地基双波长偏振激光雷达对格尔木地区卷云观测的个例研究

中国科学院大气物理研究所研制了一台双波长偏振激光雷达,在格尔木市气象局进行了为期一年的不连续观测。本文选择了其中一天的观测个例,分别从雷达硬件结构、数据类型、数据处理方法等方面进行了系统的介绍和分析。结果表明,此次观测个例中,卷云位于地表以上4.7 km~7 km处,光学厚度均小于0.1,532 nm和1064 nm上的平均激光雷达比分别为24.3 Sr(激光雷达比)和29.9 Sr,色比多集中在0.8~1之间,此外532 nm波长上的退偏比多集中在0.25~0.3之间。此雷达对高空卷云能进行有效探测,为下一步研究青藏高原地区卷云长期时空分布特征奠定基础。     

Observations of the temperature and polarization anisotropies with Boomerang 2003

The Boomerang experiment completed its final long duration balloon (LDB) flight over Antarctica in January 2003. The focal plane was upgraded to accommodate four sets of 145 GHz polarization sensitive bolometers (PSBs), identical to those to be flown on the Planck HFI instrument. Approximately, 195 hours of science observations were obtained during this flight, including 75 hours distributed over 1.84% of the sky and an additional 120 hours concentrated on a region covering 0.22% of the sky. We derive the angular power spectra of the cosmic microwave background (cmb) temperature and polarization anisotropies from these data. The temperature anisotropies are detected with high signal to noise on angular scales ranging from several degrees to 10 arcminutes. The curl-free (EE) component is detected at 4.8σ, and a two-sigma upper limit on the curl (BB) component of 8.6 μK² is obtained on scales corresponding to 0.5°. Both the temperature and polarization anisotropies are found to be consistent with a concordance ΛCDM cosmology that is seeded by adiabatic density perturbations. In addition to the cmb observations, Boomerang03 surveyed a 300 square degree region centered on the Galactic plane. These observations represent the first light for polarization sensitive bolometers, which are currently operational in two South-Pole based polarimeters, as well as Planck HFI, at frequencies ranging from 100 to 350 GHz (3 mm to 850 μm).     

Improving the Wishart Synthetic Aperture Radar image classifications through Deterministic Simulated Annealing

This paper proposes the use of Deterministic Simulated Annealing (DSA) for Synthetic Aperture Radar (SAR) image classification for cluster refinement. We use the initial classification provided by the maximum-likelihood classifier based on the complex Wishart distribution that is then supplied to the DSA optimization approach. The goal is to improve the classification results obtained by the Wishart approach. The improvement is verified by computing a cluster separability coefficient. During the DSA optimization process, for each iteration and for each pixel, two consistency coefficients are computed taking into account two kinds of relations between the pixel under consideration and its neighbors. Based on these coefficients and on the information coming from the pixel itself, it is re-classified. Several experiments are carried out to verify that the proposed approach outperforms the Wishart strategy. We try to improve the classification results by considering the spatial influences received by a pixel through its neighbors. Finally, a link about the contribution of DSA to thematic mapping is also established.     

张家口-渤海地震带与山西地震带交汇区的地壳剪切波分裂

张家口—渤海地震带(简称张渤地震带)与山西地震带交汇区域(113°E～117°E,39°N～42°N)是华北地区北部三个构造单元华北沉降、燕山隆起和太行山隆起的交界处.本文采用张渤带西端的流动地震台网和华北地区北部的区域数字地震台网的地震波形数据,使用SAM方法对该区域地壳介质剪切波分裂参数进行研究.结果表明,北部的燕...     

电偶源频率电磁测深激发极化效应研究

本文研究含激电效应(IP)电偶源频率电磁测深问题.首先,通过对电偶源频率电磁测深电磁场分量分辨率的分析,提出利用电场Ex分量提取IP信息的合理性;然后,给出了同时存在激电和电磁效应时的理论计算公式和算法,对一些典型地电断面进行理论计算并对计算结果进行分析;最后,提出提取IP信息的几种可能方案.这些工作不仅为野外实测资料...     

