Characteristics of dry-wet abrupt alternation events in the middle and lower reaches of the Yangtze River Basin and the relationship with ENSO

During recent decades, more frequent flood-drought alternations have been seen in China as a result of global climate change and intensive human activities, which have significant implications on water and food security. To better identify the characteristics of flood-drought alternations, we proposed a modified dry-wet abrupt alternation index (DWAAI) and applied the new method in the middle and lower reaches of the Yangtze River Basin (YRB-ML) to analyze the long-term spatio-temporal characteristics of dry-wet abrupt alternation (DWAA) events based on the daily precipitation observations at 75 rainfall stations in summer from 1960 to 2015. We found that the DWAA events have been spreading in the study area with higher frequency and intensity since 1960. In particular, the DWAA events mainly occurred in May and June in the northwest of the YRB-ML, including Hanjiang River Basin, the middle reaches of the YRB, north of Dongting Lake and northwest of Poyang Lake. In addition, we also analyzed the impact of El Niño Southern Oscillation (ENSO) on DWAA events in the YRB-ML. The results showed that around 41.04% of DWAA events occurred during the declining stages of La Niña or within the subsequent 8 months after La Niña, which implies that La Niña events could be predictive signals of DWAA events. Besides, significant negative correlations have been found between the modified DWAAI values of all the rainfall stations and the sea surface temperature anomalies in the Nino3.4 region within the 6 months prior to the DWAA events, particularly for the Poyang Lake watershed and the middle reaches of the YRB. This study has significant implications on the flood and drought control and water resources management in the YRB-ML under the challenge of future climate change.     

Attribution of trends in meteorological drought during 1960–2016 over the Loess Plateau,China

This study uses two forms of the Palmer Drought Severity Index(PDSI), namely the PDSI_TH(potential evapotranspiration estimated-by the Thornthwaite equation) and the PDSI_PM(potential evapotranspiration estimated by the FAO Penman-Monteith equation), to characterize the meteorological drought trends during 1960–2016 in the Loess Plateau(LP) and its four subregions. By designing a series of numerical experiments, we mainly investigated various climatic factors' contributions to the drought trends at annual, summer, and autumn time scales. Overall, the drying trend in the PDSI_TH is much larger than that in the PDSI_PM. The former is more sensitive to air temperature than precipitation, while the latter is the most sensitive to precipitation among all meteorological factors. Increasing temperature results in a decreasing trend(drying) in the PDSI_TH, which is further aggravated by decreasing precipitation, jointly leading to a relatively severe drying trend. For the PDSI_PM that considers more comprehensive climatic factors, the drying trend is partly counteracted by the declining wind speed and solar radiation. Therefore, the PDSI_PM ultimately shows a much smaller drying trend in the past decades.     

近20年来济南泉水补给区景观格局及其功能变化分析

本文以济南市泉水补给区为研究对象,利用GIS空间分析方法,在其景观变化分析的基础上,参照中国陆地生态系统的生态服务价值系数,估算了泉水补给区生态服务功能价值变化,重点分析景观变化对研究区生态服务功能的影响,进而为区域可持续发展和城市建设提供理论支持。结果表明:(1)20世纪90年代以来,泉水补给区耕地和草地景观面积呈减少趋势,林地、园地和建设用地景观面积大幅增加,其中,以林地面积增加最大;从景观类型转化看,耕地与其他景观类型相互转化较为密切,特别是与建设用地和园地之间的转化;林地面积的增加主要来源于草地和耕地;(2)泉水补给区生态服务功能价值主要由林地和耕地景观生态服务价值构成,其变化对该研究区生态服务价值变化起决定作用;从生态服务价值构成类型来看,该地区土壤形成与保护服务功能单项价值所占比重最大,约占总服务功能价值的20%;(3)90年代以来,该地区总生态服务价值呈增加趋势;从单项服务价值变化来看,水源涵养、废物处理和食物生产服务功能价值则呈现出减小趋势,其中,以水源涵养减幅最大,为4.01%,主要是由该区建设用地增加,地面硬化面积增多而引起的。研究认为,济南市南部山区作为重要的泉水补给区,其生态服务功能尤为重要,特别是水源涵养功能,因此,研究区水源涵养服务功能价值的降低应在今后南部山区开发过程中得到足够的重视与保护,逐步增加泉水补给区的整体生态效益。     

SASW法在粉土液化判别中的应用

文章介绍了面波法(SASW法)的基本原理与测试方法,并将该方法用于判别黄河三角洲饱和粉土的液化势.通过标准贯入试验结果与瑞雷波法判别结果的对比,说明以剪切波速为土性指标的液化判别方法是一个很有前景的方法,但由于资料太少,建议继续收集液化调查资料,以发展出一个有充分根据的液化判别方法.     

