Study on Multi-Parameter Seismic Observation Technique Based on Optic Fiber Sensing

”Deep well, wide band, multi-component comprehensive observation” is the development direction of seismic observation. In order to promote the application and development of underground integrated observation system, key technologies, such as high temperature resistance sensor, interference isolation of sensor unit and miniaturization of instrument, need to be developed. Optic fiber sensors have the advantages of small size, passive nature, resistance to electromagnetic interference, being easy to long distance transmission and multi-parametric network observation, which are expected to provide new technology for the comprehensive observation of multi-parameter earthquakes in deep wells. This paper proposed a comprehensive observation technique of seismic wave, crustal deformation and temperature. An integrated borehole seismic sensor based on fiber Bragg grating resonators was designed for measuring three-component earthquake, three-component crustal deformation and temperature signal. A new technique for simultaneous measurement of multi-parameters of temperature and strain of fiber based on effective cavity length was presented. The technique of high precision optical fiber signal demodulation based on single side band sweep laser and the design of multi-parameter integrated optical fiber probe were introduced. The resolution of strain and temperature measurement of the fiber multi-parameter sensor system reached 4.7 \times 10^-10 and 6×10^-5 ℃ , respectively. A comprehensive multi-parameter earthquake observation experiment was carried out at the seismic station. The results show that the integrated optical fiber multi-parameter seismic observation system can simultaneously record the earth tide signal, seismic wave signal and environmental temperature disturbance, and has good anti-environmental interference ability and long-term stability, which is expected to provide a new technique for crustal deformation observation.     

勘查地球化学数据挖掘与弱异常识别

我国积累的大量高质量、多元素、多尺度的地球化学数据,为矿产勘查与环境评价提供了有效的数据支撑。如何对这些数据进行二次开发和再利用,提取有价值的地球化学异常信息并带动找矿突破,是缓解当前矿产资源短缺的重要途径之一。在覆盖区和深部的找矿实践中,由于矿体埋深和覆盖层的影响,往往在表生介质中形成弱小的地球化学异常,识别和评价弱小地球化学异常是当前勘查地球化学数据处理的重要方向之一。本文围绕地球化学异常信息的提取和评价,主要从以下几个方面讨论了相关的国内外研究进展和发展趋势:勘查地球化学数据处理与异常识别方法和模型,勘查地球化学数据闭合效应的影响及其解决方案,基于大数据和机器学习的勘查地球化学数据处理以及弱小地球化学异常的识别和评价。研究发现,在地质环境的约束下,基于大数据思维和机器学习相结合的方法,注重地球化学空间分布模式与已发现矿床的相关关系,同时使用所有地球化学变量能有效刻画具有非线性特征的地球化学空间分布模式,可识别出传统方法无法识别的异常,为开展地球化学空间模式识别与异常提取提供了新的途径。     

东亚高空急流协同变化对冬季欧亚遥相关型气候效应的影响

利用NCEP/NCAR再分析资料和我国地面735站气温和降水资料,首先分析了欧亚遥相关型的时间演变和结构特征,在此基础上探讨了欧亚遥相关型不同位相时东亚大气环流的差异,并进一步研究了欧亚遥相关型影响我国冬季气温和降水过程中东亚高空急流的重要作用。从结构上看,欧亚遥相关型位势高度异常中心位于250 hPa高度,表现出准正压的结构。欧亚遥相关型位于正位相时,东亚温带急流强度偏弱且位置向北移动;副热带急流强度偏强,两支急流在45°N附近有明显分界;西伯利亚高压和阿留申低压强度增强;东亚大槽加深,槽线倾斜不明显。负位相时则相反。欧亚遥相关型与东亚高空急流的联系是其影响我国气温降水的重要原因。正欧亚遥相关型时,偏弱的温带急流区较强的北风分量有利于北方冷空气南下,从而造成我国气温偏低;偏强的副热带急流区增强的南风将副热带地区暖湿空气向北输送,两支急流协同变化,影响我国冬季降水异常的分布。去掉温带急流或副热带急流偏强的年份,欧亚遥相关型与我国温度、降水的相关性显著减弱,说明欧亚遥相关型是通过东亚高空急流协同变化的桥梁,对我国温度和降水异常产生影响。进一步研究发现,欧亚遥相关型与副热带急流的关系不如其与温带急流稳定,导致在欧亚遥相关型同一位相时东亚高空急流存在两种不同的配置,这种高空急流配置的不唯一性使得东亚高空急流能对欧亚遥相关型的气候效应起到调控作用。     

基于EVI的中国最近10 a植被覆盖变化特征分析

通过对2000—2009年增强型植被指数(EVI)数据的分析发现:在过去的10 a里,中国的植被覆盖度明显增加,植被活动在增强。植被覆盖的年变化和季节变化特征如下:(1)10 a来植被覆盖地区的面积呈增加趋势,植被稀少地区的面积呈减少趋势;(2)无论是植被覆盖区还是全国平均,单位面积EVI年平均值都呈增加趋势;(3)在生长季节(夏季、春季)植被活动增加更明显,EVI增加速率按季节排列如下:夏季春季秋季冬季。植被覆盖的空间变化特征显示,尽管总体上中国植被覆盖呈增加趋势,但存在空间异质性。结合同期的温度、降水和森林资源清查数据,从两个方面初步解释了植被覆盖度增加的原因,即:温度的上升和春季降水量的增加;近年来中国开展的大型林业生态建设工程。     

