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1.
用近５０个中纬（磁纬在±２０°-５０°之间）电离层垂测站的ｆ０Ｆ２资料,分析与磁暴相伴的电离层暴事例表明：地磁Ｄｓｔ指数与中纬电离层ｆ０Ｆ２暴时变化Ｄｓ（ｆ０Ｆ２ ）有大致相似的发展趋势。但用时序叠加法求得的强度不同、发展过程和持续时间不同的多次电离层暴ｆ０Ｆ２变化的平均值,其物理意义是很不明确的。暴时ｆ０Ｆ２变化的地方时分布Ｄｓ（ｆ０Ｆ２）中,一般说以全日周期扰动幅度（Ａ１）为最强,但电离层负暴峰值后常出现半日周期扰动（Ａ２）的增强,且有时Ａ２＞Ａ１．Ａ１的涨落趋势与Ｄｓｔ（ｆ０Ｆ２）相似,但特强磁暴时,Ａ１值有可能反而变小．以Ａ１ｓｉｎ（ω ｔ＋ １）表示的全日周期扰动中,初位相１值随暴时的发展而变小表明,扰动分布形态是基本上随地球一起转动的。 相似文献
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本文详细研究了一次地震发生后其继发地震的时空免疫性特征、研究结果表明，青海地震的免疫性特征是十分明显的，它对进一步认识地震发生的时空特征有着重要的意义。相邻两次地震的时间间隔，和空间距离ｄ的临界直线关系为ｄ∞τ（－１．０），其迁移速率ｖ的关系为ｖ∞τ（－２．０）。这也是齐夫（ｚｉｐｆ）法则所约定的分维值，十分类似于１／ｆ谱。我们形象的称ｄ∞τ（－１．０）分布是“随机音乐”；ｖ∞τ（－２．０）分布是“布朗音乐”。 相似文献
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作者发现：太阳辐射,地球自转与公转,黄、赤交角的存在,陆地和海洋在地球表面南、北半球的不规则、不对称地理分布,及地球内部因〖ZZ(〗核外液体〖ZZ)〗形成的分层结构,构成了一套天然的能使地球产生自由章动的日、地间动量（能量）相耦合的物理机制.经研究,由该机制产生的极移具有以下主要特征：（1）极移轨迹的运动周期为13个月（0.92周/年）,该周期由二个主要分量组成,一个为12个月（1周/年）,另一个是14.1个月（0.85周/年,即钱德勒周期）.（2）极移运动轨迹是是椭圆,短半轴（b）与长半轴(a)之比为0.86;扁率（a\|b/a）为1：7.1.（3）瞬时极移振幅|m|的变化：对1周/年项,|m|随太阳回归运动而变化,在二至点时最大,在二分点时最小,具有对称性;对0.85周/年项,|m|随太阳回归运动而变化,在夏至点最大,每年12月5日左右最小.（4）瞬时极移存在反向运动（由东向西）.在1周/年项极移运动中,自转极的正、反方向运动振幅的贡献各占50%;在0.85周/年项的极移运动中,反向运动的时间仅有33天,约占正向运动时间的1/10,正向运动振幅的贡献占96%,反向运动振幅的贡献大约占4%.（5）若以国际极点（CIO）为原点,自转极相对CIO的位移运动轨迹必然落在偏向于CIO的西侧.（6）极移振幅将长期保持下去而不会衰减,原因是太阳辐射为自转轴受迫摆动提供了长期、稳定的激发能源. 相似文献
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通过分析１９００年以来每５ａ地球磁场各阶球谐系数的相关系数发现,地球磁场偶极子分量的ρ值在１９０５-１９７０年基本保持不变,１９７０-１９８５年下降,１９８５-１９９５年又上升,呈Ｖ字型变化。而非偶极子分量的 值则具有周期性变化,在１９１５年、１９４５年和１９８０年出现峰值,在１９３５年和１９６５年则处于低谷,变化周期约为３０ａ。通过分析地球磁场非偶极子分量 值周期变化与日长周期变化的相关性,得出两点新的认识：１．非偶极子分量的周期性变化与核幔边界耦合过程相关,而偶极子分量的变化对应外核的深部过程;２．外核顶部流体具有周期性的变化,其变化周期与日长及非偶极子分量的变化周期一致。 相似文献
