基于PALSAR数据的青藏高原冻土形变检测方法研究   总被引：1，自引：0，他引：1  

谢酬  李震  李新武 《国土资源遥感》2008,19(3):15-19

季节性冻胀和融沉导致的地面形变是青藏高原冻土区建设施工与维护的主要问题。对冻融造成的形变进行有效监测是青藏铁 路建设与维护的前提。差分干涉测量技术是地表形变监测的重要手段之一,PALSAR（L波段的合成孔径雷达）数据在非城市区域具 有较高的相关性,适合青藏高原冻土区的地表形变监测。本文选用4景覆盖研究区域的PALSAR数据,研究利用该数据进行冻土形变 检测的方法,并对其检测结果进行了分析。结果表明,该方法与水准测量方法有较好的一致性。  相似文献   

Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay     

Jérôme Harlay  Caroline De Bodt  Anja Engel  Sandra Jansen  Quentin d’Hoop  Judith Piontek  Nicolas Van Oostende  Steve Groom  Koen Sabbe  Lei Chou 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1251-1265

The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEP_micro) and colorimetric (TEP_color) methods, showed abundant (6.1×10⁶–4.4×10⁷ L^?1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEP_micro and similar vertical profiles of TEP_color. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L^?1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.  相似文献   

Flow around sunspots from it p-mode frequency shift measurements     

Sun  Ming-Tsung  Chou  Dean-Yi  Lin  Chia-Hsien  Team  The TON 《Solar physics》1997,176(1):59-65

We use five-day helioseimic data from the Taiwan Oscillation Network to study the flow around a sunspot, NOAA 7887. The p-mode oscillations in an annular region centered at the sunspot are decomposed into the modes propagating toward and away from the sunspot. We find that the frequency of an outgoing mode is greater than that of the corresponding incoming mode. This indicates that the plasma is flowing outward from the sunspot. The outflow velocity is estimated to be about 40–80 m s^-1.  相似文献   

The Effect of Helicity Dissipation on the Critical State of an Avalanche Model for Solar Flares     

Yung-Ping Chou 《Solar physics》2001,199(2):345-369

We perform numerical simulations using an avalanche model for solar flares, in which the effect of avalanche event duration is included and the lateral boundary condition can be either open or periodic. The results from the simulations show that self-organized criticality (SOC) exists under a variety of conditions of helicity dissipation, and they are similar in the sense that the indices of power-law distributions of avalanche sizes are the same, while the duration and waiting time distributions differ little. Of interest are: (1) if there exists helicity dissipation in the course of avalanches, SOC exists only when the amount of helicity dissipation per avalanche is small; (2) sudden reductions in the total helicity of the system do not severely disturb SOC, if the amount reduced is moderate; (3) the distribution of waiting times is shown to be exponential, in consistent with the Poisson statistics other avalanche models have predicted, and the exponent increases as the effect of event duration becomes larger. The self-similar structure of the avalanche time series is also examined. These results imply that, although helicity is dissipated in resistive diffusion of flares, the amount of dissipation should be small and the conservation law of helicity thus holds in an approximate sense. Also, the coronal mass ejections (CMEs), observed to take helicity out of the solar corona in an eruptive way, may disrupt the statistical equilibrium of the corona only temporarily.  相似文献   

数值天气预报的创新之路--从初值问题到反问题   总被引：2，自引：2，他引：2  

丑纪范 《气象学报》2007,65(5):673-682

基于大气并非是一个确定论的系统,从信息论的视角考察了数值天气预报问题。认为表征初值和边值的数据可以视为输入信息(信息源),而数值模式则不过是一个信息变换机构,它把输入信息变换成预报结论而输出来,输出的预报结论则是未来天气状况的信息。于是预报的准确性受制于:一是输入信息所包含的输出信息的信息量,另一是信息在变换过程中丢失的信息量。从初值的形成过程揭示出了当前观测系统在一个时刻提供的数据没有包含初值所要求的全部信息,而缺失的部分或多或少的隐藏在过去的观测数据中。提为初值问题意味着只依据一个时刻的状态导致输入的信息量缺失,应考虑过去的历史数据以增加输入数据中所包含的预报量的信息。文中指出由于输出信息比输入还多的数值模式是不存在的,这样的改进带有根本性。进一步论证了数值模式的误差信息,也或多或少的隐藏在过去的历史数据中,为了充分使用过去的观测数据,本文建议改变问题的提法,不提成初值问题,提成反问题。资料同化本质上是反问题,其欠定性不应人为夸大。提成反问题的数值天气预报能充分应用过去的历史资料,将天气方法、统计方法、动力方法有机地结合在一起。对于这个反问题如何具体求解方面,在分析了业务和研究的区别,模式的普适性和针对性的统一的基础上,给出了反问题的具体解决途径。强调无需构建新模式(这是非常困难的工作),只需运行现成的模式,借助所关心的预报对象的历史数据来改造现成模式,因而是完全可行的。  相似文献   

Fate of paralytic shellfish poisoning toxins in purple clam Hiatula rostrata,in outdoor culture and laboratory culture   总被引：1，自引：0，他引：1  

