Twenty-five years of spectral UV-B measurements over Canada,Europe and Japan: Trends and effects from changes in ozone,aerosols, clouds,and surface reflectivity

Spectral UV records of solar irradiance at stations over Europe, Canada, and Japan were used to study long-term trends at 307.5 nm for a 25-year period, from 1992 to 2016. Ground-based measurements of total ozone, as well as satellite measurements of the Aerosol Index, the Total Cloud Cover and the surface reflectivity were also used in order to attribute the estimated changes of the UV to the corresponding changes of these factors. The present study shows that over the Northern Hemisphere, the long-term changes in UV-B radiation reaching the Earth's surface vary significantly over different locations, and that the main drivers of these variations are changes in aerosols and total ozone. At high latitudes, part of the observed changes may also be attributed to changes in the surface reflectivity. Over Japan, the UV-B irradiance at 307.5 nm has increased significantly by ∼3%/decade during the past 25 years, possibly due to the corresponding significant decrease of its absorption by aerosols. It was found that the greatest part of this increase took place before the mid-2000s. The only European station, over which UV radiation increases significantly, is that of Thessaloniki, Greece. Analysis of the clear-sky irradiance for the particular station shows increasing irradiance at 307.5 nm by ∼3.5%/decade during the entire period of study, with an increasing rate of change during the last decade, possibly again due to the decreasing absorption by aerosols.     

白垩纪地球表层系统重大地质事件与温室气候变化研究

国家重点基础研究发展计划（973）项目“白垩纪地球表层系统重大地质事件与温室气候变化”，将以白垩纪与碳循环相关的重大地质事件和温室气候变化的关系为主线，以大洋缺氧事件—富氧作用转变过程和机制研究为突破口，进行海陆相整合研究，重点追溯东特提斯洋和我国大陆地球表层系统重大地质事件的记录，探讨这些事件与碳循环、快速气候变化的正/负反馈机制。项目将充分利用中国大陆发育完好的白垩纪海相、陆相地层及古生物记录，通过松辽盆地白垩系科学钻探全岩芯取样和多学科综合研究的途径，着眼于厘定反映地质事件和气候变化的层位及标志和时间格架，解决高分辨率海、陆相沉积事件的精确对比，分析地层记录中气候标志和古生物类群的地理分布，集中研究陆地和海洋环境对同一事件的响应机制，重溯白垩纪地球表层系统重大地质事件过程及成因，探究陆相烃源岩大规模形成、陆地生物群更替与温室气候变化和碳循环之间的正/负反馈关系和机制等科学问题，为预测全球长时间尺度上的气候变化趋势提供科学依据。     

青藏高原北麓河地区沥青路面辐射特征分析

沥青路面是寒区道路工程主要路面类型之一, 其对热量的吸收易诱发寒区道路病害. 在青藏高原北麓河试验场对沥青路面和天然地表的太阳辐射和地面辐射通量进行了观测, 对比分析了两种地面类型在能量辐射方面的差异. 结果表明: 天然地表的反照率是沥青路面的2~3倍. 沥青路面和天然地表的辐射通量总体呈夏季 >秋季 >春季 >冬季特点. 到达沥青路面的向下长、短波辐射量均大于天然地表, 沥青路面向上的长波辐射通量大于天然地表. 2009年9月-2010年8月沥青路面的净辐射量比天然地表多302.2 MJ·m^-2, 2010年9月-2011年8月向上的短波辐射相对增加, 使得沥青路面的净辐射量仅比天然地表多28.21 MJ·m^-2. 在5 cm深度, 沥青路面的温度比天然地表高约1.15~8.6 ℃. 对短波辐射的削减和对长波的吸收是其净辐射量增加的重要原因, 在能量辐射方面的差异是造成沥青路面吸热的重要原因之一.     

