全覆盖植被冠层水分遥感监测的一种方法: 短波红外垂直失水指数

利用叶片辐射传输模型PROSPECT、植被冠层辐射传输模型SailH和地气辐射传输模型6S, 进一步探索近红外、短波红外反射光谱特征, 从光谱特征空间的角度, 分析地物在NIR-SWIR空间的分异规律, 建立监测植被冠层水分含量的新方法-短波红外垂直失水指数(SPSI). 通过实地观测数据和叶片、冠层辐射传输模型验证本文提出的新方法, 结果表明SPSI和实地观测的植被冠层水分含量(FMC)具有较高的相关性, R2和RMSE分别为0.79, 26.41%, 证明了SPSI在FMC反演方面有一定的应用潜力.     

A remote sensing model for monitoring soil evaporation based on differential thermal inertia and its validation

To develop geosciences quantification and multi-dimensional researches will be an inevitable trend in the 21st century. The interaction between the land surface and the atmosphere not only serves as an important component in geosciences quantification, bu…     

Evaluation, modification, and application of the Effective Drought Index to 200-Year drought climatology of Seoul, Korea

In this paper, progressive methods for assessing drought severity from diverse points of view were conceived. To select a fundamental drought index, the performances of the Effective Drought Index (EDI) and 1-, 3-, 6-, 9-, 12-, and 24-month Standardized Precipitation Indices (SPIs) were compared for drought monitoring data accumulated over 200-year period from 1807 to 2006 for Seoul, Korea. The results confirmed that the EDI was more efficient than the SPIs in assessing both short and long-term droughts.We then proposed the following methods for modifying and supplementing the EDI: (1) CEDI, a corrected EDI that considers the rapid runoff of water resources after heavy rainfall; (2) AEDI, an accumulated EDI that considers the drought severity and duration of individual drought events; and (3) YAEDI, a year-accumulated negative EDI representing annual drought severity. In addition to these indices, to more accurately measure and diagnose droughts, we proposed the utilization of (4) the Available Water Resources Index (AWRI), an existing index that expresses the actual amount of available water.Using the improved methods above, we assessed and summarized important droughts that have occurred in Seoul over the 200 years from 1807 to 2006.     

陇东黄土高原下垫面不均匀性指标的建立及其对大孔径闪烁仪(LAS)观测感热通量的影响

目前定量研究下垫面不均匀性对大孔径闪烁仪(LAS)、涡动相关仪(ECS)观测感热通量差异的影响还比较少.本文利用黄土高原庆阳观测站2012年6、7月典型晴天两主风向范围E-SE和SW-W的陆面过程数据,在建立了下垫面不均匀性定量化指标的基础上,分析了下垫面不均匀性与地表温度变率的关系及其对LAS、ECS观测感热通量差异的影响.结果表明:庆阳站下垫面不均匀性大小η和地表温度变率г具有很好的相关性,相关系数达到0.566以上,证明了新建立指标的合理性.下垫面不均匀性大小η和LAS、ECS观测的感热通量差异HLAS-HECS具有很好的一致性,相关系数达到0.634.下垫面不均匀性对LAS和ECS的感热通量差异影响显著,下垫面越不均匀LAS和ECS测量的感热通量差异越大.对两主风向分别进行分析,在E-SE风向范围η和HLAS-HECS的相关系数为0.430,HLAS和HEC拟合的线性趋势系数为1.279,在SW-W风向范围η和HLAS-HECS的相关系数为0.680,HLAS和HEC拟合的线性趋势系数为1.297.下垫面不均匀性的影响程度越大,LAS和ECS观测的感热通量差异越大.     

Evaluation of a surface energy balance method based on optical and thermal satellite imagery to estimate root‐zone soil moisture

Various remote‐sensing methods are available to estimate soil moisture, but few address the fine spatial resolutions (e.g. 30‐m grid cells) and root‐zone depth requirements of agricultural and other similar applications. One approach that has been previously proposed to estimate fine‐resolution soil moisture is to first estimate the evaporative fraction from an energy balance that is inferred from optical and thermal remote‐sensing images [e.g. using the Remote Sensing of Evapotranspiration (ReSET) algorithm] and then estimate soil moisture through an empirical relationship to evaporative fraction. A similar approach has also been proposed to estimate the degree of saturation. The primary objective of this study is to evaluate these methods for estimating soil moisture and degree of saturation, particularly for a semi‐arid grassland with relatively dry conditions. Soil moisture was monitored at 28 field locations in south‐eastern Colorado with herbaceous vegetation during the summer months of 3 years. In situ soil moisture and degree of saturation observations are compared with estimates calculated from Landsat imagery using the ReSET algorithm. The in situ observations suggest that the empirical relationships with evaporative fraction that have been proposed in previous studies typically provide overestimates of soil moisture and degree of saturation in this region. However, calibrated functions produce estimates with an accuracy that may be adequate for various applications. The estimates produced by this approach are more reliable for degree of saturation than for soil moisture, and the method is more successful at identifying temporal variability than spatial variability in degree of saturation for this region. Copyright © 2015 John Wiley & Sons, Ltd.     

