黑河流域荒漠区土壤水分对降水脉动响应   总被引：16，自引：5，他引：11  

刘冰  赵文智  常学向  李守波 《中国沙漠》2011,30(3):716-722

 利用气象站资料,对黑河流域荒漠区降水特征及其土壤水分对降水脉动响应进行了系统研究。结果表明,荒漠区降水属于降水脉动事件,降水前后土壤水分特征存在显著差异,且随土层增加差异逐渐变小。土壤水分在降水量、土壤深度和降水前后的差异极显著,交互效应也极显著(P<0.0001),表明荒漠区土壤水分对降水脉动具有显著的响应现象。土壤水分的降水脉动响应表现为降水后土壤含水量激增,在蒸散作用下缓慢减小。降水前后土壤含水量的时间序列变异规律均能较好地拟合成变异函数的理论模型。降水前后土壤含水量随机变异均小于结构性变异,反映出荒漠区土壤水分在时间尺度上具有较强的自相关性格局。降水使土壤水分空间结构差异呈现下降趋势,在时间序列上异质性降低。  相似文献   

气象综合信息电子屏在新农村建设中的应用及思考   总被引：1，自引：0，他引：1  

杨志军  樊盛  毛卫芳 《气象研究与应用》2011,32(1):94-97

通过对气象综合信息电子屏应用情况进行分析和探讨,得出一些应用初步结论和思考,以期抛砖引玉,使该项工作能在新农村建设中加快应用步伐,为真正解决农村信息覆盖"最后一公里"的瓶颈提供参考.  相似文献   

磁暴主相多阶发展行星际起因的初步分析          下载免费PDF全文

佟亚男  刘四清  张效信  林瑞淋  龚建村 《地球物理学报》2011,54(6):1439-1456

本文利用1998～2006年与磁云有关的80起中强磁暴(Dst*≤-50 nT),对其主相期间不同发展阶数磁暴的行星际起因进行了统计分析.重点研究了鞘区磁场单独作用、磁云本体单独作用、鞘区与磁云共同作用以及其他复杂行星际结构在磁暴主相多阶发展中的相对重要性,并对导致磁暴主相增加一阶的行星际起因做了初步分析.统计结果表明...  相似文献   

汶川MS8.0级大震前天基与陆基电场资料联合应用研究   总被引：3，自引：0，他引：3       下载免费PDF全文

安张辉  杜学彬  范莹莹  刘君  谭大诚  陈军营  解滔 《地球物理学报》2011,54(11):2876-2884

利用边际谱方法对2008年5月12日四川汶川地震前天基和陆基电场变化情况进行了联合分析研究,结果表明:(1)空间电场方面,由重复轨道和连续轨道电场边际谱演化看出,电离层电场从2008年4月27日左右开始,其边际谱出现了明显的增强现象(增大1~2个量级),这种现象一直持续到汶川地震发生.(2)陆基电场方面,中法合作的松山...  相似文献   

甘肃嘉峪关地震台大地电场观测数据干扰分析   总被引：1，自引：0，他引：1  

张彩艳  赵洁  雷功明  程鹏  曹喜  赵月梅 《山西地震》2011,(4):25-28

文章对甘肃嘉峪关地震台2001年至2009年以来大地电场分钟值资料做了全面的分析和整理。对造成观测资料相关性低的电暴（磁暴）、人类活动、雷电、降水、观测系统本身变化（包括更换电极）、电阻率测量、公用接地网等干扰因素进行分析,并做出相关的解释。这将对分析和运用地电场资料进行地震预报有一定的意义。  相似文献   

Effect of near-fault earthquakes with forward directivity on telecommunication towers     

M.Yahyai  B.Rezayibana  E.Mohammadrezapour 《地震工程与工程振动(英文版)》2011,10(2):211-218

In this paper, the effect of pulse-type motions caused by forward directivity that can release huge amounts of energy in a short time period is studied on a telecommunication tower. Since telecommunication towers have longer periods, they are not as affected by seismic forces. Nevertheless, near source earthquakes characterized by high velocity and velocity pulses can change the behavior of these structures. For this reason, a telecommunication tower located near active faults was selected in this study. Considering the probable earthquake magnitude at the site and the distance of the tower from adjacent faults, nine simulated pulses and three near-fault earthquake records with forward directivity are selected and applied to a 3D fi nite element model of the tower. The results of nonlinear dynamic analysis, i.e., displacements and damage in the tower, indicate that the maximum displacement and drift ratio of the tower under the pulses are obviously affected by the ratio of the structure period to pulse period. When this ratio is decreased and close to 1.0, the maximum displacement and drift ratio are sharply increased and cause large displacements in the tower.  相似文献   

