A strategy for merging objective estimates of global daily precipitation from gauge observations,satellite estimates,and numerical predictions

This paper describes a strategy for merging daily precipitation information from gauge observations, satellite estimates(SEs), and numerical predictions at the global scale. The strategy is designed to remove systemic bias and random error from each individual daily precipitation source to produce a better gridded global daily precipitation product through three steps.First, a cumulative distribution function matching procedure is performed to remove systemic bias over gauge-located land areas. Then, the overall biases in SEs and model predictions(MPs) over ocean areas are corrected using a rescaled strategy based on monthly precipitation. Third, an optimal interpolation(OI)–based merging scheme(referred as the HL-OI scheme)is used to combine unbiased gauge observations, SEs, and MPs to reduce random error from each source and to produce a gauge—satellite–model merged daily precipitation analysis, called BMEP-d(Beijing Climate Center Merged Estimation of Precipitation with daily resolution), with complete global coverage. The BMEP-d data from a four-year period(2011–14) demonstrate the ability of the merging strategy to provide global daily precipitation of substantially improved quality.Benefiting from the advantages of the HL-OI scheme for quantitative error estimates, the better source data can obtain more weights during the merging processes. The BMEP-d data exhibit higher consistency with satellite and gauge source data at middle and low latitudes, and with model source data at high latitudes. Overall, independent validations against GPCP-1DD(GPCP one-degree daily) show that the consistencies between BMEP-d and GPCP-1DD are higher than those of each source dataset in terms of spatial pattern, temporal variability, probability distribution, and statistical precipitation events.     

Estimating the Numbers and the Areas of Collapsed Buildings by Combining VHR Images,Statistics and Survey Data: a Case Study of the Lushan Earthquake in China

Accurately obtaining the structures and damage types of buildings in earthquake stricken areas is fundamental to supporting rescue forces and estimating economic losses and casualties. As the stricken areas are often much larger than the areas covered by very high resolution (VHR) images, the information obtained from VHR images cannot satisfy practical needs. This study developed a method for estimating the structures and types of damaged buildings by combining VHR images, statistics and ground survey data. First, the rates of damaged buildings with different structures and damage types were manually interpreted from VHR images covering a small part of the stricken area, and further corrected by ground survey data. Second, the corrected rates were reallocated to the seismic intensity zones. Third, the rates in the seismic intensity zones and the statistical data were combined to estimate the numbers and areas of damaged buildings in villages, towns and counties. The presented method was applied to estimate the damages caused by the Lushan earthquake in China. The results indicated that our method can efficiently estimate the amount of the damages and complement existing work on only automatic extracting damaged buildings from VHR images.     

Elastic wave velocity monitoring as an emerging technique for rainfall-induced landslide prediction

Landslides are recurring phenomena causing damages to private property, public facilities, and human lives. The need for an affordable instrumentation that can be used to provide an early warning of slope instability to enable the evacuation of vulnerable people, and timely repair and maintenance of critical infrastructure is self-evident. A new emerging technique that correlates soil moisture changes and deformations in slope surface by means of elastic wave propagation in soil was developed. This approach quantifies elastic wave propagation as wave velocity. To verify its applicability, a series of fixed and varied slope model tests, as well as a large scale model test, were conducted. Analysis of the results has established that the elastic wave velocity continuously decreases in response of moisture content and deformation, and there was a distinct surge in the decrease rate of wave velocity with failure initiation, soil deformation was thus envisaged to have more significant effect on elastic wave velocity than water content. It is proposed that a warning be issued at switch of wave velocity decrease rate. Based on these observations, expected operation of the elastic wave velocity monitoring system for landslide prediction in the field application is presented. Consequently, we conclude that the elastic wave velocity monitoring technique has the potential to contribute to landslide prediction.     

巴丹吉林沙漠降水稳定同位素特征与水汽再循环

了解沙漠降水稳定同位素特征,有助于研究干旱区水循环过程.根据2015-2016年取自巴丹吉林沙漠4个站点的降水样品,分析了δ2H、δ18O的时空分布特征及影响因素;借助后向气团轨迹模型分析了降水水汽来源;采用氘盈余模型计算了水汽再循环比.结果显示,降水δ2H、δ18O均表现出季节效应,夏高冬低;沙漠腹地较外围山区δ2H、δ18O偏正,d-excess偏负,反映出腹地降水的蒸发程度更高.年内降水主要来自西风水汽,夏季部分受东南季风影响.沙漠湖泊区再循环比为10.3%~10.9%,略大于山区的8.5%;再循环水汽在总蒸发量中占比11.1%,反映出沙漠强烈的蒸发对本地降水的贡献较为有限.      

