基于VIIRS数据的中国东部气溶胶光学厚度反演算法改进

VIIRS(Visible Infrared Imaging Radiometer Suite)作为MODIS(The MODerate resolution Imaging Spectroradiometer)的后继传感器,可在全球范围内实现对气溶胶的连续时空监测.卫星反演的气溶胶光学厚度(Aerosol Optical Depth,AOD)是研究地球能量收支平衡、气候效应和空气质量的重要大气参数.但在中国重污染天气情况下,现有的VIIRS陆地气溶胶产品存在一定不足.因此,本研究改进云识别方法,优化像元筛选,约束气溶胶类型选择,实现重污染情况下AOD的反演.基于地基AERONET(AErosol RObotic NETwork)的验证结果表明,相比NOAA(National Oceanic and Atmospheric Administration)产品,改进后的反演结果克服了反演值偏低的问题,且表现出更好的相关性,RMSE从0.236下降到0.219.为验证在重污染条件下改进算法的适用性和准确性,本文对比了两种污染条件下的反演结果(0.61).统计结果表明,在较重污染天气条件下(AODAERONET>1),相比NOAA的AOD产品,本文结果的反演率从32.3%提升为68.8%,回归分析的斜率提高为0.80,相关系数达到0.76,均方根误差为0.307,在增加反演量的同时保证了反演的精度.     

徐州地震台2016年11月—2017年YRY-4分量钻孔应变仪异常核实

2016年11月-2017年,徐州地震台YRY-4分量钻孔应变曲线出现"漏斗"状向下凹陷的压性变化,从场地环境、观测环境、观测系统进行现场核实,并对异常期间的观测数据进行对比分析,排除外界干扰及仪器自身问题,认为此次数据畸变可能反映了地下应力的真实变化,应为地下地质构造发生变化所致。     

The effects of the thermal state of overriding continental plate on subduction dynamics: Two-dimensional thermal-mechanical modeling

The dynamic process of ocean-continent subduction depends on not only the properties of the subducting oceanic plate, but also the characteristics and state of the overriding continental plate. Numerical models conducted to date have mostly focused on the oceanic lithosphere in this regard; research on the properties of overriding continental lithosphere remains relatively limited, especially the influence of its thermal state on subduction dynamics. Here we explored the performance of continental lithosphere with different thermal states during the subduction process using two-dimensional thermal-mechanical modeling and systematically investigated the effects of the thermal state of overriding continental plate, the age of subducting oceanic plate, and relative convergence rate on subduction dynamics. Modeling results show that:(1) When the geothermal gradient of continental crust is low(between 10 and 15 ℃ km~(-1)), the oceanic plate first subducts at a low angle. As subduction continues, the slab dip gradually increases and the slab begins to retreat rapidly driven by its negative buoyancy, opening an ocean basin ranging from 600 to 1100 km in width. This leads to the decoupling between the overriding continental plate and oceanic plate. As the trench retreat continues, the horizontal deviatoric stress inside the overriding continental crust alternates between being positive and negative in a local area. Thinning of the overriding lithosphere mainly occurs at the region adjacent to the subduction zone, where the surface experiences significant subsidence.(2) When the geothermal gradient of continental crust is higher(greater than 15 ℃ km~(-1)), oceanic plate retreat causes the overriding continental plate to be strongly stretched. In this case, the trench retreat distance decreases and the width of the ocean basin also reduces by between 100 and 1000 km. The horizontal deviatoric stress inside the whole overriding continental crust first manifests as compression and then changes into extension, which causes the surface to first uplift and then slowly subside.(3) Increasing the age of oceanic lithosphere accelerates trench retreat and promotes overriding plate thinning.(4) An advancing overriding continental plate slows down trench retreat. In cases where the geothermal gradient of continental crust is greater than 17.5 ℃ km~(-1), the hot continental crust experiences gravitational collapse and is overthrusted onto oceanic lithosphere, resulting in slow trench retreat. We analyzed the subduction process of the western Paleo-Pacific Plate in the Early Cretaceous based on our modeling results and discussed its possible control on the tectonic evolution of the rift basins in east Asia. We suggest that the development of a wide rift basin system on the Amurian Superterrane in the Early Cretaceous was likely related to slow trench retreat and the collapse of the hot crust, and the formation of a series of passive rift basins in the North China Craton was likely caused by the relatively cold thermal state of the lithosphere and the rapid retreat of the Paleo-Pacific Plate.     

