浮子数字水位仪动水位观测实验

针对投入式水位仪存在稳定性差、零漂大等缺点,研制浮子式JS-1数字水位仪,基于观测原理和仪器结构,在苏18井开展动水位观测实验,结果发现:JS-1数字水位仪在动水位观测中可行,产出数据质量优良,并且在对零漂控制、观测数据质量、观测精度等方面具有一定优势。     

数字化水位仪零漂特征的对比实验研究

基于对5口流体观测井使用的3种数字化水位仪的校测对比实验及与气温、气压、供电交流电压等因素的相关性分析,对数字化水位仪的零漂特征及影响因素进行了研究,结果表明:1水位仪的零漂变化呈非线性的特征,每种水位仪、甚至每台水位仪的零漂变动规律均不完全相同,相比较而言,SWY-1A型水位仪的零漂变动更平稳,变幅较小;2水位仪零漂与气温、气压和供电交流电压的相关系数较低,基本可以排除气温、气压和电源电压对水位仪零漂的影响;3水位仪零漂源于探头,主要受探头老化等因素的影响。探头安装时对探头线测量的精准度、探头线因重力作用的拉长、调整探头埋深时对探头线测量的精准度以及水位校测的人为误差等,往往会导致零漂计算结果上的偏差;4数字化水位观测应定期、规范化地进行水位校测并根据零漂变化对观测数据予以校正,以确保观测数据真实、可靠,能更好地发挥地震预测效能。     

山西孝义井LN-3A数字水位仪零漂分析

简要介绍山西孝义地震台晋9-1井的观测概况,对2015年12月数字水位仪校测时发现的测量误差增大的原因进行分析,认为可能存在仪器零漂问题。通过与模拟观测资料对比,明确数字水位仪零漂特征,为今后观测提供参考。     

数字化水位观测仪零漂分析

数字化水位LN-3型观测仪器存在一定的零漂问题,并通过宁德1号井实验结果表明,仪器室温度、气温、井水温、传感器埋深变化是数字化水位仪器零漂的重要原因,而水位仪器的零漂与湿度、公共数采无关,据此提出解决方案和建议,以提高水位观测资料的可靠性和连续性.     

塔院井数字化水位观测中的零漂问题

通过对塔院井数字化水位观测系统的校测，揭示出水位观测中的仪器零漂现象，分析了零漂的特征，提出了解决零漂问题的对策。     

广东数字化形变观测资料质量评价

通过对广东各数字化形变观测仪器潮汐因子中误差、相位滞后及仪器零漂等参量的计算,对仪器观测资料的连续性、稳定性及观测质量进行了分析和评价.分析结果认为:各台仪器的观测精度基本达到了中国地震局形变Ⅰ类台的标准;地倾斜类观测仪器精度高,稳定性好,尤其是水管倾斜仪的稳定性及精度较高;垂直摆倾斜仪的漂移较大且资料精度较低.伸缩仪...     

数字化水位仪探头现场检查之检讨

介绍在静水位井中观测的数字化水位仪探头的两种现场检查方法及结果 ,讨论这两种检查方法的优点及不足,提出现场检查方法的改进意见和允许特殊井孔内观测的数字化水位仪现场检查频率降低和定期消除数字化水位仪零漂影响的建议。     

763地震仪水平向拾震器抗干扰性能的探索

通过对攀枝花台、成都台763仪调试架设的实践,结合H763仪结构特点,分析了仪器零漂出现的原因和提高仪器抗干扰性能的方法;同时,提出了H763仪安装架设的技术指标及仪器密封方式改善的方法。     

静乐井SWY-Ⅱ和LN-3A水位仪的对比分析

对静乐井SWY-Ⅱ水位仪和LN-3A水位仪从稳定性、数据一致性、内在质量、系统漂移、水震波、气压效应、自然环境干扰7方面进行了对比分析,结果显示:①SWY-Ⅱ水位仪和LN-3A水位仪运行稳定;②两套仪器观测数据一致性较好;③两套仪器测量精度均优于0.001m,平均值一致性较好。④通过计算分钟值数据,两套仪器M2波潮汐因子及其观测精度较为接近;⑤通过与SW40-1水位仪进行对比,两套仪器均存在不同程度系统漂移;⑥两套仪器分钟值数据记录水震波时间及振幅差异明显;⑦两套仪器的气压效应、受自然环境干扰影响较为一致。     

影响张道口-1井数字化水位观测内在质量的因素

采用“水位调和分析(M2波计算)”程序,对天津张道口地震台张道口-1井模拟、数字化水位内在质量变化进行了对比研究。从高频干扰、周围井孔的地下水开采、仪器零漂、探头位置与观测精度变化的关系、仪器自身原因5个方面分析了影响张道口-1井数字化水位内在质量的因素,并提出了数字化水位在日常观测中的注意事项。     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.