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41.
1991年夏,我们利用自制的单站闪电探测及定位系统(M—LDARS),在北京地区进行了对比实验,并对所记录的地闪回击信号作了分析。本文提出了我们得到的北京地区云地闪回击信号的峰值时间、半峰时间、峰值电流以及电流上升率的统计分布和频谱特征的典型结果,并与国内外同类观测的结果进行了对比。 相似文献
42.
Observations obtained over a glacier surface in a predominantlykatabatic flow and with a distinctwind maximum below 13-m height are presented. The data werecollected using a 13-m high profilemast and two sonic anemometers (at about 2.5-m and 10-m heights).The spectra at frequencies belowthat of the turbulence range appear to deviate considerably fromthe curves obtained by Kaimal andco-workers during the 1968 Kansas experiment. The characteristicsof these deviations are compared tothe observations of others in surface-layers disturbed by anykind of large-scale outer-layer (orinactive) turbulence. In our case the disturbances arelikely to be induced by the highmountain ridges that surround the glacier. Moreover, the deviationsobserved in the cospectra seemto result from an, as yet, unspecified interaction between theinactive outer-layer turbulenceand the local surface-layer turbulence. Near the distinctwind maximum turbulence production ceasedwhile turbulence itself did not, probably the result ofturbulence transport from other levels. Consequently, we studied thelocal similarity relations using w instead of u* as an alternative velocity scale. Wellbelow the wind maximum, and for relatively low stability(0< Rig <0.2), the flow behaves accordingto well established local-scaling similarity relationshipsin the stable boundary layer. For higherstability (Rig > 0.2), and near or above the wind maximum, the boundary-layer structure conforms tothat of z-less stratification suggesting that the eddy sizeis restricted by the local stability ofthe flow. In line with this we observed that the sensibleheat fluxes relate remarkably well to thelocal flow parameters. 相似文献
43.
欧亚大陆山地垂直带数字集成系统的设计与应用 总被引:1,自引:0,他引:1
在欧亚大陆山地垂直带880个带谱点数据采集的基础上,设计和开发了山地垂直带数字集成系统。其功能:(1)垂直带谱可视化显示功能:实时生成垂直带地理分布图、垂直带堆积柱状图、上下限高度随经纬度变化曲线;(2)垂直带上下限提取和绝对高度和相对高度转化功能:提取山地垂直自然带分布上限和下限高度,进行垂直带的宽度和垂直带上限海拔... 相似文献
44.
福建省海岸带泥沙分布的气象卫星遥感监测 总被引:3,自引:0,他引:3
根据水体对太阳辐射光谱的反射率变化特性,利用NOAA极轨气象卫星遥感资料,动态监测福建省海岸带悬浮泥沙的分布,并从十几幅质量较好的不同时相的泥沙分布图中得出初步的监测结果。 相似文献
45.
系统地总结和讨论了固体硼氧酸盐11BMASNMR和硼氧酸盐水溶液11BNMR波谱学研究结果。对于固体硼氧酸盐11BMASNMR谱.虽然可以从中定量计算BO3与BO4比值,但因为11B化学位移变化小,很难将配位多面体与它们的配位环境相联系,用其作为表征固体硼氧酸盐尚缺少特征性。而对于硼氧酸盐水溶液11BNMR谱,由于在NMR谱仪时间规模下一些硼氧酸盐阴离子中不同化学位置上B核交换速率影响,在11BNMR波谱上没有观察到信号。实践证明,溶液11BNMR波谱与Raman光谱的联合使用,将是研究水溶液中硼氧酸盐阴离子结合最直接和有力的手段。 相似文献
46.
We discuss the accuracy requirements for measuring mesoscale (roughly horizontal scales > 10 km or 5 to 10 times the planetary
boundary-layer (PBL) depth) fluxes in the convective PBL, and the ability of current research aircraft to achieve this accuracy.
We conclude that aircraft equipped with inertial nagivation systems capable of < 3 km hr−1 navigational accuracy are able to resolve mesoscale fluctuations in velocity, and thus variances and fluxes on the mesoscale.
We then discuss measurements of velocity and scalar spectra, and cospectra of vertical velocity with horizontal velocity components
and scalars, obtained from long flight legs with the National Center for Atmospheric Research Electra aircraft over the boreal
forest of Canada in summer during the BOreal Ecosystem-Atmosphere Study (BOREAS), over the tropical Pacific Ocean from the
Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), and over the East China Sea during
wintertime cold-air outbreaks from the Air Mass Transformation Experiment (AMTEX). Each of these studies has somewhat different
forcings and boundary conditions, so we can compare their consequences on the spectra and cospectra. On average, we found
no significant scalar or momentum fluxes for horizontal scales > 10 km. We also develop a simple model based on observed
thermal structure to explain the phase angle between vertical velocity and the along-wind horizontal velocity as a function
of height, which shows good agreement with the observed phase angle in AMTEX.
The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
47.