HNCORS在电力工程测量中的应用     

孙建勇  张中原 《测绘与空间地理信息》2011,34(3):121-122,125

介绍了连续运行参考站网系统的有关概念,结合HNCORS系统的建设运行,详细探讨了CORS系统在电力工程测量中的应用.  相似文献   

加速迭代硬阈值ISAR稀疏成像     

雷大力  洪峻  王宇  费春娇 《遥感学报》2015,19(5):770-779

加速迭代硬阈值(AIHT)作为一种压缩感知(CS)算法,具有计算复杂度低、内存占用小的特点,在较小数目的观测下,经过有限次迭代便能获得较好的重建效果。因此,本文将该算法应用到逆合成孔径雷达(ISAR)稀疏成像,对该方法的具体特征和适用性进行了详细分析。仿真结果表明,在相同信噪比和回波脉冲数条件下,基于AIHT的ISAR成像方法,相比于稀疏贝叶斯算法(SBL),在重建时间上缩短了至少2个量级;相比于迭代加权最小二乘法(IRLS)和平滑l0范数算法,在重建质量上提高了约3倍。经实测数据处理结果验证,在1/4原始脉冲数条件下,该方法仍具有良好的聚焦性能和压低旁瓣效果。  相似文献   

Varying water utilization of Haloxylon ammodendron plantations in a desert‐oasis ecotone          下载免费PDF全文

Hai Zhou  Wenzhi Zhao  Gefei Zhang 《水文研究》2017,31(4):825-835

Haloxylon ammodendron is a desert shrub used extensively in China for restoring degraded dry lands. An understanding of the water source used by H. ammodendron plantations is critical achieving sustainable vegetation restoration. We measured mortality, shoot size, and rooting depth in 5‐, 10‐, 20‐, and 40‐year‐old H. ammodendron plantations. We examined stable isotopic ratios of oxygen (δ¹⁸O) in precipitation, groundwater, and soil water in different soil layers and seasons, and in plant stem water to determine water sources at different shrub ages. We found that water acquisition patterns in H. ammodendron plantations differed with plantation age and season. Thus, the main water source for 5‐year‐old shrubs was shallow soil water. Water sources of 10‐year‐old shrubs shifted depending on the soil water conditions during the season. Although their tap roots could absorb deep soil water, the plantation main water sources were from soil water, and about 50% of water originated from shallow and mid soil. This pattern might occur because main water sources in these plantations were changeable over time. The 20‐ and 40‐year‐old shrubs acquired water mainly from permanent groundwater. We conclude that the main water source of a young H. ammodendron plantation was soil water recharged by precipitation. However, when roots reached sufficient depth, water originated mainly from the deep soil water, especially in the dry season. The deeply rooted 20‐ and 40‐year‐old shrubs have the ability to exploit a deep and reliable water source. To achieve sustainability in these plantations, we recommend a reduction in the initial density of H. ammodendron in the desert‐oasis ecotone to decelerate the consumption of shallow soil water during plantation establishment.  相似文献   

The response of CO2 flux to rain pulses at a saline desert     

Jie Ma  Xin‐Jun Zheng  Yan Li 《水文研究》2012,26(26):4029-4037

As the substantial component of the ecosystem respiration, soil CO₂ flux is strongly influenced by infrequent and unpredictable precipitation in arid region. In the current study, we investigated the response of soil CO₂ flux to rain pulses at a saline desert in western China. Soil CO₂ flux was measured continuously during the whole growing season of 2009 at six sites. We found that there were remarkable changes in amplitude or diurnal patterns of soil CO₂ flux induced by rainfall events: from bimodal before rain to a single peak after that. Further analysis indicated that there is a significant linear relationship (P < 0.001) between soil CO₂ flux and soil temperature (T_soil). However, a hysteresis between the waveform of diurnal course of CO₂ flux and T_soil was observed: with soil CO₂ flux always peaked earlier than T_soil. Furthermore, a double exponential decay function was fitted to the soil CO₂ flux after rainfall, and total carbon (C) releases were estimated by numerical integration for rainfall events. The relative enhancement and total C release, in association with the rain pulses, was linearly related to the amount of precipitation. According to the size and frequency of rainfall events, the total amount of C release induced by rain pulses was computed as much as 7.88 g C·m^–2 in 2009, equivalent to 10.25% of gross primary production. These results indicated that rain pulses played a significant role in the carbon budget of this saline desert ecosystem, and the size of them was a good indicator of rain‐induced flux enhancement. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献