风廓线雷达资料在暴雨天气过程特征分析中的应用     

董保举  付志嘉  李明  杨艳军 《气象科技》2012,40(1):74-78

为了研究风廓线雷达在暴雨天气过程预报中的作用,对2008年6月1日至6月2日云南大理发生的一次暴雨过程进行研究。结果表明,降水前三维风的脉动变化较大,水平风在垂直方向上存在风速切变,最大探测高度明显升高;降水期间可以对降水性质进行判断;降水期间功率谱密度出现双峰谱,能测出垂直气流速度及下降粒子速度,通过这样的分析,便于开展更深层次的降水物理过程研究。  相似文献   

Turbulent Intensities and Velocity Spectra for Bare and Forested Gentle Hills: Flume Experiments   总被引：1，自引：1，他引：0  

Davide Poggi  Gabriel G. Katul 《Boundary-Layer Meteorology》2008,129(1):25-46

To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted above a bare surface while the second experiment was conducted within and above a densely arrayed rod canopy. The velocity variances and spectra from these two experiments were compared in the middle, inner, and near-surface layers. In the middle layer, and for the canopy surface, longitudinal and vertical velocity variances () were in phase with the hill-induced spatial mean velocity perturbation (Δu) around the so-called background state (taken here as the longitudinal mean at a given height) as predicted by rapid distortion theory (RDT). However, for the bare surface case, and remained out of phase with Δu by about L/2, where L is the hill half-length. In the canopy layer, wake production was a significant source of turbulent energy for , and its action was to re-align velocity variances with Δu in those layers, a mechanism completely absent for the bare surface case. Such a lower ‘boundary condition’ resulted in longitudinal variations of to be nearly in phase with Δu above the canopy surface. In the inner and middle layers, the spectral distortions by the hill remained significant for the background state of the bare surface case but not for the canopy surface case. In particular, in the inner and middle layers of the bare surface case, the effective exponents derived from the locally measured power spectra diverged from their expected  − 5/3 value for inertial subrange scales. These departures spatially correlated with the hill surface. However, for the canopy surface case, the spectral exponents were near  − 5/3 above the canopy though the minor differences from  − 5/3 were also correlated with the hill surface. Inside the canopy, wake production and energy short-circuiting resulted in significant departures from  − 5/3. These departures from  − 5/3 also appeared correlated with the hill surface through the wake production contribution and its alignment with Δu. Moreover, scales commensurate with Von Karman street vorticies well described wake production scales inside the canopy, confirming the important role of the mean flow in producing wakes. The spectra inside the canopy on the lee side of the hill, where a negative mean flow delineated a recirculation zone, suggested that the wake production scales there were ‘broader’ when compared to their counterpart outside the recirculation zone. Inside the recirculation zone, there was significantly more energy at higher frequencies when compared to regions outside the recirculation zone.  相似文献   

利用激发极化驰豫时间谱确定渗透率的实验研究   总被引：1，自引：1，他引：0  

童茂松  王伟男  范清华  姜亦忠  王荣  杜国同 《吉林大学学报(地球科学版)》2004,34(4):625-629

激发极化驰豫时间是孔隙大小的函数,采用奇异值分解方法对激发极化衰减曲线进行多指数反演,得到光滑的驰豫时间谱,该谱呈现多峰特性.实验结果表明,溶质对该谱的影响主要是由于溶质离子的扩散系数不同所致.对于同一块岩心,衰减谱随扩散系数的增大而向小驰豫时间方向移动.结合岩心地层因素F,研究了激发极化驰豫时间几何平均值Tg与岩石的渗透率K的关系,结果表明,logK和log(T1/2g/F)、log(Tg/F)呈现良好的线性关系.  相似文献   

Presence of LaO, ScO and VO Molecular Lines in Sunspot Umbral Spectra     

P. Sriramachandran  S. P. Bagare  N. Rajamanickam  K. Balachandrakumar 《Solar physics》2008,252(2):267-281

High-resolution Fourier Transform Spectrometer sunspot umbral spectra of the National Solar Observatory/National Optical Astronomy Observatory at Kitt Peak were used to detect rotational lines from 19 electronic transition bands of the molecules LaO, ScO and VO, in the wavenumber range of 11 775 to 20 600 cm⁻¹. The presence of lines from the following transitions is confirmed: A ² Π _r1/2 – X ² Σ ⁺(0, 0; 0, 1), A ² Π _r3/2 – X ² Σ ⁺(1, 0), B ² Σ ⁺ – X ² Σ ⁺(0, 0; 0, 1; 1, 0) and C ² Π _r1/2 – A′²Δ _r3/2(0, 0; 1, 1) of LaO; A ² Π _r3/2 – X ² Σ ⁺(0, 0), A ² Π _r1/2 – X ² Σ ⁺(0, 0) and B ² Σ ⁺ – X ² Σ ⁺(0, 0) of ScO; and C ⁴ Σ ⁻ – X ⁴ Σ ⁻(0, 1; 1, 0; 0, 2) and (2, 0) of VO. However, the presence of A ² Π _r3/2 – X ² Σ ⁺(0, 0) and C ² Π _r3/2 – A′²Δ _r5/2(0, 0; 1, 1) of LaO and C ⁴ Σ ⁻ – X ⁴ Σ ⁻(0, 0) of VO are found to be doubtful because the lines are very weak, and detections are difficult owing to heavy blending by strong rotational lines of other molecules. Equivalent widths are measured for well-resolved lines and, thereby, the effective rotational temperatures are estimated for the systems for which the presence is confirmed.  相似文献   

