干雪深度反演的同极化相位差模型

积雪深度是积雪的重要结构参数,获取高精度雪深空间分布信息对于流域尺度水资源管理、气候变化研究和灾害预报等具有重要意义.本文以新疆阿尔泰山南坡克兰河上游为研究区,利用C波段全极化GF-3数据及地面同步观测数据,根据VV与HH极化信号在积雪中折射率不同导致相位差异的原理,使用Maxwell-Garnett方程构建同极化相位差(co-pol arized phase difference,CPD)的正演模型,并基于CPD与雪深关系构建了雪深反演模型.通过对具有不同积雪条件的浅雪区与深雪区分别进行雪深反演,获得雪深空间分布信息.同时对反演不确定性进行了分析,并与已有方法进行比较,研究结果表明:①假定研究区积雪各向异性介电常数恒定的理想情况下,CPD仅是雪深的函数,可用半经验的线性模型反演雪深,反演精度的高低与计算CPD过程中使用的滤波器的窗口大小有关,浅雪区的最优滤波窗口为59×59像元,反演精度R为0.83,RMSE为2.72 cm,深雪区的最优滤波窗口为33×33像元,反演精度R为0.54,RMSE为11.69 cm;②雪深反演误差与坡度显著相关,随着坡度的增加,雪深的反演误差呈现出显著增加的趋势,雪深反演不确定性受雪层变质程度、含水量及卫星入射角观测几何条件影响,反演方法对于干燥、雪层变质结晶程度低、均质的积雪及具有大入射角的SAR卫星有更好的适用性;③对比已有基于CPD模型的雪深反演方法,本文方法已经将反演所需要的参数减少为遥感获取的CPD数据,以及进行模型拟合的实测雪深数据,反演精度更高.研究表明CPD模型反演山区雪深空间分布是有效和可行的,研究成果为山区雪深遥感反演提供了新思路.     

Clay mineral assemblages of the oceanic red beds in the northern South China Sea and their responses to the Middle Miocene Climate Transition

Science China Earth Sciences - The Middle Miocene Climate Transition (MMCT, ～14 Ma) is the largest cooling event in the Cenozoic “Coolhouse”, which significantly impacts the...     

A glimpse into rapid freezing processes in clay with x-ray tomography

Acta Geotechnica - This short paper proposes time-series x-ray tomography as a valuable tool for quantifying freezing processes in a remoulded clay. As an example, three simple closed system...     

Streamflow change of major rivers over the Tibetan Plateau during the last half century and its possible causes

The streamflow on the Tibetan Plateau (TP) plays an important role in the water supply of Asia's main river basins. To enhance understanding of hydrologic cycle under the pronounced warming over the TP, this study comprehensively investigates the streamflow changes at the upstream of six major rivers (Yellow River, Yalong River, Jinsha River, Lancang River, Nu River, and Yarlung Zangbo River) originating from the TP, and then diagnoses their possible causes by analysing the impacts of climate variability and human activities. Results indicate that these six major rivers studied have generally insignificant increasing trends in annual streamflow during the last half century, except for two stations. The significant increase appears at the Tuotuohe station in the headwater area of Jinsha River, while the dramatic decrease occurs at the Yunjinghong station in the downstream of Lancang River. In terms of climate factors, the six river basins show a distinct warming trend, along with a noticeable increase in precipitation over the central and northern regions. Pan evaporation, wind speed, sunshine duration, and relative humidity have been found to gradually decrease in most areas. As for the Tuotuohe station, both warming-induced meltwater and increasing precipitation might jointly contribute to the increasing streamflow. But for the Yunjinghong station, the results simulated by the Variable Infiltration Capacity (VIC) model indicate that human activities, especially for the impoundment processes of Xiaowan and Nuozhadu dams, significantly influenced the streamflow, contributing to approximately 69% of the streamflow reduction during 2009–2013. In the context of accelerated global warming, greater attention should be paid to hydrometeorological changes on the TP to offer further insights for the water resources management of the ‘Asian Water Tower’.     

城乡用地协同调控系统集成应用研究——以成都平原为例

针对成都平原各类国土资源管理信息系统特定性较强、不易共享等问题,在探讨当前主流GIS集成策略不足之处的基础上,通过设计元数据库对应关系,对成都平原多源异构数据进行集成,以此为基础建立了城乡用地协同调控系统,并讨论其中的关键技术.     

中药熏蒸治疗腰椎间盘突出症的用药规律探析

目的：分析中药熏蒸治疗腰椎间盘突出症（LDH）的用药规律。方法：计算机检索2017年1月1日至2022年7月31日中国知网（CNKI）、万方数据(WANFANG DATA)、维普中文科技期刊数据库（VIP）中关于中药熏蒸治疗LDH的处方,借助中医传承辅助平台（V2.5）分析药物的频次、性味、归经,基于关联规则和复杂系统熵聚类分析核心药物组合等遣方规律。结果：共纳入处方150首,涉及中药171味。使用频.次≥30次的药物有18味,排前10位的分别为红花、伸筋草、透骨草、川芎、当归、威灵仙、独活、牛膝、桂枝和川乌。药性以温、平、寒为主;药味以辛、苦、甘、咸为主;归经主要归肝、心、肾、脾和膀胱经。关联规则分析得到常用药物组合19组。复杂系统熵聚类分析得到核心药物组合12组与新处方6首。结论：中药熏蒸治疗LDH多采用祛风湿、活血化瘀之药,兼以补益肝肾药。     

