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1.
Based upon the effect of land-sea interaction on the paleomonsoon variation and the time series of climatic proxy-indicators, the historical Asian monsoon variation over the last 130,000 and 18,000 years has been reconstructed with an emphasis on the basic characteristics of summer monsoon circulation. The monsoon-climatic cycles and associated model of environmental development over the central and eastern China are proposed and the mechanism of paleomonsoon variation of China preliminarily discussed. The variation of East Asian monsoon circulation should be regarded as a regional result of both solar-radiation changes and the global glacial-interglacial cycles. The episodic uplifting of the Qinghai-Xizang Plateau since the late Miocene has to a large extent controlled the forming and evolution of the paleomonsoon circulation of China.  相似文献   

2.
On the basis of the data of sporo-pollen analysis, the weathering index of loess and paleosol layers and the climatic differences between the periods of the formation of loess and paleosol as reflected by intensities of natural remanent magnetization of loess and paleosol, it may be confirmed that the loess layers represent the climate of glacial stages, while paleosol was formed during interglacial stages. The climatic changes in the loess area of China have undergone 23 cycles which were combined with the paleomagnetic dating. TL ages of paleosol layers and the average ages of termination could be excellently correlated with the δ~(18)O stages of deep sea core V_(28-239). Thus, it may be recognized that the Luochuan and Xi'an loess-paleosol sequences are the typical climatostratigraphy in China and even in the world.  相似文献   

3.
Numerical experiments on the influence of soil moisture and vegetation on the persistence of short-term climatic anomalies are performed with a vertical one-dimensional climate model in the atmosphere-soil-vegetation system.The experimental results indicate that, as shown by theoretical analysis in Part Ⅰ of this paper,soil hydrology is crucially important for maintenance of short-term climatic anomalies over land areas. Possible physical process concerned with impact of soil moisture and vegetation on the persistence is further discussed.  相似文献   

4.
Daihai Lake, located in NW margin of SE monsoon region, belongs to the sensitive area for climatic fluctuation. The analysis of continuous sedimentary column with an age of 100 ka indicates that there exists the different quasiperiodicity in time scales for monsoon shift. The climatic fluctuation in the Daihai Basin shows all along the alternation of cold and dry with a warm and wet climatic pattern, suggesting that the strength and drift of SE monsoon play a controllable role in the climatic change.  相似文献   

5.
Influence of soil moisture and vegetation on persistence of short-term climate anomalies isanalyzed theoretically through a heat and water balance model in coupled air-land system.It is shown that the soil hydrologic condition, rather than the soil thermal situation, is adominant factor in maintenance of climatic anomalies. The persistence of climate anomaliesis dependent largely on the capacity of water and heat exchange on the land surface. The cli-mate anomalies would persist longer for less soil moisture or vegetation cover. Furthermore,compared with humid areas, the climate anomalies persist longer in an arid climate envi-ronment.  相似文献   

6.
This paper has analysed the major characteristics of long-term variation, of summermonsoon climate in South Asia since 1888. An abrupt enhancement of summer monsoon inthe 1920s and its synchronism with the global rapid warming have been detected by theMann-Kendall Rank Statistic test. Based on diagnostic analysis on the atmospheric circulationover the monsoon region and the thermal conditions of both ocean and land during theperiod of abrupt change, it is found that the warming over land was stronger and earlierthan that over the ocean, which would enhance the land-sea thermal contrast and thereforebe favorable to the development of monsoon low and the disturbance in the monsoon flow.This may be a direct factor for the abrupt enhancement of summer monsoon.  相似文献   

7.
A Monte Carlo algorithm has been established for multi-dispersive copolymerization system, based on the experimental data of copolymer molecular weight and dispersion via GPC measurement. The program simulates the insertion of every monomer unit and records the structure and microscopical sequence of every chain in various lengths. It has been applied successfully for the ring-opening copolymerization of 2,2-dimethyltrimethylene carbonate (DTC) with δ-caprolactone (δ-CL). The simulation coincides with the experimental results and provides microscopical data of triad fractions, lengths of homopolymer segments, etc., which are difficult to obtain by experiments. The algorithm presents also a uniform frame for copolymerization studies under other complicated mechanisms.  相似文献   