Lithium abundance in sunspots     

E. A. Baranovsky  V. P. Tarashchuk 《Bulletin of the Crimean Astrophysical Observatory》2008,104(1):19-25

The observations of lithium were carried out with the TST-2 telescope at CrAO on August 15–20, 2006. A sunspot model was calculated for the dates of observations. The lithium abundance in a sunspot and in the undisturbed photosphere was determined. It is log(N _Li) = 1.35 for the sunspot and log (N _Li) = 1.05 for the undisturbed photosphere.  相似文献   

张家口地震台和兴隆地震台地脉动信号初步分析   总被引：1，自引：0，他引：1  

张从珍  高景春  刁桂苓  赵英萍  宋梦真 《华北地震科学》2004,22(3):56-60

选取河北省张家口和兴隆2个台站的数字化地震仪连续1年,每日02～03时的地脉动记录,计算功率谱和自相关函数。结果发现兴隆台脉动谱中有4个比较突出的峰值,分别为0．3Hz、3Hz、8Hz、15Hz,张家口台只有3个峰值0．3Hz、3Hz、15Hz。兴隆台UD向的自相关函数呈现出一种比较典型的“红噪声”形态,EW向则呈现出负相关特征,认为可能是只作用于水平向的倾斜脉动的影响。小幅度的仪器干扰信号无论从脉冲标定还是地震波形中都很难发现的,而对脉动进行谱分析则很容易分辨。兴隆台和张家口台地脉动卓越周期时间曲线,基本集中在0．3秒,比较稳定。  相似文献   

ATMOSPHERIC TURBULENCE STRUCTURE AND SPECTRAL CHARACTERISTICS AT NEAR SURFACE LAYER ON TROPICAL COASTS     

邓雪娇  吴兑 《热带气象学报(英文版)》1997,3(1):27-34

By use of an observational experiment at the village of Tianwei, Haikou, Hainan province in 1990,characteristic turbulence values such as velocity component spectra and turbulence intensity are studied.The data were mostly obtained in cloudy condition, so that the stability parameter (L) and thermal flux (wt) did not vary diurnally while the turbulent energy and mean-temperature did. The basic characteristics of turbulence spectra are similar to those with fine weather, hems close to local isotropy in the inertial subrange. The velocity spectra agree with the law of "-2/3 th power"in Kolmogrov's similarity theory. The relationship between turbulent intensity of components δ_i/U (i=u,v,w) and stability Z/L is studied follow ins the Monim-Obukhov(M-O) similarity theory. It is shown that the two observe the law of "1/3 th power", though the turbulent intensity and energy are generally larger than those on the flat underlying topography.  相似文献   

极光粒子沉降研究:谱形式及其在极区大气中的传输   总被引：1，自引：0，他引：1       下载免费PDF全文

宗秋刚  付绥燕  濮祖荫  叶宗海  余彬 《极地研究》1999,11(3):203-220

分析了近年来南极地区极光沉降粒子的卫星、火箭、地面观测和研究结果,分别给出了极光椭圆区、极盖区、南大西洋异常区和极尖／极隙区粒子沉降的形式来源和特点。并根据磁尾研究的新进展,提出极光粒子沉降谱存在另外两种形式谱：（１）κ分布谱;（２）κ分布加上一个或多个脉冲谱,这两种谱来源于磁尾中性片区（绝热区非绝热区）。南极不同的区域,极光粒子有不同的沉降特点。这些沉降对极区电离层产生极大的影响。根据带电粒子在磁化大气中运动的Ｆｏｋｋｅｒ Ｐｌａｎｋ 方程,利用带电粒子在大气中传输的电离理论,导出极光粒子谱在极区大气中传播的解析表达式,对各种极光粒子谱在极区中的演化规律加以分析,并以此来解释在南极地区探测到的不同高度的极光电子谱的演化  相似文献   

A record of changing redox conditions in the northern Peru Basin during the Late Quaternary deduced from Mn/Fe and growth rate variations in two diagenetic manganese nodules     

A. Bollhfer  N. Frank  S. Rohloff  A. Mangini  J.C. Scholten 《Earth and Planetary Science Letters》1999,170(4):91-415

Two diagenetic manganese nodules from the Peru Basin were investigated by thermal ionization mass spectrometry and high resolution alpha spectrometry for uranium and thorium. The TIMS concentrations for nodule 62KD (63KG) vary as follows: 0.12–1.01 ppb (0.06–0.59) ²³⁰Th, 0.51–1.98 ppm (0.43–1.40) ²³²Th, 0.13–0.80 ppb (0.09–0.49) ²³⁴U, and 1.95–13.47 ppm (1.66–8.24) ²³⁸U. Both nodules have average growth rates of 110 mm per million years. However, from the variations of excess ²³⁰Th with depth we estimate partial accumulation rates which range from 50 to 400 mm per million years. The δ²³⁴U dating method cannot be applied due to remobilization of U from the sediment and subsequent incorporation into the nodules' crystal lattice, reflected by decay corrected δ²³⁴U values far above the ocean water value. Sections of fast nodule growth are related to those layers having high Mn/Fe ratios (up to 200) and higher densities. As a possible explanation we develop a scenario that describes similar glacial/interglacial trends in both nodules as a record of regional changes of sediment and/or deep water chemistry.  相似文献   

星叶石族矿物红外光谱研究   总被引：4，自引：0，他引：4  

李国武  马喆生  施倪承  N.A.Yamnova 《矿物学报》1999,19(1):9-14

在新测定的星叶石晶体结构资料的基础上,对星叶石矿物进行了详细和红外光谱研究,对比了单斜及三斜星叶石的红光谱特征,并对星叶石中工外吸收振动的归属问题进行了讨论。  相似文献