Satellite evidence for no change in terrestrial latent heat flux in the Three-River Headwaters region of China over the past three decades

Terrestrial latent heat flux (LE) in the Three-River Headwaters region (TRHR) of China plays an essential role in quantifying the amount of water evaporation and carbon sink over the high altitude Tibetan Plateau (TP). Global warming is expected to accelerate terrestrial hydrological cycle and to increase evaporation. However, direct field observations are lacking in this region and the long-term variability in LE remains uncertain. In this study, we have revised a semi-empirical Penman LE algorithm based on ground eddy covariance (EC) observations from an alpine grass site and provided new satellite-based evidence to assess LE change in the TRHR during 1982–2010. Our results show that the average annual terrestrial LE in the TRHR is about 38.8 W/m ² and there is no statistically significant change in annual LE from 1982 to 2010. We also found that during the same time period, terrestrial LE over the east region of the TRHR significantly decreased, on average, by 0.7 W/m ² per decade, which was driven primarily by the surface incident solar radiation (R_s) limitation, offsetting the increased LE over the west region of the TRHR caused by the increased precipitation (P) and soil moisture (SM).     

珠穆朗玛峰北坡海拔6523m辐射平衡观测结果分析

利用2005年5月1日至7月22日在东绒布冰川海拔6523m的若普拉垭口架设的自动气象站获得的各辐射参数资料,分析了该地区总辐射、地面反射辐射、地面长波辐射、天空长波辐射的日平均变化和平均日变化,并计算了反射率和辐射平衡.结果表明:1)短波辐射的平均日变化都随着太阳高度角的增大而加强,并且总辐射和地面反射辐射的日平均变化有很好的相关性,观测期间二者的月平均值都在5月份最大.由于垭口新降雪较多,雪面的反射率也很高;2)天空长波辐射的平均日变化比地面长波辐射变化滞后2 h,且其日平均变化幅度比地面长波辐射的变化幅度大;3)净辐射的平均日变化随着太阳高度角的变化而变化,下午14:00时净辐射最大,其日平均变化在观测期间整体上有增大趋势.     

地面辐射气候学研究进展——从卫星反演地面辐射能收支的若干问题

地面辐射气候学研究的开展对了解当今地球气候是一重要步骤。为了能获取全球范围具有一定空间，时间分辨率的资料，卫星观测的应用是必不可少的。本文对地气系统辐射能收支的卫星观测研究取得的成果作简要回顾后，重点介绍了地面短波，长波辐射通地面净辐射的地面短波、长波辐射通量及地面净辐射的卫星反演取得的进展，存在问题及今后的发展趋势。     

地面辐射气候学研究进展───从卫星反演地面辐射能收支的若干问题

地面辐射气候学研究的开展对了解当今地球气候是一重要步骤。为了能获取全球范围具有一定空间、时间分辨率的资料，卫星观测的应用是必不可少的。本文对地气系统辐射能收支的卫星观测研究取得的成果作简要回顾后，重点介绍了地面短波、长波辐射通量及地面净辐射的卫星反演取得的进展、存在问题及今后的发展趋势。     

Research on Dynamic of Terrestrial System of China: Academic Logic and Synthetic Scheme

Land surface, the environment where human survive and develop, is a synthesis formed with multi-scaled and multi-process interactions between natural factors. The terrestrial system, which is the core study field of physical geography, can be defined as the land surface synthesis with spatially ordered distribution and temporally dynamic balance. In the past century, natural variations and human activities have had profound influences on land surface. How they drove the changed interactions between land surface factors, and further altered the land surface pattern, are the frontier and basis for global change and geography studies. Based on the brief review of research on terrestrial system at home and abroad, the paper summarized the existing difficulties and problems, and then proposed the academic logic for studies of dynamic of terrestrial system. The research should be conducted following the logic of elements, patterns and dynamic, with emphasis on themes of processes and feedback, variation in regions and terrestrial system. At last, the synthetic scheme was designed for research on dynamic of terrestrial system. Aimed at innovation of regionalization methodology and detection on driving mechanism of dynamic of terrestrial system, the following four aspects should be included: Changes and interaction mechanism of key factors (i.e. water, soil, climate and plant) and their spatial-temporal variation; Quantifying the influences of factor interactions on regionalization formation and conversion; Quantified assessment on changing tendency and magnitude of land surface pattern under global climate change; Accomplishment of dynamic land surface pattern at different past and future stages. Correspondingly, the technical route should combine bottom-up and top-down methodologies, with field survey, earth observation, station monitoring and mathematical simulation to build the comprehensive database. Conducting research on dynamic of terrestrial system can be helpful for developing theory of integrated physical geography, deepening cognition on dynamic land surface pattern, and providing scientific basis for regional sustainable resources utilization and countermeasure establishment of climate change adaptation.     