Chen CY  Chou HN 《Marine pollution bulletin》2002,44(8):733-738

Purple clams (Hiatula rostrata Lighttoot) accumulate paralytic shellfish poisoning (PSP) toxins produced by a toxic strain of the dinoflagellate Alexandriun minutum Halim. The results confirm the data of our previous study concerning the muscle and siphon that were not showing a gradual rise in toxicity when shellfish accumulated more A. minutum. However, muscle and siphon are intermittently toxic both in exposure and depuration period in laboratory cultured purple clams. PSP toxins were detected in outdoor cultured purple clams, whereas no A. minutum were found in the culture pond during most of the survey time. The outdoor cultured purple clams need longer time to decrease toxicity to allowable levels than laboratory cultured purple clams. It was shown that laboratory data may not predict times over which pond-cultured purple clams may prove toxic to consumers.  相似文献   

The carbonate system in the East China Sea in winter     

Wen-Chen Chou  Gwo-Ching Gong  Chun-Mao Tseng  David D. Sheu  Chin-Chang Hung  Lo-Ping Chang  Li-Wen Wang 《Marine Chemistry》2011,123(1-4):44-55

Measurements of dissolved inorganic carbon (DIC), pH, total alkalinity (TA), and partial pressure of CO₂ (pCO₂) were conducted at a total of 25 stations along four cross shelf transects in the East China Sea (ECS) in January 2008. Results showed that their distributions in the surface water corresponded well to the general circulation pattern in the ECS. Low DIC and pCO₂ and high pH were found in the warm and saline Kuroshio Current water flowing northeastward along the shelf break, whereas high DIC and pCO₂ and low pH were mainly observed in the cold and less saline China Coastal Current water flowing southward along the coast of Mainland China. Difference between surface water and atmospheric pCO₂ (ΔpCO₂), ranging from ~ 0 to ? 111 μatm, indicated that the entire ECS shelf acted as a CO₂ sink during winter with an average flux of CO₂ of ?13.7 ± 5.7 (mmol C m^? 2 day^? 1), and is consistent with previous studies. However, pCO₂ was negatively correlated with temperature for surface waters lower than 20 °C, in contrast to the positive correlation found in the 1990s. Moreover, the wintertime ΔpCO₂ in the inner shelf near the Changjiang River estuary has appreciably decreased since the early 1990s, suggesting a decline of CO₂ sequestration capacity in this region. However, the actual causes for the observed relationship between these decadal changes and the increased eutrophication over recent decades are worth further study.  相似文献   

Luminescence dating of Late Pleistocene faults as evidence of uplift and active tectonics in Sardinia,W Mediterranean     

Leonardo Casini  Stefano Andreucci  Daniele Sechi  Chun‐Yuan Huang  Chuan‐Chou Shen  Vincenzo Pascucci 《地学学报》2020,32(4):261-271

Precise dating of the activity of Late Pleistocene to Holocene neo‐tectonic structures is crucial to quantify the rate of deformation in low‐seismicity regions. Sardinia is a relatively stable continental fragment set in the middle of the tectonically active Western Mediterranean belt. This paper provides evidences of significant uplift of northwest Sardinia that support an ongoing tectonic activity since the Marine Isotopic Stage 7 (MIS 7; ca. 220 ka). In particular, it documents for the first time Late Pleistocene to Holocene tectonics based on luminescence dating of travertine sealing a major NNE‐SSW fault.  相似文献   

The Discovery of Natural Native Uranium and Its Significance   总被引：2，自引：0，他引：2  

LI Ziying  HUANG Zhizhang  LI Xiuzhen  GUO Jian  FAN Chou 《《地质学报》英文版》2015,89(5):1561-1567

This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy (XPS). A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium. This is the first discovery of the existence of native uranium in nature. It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth.  相似文献   

Analyses of extreme climate events over china based on CMIP5 historical and future simulations   总被引：1，自引：0，他引：1  

Shili Yang  Jinming Feng  Wenjie Dong  Jieming Chou 《大气科学进展》2014,31(5):1209-1220

Based on observations and 12 simulations from Coupled Model Intercomparison Project Phase 5 （CMIP5） models, cli- matic extremes and their changes over China in the past and under the future scenarios of three Representative Concentration Pathways （RCPs） are analyzed. In observations, frost days （FD） and low-temperature threshold days （TN10P） show a de- creasing trend, and summer days （SU）, high-temperature threshold days （TX90P）, heavy precipitation days （R20）, and the contribution of heavy precipitation days （P95T） show an increasing trend. Most models are able to simulate the main char- acteristics of most extreme indices. In particular, the mean FD and TX90P are reproduced the best, and the basic trends of FD, TN10P, SU and TX90P are represented. For the FD and SU indexes, most models show good ability in capturing the spatial differences between the mean state of the periods 1986--2005 and 1961-80; however, for other indices, the simulation abilities for spatial disparity are less satisfactory and need to be improved. Under the high emissions scenario of RCP8.5, the century-scale linear changes of the multi-model ensemble （MME） for FD, SU, TN10P, TX90P, R20 and P95T are -46.9, 46.0, -27.1, 175.4, and 2.9 days, and 9.9%, respectively; and the spatial change scope for each index is consistent with the emissions intensity. Due to the complexities of physical process pararneterizations and the limitation of forcing data, great uncertainty still exists with respect to the simulation of climatic extremes.  相似文献