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使用国际地球物理年（ＩＧＹ）和国际地球物理合作年（ＩＧＣ）期间全球地磁台网的资料和中国台站的同期地磁记录，对地磁场太阳日变化Ｓｑ的经度效应和ＵＴ变化进行了分析研究．将适用于瞬时全球磁场的球谐分析法与适用于平均场的双调和分析法相结合，提出了一种分析Ｓｑ磁场的新方案，得到了（θ，Ｔ，ｔ）坐标系中组成Ｓｑ场的三个部分，即仅随地方时ＬＴ变化的部分ＳＬＴ，仅随世界时ＵＴ变化的部分ＳＵＴ以及既随ＬＴ变化又随ＵＴ变化的部分ＳＬＵＴ．从全球来看，在ＩＧＹ／ＩＧＣ期间，这三部分的强度之比分别为：Ｘ分量１．０：０．２：０．３，ｙ分量１．０：０．１：０．６，Ｚ分量１．０：０．４：１．０．Ｓｑ的经度效应和ＵＴ变化虽然表现了同一物理过程，但它们有不同的表达形式，其决定因素是地磁轴对地理轴的倾斜，地磁场的非偶极子成分（即区域性异常）和地球内部电性的横向不均匀性（包括海陆分布、地壳上地幔电导率的区域差异） 相似文献
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由速度谱测定微震的地震矩 总被引：2，自引：0，他引：2
本文根据Ｋ．Ａｋｉ（１９８０）提出的ω平方、常应力参数谱衰减模式．研究了地面运动速度谱衰减的带宽效应，导出了用速度谱直接估算地震矩Ｍ０的新方法。利用中日合作在滇西地震预报实验场区的洱源、脉地、松桂三个地区新获得的三次微震群序列数字化记录资料，通过不同参数Ｑ值和△σ值的计算比较，选取Ｑ＝３００，△σ＝１．０ＭＰａ作为测定的参数值，计算了Ｐ波和Ｓ波速度谱的理论量板，并且与实际观测点的低频速度谱值相比较，用这样的方法测定了三次震群序列的地震矩Ｍ０和震源参数。结果给出，在震级为１．０～２．５级的范围内，地震矩Ｍ０＝１０（１０）～１０（１３）（Ｎ·ｍ），震源破裂半径ａ＝７０～２００（ｍ），Ｐ波和Ｓ波的拐角频率比ｆ（ｏｐ）／ｆ（ｏｓ）＝１．５８。用Ｐ波或Ｓ波三分量的速度谱值测定的地震矩比较一致，以及在相同震级范围内，用速度谱方法测定的结果与其它方法测定的结果也基本一致。本文提出的速度谱测地震矩的方法是一种简便实用的方法，当地震矩和观测低频谱值（如ｆ＝１．０ＨＺ）已知时，可通过查函数表值快速测定Ｍ０值。 相似文献
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若尔盖盆地RH孔近80万年来δ13Corg气候特征的频谱分析 总被引：5，自引：3，他引：2
运用最大熵谱方法,对若尔盖深钻８００ｋａＢ．Ｐ．以来有机碳同位素序列进行了频谱分析,结果表明;１）０－８００ｋａＢ．Ｐ该地区存在有准８０ｋａ,６０ｋａ,４１ｋａ和２０ｋａ的周期,其中４１ｋａ和２０ｋａ的周期来米氏计算的地倾角及岁差周期较一致;２）０－４８０ｋａＢ．Ｐ,以１００ｋａ周期为主,其次为４１ｋａ和２０ｋａ,与米氏计算的各天文周期相一致;３）４８０－８００ｋａＢ．Ｐ．出现有１１５ｋａ,３３ｋ 相似文献
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在张北－尚义地震区震前已有大地电磁资料测点（５１１点）进行了两次重复观测,在震中区测点（ＭＭＣ点）进行了连续４昼夜的观测。测量结果显示：（１）与震前资料相比,５１１测点沿电性构造走向方向（ＮＮＷ）在０．２～４ｓ周期范围内的视电阻率减小,垂直走向方向的视电阻率增大;（２）ＭＭＣ测点两个方向在０．２～１０ｓ周期范围内的视电阻率随测量时间逐渐增大;（３）５１１测点两次重复观测和ＭＭＣ的观测可能都反映出震后电阻率正在逐渐恢复。此外,还对地震前后地下结构的变化进行了分析。初步推测,观测到的电阻率变化是由于地下流体活动引起的 相似文献
10.