稳定碳同位素在第四纪古环境研究中的应用

文章对陆相沉积物、湖沼相沉积物以及脊椎动物牙齿中的δ¹³C研究作了系统的综述,特别对存在的问题提出了一些看法,认为黄土-古土壤序列中有机质δ¹³C与碳酸盐δ¹³C变化趋势相反的原因是CO₂与碳酸盐交换平衡时的分馏系数在古土壤堆积时和黄土发育时不一致造成的;陆相沉积物的有机质δ¹³C较碳酸盐δ¹³C能更加直接地反映沉积时地表植被状况,陆相沉积物的碳酸盐δ¹³C在古生态中的应用还有待于对它的形成机制和形成过程进行进一步的研究;我国黄土高原末次冰期的气候不利于C4的生长.文章强调古环境、古生态研究应该从现代过程入手,了解现代植物δ13C与气候参数的关系以及现代C4植物的分布规律.同时还认为分子化石的稳定同位素研究这一新研究手段将会给第四纪研究带来更新的活力.     

高寒湿地太阳辐射和地表反射率变化的统计学特征

依据祁连山海北高寒湿地植物生长期观测的太阳总辐射(E_g)和反射辐射(Er)资料,分析了高寒湿地E_g和地表反射率(A)的日及季节变化特征.结果表明:祁连山海北高寒湿地,有较强的E_g,但A较低.年内1-12月E_g的平均日总量达17.3 MJ·m^-2,其中植物生长期的5-9月平均日总量为20.0MJ·m^-2,表现出4-7月高,冷季低的变化特征.A的日、季节变化均表现“U”型变化过程.2004年1-12月A的年平均值为0.32,植物生长季的5-9月平均值为0.18,植物非生长季的10月-翌年4月平均值为0.43.其中1月最高(0.70),7月最低(0.16).     

硅的生物地球化学循环研究进展

生命元素硅在陆地生态系统和水生生态系统中都扮演着重要的角色。它的生物地球化学循环与全球碳循环和全球气候交化密切相关。因此,近年来逐渐成为研究的热点。本文概述了近年来国内外有关硅的生物地球化学循环的研究进展,包括陆地和海洋中硅的生物地球化学循环过程及人类活动对硅循环的影响等方面,指出日前研究中存在的问题,展望了研究的重点。     

The geochemical composition of the terrestrial surface (without soils) and comparison with the upper continental crust

The terrestrial surface, the “skin of the earth”, is an important interface for global (geochemical) material fluxes between major reservoirs of the Earth system: continental and oceanic crust, ocean and atmosphere. Because of a lack in knowledge of the geochemical composition of the terrestrial surface, it is not well understood how the geochemical evolution of the Earth’s crust is impacted by its properties. Therefore, here a first estimate of the geochemical composition of the terrestrial surface is provided, which can be used for further analysis. The geochemical average compositions of distinct lithological classes are calculated based on a literature review and applied to a global lithological map. Comparison with the bulk composition of the upper continental crust shows that the geochemical composition of the terrestrial surface (below the soil horizons) is significantly different from the assumed average of the upper continental crust. Specifically, the elements Ca, S, C, Cl and Mg are enriched at the terrestrial surface, while Na is depleted (and probably K). Analysis of these results provide further evidence that chemical weathering, chemical alteration of minerals in marine settings, biogeochemical processes (e.g. sulphate reduction in sediments and biomineralization) and evaporite deposition are important for the geochemical composition of the terrestrial surface on geological time scales. The movement of significant amounts of carbonate to the terrestrial surface is identified as the major process for observed Ca-differences. Because abrupt and significant changes of the carbonate abundance on the terrestrial surface are likely influencing CO₂-consumption rates by chemical weathering on geological time scales and thus the carbon cycle, refined, spatially resolved analysis is suggested. This should include the recognition of the geochemical composition of the shelf areas, now being below sea level.     

