电离层时空变化效应对星载及月基SAR成像影响:现状与展望     

陈锟山  许镇 《南京气象学院学报》2020,12(2):135-149

合成孔径雷达（SAR）作为一种主动传感器,具备全天时、全天候的观测能力,已广泛应用于对地观测中.然而,无线电信号在空间传播过程中会不可避免地受到电离层效应的影响,导致信号的相位、幅度发生变化,使得工作在电离层之上的SAR系统的成像性能受到干扰.本文分别从法拉第旋转、背景电离层和电离层不规则体三个方面介绍了电离层效应对不同轨道SAR系统成像性能的影响,并总结了电离层效应的补偿修正方案.最后,给出了电离层效应对星载和月基SAR成像影响的一些亟待解决的问题,以促进星载和月基SAR成像的发展及应用.  相似文献   

Relativistic corrections to the Kompaneets equation     

《Astroparticle Physics》2015

We study the Sunyaev–Zeldovich effect for clusters of galaxies. We explore the relativistic corrections to the Kompaneets equation in terms of two different expansion approximation schemes, namely, the Fokker–Planck expansion approximation and delta function expansion approximation. We show that two expansion approximation formalisms are equivalent under the Thomson approximation, which is extremely good approximation for the CMB photon energies. This will clarify the situation for existing theoretical methods to analyse observation data.  相似文献   

菲律宾宿务岛地区矿化蚀变图像识别与提取分析          下载免费PDF全文

郑纬  朱谷昌  张远飞  石菲菲  王冬寅  李红 《地质找矿论丛》2011,26(2):222-228

文章通过遥感多波段数据的背景端元数M值的估计方法、回归偏度曲线分析和地物光谱反射特征来选择信息提取的特征波段;在综合分析的基础上,选择基于Crosta法的F因子与H因子分析方法,根据不同蚀变信息提取的波段选择,以自行开发的软件对律宾宿务岛地区遥感图像进行矿化蚀变信息检测与提取.提取结果表明,区内已知的矿床(点)和矿化蚀...  相似文献   

核电厂环境放射性本底调查现场工作技术方法     

贝新宇 《国外铀金地质》2011,(4):240-244

针对某核电厂环境放射性本底调查项目,在明确调查目的和调查内容基础上,依据相关标准规范,结合调查范围内自然和社会环境状况,形成一套高效、实用的现场工作技术方法,并解决了样品采集、测量参数的设定等一系列关键问题,为后续同类项目的顺利实施积累了宝贵经验。  相似文献   

Assimilation of temperature and salinity using isotropic and anisotropic recursive filters in Tropic Pacific     

LIU Ye  ZHAO Yanling 《海洋学报(英文版)》2011,30(1):15-23

A data assimilation scheme used in the updated Ocean three-dimensional Variational Assimilation System (OVALS),OVALS2,is described.Based on a recursive filter (RF) to estimate the background error covariance (BEC) over a predetermined scale,this new analysis system can be implemented with anisotropic and isotropic BECs.Similarities and differences of these two BEC schemes are briefly discussed and their impacts on the model simulation are also investigated.An idealized experiment demonstrates the ability of the updated analysis system to construct different BECs.Furthermore,a set of three years experiments is implemented by assimilating expendable bathythermograph (XBT) and ARGO data into a Tropical Pacific circulation model.The TAO and WOA01 data are used to validate the assimilation results.The results show that the model simulations are substantially improved by OVALS2.The inter-comparison of isotropic and anisotropic BEC shows that the corresponding temperature and salinity produced by the anisotropic BEC are almost as good as those obtained by the isotropic one.Moreover,the result of anisotropic RF is slightly closer to WOA01 and TAO than that of isotropic RF in some special area (e.g.the cold tongue area in the Tropic Pacific).  相似文献   

The bulk transfer coefficients in the permafrost region at the Tanggula Pass of Tibetan Plateau     

LiangLei Gu  JiMin Yao  Lin Zhao  ZeYong Hu  YongPing Qiao 《寒旱区科学》2011,3(4):0366-0373

This paper presents research on the surface drag coefficients, C_D, and the bulk transfer coefficients of sensible heat flux, C_H, in the permafrost region at the Tanggula Pass of the Tibetan Plateau. The data were obtained from the Open-Path Eddy Covariance System and the 10-m Automatic Weather Station (AWS) at the TGLMS site which supported by Cryosphere Research Station (Chinese Academy of Science) on the Qinghai-Xizang Plateau (Tibetan Plateau). The characteristics of C_D and C_H in relation to atmospheric instability and wind velocity are discussed, and it was found that the bulk transfer coefficients varied with air conditions and were different in different months. However, the bulk transfer coefficients obtained from the eddy covariance system did not show a significant increasing trend with increasing atmospheric instability, and the bulk transfer coefficients did not change greatly with increasing wind velocity at 10 m.  相似文献   

Estimating sublimation of intercepted and sub‐canopy snow using eddy covariance systems     