用最小二乘法处理泾阳台ＤＤ－１地震仪记录资料，拟合适于泾阳台由地震波持续时间求算近震震级ＭＤ的公式：ＭＤ＝２．７ｌｇｒ—２．４（Δ≤１０ｋｍ），ＭＤ＝２．２９ｌｇｒ＋０．００１１８Δ－２．２５（１０ｋｍ＜Δ≤５２０ｋｍ），并对震级ＭＬ和ＭＤ进行误差分析。 相似文献
11.
It is more and more popular to estimate the exchange of water vapor, heat and CO2fluxes between the land surface and the atmosphere using the eddy covariance technique. To get believable fluxes, it is necessary to correct the observations based on the different surface conditions and to determine relevant techinical parameters. The raw 10 Hz eddy covariance data observed in the Yucheng and Changbai Mountains stations were recalculated by various averaging periods (from 1 to 720 min) respectively, and the recalculated results were compared with the results calculated by the averaging period of 30 mins. Meanwhile, the distinctions of fluxes calculated by different averaging periods were analyzed. The continuous 15 days observations over wheat fields in the Yucheng station were mainly analyzed. The results are shown that: (i) In the Yucheng station, compared with the observations by 30 min, when the averaging period changes from 10 to 60 min, the variations of the eddy-covariance estimates of fluxes were less than 2%; when the averaging period changes less than 10 min, the estimate of fluxes reduced obviously with the reduction of the averaging period (the max relative error was -12%); and when the averaging period exceeds 120 min, the eddy covariance estimates of fluxes will be increased and become unsteady (the max relative error is over 10%); (ii) the eddy covariance estimates of fluxes over wheat field in the Yucheng station suggusted that it is much better to take 10 min as an averaging period in studying diurnal change of fluxes, and take 30min for a long-term flux observation; and (iii) normalized ratio was put forward to determine the range of averaging period of eddy covariance measurements. By comparing the observations over farmlands and those over forests, it is indicated that the increase of eddy covariance estimates over tall forest was more than that over short vegetation when the averaging period increased. 相似文献
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分析了1999年7月-2003年12月发生在云南地区的由22个地震台站记录的5 668次地震的数字波形资料,从中选出保山、永胜、丽江、鹤庆、易门和禄劝6个地震台用扩展的尾波归一化方法计算P波、S波衰减.这6个台分为3个研究区,保山研究区内Qs-1=0.008 67f-0.86,Qp-1=0.011 55f-0.93;永胜、丽江、鹤庆研究区内Qs-1=0.018 24f-0.94,Qp-1=0.022 88f-0.92;禄劝、易门研究区内Qs-1=0.016 47f-0.91,Qp-1=0.028 26f-0.97.后两个研究区衰减结果比较接近,而保山研究区的P波、S波衰减明显偏低.与全球其它地区采用同样方法得到的P波、S波衰减结果对比表明:永胜、丽江、鹤庆研究区和禄劝、易门研究区的P波、S波衰减与日本关东地区很接近,而远高于韩国东南部的衰减;保山研究区的P波、S波衰减略高于韩国东南部.此外,还与前人得到的云南地区的尾波衰减结果进行了对比分析,发现本文S波衰减值与他们的结果相近. 相似文献
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目的:探讨低剂量胸部CT（LDCT）原始数据迭代重建（SAFIRE）增强等级与不同类型（实性、部分实性及纯磨玻璃）肺小结节优化显示的对应关系。材料与方法:分析2020年9月至2021年1月行LDCT并符合肺小结节入组标准受试者101例105个肺小结节,依结节性质分为实性结节组（n=27）,部分实性结节组（n=37）和纯磨玻璃结节组（n=41）。采用单因素方差分析、卡方检验或Kruskal-Wallis H检验先分析组间一般资料,再以滤波反投影算法（FBP,B50f）为参照,比较SAFIRE I50f和I70f（分别1~5级）各模式下客观图像质量（噪声值、肺小结节CT值、SNR和CNR）和主观图像质量评分。结果:①三组在性别、身体质量指数和结节分布无显著差异,纯磨玻璃结节组年龄和结节长径均小于实性和部分实性结节组;② SAFIRE I50f 1~5和I70f-5图像噪声值均低于FBP B50f,其中SAFIRE I50f-5噪声值最低,不同模式下肺小结节CT值无显著差异,SAFIRE I50f-5肺小结节SNR和CNR均高于FBP B50f和其他SAFIRE模式;③ SAFIRE I50f 3~5实性和部分实性肺小结节图像质量主观评分高于FBP B50f和除I70f-5外SAFIRE其他模式,SAFIRE I50f-4纯磨玻璃肺小结节图像质量主观评分高于FBP B50f和除I50f-3、I50f-5外SAFIRE其他模式且组间评分无显著差异。结论:SAFIRE I50f-4在LDCT实性、部分实性和纯磨玻璃肺小结节图像质量客观、主观评价方面均表现良好且均衡,可适用于各类型肺小结节LDCT评价。 相似文献