深部碳循环的环境气候效应SCIEI北大核心CSCD

地球表层温度主要由接收的太阳辐射能量及大气温室气体的保温能力共同控制。CO_(2)等温室气体通过对大气温度的调节影响着全球环境气候变化,工业革命以来全球CO_(2)排放量的增加被认为是全球变暖的重要原因,地质历史时期大气CO_(2)浓度的波动与温室和冰室气候的交替出现相对应。地球超过90%的碳赋存于深部,因此地球深部过程的些许波动便会影响到地表碳含量,进而深刻影响着地球的环境气候变化。以往的研究注重地表碳循环对环境气候的影响,对深部碳的贡献考虑不足。最近十余年全球开展了详细的深部碳循环研究,基于已经取得的重要成果,本文从大火成岩省、裂谷和俯冲带的视角对深部碳循环驱动的环境气候效应进行了系统回顾。认为未来的研究需要对地球深部碳循环通量和碳同位素组成进行更精确的定量,这是我们认识深部碳循环对地表环境气候影响的基础;除了碳元素本身我们还需要关注其他挥发性元素和有害金属元素的综合效应;俯冲带作为全球壳-幔相互作用和物质交换循环最重要的场所,应该是进行深部碳循环观察和环境气候效应研究的重点。     

氮输入对陆地生态系统碳循环关键过程的影响

碳氮作为陆地生态系统最关键的两大生源要素,它们在自然界的循环过程中不仅各自对全球变暖做出重要贡献,而且两者的循环过程显著耦合,互相影响各自的作用和效果。从氮元素对植物光合作用、呼吸作用以及土壤呼吸作用影响的角度入手,综述了氮输入对陆地生态系统碳固定和碳排放这两个碳循环关键过程的影响特征和机理,分析了陆地生态系统碳源汇对氮素变化响应的不确定性,在此基础上对未来的相关重点研究方向进行了探讨和展望。     

土地利用对岩溶作用碳汇的影响研究综述

耦合水生光合作用的岩溶作用碳汇新模式的提出使得碳酸盐岩的风化过程成为寻找“陆地剩余碳汇”(residual land sink) 的新方向。传统意义上,碳酸盐岩风化在全球碳循环模型中被认为是未快速响应地表环境变化的地质过程,然而最新一系列研究表明人类土地利用显著改变了这一地质循环过程。文章总结了岩溶作用碳汇对不同土地利用/覆被变化的具体响应,并对其机理进行了系统分析。发现土地利用与覆被变化影响岩溶作用碳循环过程主要源自土壤CO2浓度和径流量变化以及外源酸（硝酸和硫酸）的介入。证据显示在土地利用对岩溶作用碳汇的调控中土壤CO2浓度与径流量是复杂且相互制约的两个机制,人类活动产生的外源酸干扰在不同层面上的影响也不同。由于地表水生生态系统所产生的内源有机碳（AOC）的巨大稳碳能力(水生碳泵效应)在以往的研究中并没有与碳酸盐岩风化过程相联系,因而其对土地利用变化的响应过程和机理是岩溶碳循环研究的最新方向。基于土地利用调控碳酸盐岩风化过程的复杂性和多样性特点,综合考虑岩溶作用产生的DIC(溶解无机碳)与AOC在不同土地利用情况下的相互关系以及定量分析各环境因素的具体效应成为了合理制定人为土地利用调控策略的必要前提,也是岩溶作用碳汇研究的未来发展方向。      

南极沿岸固定冰观测与研究述评

南极固定冰的变化能够直接反映南极的局地气候变率,因此是数值模式验证的理想载体,对固定冰的观测研究结论也能用于评估南极海冰的年际变化。现今国际上对南极固定冰的观测和研究日渐丰富和深入,并逐渐形成了由多个国家参加的联合观测网。就海冰厚度、冰芯结构、表面辐射收支等现场测量和相机、卫星等遥感观测方面,总结了目前国内外南极固定冰观测的技术手段和研究进展,并分析了不同空间尺度上的南极固定冰年际变化特征。对南极固定冰观测研究目前存在的问题和未来的发展方向进行了探讨。     

Research advances in passive microwave remote sensing of surface freeze-thaw state北大核心CSCD