Embodied carbon emissions in China-US trade

China-US trade holds great significance for the world's political and economic landscape. Since 2018, the US government has imposed additional tariffs on Chinese exports on the grounds of the US trade deficit with China. However, the transfer of pollutants embodied in trade and the differences in environmental costs between China and the US have not been widely recognized. In this study, we quantify the embodied carbon emissions(the "virtual" emissions associated with trade and consumption) in China-US trade by constructing a carbon dioxide emissions inventory and a multiregional input-output model.The study shows that the US benefits from a trade surplus of environmental costs by importing energy-intensive and pollutionintensive products from China, which increases China's environmental pollution and abatement costs. In 2017, 288 Mt CO_2 emissions were associated with products produced in China but finally consumed in the US, and only 46 Mt CO_2 were associated with the US products that were consumed in China. From this perspective, China-US trade results in a net transfer of 242 Mt CO_2 per year from the US to China, accounting for approximately 5% of the total CO_2 emissions in the US. More importantly, for Chinese products exported to the US, the carbon emissions embodied in one unit of economic value amount to 0.92 kg/$(RMB:USD=6.8:1), but for US products exported to China, the carbon emissions embodied in one unit of economic value amount to 0.53 kg/$, which means China will incur environmental costs that are 74% higher than those of the US while enjoying the same economic benefits. This environmental trade deficit has burdened China with higher environmental costs than economic benefits.To address this environmental trade deficit, China should actively promote further industrial upgrading and energy structure adjustment and increase investment in innovation and RD, thereby increasing the value added per unit of export products and reducing the environmental cost of producing export products.     

甲醛溶液对发头裸腹溞及其体表聚缩虫影响的试验

不同浓度的甲醛溶液对枝角类发头裸腹溲Ｍｏｄｉｎａｉｒｒａｓａ的致毒效应以及对其体表附着的聚缩虫Ｚｏｏｔｈａｍｉｕｍｓｐ．的杀灭效果的试验结果表明,１２ｈ、２４ｈ两俱和用时段中,甲醛浓度与发头裸腹溲相对存活率之间以及甲醛浓度与发头裸腹溲体表聚缩虫营养体脱落率之间存在一定的函数关系。     

中国苦草属(Vallisneria)植物萌发与生长的影响因素

由于人类生产生活对众多淡水水体的扰动、污染,我国苦草属(Vallisneria)植物的种群规模出现了严重的退化.明确苦草属植物萌发和生长的影响因素,阐明苦草属植物退化的原因,是保护和恢复该属植物亟需解决的科学问题.通过对已发表的文献进行收集和分析,总结了影响苦草属植物萌发和生长的主要因素,并通过挖掘文献中的数据,对重要环境因子与苦草属植物萌发和生长参数的关系进行了分析.结果表明:(1)涉及苦草(V.natans(Lour.) Hara)的研究较多,而涉及刺苦草(V.spinulosa Yan)和密刺苦草(V.denseserrulata Makino)的研究较少;(2)苦草属植物种子的萌发受到温度、光照强度、水深、掩埋深度、基质情况和储存方式等因素的影响;(3)苦草属植物生长受到光照强度、水深、水体营养水平、底泥营养水平、底泥有机质和动物牧食等因素的影响;(4)其他条件适宜时,苦草和刺苦草种子在20～30℃都保持较高的萌发率(均值 50%);(5)苦草种子萌发率随着掩埋深度的增加而快速下降;(6)苦草的相对生长率随光照强度的增加而升高,随水深增加而下降;(7)苦草的相对生长率随着氨氮浓度增加而下降;(8)水体和底泥中高含量的总氮和总磷对苦草属植物生长的抑制作用主要是通过促进浮游植物和附着藻生长导致的遮光,而不是直接毒害作用.未来需要进一步加强苦草属植物萌发、生长参数与环境因子关系的定量研究,更好地服务于该属植物的保护和恢复.     

