

Planetary nebulae (PNe) are formed in a very fast process. In just about 1000 years, the nebula evolves from a spherical and slowly expanding AGB envelope to a PN, with usually axial symmetry and high axial velocities. Molecular lines are known to probe most of the nebular material in young PNe and protoplanetary nebulae (PPNe), and are therefore very useful to study such an impressive evolution. Many quantitative results on these objects have been so obtained, including general structure, total mass and density distribution, kinetic temperatures, velocity fields, etc. Existing observations probe both the gas accelerated by post-AGB shocks and the quiescent components. But the study of crucial regions to understand PN formation (recently shocked shells, regions heated by the stellar UV and inner rotating disks) requires observations at higher frequency and with better spatial resolution.   相似文献   

Investigation on piezoelectric lead zirconate titanate detector bombarded obliquely with hypervelocity iron particles     

S. Takechi  T. Onishi  T. Miyachi  N. Hasebe  K. Nogami  S. Sasaki  T. Iwai  R. Srama 《Planetary and Space Science》2008,56(9):1309-1313

A cosmic dust detector for use onboard a satellite is currently being constructed from piezoelectric lead zirconate titanate (PZT). The characteristics of the PZT detector were studied by bombarding it with hypervelocity iron particles, which were supplied by a Van de Graaff accelerator. There was a linear relationship between the rise time of the signal observed from the detector and the particle's velocity, which was above 10 km/s on impact. It was also found that the rise time was almost independent of the collisional angle between the particles and the PZT surface within the limits of the particle's parameters used in this experiment.  相似文献   

The Norma cluster (ACO 3627) – I. A dynamical analysis of the most massive cluster in the Great Attractor     

P. A. Woudt  R. C. Kraan-Korteweg  J. Lucey  A. P. Fairall  S. A. W. Moore 《Monthly notices of the Royal Astronomical Society》2008,383(2):445-457

A detailed dynamical analysis of the nearby rich Norma cluster (ACO 3627) is presented. From radial velocities of 296 cluster members, we find a mean velocity of 4871 ± 54 km s⁻¹ and a velocity dispersion of 925 km s⁻¹. The mean velocity of the E/S0 population (4979 ± 85 km s⁻¹) is offset with respect to that of the S/Irr population (4812 ± 70 km s⁻¹) by  Δ v = 164 km s⁻¹  in the cluster rest frame. This offset increases towards the core of the cluster. The E/S0 population is free of any detectable substructure and appears relaxed. Its shape is clearly elongated with a position angle that is aligned along the dominant large-scale structures in this region, the so-called Norma wall. The central cD galaxy has a very large peculiar velocity of 561 km s⁻¹ which is most probably related to an ongoing merger at the core of the cluster. The spiral/irregular galaxies reveal a large amount of substructure; two dynamically distinct subgroups within the overall spiral population have been identified, located along the Norma wall elongation. The dynamical mass of the Norma cluster within its Abell radius is  1–1.1 × 10¹⁵  h ⁻¹₇₃ M_⊙  . One of the cluster members, the spiral galaxy WKK 6176 which recently was observed to have a 70 kpc X-ray tail, reveals numerous striking low-brightness filaments pointing away from the cluster centre suggesting strong interaction with the intracluster medium.  相似文献   

The old metal-poor open cluster ESO 92-SC05: accreted from a dwarf galaxy?     

S. Ortolani †  E. Bica  B. Barbuy 《Monthly notices of the Royal Astronomical Society》2008,388(2):723-728

The study of old open clusters outside the solar circle can bring constraints on formation scenarios of the outer disc. In particular, accretion of dwarf galaxies has been proposed as a likely mechanism in the area. We use BVI photometry for determining fundamental parameters of the faint open cluster ESO 92-SC05. Colour–magnitude diagrams are compared with Padova isochrones, in order to derive age, reddening and distance. We derive a reddening   E ( B − V ) = 0.17  , and an old age of ∼6.0 Gyr. It is one of the rare open clusters known to be older than 5 Gyr. A metallicity of   Z ∼ 0.004  or  [M/H]∼−0.7  is found. The rather low metallicity suggests that this cluster might be the result of an accretion episode of a dwarf galaxy.  相似文献   

The High-Resolution Solar Reference Spectrum between 250 and 550 nm and its Application to Measurements with the Ozone Monitoring Instrument     

Marcel Dobber  Robert Voors  Ruud Dirksen  Quintus Kleipool  Pieternel Levelt 《Solar physics》2008,249(2):281-291

We have constructed a new high resolution solar reference spectrum in the spectral range between 250 and 550 nm. The primary use of this spectrum is for the calibration of the Dutch – Finnish Ozone Monitoring Instrument (OMI), but other applications are mentioned. The incentive for deriving a new high resolution solar reference spectrum is that available spectra do not meet our requirements on radiometric accuracy or spectral resolution. In this paper we explain the steps involved in constructing the new spectrum, based on available low and high resolution spectra and discuss the main sources of uncertainty. We compare the result with solar measurements obtained with the OMI as well as with other UV-VIS space-borne spectrometers with a similar spectral resolution. We obtain excellent agreement with the OMI measurements, which indicates that both the newly derived solar reference spectrum and our characterization of the OMI instrument are well understood. We also find good agreement with previously published low resolution spectra. The absolute intensity scale, wavelength calibration and representation of the strength of the Fraunhofer lines have been investigated and optimized to obtain the resulting high resolution solar reference spectrum.  相似文献   

Gravity and effective temperature distribution on the surface of contact binary systems     

S. Tsantilas  H. Rovithis‐Livaniou 《Astronomische Nachrichten》2008,329(6):596-601

The aim of this work is to study the gravity and the effective temperature distribution on the outer equipotential surface of a contact binary. In particular, the lines of constant g, (the iso‐g curves), are computed and plotted on the outer surface C_s of contact configurations. Since the gravity distribution would also specify the effective temperature distribution on the binary's common photosphere through the gravity darkening effect, these lines correspond to isothermals too. Applications have been made to two contact binaries; namely, to AW UMa and OO Aql, two systems with very different mass ratios. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Reanalysis of the Historic AFTAC Bolide Infrasound Database     

Douglas O. ReVelle  Elizabeth A. Sukara  Wayne N. Edwards  Peter G. Brown 《Earth, Moon, and Planets》2008,102(1-4):337-344

We have recently digitized and partially reanalyzed the historic bolide infrasonic database. These 10 events were originally detected by the U.S. Air Force Technical Applications Center (AFTAC) from ∼1960 to 1974. In this paper we present the first preliminary reanalysis results for two of the 10 bolide events, namely the Revelstoke bolide of 3/31/1965 as well as the Prince Edward Islands (P.E.I). S. African bolide of 8/03/1963, which were among the largest bolides detected during this time period. These bolides have been investigated initially since they are most likely to have had a significant effect on the computed global influx rate of ReVelle (Global Infrasonic Monitoring of Large Bolides, pp 483–490, 2001) as indicated in Brown et al. (Nature, 420:314–316, 2002). We are in the process of recomputing all relevant infrasonic propagation quantities such as plane wave back azimuth, signal velocities, power spectra, spectrograms, as well as energy estimates using multiple techniques. In a future paper we will present a complete digital reanalysis of the AFTAC bolide infrasonic data and its final resulting global bolide influx implications.  相似文献