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Extreme floods often follow wildfire in mountainous watersheds. However, a quantitative relation between the runoff response and burn severity at the watershed scale has not been established. Runoff response was measured as the runoff coefficient C, which is equal to the peak discharge per unit drainage area divided by the average maximum 30 min rainfall intensity during each rain storm. The magnitude of the burn severity was expressed as the change in the normalized burn ratio. A new burn severity variable, hydraulic functional connectivity Φ was developed and incorporates both the magnitude of the burn severity and the spatial sequence of the burn severity along hillslope flow paths. The runoff response and the burn severity were measured in seven subwatersheds (0·24 to 0·85 km2) in the upper part of Rendija Canyon burned by the 2000 Cerro Grande Fire near Los Alamos, New Mexico, USA. A rainfall–discharge relation was determined for four of the subwatersheds with nearly the same burn severity. The peak discharge per unit drainage area was a linear function of the maximum 30 min rainfall intensity I30. This function predicted a rainfall intensity threshold of 8·5 mm h?1 below which no runoff was generated. The runoff coefficient was a linear function of the mean hydraulic functional connectivity of the subwatersheds. Moreover, the variability of the mean hydraulic functional connectivity was related to the variability of the mean runoff coefficient, and this relation provides physical insight into why the runoff response from the same subwatershed can vary for different rainstorms with the same rainfall intensity. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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电离层F层参数对电离层空间天气研究与电波传播应用具有重要意义,以往工作主要针对电离层f_0F_2、TEC等参数.本文利用我国中纬地区的兰州、中低纬过渡区的昆明、低纬地区的海口三个观测站的电离层垂直探测数据,分析了电离层峰高h_mF_2、F层虚高h’F和定性表征的厚度h_mF_2—h’F的周日、季节、太阳活动变化特征.研究表明:(1)兰州h_mF_2在太阳活动高年和低年的数值接近,海口在太阳活动高年白天的h_mF_2比低年白天高20~30 km.(2)在海口和昆明,h_mF_2最大值多出现在中午时段,兰州站的最大值出现在夜间.(3)海口的h_mF_2在01-3LT期间出现很强的"午夜衰落"现象,此后迅速增大.(4)利用h_mF_2-h'F来表征电离层的厚度时,其季节和周日变化特征与常用的B_0存在相似之处,但未出现清晨与午后凹陷等现象.这些结果对于提高我国电离层变化特性的认识和模式化研究水平具有重要的科学意义. 相似文献
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Although changes in rainfall characteristics have been noted across the world, few studies have reported those in mountainous areas. This study was undertaken to clarify spatial and temporal variations in rainfall characteristics such as annual rainfall amount (Pr), mean daily rainfall intensity (η), and ratio of rain days (λ) in mountainous and lowland areas in Taiwan. To this aim, we examined spatial and year‐to‐year variations and marginal long‐term trends in Pr, η, and λ, based on rainfall data from 120 stations during the period 1978–2008. The period mean rainfall () at the lowland stations had strong relationships with the period mean daily rainfall intensity () and the period mean ratio of rain days () during those 31 