Riparian thermal conditions across a mixed rural and urban landscape

Riparian corridors have the potential to function as thermal refuges, moderating extremes of local temperature variation. However, although demonstrated at individual sites, and over short periods, the consistency of this effect at wider temporal and spatial scales is poorly understood. The aim of this study is to assess the temperature differences between riparian corridors and adjacent non-riparian habitats and to explore the influence of environmental characteristics on these differences. Air temperature was monitored hourly at 20 paired locations (riparian and non-riparian) for two consecutive years. Urban index and canopy cover were characterised by calculating the percentage of impervious surface area and tree canopy cover within a 100 m radius from the centre of each sampling site. Canopy cover reduced summer thermal stresses in both urban and rural areas whereas high urban index tended to increase the daily thermal indices. Rivers had a significant mitigating effect on the urban riparian thermal condition, particularly in extreme hot weather. Riparian corridors were generally 1 °C cooler than non-riparian locations in summer and could be up to 3 °C cooler at some sites in extreme hot weather. Furthermore, riparian corridors at some sites were warmer than non-riparian locations in winter. These findings suggest that the proximity of rivers can modify riparian thermal environments, potentially reducing the heat stress of riparian corridors across landscapes.     

Estimating the Correlated Observation-Error Characteristics of the Chinese FengYun Microwave Temperature Sounder and Microwave Humidity Sounder

In operational data assimilation systems, observation-error covariance matrices are commonly assumed to be diagonal.However, inter-channel and spatial observation-error correlations are inevitable for satellite radiances. The observation errors of the Microwave Temperature Sounder(MWTS) and Microwave Humidity Sounder(MWHS) onboard the FengYun-3A(FY-3A) and FY-3B satellites are empirically assigned and considered to be uncorrelated when they are assimilated into the WRF model's Community Variational Data Assimilation System(WRFDA). To assimilate MWTS and MWHS measurements optimally, a good characterization of their observation errors is necessary. In this study, background and analysis residuals were used to diagnose the correlated observation-error characteristics of the MWTS and MWHS. It was found that the error standard deviations of the MWTS and MWHS were less than the values used in the WRFDA. MWTS had small inter-channel errors, while MWHS had significant inter-channel errors. The horizontal correlation length scales of MWTS and MWHS were about 120 and 60 km, respectively. A comparison between the diagnosis for instruments onboard the two satellites showed that the observation-error characteristics of the MWTS or MWHS were different when they were onboard different satellites. In addition, it was found that the error statistics were dependent on latitude and scan positions.The forecast experiments showed that using a modified thinning scheme based on diagnosed statistics can improve forecast accuracy.     

夏季厄尔尼诺-Modoki和东部型ENSO海表温度异常分布型特征及其与海洋性大陆区域气候异常的联系

2007年,Ashok等揭示了赤道太平洋区域存在一种三极型分布海表温度异常并称之为厄尔尼诺-Modoki,同时定义了相应的海表温度异常指数EMI（记为I_EM）。在此基础上,利用英国哈得来中心逐月海表温度资料、美国NCEP/NCAR月平均再分析数据集、美国国家海洋和大气管理局（NOAA）逐月降水资料（CMAP）,通过在太平洋海表温度异常中扣除厄尔尼诺-Modoki信号后,在Nino1+2区域上定义了东太平洋型海表温度异常指数EPNI（I_EPN）。据此,由I_EPN和I_EM可构成描述热带太平洋海表温度异常变化的一对指数。分析了两个指数相应的海气状态及对海洋性大陆区域气候异常的影响。结果表明,厄尔尼诺-Modoki和东太平洋型海表温度异常及其影响存在显著差异。在北半球夏季,当I_EM处于正位相时,热带太平洋海表温度异常呈现“负-正-负”的结构,海洋性大陆大部分区域海表温度异常为负,此时对流层低层太平洋地区辐合,海洋性大陆地区辐散,对流层高层太平洋地区辐散,海洋性大陆地区辐合。对应于辐合辐散中心,存在着自赤道中太平洋分别向赤道东太平洋和海洋性大陆中东部地区的异常垂直环流圈,同时也存在自海洋性大陆西部向印度洋西部的垂直环流。大气在海洋性大陆区域北部加热,南部冷却;在太平洋地区西部加热而东部冷却;在海洋性大陆区域10°N以南降水偏少,而10°N以北降水偏多。当I_EPN处于正位相时,热带太平洋海表温度异常呈现“西负东正”分布型,海洋性大陆区域海表温度异常呈现“西正东负”分布,对流层低层海洋性大陆地区辐散中心范围偏大、位置偏东、强度偏强,太平洋地区辐合中心范围偏小、位置偏东,热带环流异常在垂直方向上呈斜压结构,海洋性大陆区域北部大气加热而南部冷却,太平洋地区大气均呈加热正异常,海洋性大陆大部分区域降水均偏少,赤道太平洋降水偏多。以上这些结果有利于深刻理解热带太平洋海表温度异常的特征及其对海洋性大陆区域气候的影响。     