国家地震台数据断记统计及批量补数自动处理

在VS2015开发环境下,使用C#语言编写国家地震台断记统计和批量补数自动处理程序,实现数据中断统计查询、数据采集器波形数据文件下载和上传波形数据文件至远程服务器的自动化。该自动处理程序在部分地震台使用以来,运行良好,数据完整率、连续率得到保障。     

Geological and geochemical characteristics of the Baogudi Carlintype gold district(Southwest Guizhou,China) and their geological implications

The newly discovered Baogudi gold district is located in the southwestern Guizhou Province,China,where there are numerous Carlin-type gold deposits.To better understand the geological and geochemical characteristics of the Baogudi gold district,we carried out petrographic observations,elemental analyses,and fluid inclusion and isotopic composition studies.We also compared the results with those of typical Carlin-type gold deposits in southwestern Guizhou.Three mineralization stages,namely,the sedimentation diagenesis,hydrothermal(main-ore and late-ore substages),and supergene stages,were identified based on field and petrographic observations.The main-ore and late-ore stages correspond to Au and Sb mineralization,respectively,which are similar to typical Carlin-type mineralization.The mass transfer associated with alteration and mineralization shows that a significant amount of Au,As,Sb,Hg,Tl,Mo,and S were added to mineralized rocks during the main-ore stage.Remarkably,arsenic,Sb,and S were added to the mineralized rocks during the late-ore stage.Element migration indicates that the sulfidation process was responsible for ore formation.Four types of fluid inclusions were identified in ore-related quartz and fluorite.The main-ore stage fluids are characterized by an H2O–NaCl–CO2–CH4±N2system,with medium to low temperatures(180–260℃)and low salinity(0–9.08%NaCl equivalent).The late-ore stage fluids featured H2O–NaCl±CO2±CH4,with low temperature(120–200℃)and low salinity(0–7.48%Na Cl equivalent).The temperature,salinity,and CO2and CH4concentrations of ore-forming fluids decreased from the main-ore stage to the late-ore stage.The calculated δ^13C,d D,and δ^18O values of the ore-forming fluids range from-14.3 to-7.0%,-76 to-55.7%,and 4.5–15.0%,respectively.Late-ore-stage stibnite had δ^34S values ranging from-0.6 to 1.9%.These stable isotopic compositions indicate that the ore-forming fluids originated mainly from deep magmatic hydrothermal fluids,with minor contributions from strata.Collectively,the Baogudi metallogenic district has geological and geochemical characteristics that are typical of Carlin-type gold deposits in southwest Guizhou.It is likely that the Baogudi gold district,together with other Carlin-type gold deposits in southwestern Guizhou,was formed in response to a single widespread metallogenic event.     

Nonstationary extreme value analysis of temperature extremes in China

In a changing climate, the common assumption of stationarity of climate extremes has been increasingly challenged, raising the need to incorporate non-stationarity in extreme value modeling. In this study, quantile regression is used to identify the trends of annual temperature extremes and their correlations with two large climate patterns, the western Pacific subtropical high (WPSH) and the Arctic Oscillation (AO) at 357 stations in China. Statistical significant positive trends and correlations between warm (or cold) temperature extremes and WPSH (or AO) have been detected at most stations. The influence of WPSH on warm extremes is significant in southern China, while the AO mainly affects the cold extremes in northern and eastern China. Then, annual temperature extremes are fitted to generalized extreme value (GEV) distributions with time-varying parameters. The summer (or winter) mean daily maximum (or minimum) temperatures and two climate indices, the WPSH index and the AO index, are chosen as covariates. In total, 16 candidate GEV distribution models are constructed, and the best fitting model with the lowest Bayesian information criterion (BIC) is selected. The 20-year return levels of annual warm (or cold) extremes in the period 1961–1980 and 1991–2010 are computed and compared. The changes of 20-year return levels of annual warm and cold extremes are jointly determined by trend and distributional changes of annual temperature extremes. Analysis of large scale atmospheric circulation changes indicate that a strengthening anticyclonic circulation and increasing geopotential height in recent decades may have contributed to the changes in temperature extremes in China.