三峡库区仙女山和九畹溪断裂带水库地震变化规律

三峡库区蓄水以来,长江周边出现了大量的水库地震,主要集中于巴东—泄滩—仙女山区域,目前已达上万次,最大震级为5.1级。通过野外地质调查及对已有水库地震数据进行研究,采用构造地质分析方法,对三峡库区仙女山和九畹溪断裂带水库地震空间上的迁移规律、时间上的周期规律以及微地震群的成因机理进行分析。结果表明：从时间上看,水库地震具有周期性,表现为长周期（与库水位相关）和短周期（与库水位快速波动相关）;从空间上看,水库地震具有迁移规律,受九畹溪断裂控制的触发型水库地震存在着逐渐向南迁移的特征,受仙女山断裂控制的触发型水库地震局限分布于仙女山断裂北延端点处,分布于仙女山断裂西侧（周坪乡附近）带状分布的水库诱发地震逐渐呈点状向南迁移。     

Construction of soil–water characteristic curve of granular materials with toroidal model and artificially generated packings

Acta Geotechnica - The soil–water characteristic curve (SWCC) of granular materials is crucial for many emerging engineering applications, such as permeable pavement and methane hydrate...     

Consistent grain size distribution of pedogenic maghemite of surface soils and Miocene loessic soils on the Chinese Loess Plateau

There is agreement that ultrafine maghemite grains (<100 nm) are responsible for the magnetic enhancement of Chinese loess. Recent studies show that grain size distribution of ultrafine pedogenic maghemite grains within the aeolian sequences on the central Chinese Loess Plateau deposited in the last 8 Ma is consistent. However, whether the observed grain size distribution of ultrafine pedogenic maghemite grains can be observed in the western Chinese Loess Plateau and modern soils is not entirely clear. Here we find that young surface soil samples across the Chinese Loess Plateau and early Neogene loessic soils from the western Chinese Loess Plateau also show consistent grain size distribution with that of ultrafine pedogenic maghemite grains on the central Chinese Loess Plateau. The fact that young surface soil samples show apparent magnetic enhancement suggests that the ultrafine pedogenic maghemite grains derive from oxidation of ultrafine magnetite grains. Copyright © 2009 John Wiley & Sons, Ltd.     

震后应急救援民生保障物资需求模型研究

根据《应急物资分类及编码》（GB/T 38565—2020）,对震后所需应急救援民生保障物资种类进行梳理,参考地震应急处置经验和有关专家学者的研究成果,制定地震应急救援基本民生保障物资最低需求标准。对2007年以来有记录的物资投入数据进行梳理统计,采用数值拟合方法构建震后物资需求模型,计算震例模型值、标准值,并对实际值与模型值及实际值与标准值偏离程度进行对比分析,提出模型应用注意事项。     

Retrieval of remotely sensed air–sea carbon flux in the Chinese Bohai Sea

ABSTRACT

Having a reliable ocean carbon flux (f(CO₂)) retrieval model is essential to monitoring the global carbon cycle and to evaluating the climate change. Remote sensing techniques provide alternatives for f(CO₂) retrieval with its advantages of wide area surveys and real-time monitoring. In the present study, a semianalytical f(CO₂) estimation model was developed based on remote sensing data and in situ measurements in the Chinese Bohai Sea. The used model performed well (R²?=?0.84) in deriving f(CO₂) based on the collected remotely sensed dataset, including sea surface temperature, estimated sea surface salinity, wind speed, Chl-a concentration. The results showed that the distribution of partial pressure of carbon dioxide (p(CO₂)) and f(CO₂) varied spatially and temporally during the 12 months in 2009. The spatial fluctuations of p(CO₂) and f(CO₂) in Bohai Sea in summer and autumn were more obvious than that in Spring and Winter. The highest values of p(CO₂) and f(CO₂) generally appeared in coastal regions. Moreover, the average f(CO₂) value of the 12 months showed that the Bohai Sea performed as a weak carbon source in 2009. The results provided technical and data support for carbon management and climate negotiation in the Bohai Sea.