全球1.5℃和2.0℃升温对中国小麦产量的影响研究

采用部门间影响模式比较计划（ISI-MIP）的气候模式,确定全球升温1.5℃和2.0℃出现的时间,并结合农业技术转移决策支持系统（DSSAT）模型模拟小麦的产量,最终选取4套数据对比研究中国小麦区温度和降水变化特征以及各区域小麦产量变化趋势,综合评价了不同升温情景对中国小麦产量的影响。结果表明：(1)在全球升温1.5℃和2.0℃背景下,我国小麦生育期内温度相对于工业革命前分别升高1.17℃和1.81℃。两种升温情景下我国春麦区升温幅度大于冬麦区升温幅度。春麦区中新疆春麦区升温幅度最大,西北春麦区升温幅度最小;冬麦区中温度变化最大和最小的麦区分别为西南冬麦区和黄淮冬麦区。(2)在全球升温1.5℃和2.0℃情景下,我国小麦生育期内降水相对于历史时段(1986—2005年)分别增加9.1%和11.3%。从各麦区来看,两种升温情景下春麦区降水增加幅度略大于冬麦区的增加幅度。所有麦区中只有新疆春麦区降水低于历史时段降水。春麦区降水增加幅度最大的麦区为北部春麦区。冬麦区中降水增加较大的麦区为北部冬麦区和黄淮冬麦区,降水增加较小的麦区为华南冬麦区和西南冬麦区。(3)两种升温情景下,我国小麦单产相对于历史时段(1986—2005年)平均减产分别为5.2%和4.6%,两种升温情景对中国小麦产量并没有显著的差异。在全球升温大背景下我国春小麦主要呈现增产趋势,冬小麦主要呈现减产趋势。减产幅度较大的麦区为华南冬麦区和青藏春麦区,增产幅度最大的麦区为西北春麦区。从各麦区产量减产面积比例上看,我国各麦区减产面积所占比例趋势为从北向南由多变少再变多,其中华南冬麦区减产面积所占比例最大,北部冬麦区最小。     

与冬季北太平洋大范围海温异常相联系的海气特征

采用1948—2014年NCEP/NCAR大气再分析资料以及延伸重建海温资料,基于大气海洋间不同的主导关系对冬季北太平洋大范围海温异常进行分类,探究其相应的海气结构特征。结果表明:1)大气影响海洋的个例多于海洋影响大气的个例,即在冬季北太平洋大气强迫海洋占主要地位,但也存在海洋对大气的反馈作用。2)对于大气影响海洋而言,SST(Sea Surface Temperature)暖异常区上空主要伴随着东北—西南走向的相当正压高低压异常(东北高西南低),对应东南风异常以及显著的深厚暖异常,表现出相当正压暖/脊结构,冷异常情况与此相反。SST异常为净热通量异常与风速异常共同作用引起。3)对于海洋影响大气而言,在SST暖异常区上空西部为南北向高低压异常(北高南低),东部为低压异常,对应偏东风异常。在SST冷异常区上空为偶极型的南北向高低压异常(南高北低),对应偏西风异常;位势高度异常表现出相当正压结构且较大气影响海洋时相对偏弱,大气暖(冷)温度异常比较浅薄且主要局限于对流层低层。4)海洋温度结构异常主要表现为,在大气影响海洋时海温异常由表层下传,海洋影响大气时为上下一致的温度异常。     

Analyzing snowfall variability over two locations in Kashmir,India in the context of warming climate

Present study focuses on examination snowfall variability over Gulmarg and Pahalgam of Kashmir Valley in India during past 31 years (1980–2010). Trends in temperature over the study area is also explored. Minimum and maximum temperature shows increasing trends which is consistent with increase in black carbon column mass density. Increase in black carbon mass density is attributed to urbanization over study area. Trends of minimum temperature is statistically significant. It is reported that snowfall over the Pahalgam shows decreasing trend except for the month of February and January. Pahalgam shows a significant decreasing trend in snowfall of about 48 mm per decade during March. Pahalgam and Gulmarg show seasonal decreasing trends of snowfall of about 15 mm and 1.8 mm per decade, respectively. These decreasing trends in snowfall are consistent with decadal increasing trends of about 1.2 °C and 0.8 °C in minimum temperature over Pahalgam and Gulmarg, respectively. Seasonal snowfall over both the regions shows decreasing trend (insignificant). Results reported in this study show a decrease of about 24.16% ± 9.86% per degree increase in minimum temperature over Pahalgam. Changing characteristics of snowfall in the context of anthropogenic warming present major challenges to the tourism and socioeconomic aspects over the Valley.