Enhanced hysteresis of suspended sediment transport in response to upstream damming: An example of the middle Yangtze River downstream of the Three Gorges Dam

The peak in sediment transport in alluvial rivers generally lags behind the peak in discharge. It is thus not clear how the hysteresis in the sediment/discharge relationship may be impacted by damming, which can fundamentally alter the water and sediment regimes in the downstream reaches of the river. In this study, a total of 500 flood events in the Yichang–Chenglingji Reach (YCR) of the Middle Yangtze River immediately downstream of the Three Gorges Dam (TGD) are analysed to study the impacts of dam operations on the hysteresis of suspended sediment transport. Sediment rating curves, hysteresis patterns, as well as lag times, are investigated to determine the relationship between suspended sediment concentration (SSC) and flow discharge (Q) at different temporal scales, from inter-annual to individual flood events, for the pre- and post-TGD period from 1992 to 2002 and from 2003 to 2017, respectively. The results showed that the TGD operation decreased the frequency and magnitude of floods. The decrease in peak flow and increase in base flow weakened the flood contribution to the annual discharge by nearly 20%. However, the relative suspended sediment load contribution during flood events was much higher than the discharge contribution, and was little impacted by the dam. At seasonal and monthly scales, more than 80% of the suspended sediment was transported by ~65% of the water discharge in the summer and early autumn. The monthly SSC–Q relationship changed from a figure-eight to an anti-clockwise pattern after the construction of the TGD. For single flood events, the TGD operations significantly modified the downstream SSC–Q hysteresis patterns, increasing the frequency of anti-clockwise loops and the lag time between peak Q and peak SSC. These adjustments were mainly caused by differences in the propagation velocities of flood and sediment waves and the sediment ‘storage–mobilization–depletion’ process, whereas the influence of lateral diversions was small. © 2020 John Wiley & Sons, Ltd.     

Prospects of interventions to alleviate rural–urban migration in Jiangsu Province,China based on sensitivity and scenario analysis

ABSTRACT

Rural–urban migration is an adaptive response to location-specific environmental or socio-economic stressors. Jiangsu Province, China is witnessing rapid economic growth fuelled by manufacturing and services sector. Rural–urban migration in Jiangsu, which brings higher stress to resource-carrying capacity of urban areas, is driven by rural “push” factors, principally labour surplus and unemployment in agriculture. This study investigates possible policy interventions aimed at relieving the rapid rural–urban migration in Jiangsu based on a sensitivity analysis of driving factors in rural agricultural production. It shows that rural–urban migration is sensitive to input elasticities of precipitation and labour. Two groups of scenario analysis corresponding to possible policy interventions are implemented. The first policy focuses on providing government subsidies to rural non-agricultural industries then compensate for the shrinking agricultural production. Another policy supports education in rural areas to provide more skilled labour resource which can be absorbed by non-agricultural industries. Both two policies are effective in reducing rural unemployment and alleviating rural–urban migration.     

中国绿色旅游基地适宜性综合评价

绿色旅游主要指以游览原生态自然山水获得身心愉悦的旅游。以多源地理信息数据为基础,基于GIS空间技术,通过综合分析绿色旅游资源、现状和潜力,对国家绿色旅游资源进行空间探索性分析,从而为国家绿色旅游基地建设、适宜性评价和基地选址提供参考。结果表明：① 中国绿色旅游发展适宜区域整体呈现出分片聚集状态,各片区中很适宜和适宜地区在空间上呈交叉分布。② 中部低纬度地区,绿色旅游资源基础、现状和潜力均较好;西部地区资源分布零散,发展现状和潜力相对薄弱,但区域特色优势显著,适宜依托区域特色进行深度开发。东北山脉地区的绿色旅游已达到一定规模,应提升旅游品质,扩大影响力;其他地区因气候、地形等因素,较难发展绿色旅游产业。     

Effect of Wetland Reclamation on Soil Organic Carbon Stability in Peat Mire Soil Around Xingkai Lake in Northeast China

Content and density of soil organic carbon(SOC) and labile and stable SOC fractions in peat mire soil in wetland, soybean field and rice paddy field reclaimed from the wetland around Xingkai Lake in Northeast China were studied. Studies were designed to investigate the impact of reclamation of wetland for soybean and rice farming on stability of SOC. After reclamation, SOC content and density in the top 0–30 cm soil layer decreased, and SOC content and density in soybean field were higher than that in paddy field. Content and density of labile SOC fractions also decreased, and density of labile SOC fractions and their ratios with SOC in soybean field were lower than that observed in paddy field. In the 0–30 cm soil layer, densities of labile SOC fractions, namely, dissolved organic carbon(DOC), microbial biomass carbon(MBC), readily oxidized carbon(ROC) and readily mineralized carbon(RMC), in both soybean field and paddy field were all found to be lower than those in wetland by 34.00% and 13.83%, 51.74% and 35.13%, 62.24% and 59.00%, and 64.24% and 17.86%, respectively. After reclamation, SOC density of micro-aggregates( 0.25 mm) as a stable SOC fraction and its ratio with SOC in 0–5, 5–10, 10–20 and 20–30 cm soil layers increased. SOC density of micro-aggregates in the 0–30 cm soil layer in soybean field was 50.83% higher than that in paddy field. Due to reclamation, SOC density and labile SOC fraction density decreased, but after reclamation, most SOC was stored in a more complex and stable form. Soybean farming is more friendly for sustainable SOC residence in the soils than rice farming.