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341.
Georg Heygster 《中国海洋大学学报(英文版)》2009,8(1):9-14
An algorithm to detect tropical deep convective clouds and deep convective overshootings based on the measurements from the three water vapor channels (183.3GHz±1 GHz, 183.3GHz±3GHz and 183.3GHz±7GHz) of the Advanced Microwave Sounding Unit-B (AMSU-B) is presented. This algorithm is an improved version of the method of Hong et al. (2005). The proposed procedure is based on the statistical analysis of seven years'(2001-2007) measurements from AMSU-B on NOAA-16 From the 1-d histograms of the brightness temperature of the three water vapor channels and the 2-d tustograms of the brightness temperature dif-ference between these channels, new thresholds for brightness temperature differences and the brightness temperature of channel 18 (183.3 GHz±1 GHz) are suggested. The new algorithm is employed to investigate the mean distribution of tropical deep convective clouds and convective overshootings from 30°S to 30°N for the years 2001 to 2007. The major concentration of deep convective clouds and convective overshootings is found over the Intertropical Convergence Zone (ITCZ), the South Pacific Convergence Zone (SPCZ), tropical Africa, South America, the Indian Ocean and Indonesia with an average fraction of 0.4%. In terms of these clouds we identify the secondary Intertropical Convergence Zone located in the eastern South Pacific and parallel to the main ITCZ in the North Pacific. The convective overshooting is more frequently observed over land than over the ocean. 相似文献
342.
Ingo Leya Jean‐Christophe David Thomas Faestermann Michaela Froehlich Niko Kivel Dominik Koll Gunther Korschinek Sarah McIntyre Silke Merchel Stefan Pavetich Georg Rugel Dorothea Schumann Thomas Smith Anton Wallner 《Meteoritics & planetary science》2020,55(4):818-831
We measured specific activities of the long‐lived cosmogenic radionuclides 60Fe in 28 iron meteorites and 53Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53Mn. This work doubles the number of existing individual 60Fe data and quadruples the number of iron meteorites studied for 60Fe. We also significantly extended the entire 53Mn database for iron meteorites. The 53Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60Fe and 53Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60Fe activity concentrations are about a factor of 2 higher, for 53Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data. 相似文献
343.
Christian Ferrarin John Rapaglia Luca Zaggia Georg Umgiesser Giovanni Maria Zuppi 《Marine Chemistry》2008,112(3-4):179-188
A mass balance of the naturally occurring short-lived radium isotopes (223,224Ra) in the Venice Lagoon was conducted by an integrated approach combining the directly estimated individual Ra contributions and hydrodynamic model results. Hydrodynamic data allows for the calculation of the Ra mass balance in sub-sections of the Venice Lagoon (boxes), which are characterized by physically homogeneous properties, instead of investigating the entire lagoon. Utilizing this method, both the seasonal and the spatial variability of the submarine groundwater discharge in the Venice Lagoon have been estimated. Between 14–83 × 109 L d− 1 of water were calculated to flow across the sediment–sea interface, corresponding to 5–28 times the mean annual river input. The submarine groundwater discharge estimates were correlated with the residence time calculation to better understand spatial and seasonal variation. 相似文献
344.
The water balance model KAUSHA (Halldin, 1989) was applied to a 100-year-old beech (Fagus sylvatica L.) forest in northern Germany. Overall, a satisfying agreement between modelled evapotranspiration values and independent micrometeorological measurements (Bowen ratio energy balance method) could be observed, although for rainy days KAUSHA showed a tendency to overestimate evapotranspiration. The model was used to predict the effects of a climate warming on the water budgets of the forest. It is shown that a temperature increase of 2°C due to a rising CO2 content of the atmosphere will not change the yearly totals of evapotranspiration significantly, but could have serious effects on the soil water balance during the vegetation period. Because under climate change conditions a higher amount of the available soil water has already been evaporated in winter and spring, soil water content will limit the transpiration of the trees from July to September much more strongly. Therefore, the yield of beech forest might also suffer from drought effects. It can be concluded that a better knowledge of the seasonal distribution of rainfall under climate change conditions is indispensable for predicting effects of rising temperatures and CO2 concentrations on ecosystems. 相似文献
345.
Keywan Riahi Shilpa Rao Volker Krey Cheolhung Cho Vadim Chirkov Guenther Fischer Georg Kindermann Nebojsa Nakicenovic Peter Rafaj 《Climatic change》2011,109(1-2):33-57
This paper summarizes the main characteristics of the RCP8.5 scenario. The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies. Compared to the total set of Representative Concentration Pathways (RCPs), RCP8.5 thus corresponds to the pathway with the highest greenhouse gas emissions. Using the IIASA Integrated Assessment Framework and the MESSAGE model for the development of the RCP8.5, we focus in this paper on two important extensions compared to earlier scenarios: 1) the development of spatially explicit air pollution projections, and 2) enhancements in the land-use and land-cover change projections. In addition, we explore scenario variants that use RCP8.5 as a baseline, and assume different degrees of greenhouse gas mitigation policies to reduce radiative forcing. Based on our modeling framework, we find it technically possible to limit forcing from RCP8.5 to lower levels comparable to the other RCPs (2.6 to 6 W/m2). Our scenario analysis further indicates that climate policy-induced changes of global energy supply and demand may lead to significant co-benefits for other policy priorities, such as local air pollution. 相似文献
346.