years. Meanwhile, was only strongly related to at mountainous stations, indicating that influences on spatial variations in were different between lowland and mountainous stations. Year‐to‐year variations in Pr at each station were primarily determined from the variation in η at most stations for both lowland and mountainous stations. Long‐term trend analysis showed that Pr and η increased significantly at 10% and 31% of the total 120 stations, respectively, and λ decreased significantly at 6% of the total. The increases in Pr were mostly accompanied by increases in η. Although stations with significant η increases were slightly biased toward the western lowland area, increases or decreases in Pr and λ were not common. These results contribute to understanding the impacts of possible climate changes on terrestrial hydrological cycles. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Temporal characteristics of the famous Matsushiro earthquake swarm were investigated quantitatively using point-process analysis. Analysis of the earthquake occurrence rate revealed not only the precise and interesting process of the swarm, but also the relation between pore water pressure and the strength of the epidemic effect, and the modified Omori-type temporal decay of earthquake activity. The occurrence rate function (t) for this swarm is represented well aswhere f(t) represents the contribution of the swarm driver, which was the erupting water from the deep in this case, and the second term represents an epidemic effect of the modified Omori type. Based on changes in the form of f(t), this two-year long swarm was divided into six periods and one short transitional epoch. The form of f(t) in each period revealed the detail of the water erupting process. In the final stage, f (t) decayed according to the modified Omori-formula form, while it decayed exponentially in the brief respite of the water eruption in the fourth period. When an exponential decay of swarm activity is observed, we have to be cautious of a sudden restart of the violent activity. The epidemic effect is stronger when the pressure of the pore water is higher. Even when the pressure is not high, the p value in the epidemic effect is small, when there is plenty of pore water. However, the epidemic effect produced about a quarter of the earthquakes even though there was not much pore water in the rocks. 相似文献
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根据石家庄市区场地脉动和剪切波速的实例资料,分析了石家庄市区场地脉动的特征以及剪切波速,并给出了场地脉动周期与场地土怪固有周期的统计关系。认为该地区的脉动周期随覆盖层厚度及覆盖层层数的增大而减小,而剪切波速则随深度的增加而增大。 相似文献
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采用高水平分辨率区域气候模式进行区域未来气候变化预估,对理解全球增暖对区域气候的潜在影响和科学评估区域气候变化有很好的参考价值.这里对国家气候中心使用25 km高水平分辨率区域气候模式RegCM3单向嵌套全球模式MIROC3.2_hires在观测温室气体(1951—2000)和IPCC A1B温室气体排放情景下(2001—2100)进行的共计150年长时间模拟结果,进行华北地区未来气温、降水和极端气候事件变化的分析.模式检验结果表明:模式对当代(1981—2000)气温以及和气温有关的极端气候事件(霜冻日数、生长季长度)的空间分布和数值模拟较好;对降水及和降水有关的极端气候事件(强降水日期、降水强度、五日最大降水量)能够模拟出它们各自的主要空间分布特征,但在模拟数值上存在偏大、偏强的误差.和全球模式驱动场相比,区域模式模拟的气温、降水和极端气候事件有明显的改进.2010—2100年华北地区随时间区域平均气温升高幅度逐渐增大,随之霜冻日数逐渐减少,生长季长度逐渐增多;同时随温室效应的不断加剧,未来降水呈增加的趋势,强降水日期和五日最大降水量逐渐增多、降水强度逐渐增大.从空间分布看,21世纪末期(2081—2100)气温、降水以及有关的极端气候事件变化比21世纪中期(2041—2060)更加明显. 相似文献