RESPONSE OF EQUATORIAL PACIFIC UPPER OCEAN CURRENT TO WESTERLY WIND BURSTS

The characteristics of the response of equatorial Pacific upper ocean current to westerly wind bursts(WWB)were analyzed in the frequency domain by using wind and ADCP data collected by the Shiyan3 during TOGA-COARE IOP,1992-1993.The preliminary results showed that the response consistedof an eastward surface jet at shallower than 60m depth,a westward counter current centering near100m and a shear layer between them,with the variations of all three being nonlinear and nearlysynchronous.The oceanic responses in the frequency domain were characterized by occurrences of a remotely forced mixed Rossby-gravity wave with period of 8-10 days in the surface jet andcountercurrent at shallower than 110 m depth,and two locally forced waves with periods of 24 daysand 4-5 days limited in shallower than 70m depth.These fluctuations of the responses depended much more on zonal wind than meridional wind.The results also revealed that the oceanic response toWWB resulted from momentum transport and energy propagation assoc     

对吐哈盆地相邻两幅遥感图像的辐射匹配

在ERDAS软件的支持下,对吐哈盆地相邻的两幅ETM遥感图像采用所介绍的直方图加减均值差和方差均值2种方法进行辐射匹配,并得出基于这2种方法的几点结论用于提高辐射匹配程度。同时为了降低匹配时存在的人为误差,提出了一种新的多样本均值的辐射匹配方法。最后通过对3种匹配方法的结果进行定量性检验,证明多样本均值的辐射匹配方法能达到较好的匹配效果,其匹配结果要优于前2种方法,具有可行性。笔者的目的在于:经过对不同方法的运用、对比及验证,提出了一种更为优越的辐射匹配方法———多样本均值法,以用于对吐哈盆地整体的辐射匹配。较好的匹配效果有助于对盆地内一些相关指数的准确评价和其砂岩型铀矿的分析研究。     

热力和动力强迫对热带海洋运动影响的数值试验

本文提出了一个赤道β平面非定常线性模式,其垂直结构在斜温层以上是具有相同密度的两个活动层,斜温层以下是密度较大的均质静止流体。数值试验表明,热强迫与风强迫相比对海洋的直接影响很小,但通过海气相互作用,它可形成风强迫作用于海洋,对海气环流系统有支配作用。     

主成分监督分类及其在水质特征遥感图像识别中的应用

建立了一种水域水质状况图像识别的主成分监督分类方法,首先通过ＴＭ水域图像数据的主成分分析,将原有各波段图谱的显著且独立的信息集中在数目尽可能少的合成图象中,再依据不同类型水体的光谱特征,分析各主成分图像的构成及其环境生态学含义,由此对整个研究区域内存在的不同标志类型及其分布特征有所了解,在此基础上,选定训练样本集,从而人有清楚的环境生态意义的标志类型,应用监督法得到较好的识别分类结果,分析表明,这     

Global ionospheric electron density estimation based on multisource TEC data assimilation

GPS Solutions - We developed a parameterized ionospheric electron density model based on the IRI-2012 model by spherical harmonic expansions in the horizontal and empirical orthogonal functions in...     

Geological Characteristics and Zircon U‐Pb Dating of Volcanic Rocks from the Beizhan Iron Deposit in Western Tianshan Mountains,Xinjiang, NW China

The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and both of the hanging wall and footwall are quartz-monzonite; the dip is to the north with thick and high-grade ore bodies downwards. Ore minerals are mainly magnetite with minor sulfides, such as pyrite, pyrrhotite, chalcopyrite and sphalerite. Skarnization is widespread around the ore bodies, and garnet, diopside, wollastonite, actinolite, epidote, uralite, tourmaline sericite and calcite are ubiquitous as gangues. Radiating outwards from the center of the ore body the deposit can be classified into skarn, calcite, serpentinite and marble zones. LA-ICP-MS zircon U-Pb dating of the rhyolite and dacite from the Dahalajunshan Formation indicates that they were formed at 301.3±0.8 Ma and 303.7±0.9 Ma, respectively, which might have been related to the continental arc magmatism during the late stage of subduction in the western Tianshan Mountains. Iron formation is genetically related with volcanic eruption during this interval. The Dahalajunshan Formation and the quartz-monzonite intrusion jointly control the distribution of ore bodies. Both ore textures and wall rock alteration indicate that the Beizhan iron deposit is probably skarn type.