Grigory Fedorov Andrei A. Andreev Elena Raschke Volker Wennrich Georg Schwamborn Olga Y. Glushkova Olaf Juschus Anja Zander Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):516-533
Lake El'gygytgyn, located in central Chukotka, Russian Arctic, was the subject of an international drilling project that resulted in the recovery of the longest continuous palaeoclimatic and palaeoenvironmental record for the terrestrial Arctic covering the last 3.6 million years. Here, we present the reconstruction of the lake‐level fluctuations of Lake El'gygytgyn since Marine Isotope Stage (MIS) 7 based on lithological and palynological as well as chronological studies of shallow‐water sediment cores and subaerial lake terraces. Reconstructed lake levels show an abrupt rise during glacial–interglacial terminations (MIS 6/5 and MIS 2/1) and during the MIS 4/3 stadial–interstadial transition. The most prominent lowstands occurred during glacial periods associated with a permanent lake‐ice cover (namely MIS 6, MIS 4 and MIS 2). Major triggering mechanisms of the lake‐level fluctuations at Lake El'gygytgyn are predominantly changes in air temperature and precipitation. Regional summer temperatures control the volume of meltwater supply as well as the duration of the lake‐ice cover (permanent or seasonal). The duration of the lake‐ice cover, in turn, enables or hampers near‐shore sediment transport, thus leading to long‐term lake‐level oscillations on glacial–interglacial time scales by blocking or opening the lake outflow, respectively. During periods of seasonal ice cover the lake level was additionally influenced by changes in precipitation. The discovered mechanism of climatologically driven level fluctuations of Lake El'gygytgyn are probably valid for large hydrologically open lakes in the Arctic in general, thus helping to understand arctic palaeohydrology and providing missing information for climate modelling. 相似文献
347.
The vegetation of the treeline ecotone of the southern declivity of arid High Asia (Hindu Kush, northern areas of Pakistan; Himalaya, northern central Nepal) is dominated by hedgehog-like open dwarf shrublands of thorny cushions. Since climatically sensitive ecotones are always also sensitive to human impact, the question arises whether the current lack of forests is a result of the Subboreal climate decline or of human impact. Due to inadequate knowledge of the pollen flora and of ecological indicator values of the plants, pollen analyses in High Asia have mainly been limited to the regional verification of globally known climatic impulses. However, the role of human impact on regional vegetation patterns has been widely neglected. We postulate that today's open dwarf shrublands replace woodlands and forests. Isolated vigorous juniper trees and successful reforestation appear to confirm our hypothesis. An abrupt decline of Pinus forests before 5700 and 5400 ka cal yr BP can be demonstrated. As the first indicator pollen of human impact appeared at both sites synchronous with the forest pollen decline, we infer human impact to be a more decisive cause for this environment change superimposing the effects of a climatic deterioration. The forests were displaced by open dwarf shrublands. 相似文献
348.
Markus Fiebig Frank Preusser Damian Steffen Edit Tham‐Bozs Michael Grabner Georg J. Lair Martin H. Gerzabek 《Geoarchaeology》2009,24(2):224-241
The validity of optically stimulated luminescence (OSL) has been tested on known‐age (historical) fluvial deposits along the rivers Danube (Austria) and Ebro (Spain). As partial bleaching of the OSL signal prior to deposition can interfere with correct age estimates, different approaches to extracting the dose accumulated during burial are compared. Using the finite mixture model gave OSL ages that are internally as well as stratigraphically consistent and in agreement with independent age control. According to these results, fluvial deposition at the Danube River study site can be attributed to different periods ranging from Bronze Age to the 18th century A.D. Fluvial deposits of Roman age and of the late 17th or early 18th century A.D. were found at the Ebro River study site. This is consistent with the morphological subdivision of the valleys and encourages further investigation of the fluvial and archaeological history of the study areas using OSL. © 2009 Wiley Periodicals, Inc. 相似文献
349.
Geophysical investigation of a sinkhole in the northern Harz foreland (North Germany) 总被引:2,自引:0,他引:2
The creek Jerstedter Bach is part of the Ringelheimer Mulde along the northern rim of the Harz Mountains in Northern Germany,
a trough structure comprising steeply dipping limestones. The limestones are well karstified and drain parts of the region
efficiently via sub-surface flow. As the entire region is intensively used by agriculture, contamination of the fast-flowing
karst aquifer is a potential problem. During 2006, a small sinkhole (Windmühlenweg) developed alongside the Jerstedter Bach
close to the city of Goslar. The sinkhole enlarged rapidly, with a small cave within the gravel cover diverting part of the
creek to the subsurface karst catchment. Geophysical methods (gravimetry, geoelectrics) were used around the sinkhole to determine
its extent and possible evolution. A negative Bouguer anomaly was found over the sinkhole, indicating more voids further downstream.
The geoelectric survey helped to identify the old meandering course of the small river, which was straightened during the
cultural land reform in the twentieth century. 相似文献
350.
The aim of the study was to identify the geogenic source for elevated arsenic (As) concentrations recently discovered in soils
of the Heubach plain, North Rhine-Westphalia, Germany. Therefore, a catalogue of conditions that an As source has to fulfil
in order to be considered as geogenic was formulated, including the source’s linkage to the sink, its mineralogy, As total
content, As mobilization potential, groundwater redox conditions and As output. Accordingly, mineralogical, geo- and hydrochemical
investigations were carried out, including X-ray diffractometry, microscopy, ICP-OES and AAS analysis and a sequential extraction
procedure. Paleo bog iron ores (PBIOs) of Tertiary age, occurring within unconsolidated sands (Haltern-layers, Santonian–Lower
Campanian), and glauconitic marlstones (Dülmen-layers, Lower Campanian) were examined. Results indicate that output from the
PBIOs is responsible for the elevated As levels. Accounting their diverse mineralogy, five types of PBIOs were defined. Type-dependent,
they at least partly fulfil all of the formulated requirements. The relations and behaviour of As sources and sinks in space
and time could be clarified for the area of interest. The approach presented in this paper may offer a tool for identifying
natural As sources worldwide. 相似文献