Noah P. Molotch  Peter D. Blanken  Mark W. Williams  Andrew A. Turnipseed  Russell K. Monson  Steven A. Margulis 《水文研究》2007,21(12):1567-1575

Direct measurements of winter water loss due to sublimation were made in a sub‐alpine forest in the Rocky Mountains of Colorado. Above‐and below‐canopy eddy covariance systems indicated substantial losses of winter‐season snow accumulation in the form of snowpack (0·41 mm d^?1) and intercepted snow (0·71 mm d^?1) sublimation. The partitioning between these over and under story components of water loss was highly dependent on atmospheric conditions and near‐surface conditions at and below the snow/atmosphere interface. High above‐canopy sensible heat fluxes lead to strong temperature gradients between vegetation and the snow‐surface, driving substantial specific humidity gradients at the snow surface and high sublimation rates. Intercepted snowfall resulted in rapid response of above‐canopy latent heat fluxes, high within‐canopy sublimation rates (maximum = 3·7 mm d^?1), and diminished sub‐canopy snowpack sublimation. These results indicate that sublimation losses from the sub‐canopy snowpack are strongly dependent on the partitioning of sensible and latent heat fluxes in the canopy. This compels comprehensive studies of snow sublimation in forested regions that integrate sub‐canopy and over‐story processes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Foundation and application of background trend line of China’s inbound tourism     

Gen-nian Sun 《中国地理科学(英文版)》2000,10(3):231-237

Modern inbound tourism in China has been developing for 20 years, a trend line of inbound tourists in statistical data began to show. This paper introduces the concept of tourism background trend line, and explores its two functions as a barometer in demonstrating fluctuation in the tourism economy and as a forecaster in forecasting tourism development. The tourism background trend line is a new concept, the word “background” derived from environment science, refers to the “trend line” which reflects the dynamic curve or dynamic equation of tourism development without considering the impact of unexpected incidents. The introduction of this concept was inspired by Karl Marx’s comments on the relation between value and price. Tourism background trend line reflects the summary of multiple factors involving tourism resources, tourism demand, population growth, the scale and speed of economic development, and the spatial interaction between tourism origins and destimations. It demonstrates the natural and stable trend and the temporal law of tourism development in a country or region. The tourism statistical curve is at random, susceptible to disruptions and disturbances from serious political, economic and environmental happenings, but it always fluctuates around the background line. Tourism background line can reveal the potential of a country’s tourism development. Compared with the statistical line, it can be used as a “barometer” indicating ups and downs of tourism industry in the past. When naturally extended, the background trend line also can be used for forecasting the trend of tourism development in future. In this paper, 4 tourism background trend lines of China’s inbound tourists, i. e. foreign tourists, Hong Kong/Macao/Taiwan tourists, overseas Chinese tourists and total tourists from abroad, were established with statistical data from 1978 to 1996. And the impacts of the Political Event in 1989 (or Tiananmen Square Incident) on China’s inbound tourism were evaluated. The result shows that the impact of the Event was not limited within one year, but it stretched over 3 years. The total loss was 20 million in tourist arrivals and $1620 million in foreign currency income. The paper also studied the trend of China’s inbound tourism in the next 4 years. Foundation item: Under the auspices of National Natural Science Foundation of China. Brography: SUN Gen-nian(1961 —), male, a native of Xi’an City, Shaanxi Province, master of science, associate professor. His research interests include environment science, geography modeling and MIS for tourism.  相似文献   

A study of the Sunyaev–Zel'dovich increment using archival SCUBA data     

Michael Zemcov &#;  Colin Borys  Mark Halpern  Philip Mauskopf  Douglas Scott 《Monthly notices of the Royal Astronomical Society》2007,376(3):1073-1098

In a search for evidence of the short wavelength increment in the Sunyaev–Zel'dovich (SZ) effect, we have analysed archival galaxy cluster data from the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope, resulting in the most complete pointed survey of clusters at 850 μm to date. SCUBA's 850-μm passband overlaps the peak of the SZ increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3. Maps of each of the clusters have been made and sources have been extracted; as an ancillary product, we generate the most thorough galaxy cluster point source list yet from SCUBA. 17 of these clusters are free of obvious active galactic nuclei (AGN) and have data deep enough to provide interesting measurements of the expected SZ signal. Specialized analysis techniques are employed to extract the SZ effect signal from these SCUBA data, including using SCUBA's short wavelength band as an atmospheric monitor and fitting the long wavelength channel to a model of the spatial distribution of each cluster's SZ effect. By explicitly excising the exact cluster centre from our analysis, we demonstrate that emission from galaxies within the cluster does not contaminate our measurement. The SZ amplitudes from our measurements are consistently higher than the amplitudes inferred from low-frequency measurements of the SZ decrement.  相似文献   

Anomalous SZ contribution to three-year WMAP data     

R. M. Bielby  T. Shanks 《Monthly notices of the Royal Astronomical Society》2007,382(3):1196-1202

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