A real-time AI-assisted seismic monitoring system based on new nodal stations with 4G telemetry and its application in the Yangbi MS 6.4 aftershock monitoring in southwest China

A rapidly deployable dense seismic monitoring system which is capable of transmitting acquired data in real time and analyzing data automatically is crucial in seismic hazard mitigation after a major earthquake. However, it is rather difficult for current seismic nodal stations to transmit data in real time for an extended period of time, and it usually takes a great amount of time to process the acquired data manually. To monitor earthquakes in real time flexibly, we develop a mobile integrated seismic monitoring system consisting of newly developed nodal units with 4G telemetry and a real-time AI-assisted automatic data processing workflow. The integrated system is convenient for deployment and has been successfully applied in monitoring the aftershocks of the Yangbi M_S 6.4 earthquake occurred on May 21, 2021 in Yangbi County, Dali City, Yunnan in southwest China. The acquired seismic data are transmitted almost in real time through the 4G cellular network, and then processed automatically for event detection, positioning, magnitude calculation and source mechanism inversion. From tens of seconds to a couple of minutes at most, the final seismic attributes can be presented remotely to the end users through the integrated system. From May 27 to June 17, the real-time system has detected and located 7 905 aftershocks in the Yangbi area before the internal batteries exhausted, far more than the catalog provided by China Earthquake Networks Center using the regional permanent stations. The initial application of this integrated real-time monitoring system is promising, and we anticipate the advent of a new era for Real-time Intelligent Array Seismology (RIAS), for better monitoring and understanding the subsurface dynamic processes caused by Earth's internal forces as well as anthropogenic activities.     

基于特大地震发生率的川滇地区地震危险性预测新模型

川滇地区是我国地震危险性较高的地区之一.本文基于对特大强震的风险性考虑,使用全球地震模型OpenQuake软件,建立了川滇地区地震危险性预测新模型.首先根据构造特征划分多个震源分区,并整理出这些震源分区内断层活动特征与滑动速率;基于震源分区和断层模型,使用GPS应变率转换成的锥形古登堡-里克特关系作为整个区域的地震积累率,并允许超过历史最大震级的特大地震的出现,结合活动断层滑动速率所积累的地震发生率,给出震源分区内断层地震源和背景地震源的地震发生率的比率分配关系;在活动断层分段上,保留了大型断裂或其主要部分,没有根据小的阶区来对断层进行详细分段,以便分配特大地震发生率;并使用地震率平滑方法分配背景地震发生率.最后在OpenQuake中加入地震动预测方程,计算出了川滇地区的PGA分布图,为区域地震危险性提供科学依据.

     

一种气泡释放过程连续监测方法及其在三峡水库香溪河CH4通量监测的应用

气泡释放是天然水体释放CH₄的主要途径之一,准确量化水体气泡释放量对于辨析其“汇、源”特性至关重要。自然水体释放气泡的不连续性、不确定性使得监测其过程较为困难。本研究针对水体气泡释放监测难题,通过改进倒置漏斗型气泡通量监测装置提出了一种气泡释放过程连续监测方法。本方法测量对象为定长时间监测水域释放气泡的体积,经室内外实验验证,其理论量程为3.6～132 mL/(m²·min),测量结果能够较好的表征10～40 m水深缓流水体气泡体积通量变化特征。运用该方法于2021年6—11月对三峡水库支流香溪河库湾开展CH4气泡通量连续监测,并分析不同环境因子对其产生的影响。结果表明:监测期间,研究水域CH₄气泡通量变化范围为0.02～8.13 mg/(m²·d),且各采样点间CH₄气泡通量呈现较高的时空变异性;CH₄气泡通量与水温、水体pH呈显著正相关关系,与水深及水体电导率呈显著负相关关系。其中,水深可能是决定水体是否通过气泡形式释放CH₄的重...     

基于误差分布的震源区波速比反演及其应用:乳山震群源区介质性质变化研究

本文利用误差分布和概率统计分析改进了波速比计算方法.对于震源位置相对集中的震群活动,对台站震相到时进行两次差分,通过对差分后的震相数据对进行二维高斯分布拟合,可以稳健地估计震群活动震源区波速比.该方法充分利用了不同台站Pg、Sg到时差的所有信息,其优势是不需要地震事件的震源位置,并且不依赖震源区以外的速度变化,有效消除了震源区到台站的传播路径效应的影响;相对于传统的平均波速比,本文方法得到的震源区波速比,更能真实地反映震源区介质的性质.我们将该方法应用到2013-2016年的乳山震群,结果显示：震源区波速比的变化与震群活动过程密切相关,波速比的变化反映了序列活动的阶段性特征.

     

断裂带震源机制节面聚类确定断裂带产状方法及在2021年漾濞地震序列中的应用

一条断裂带上发生地震的破裂面通常与断裂带形状接近,同一地震破裂带上大量震源机制节面中应该有集中于断层面形状的一个集合,求出此集合的节面中心就可以得到断裂带的几何形状.根据这个原理,本研究给出了震源机制节面之间距离的方法,将带有噪声、基于密度的空间聚类方法(DBSCAN)应用于震源机制的节面聚类分析,并应用于2021年云...     

曲化平用最佳等效源模型及其单位位场表达式推导的新方法

本文以Hanson R.O.和Miyazaki Y.的论文(1984)为基础定义了"曲化平用最佳等效源模型",并利用这一模型研制出了能快速、高精度地对大面积位场观测数据实施曲化平处理的软件程序.在严格推导该模型"单位位场正演表达式"的过程中,作者根据模型与其位场正演表达式之间的映射关系,提出了推导位场正演公式的"模型变换法".采用该方法很容易地导出了该模型的形式极其简短的"单位位场正演表达式". 作者认为,推导位场正演表达式的模型变换法可能具有普遍性,建议位场理论和方法技术研究者对此给予关注,以便在自己的研究实践中遇到类似问题时,参考、试用,并予以发展和完善.