Soil freeze-thaw cycles have important effects on surface water and energy balance,and then affect vegetation growth,soil water content,carbon cycle and terrestrial ecosystem. Passive microwave plays an important role in monitoring global and regional surface freeze-thaw processes due to its high temporal resolution,abundant data and sensitivity to soil moisture. With the launch of passive microwave sensors at home and abroad,it provides conditions for the study of permafrost interannual variation,seasonal variation,diurnal variation and long time series of near-surface soil freeze-thaw cycle. In recent years,the study of surface freeze-thaw cycle using passive microwave data has gradually increased. Based on previous studies,this paper summarizes the types of passive microwave remote sensing data and the characteristics of the bands contained in them. Expounded the principle of passive microwave monitoring data used for freezing and thawing,focus on passive microwave data in five categories in the study of freezing and thawing monitoring algorithms,including double index algorithm,the decision tree algorithm,freeze-thaw discriminant algorithm,seasonal threshold algorithm and based on the freezing L-band relative factors discriminant algorithm threshold,and analysis of 5 kinds of algorithms are compared;The freeze-thaw products based on different algorithms and passive microwave data were combed. Finally,the problems and future research directions of passive microwave remote sensing in surface freeze-thaw applications are summarized. In the acquisition of passive microwave data,it is found that the passive microwave data is missing due to the physical characteristics of the sensor,the shape and orbit of the earth,and the low resolution of passive microwave data leads to the low precision of freeze-thaw discrimination. For the problem of missing passive microwave data,it is proposed to use the average value of passive microwave data before and after two days to fill the missing brightness temperature data,or establish statistical function to complement the missing data. For the problem of low passive microwave resolution,the current development trend is to scale down based on passive microwave data and combine with multiple data products,such as ground temperature and active microwave data,or perform probability discrimination on surface freezing-thawing state in pixels,so as to better describe surface freeze-thaw state. In terms of the algorithm for discriminating surface freezing-thawing,based on the problem that dual-index algorithm,decision tree algorithm,freezing-thawing discriminant algorithm and seasonal threshold algorithm cannot accurately distinguish snow and frozen soil,this paper proposes to adopt the method of data assimilation or start from the snow radiation and frozen soil dielectric model. Optimization of the algorithm for the snow covered surface can further improve the accuracy of freeze-thaw classification. Based on existing freeze-thaw products,Although SMAP freeze-thaw products continue to be updated,SAMP satellite was launched late,and SAMP freeze-thaw products have a short time series. In the future,the time span of this algorithm for freezing-thawing products can be extended by combining L-band data provided by SMOS satellite. The problems mentioned above and the direction of further research are of great significance for improving the accuracy of freezing and thawing discrimination and improving the understanding of the variation law of freezing and thawing cycles,and also have certain research space. © 2022 Science Press (China).     

http://www.sciencedirect.com/science/article/pii/S1674987112001028

A study on the effect of the solar ultra-violet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation.A CO2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition.The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically.The intensity of the collected light was monitored by a portable spectrophotometer housed inside.The human skin fibroblast cells were incubated in the CO2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan.The results showed cell damage by strong UV radiation.The production of matrix metalloproteinase-2 was prompted by the moderate UV-B,but was inhibited by the strong UV-B radiation,as studied under laboratory conditions in Japan.The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm2.     

Late Quaternary vegetation changes around Lake Rutundu,Mount Kenya,East Africa: evidence from grass cuticles,pollen and stable carbon isotopes

Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C₄ photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C₄ grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC₄ subpathway. Copyright © 2003 John Wiley & Sons, Ltd.     

Apparent seasonal variations in iron photoreduction in acidic discharge from a former pyrite mine,Oakland, California

This study investigates a watershed influenced by acid mine drainage emanating from the former Leona Heights Sulfur Mine, located in Oakland, California. The primary factors that temporally controlled the magnitude of iron photoreduction included initial iron concentration, incident ultraviolet radiation, water temperature, biotic oxidation, flow rates, and the Fe(III) species present. Vegetation was not expected to seasonally influence the amount of incoming solar radiation reaching the water surface as the tree canopy contained significant cover during both the April and July monitoring events. Accordingly, it was anticipated that iron photoreduction would be greatest during the summer when both incoming ultraviolet radiation and dissolved iron were at a maximum. This was, however, not the case. A substantial decline in the apparent magnitude of iron photoreduction occurred during the summer/dry season (July) with respect to measurements taken during the spring/wet season (April). The primary reasons for the observed phenomenon were attributed to factors which may seasonally control the physical presence of iron oxidizing bacteria at the site and water temperature, which influences the optimum rate of bacterially mediated iron oxidation.