平面平行大气中偏振辐射传输的数值计算

利用离散纵坐标(DISORT)法的基本原理,开发了平面平行大气中偏振辐射传输的数值计算模型,并利用解析插值原理实现了对任意天顶方向散射斯托克斯参量的求解.为检验计算模型的可靠性,分别针对分子和气溶胶散射大气进行了数值模拟,并与Coulson等1960年、Garcia等1989年的计算结果进行了比较.结果表明,模型计算结...     

The polarization-free approximation applied to multi-level non-LTE radiative transfer

The polarization-free (POF) approximation (Trujillo Bueno and Landi Degl'Innocenti, 1996) is capable of accounting for the approximate influence of the magnetic field on the statistical equilibrium, without actually solving the full Stokes vector radiative transfer equation. The method introduces the Zeeman splitting or broadening of the line absorption profile I in the scalar radiative transfer equation, but the coupling between Stokes I and the other Stokes parameters is neglected. The expected influence of the magnetic field is largest for strongly-split strong lines and the effect is greatly enhanced by gradients in the magnetic field strength. Formally the interaction with the other Stokes parameters may not be neglected for strongly-split strong lines, but it turns out that the error in Stokes I obtained through the POF approximation to a large extent cancels the neglect of interaction with the other Stokes parameters, so that the resulting line source functions and line opacities are more accurate than those obtained with the field-free approach. Although its merits have so far only been tested for a two-level atom, we apply the POF approximation to multi-level non-LTE radiative transfer problems on the premise that there is no essential difference between these two cases. Final verification of its validity in multi-level cases still awaits the completion of a non-LTE Stokes vector transfer code.For two realistic multi-level cases (CaII and MgI in the solar atmosphere) it is demonstrated that the POF method leads to small changes, with respect to the field-free method, in the line source functions and emergent Stokes vector profiles (much smaller than for a two-level atom). Real atoms are dominated by strong ultraviolet lines (only weakly split) and continua, and most lines with large magnetic splitting (in the red and the infrared) are at higher excitation energies, i.e. they are relatively weak and unable to produce significant changes in the statistical equilibrium. We find that it is generally unpredictable by how much the POF results will differ from the field-free results, so that it is nearly always necessary to confirm predictions by actual computations.The POF approximation provides more reliable results than the field-free approximation without significantly complicating the radiative transfer problem, i.e. without solving any extra equations and without excessive computational resource requirements, so that it is to be preferred over the field-free approximation.     

Characteristics of the linear polarization observed in the 16 May 1991 solar flare

In a search for linear polarization effects, 37 profiles of the H line emitted in the 16 May 1991 flare have been analyzed. Linear polarization is clearly present in the central part of line. On average, the degree of polarization is 7 %, but it reaches 20 % in regions with lower H _ga emission. Generally the orientation of the plane of polarization coincides with the flare to disk center direction, except for sections where the H _ga line has the characteristic form observed in moustaches. We believe that the linear polarization observed in the 16 May 1991 flare was caused by bombardment of the chromosphere by beams of accelerated particles, protons in the main part of the flare and electrons at locations where the H _ga line has the characteristic moustache structure.     

唐山地区剪切波分裂研究

本文利用唐山地区的数字化地震资料,研究了唐山地区的剪切波分裂现象。通过对唐山强地面运动台网中七个台的三分向数字化记录资料的研究发现,1982—1984年发生的大部分地震都有较明显的S波分裂现象。七个台站的初至分裂S波的极化方向都在近东西方向,这与该地区的主压应力场方向相一致。各台慢S波延时的平均值在0.005—0.008s/km之间,由此可以粗略地估计得到各个台站的裂纹密度为:0.019(TS01,TS02,TS15),0.015(TS03,TS07,TS18)和0.024(T19)。     

大气重力波产生的大尺度赤道电离层扰动

本文研究了大气重力波产生的大尺度赤道电离层扰动的性质．当重力波的传播方向与磁场方向倾斜相交时，重力波在Ｆ区产生行进电离层扰动．当重力波垂直于磁场传播时，能触发等离子体Ｒａｙｌｅｉｇｈ－Ｔａｙｌｏｒ不稳定性，形成大尺度赤道扩展Ｆ不均匀体．重力波引起的扩展Ｆ主要出现于晚上，行进电离层扰动则可能出现于任何时间．本文建立了行进电离层扰动和大尺度赤道扩展Ｆ的统一理论模型，深入全面地揭示了电离层扰动的性质．