Profile and eddy-correlation (heights of 4 and 10 m) measurements performed on the Pasterze glacier (Austria) are used to study the characteristics of the stable boundary layer under conditions of katabatic and large-scale forcing. We consider cases where large-scale forcing results in a downslope (or following) ambient wind. The analysis of averaged spectra and cospectra reveals low frequency perturbations that have a large influence on the variances of temperature and horizontal wind components and also alter the cospectra of momentum and sensible heat flux. Only the spectrum of the vertical wind speed is comparable to universal spectra. The low frequency perturbations occur as brief intermittent events and result in downward entrainment of ambient air thereby producing enhanced downward sensible heat fluxes and downward as well as upward momentum fluxes with various magnitudes and timescales. After the variances were high pass filtered, the normalised standard deviations of wind speed and temperature compare favourably to findings in the literature within the range 0>z/L>0.5. For larger z/L they deviate as a result of an increased influence from low frequency perturbations and thus non-stationarity. In line with this, the turbulent kinetic energy budget (at 4 m height) indicates that production (shear) is in balance with destruction (buoyancy and dissipation) within the range 0>z/L>0.3. Non-dimensional gradients of wind speed within the range 0>z/L>0.3 have a slope of about 3.5. The scatter for the dimensionless temperature gradient is quite large, and the slope is comparable to that for wind speed gradients. For z/L>0.3 the imbalance in the turbulent kinetic energy budget grows and non-dimensional gradients for wind speed and temperature deviate considerably from accepted values as a result of increased non-stationarity. Average roughness lengths for momentum and sensible heat flux derived from wind speed and temperature profiles are respectively 1 × 10-3 m and 6 × 10-5 m, consistent with the literature. The ratio (z0h/z0m) compares to those predicted by surface renewal models. A variation of this ratio with the roughness Reynolds number is not indicated by our data. 相似文献
48.
A. G. Nikoghossian 《Astrophysics》2007,50(1):94-104
This paper is devoted to a determination of the statistical mean quantities describing spectral line radiation of dynamically
active stochastic and multicomponent atmospheres. The lines in LTE are considered so that the effects of multiple scattering
can be neglected. Two types of problem are discussed. In the first it is assumed that the realization of one or another type
of nonthermal motion depends on the type of structural element and in the other this type of dependence is absent, i.e., it
is supposed that the assumed random values of the velocity are distributed according to a law that is common to all the components.
Particular attention is paid to a determination of the relative mean square deviation of the intensity of the observed radiation.
It appears that the distinctive feature of the relative mean square deviation of the radiation in a line formed in a dynamically
active stochastic atmosphere is local “spikes” (maxima) in the wings of the line. The theoretical results in this paper are
compared with spectral observations of quiescent solar prominences obtained in framework of the SOHO space mission.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 121–134 (February 2007). 相似文献
49.
Javier Garcia-Guinea E. Crespo-Feo V. Correcher J. Rubio M. V. Roux P. D. Townsend 《Physics and Chemistry of Minerals》2009,36(8):431-438
Natural hydrothermal ZnCO3 crystal aggregates are nominally anhydrous phases with interfacial water, with substitutional divalent cations and decarbonation
c. 300°C. All these common features must be involved during the experimental heating of a thermoluminescence (TL) glow curve
up to 500°C: dehydration–dehydroxylation, phase transition and ion transition of point defects in Zn2+ positions. A representative specimen of natural smithsonite was analysed by X-ray fluorescence spectrometry, field emission
scanning electron microscopy (FESEM) with a chemical probe of energy dispersive spectrometer, high temperature in situ X-ray
diffraction, differential scanning calorimetry, differential thermal analyses coupled to thermogravimetry, TL, radioluminescence
and high resolution spectra thermoluminescence (3DTL), to gain an overview of the spectra emission and defects linkages modified
by heating from room temperature up to 500°C. The ZnCO3 specimen contains minor amounts of Ca, Cu, Cr, Cd, Pb, Ce, Co, Ni, Mn and Fe. Under FESEM, it displays CaCO3 clusters and oscillatory zoning distribution with lamellae ranging from Ca0.11Zn0.89 to Ca0.19Zn0.81. The analytical results suggest assignments of defects and processes to measured 3DTL emission bands, as follows: (1) peak
at ~260°C, ~360 nm bonds, breaking during the thermal decarbonation process; (2) peak ~120°C, ~340 nm: non-bridging oxygen
centres associated to a complex dehydration–dehydroxylation process and (3) peak at ~170°C, ~650 nm, crystal field effects
on the thermoluminescence of Mn2+ centres and associated transitional elements in the ZnCO3 phase.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
50.
利用沿井剖面滑动时窗内的FFT和最大熵谱估计算法,选择合适的滤波器、窗长和步长,从测井曲线中分析出了Milankovitch周期.研究了波长比,谱峰等特征与周期的关系,确定出沉积速率的渐变与突变,求出了沉积速率,经分析,与岩性结果相符合. 相似文献