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     

《Comptes Rendus Geoscience》2018,350(7):393-402

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.  相似文献   

The relationship between groundwater and natural vegetation in Qaidam Basin          下载免费PDF全文

Dang Xue-ya  Lu Na  Gu Xiao-fan  Jin Xiao-mei 《地下水科学与工程》2021,9(4):341-349

To accurately evaluate ecological risks trigged by groundwater exploitation, it must be clarified the relationship between vegetation and groundwater. Based on remote sensing data sets MOD13Q1, groundwater table depth (WTD) and total dissolved solids (TDS), the relationship between groundwater and natural vegetation was analyzed statistically in the main plain areas of Qaidam Basin. The results indicate that natural vegetation is groundwater-dependent in areas where WTD is less than 5.5 m and TDS is less than 7.5 g/L. Aquatic vegetation, hygrophytic vegetation and hygrophytic saline-alkali tolerant vegetation are mainly distributed in areas with WTD <1.1 m. Salt-tolerant and mesophytic vegetation mainly occur in areas with WTD of 1.4-3.5 m, while the xerophytic vegetation isprimarily present in areas where WTD ranges from 1.4 m to 5.5 m. Natural vegetation does not necessarily depend on groundwater in areas with WTD >5.5 m. For natural vegetation, the most suitable water TDS is less than 1.5 g/L, the moderately suitable TDS is 1.5-5.0 g/L, the basically suitable TDS is 5.0-7.5 g/L, and the unsuitable TDS is more than 7.5 g/L.  相似文献   

北半球臭氧总量与平流层环流关系的分析   总被引：2，自引：7，他引：2  

郑光  吴统文 《高原气象》1991,10(3):277-286

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新疆北天山地区震磁预报研究     

王瑞琴 《内陆地震》1994,8(3):229-233

采用统一的分析方法和标准从北天山地区的地磁场总强度资料中提取异常信息．结果表明，在区内发生的一些中强地震前，震中周围的台站存在较明显的中、短期异常．  相似文献   

Low-latitude total ozone measurements in the Brazilian sector     

Y. Sahai  R. P. Kane  N. R. Teixeira 《Pure and Applied Geophysics》1982,120(4):615-625

Regular measurements of the atmospheric ozone in the Brazilian sector were started at Cachoeira Paulista (22.7°S, 45.0°W), and Natal (5.8°S, 35.2°W) in May 1974 and November 1978, respectively. The results of the total ozone measurements carried out at these two stations up to 1981 are presented in this communication and compared with other low-and mid-latitude stations. Although Natal is an equatorial station, it presents a prominent annual variation, and the average total ozone content is high compared to satellite measurements. During 1977–78, abnormally low values of total ozone were observed at Cachoeira Paulista. Some preliminary results about the QBO 9quasi-biennial oscillation) during 1974–81 are also presented.  相似文献   

Total precipitable water in the atmosphere over India     

S. Rangarajan  A. Mani 《Journal of Earth System Science》1982,91(3):189-207

Electromagnetic radiation, in its passage through the atmosphere, is attenuated by absorption and scattering by atmospheric gases, dust and aerosols. The most important absorber is water vapour and the most significant parameter in atmospheric absorption studies is the total precipitable water in the atmosphere. The present paper summarises the results of a study made to compute the total precipitable water in the atmosphere over India using radiosonde and other data, as part of a programme for the computation of direct, global and diffuse solar radiation at the ground from the solar constant. Using values of air temperature and dew point from the ground up to 250 mb at 19 radiosonde stations and surface water vapour mixing ratio values at 105 surface observatories in India, precipitable water amounts have been computed for 124 stations, for each month and for the whole year. The paper describes the techniques used to extend the total precipitable water amounts derived from radiosonde data at 19 stations to 124 stations covering the major climatic zones in the country and presents the results in the form of 12 maps showing the spatial and temporal distribution of total precipitable water over India  相似文献   

森林地下碳分配(TBCA)研究进展     

陈光水  杨玉盛  刘乐中  李熙波  赵月彩  袁一丁 《福建地理》2007,(1)

森林地下碳分配(TBCA)是森林碳循环的重要通量,对森林碳吸存有十分重要作用.TBCA是森林生态系统GPP中一个最大的汇,可占GPP的21%～61%,土壤呼吸的2/3来自TBCA.目前国际上常用的TBCA测定方法为碳平衡法,在假定地下碳库处于稳定状态时,TB-CA可由土壤呼吸减去凋落物量获得,但该方法存在一系列问题.影响森林TBCA的因素有生产力、森林类型、树龄和森林演替阶段、土壤养分和水分有效性、林分密度和树种组成、气候变化因素等.TBCA中各个组成部分均较难以测定和量化,通常假定TBCA中根系呼吸与根系生产力各约占50%,而TBCA中菌根菌和根系分泌物的贡献则仍不清楚.有关TBCA各组分去向及影响机理的研究亦很少.TBCA未来的研究应致力于揭示TBCA的根本驱动因子和其对全球变化的响应机理,以及TBCA转化为土壤新碳的效率及控制因素;同时应提高TBCA测定方法的确定性,特别是应将碳同位素法、微根管法及碳平衡法三者相结合.  相似文献   

National and institutional productivity and collaboration in Antarctic science: an analysis of 25 years of journal publications (1980–2004)     

Prabir G. Dastidar 《Polar research》2007,26(2):175-180

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The distribution of Potamothrix bavaricus (Oeschmann, 1913) (Oligochaeta) in anthropogenic freshwater habitats of an industrialised area (Upper Silesia, Poland)     

Mariola Krodkiewska   《Limnologica》2007,37(3):259-263

The studies have revealed that Potamothrix bavaricus (Oeschmann, 1913), generally rare in Poland, is a common species in the benthic oligochaete fauna of different anthropogenic freshwater habitats in a heavily industrialised area of Poland. It was often found in habitats with significant salinity, a high total hardness and a large content of nutrients. The evident resistance to various pollutants enables the settlement of P. bavaricus in such habitats, which are unsuitable for other oligochaete species.  相似文献   

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations   总被引：1，自引：1，他引：1  

Andrzej Krankowski  Irk I. Shagimuratov  Lubomir W. Baran  Galina Yakimova 《Acta Geophysica》2007,55(4):490-508

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.  相似文献