8.
KONG  De-Ming SHEN  Han-Xi 《中国化学》2003,21(5):556-561
A new method based on the incorporation of a single-lablled probe-primer into polymerase chain reaction(PCR) for the detection of PCR-amplified DNA in a closed system is reported.The probeprimerc consists of a specific probe sequence on the 5‘‘‘‘‘‘‘‘-end and a primer sequence on the 3‘‘‘‘‘‘‘‘-end.A flurophore is located at the 5‘‘‘‘‘‘‘‘end.The primeR-quencher is an oligonucleotide,which is complementary to the probe sequence of probe-primer and labelled with a quencher at the 3‘‘‘‘‘‘‘‘-end.In the duplex formed by probe-primer and primer-quencher.the fluorophore and quencher are kept in close proximity to each other.Therefore the fluorescence is quenched.During PCR amplificatio,the specific probe sequence of probeprimer binds to its complement within the same strand of DNA,and is cleaved by Taq DNA polymerase,resulting in the restoration of fluorescence.This system has the same energy transfer mechanism as molecular beacons,and a good quenching effciency can be ensured.Following optimization of PCR conditions,this method was used to detect hepatitis b virus(HBV) dna in patient sera.This technology eliminates the risk of carry-over contamination,simplifies the amplification assay and opens up new possibilities for the real-time detection of the amplified DNA.  相似文献   

9.
A giant earthquake of magnitude 9.0 occurred in Pacific Ocean off of Tohoku District Japan on March 11, 2011. The highest seismic intensity of 7 in JMA scale was recorded in Miyagi. In the Tohoku district, around 230 buildings are seismically isolated (hereafter, SI) mainly by elastomeric isolators (seismic rubber bearings). According to the official survey reports by several organizations (for example[1]), the records of those buildings have verified the effectiveness of the seismic isolation. The response acceleration of the SI buildings was reduced by 30% to 50% of the input ground acceleration. Additionally, the difference of the conditions inside the room between SI and the fixed-base buildings was obvious as well as the damage in main structures of the buildings. The displacements of the isolators by the earthquake were around 200 mm according to the records of the instruments. As a result, the performance of SI buildings and the elastomeric isolators in the Tohoku District―Off the Pacific Ocean Earthquake 2011 were excellent, and the efficiency of the seismic isolation was verified by the records of many buildings in wide area.  相似文献   

10.
The information preserved in the surface layer of the Antarctic ice sheet is so abundant and detailed that in the areas with a high accumulation rate the annual climatic changes in the past can be distinguished. After conducting an investigation into the stratigraphical features of ice cores from two typical shallow boreholes in the Wilkes Land, one inland and another near the margin, analyzing δ(~18)O and the gross β radioactivity in the cores, as well as anslyzing the power spectra of δ~(18)O, the authors present some important assessments on the climatic information in the past several decades therein such as the annual mean temperature and precipitation, and suggest that there is a period of 11 years with which the climate changes cyclically in East Antactica. Such a studying method will be of value in both theory and practice to the inland Antarctica, where direct meteorological observation is deficient.  相似文献   

11.
The Climatic Fluctuation and Important Events of Holocene Megathermal in China   总被引:12,自引:0,他引:12  
Data from various sources including the ice core, inland lakes , paleosols in loess and eolian sands, sea level fluctuations, paleozoological, archeological evidences especially palynology and bontanical studies of China are reviewed . Holocene Megathermal mainly appeared during 8. 5-3 ka BP and lasted for 5. 5 ka. There were several strong climatic fluctuations and cooling events during this period, e. g. it was an unstable temperature fluctuation phase during 8. 5-7. 2 ka BP and was accompanied with the increase of the precipitation as well as the northward and westward migration of the vegetation zone ; the rapid development of Neolithic Culture happened in this phase. It was a stable warm and wet phase from 7. 2 to 6 ka BP, i. e. Megathermal Maximum, when monsoon was rainfall almost throughout China, plants were unprecedentedly flourished, and the Yangshao Culture reached its climax. It is characterized by strong climatic fluctuation and adverse environment during 6-5 ka BP and the impact of strong  相似文献   

12.
The Mangalore and Udupi region on the south-west coast of India is characterized by small west-flowing rivers (150-250 km in length) originating in the Western Ghats (up to 1940 meters above sea level (m asl)) and joining the Arabian Sea. The area experiences a humid tropical climate with frequent, high-intensity rainfall (4000 mm annual average). Nevertheless, there is a shortage of water during the peak dry season immediately before the onset of monsoon because of a rapid fall in the groundwater level. From the humid high-altitude forests to the intense agriculture in the coastal area, there is an urgent need to understand the movement of water between evapotranspiration, rainfall, river systems and the groundwater compartments in order to achieve better water resource management. Demographic pressure on the area with over half a million inhabitants and industrial activity strongly influence this fragile ecosystem. The coastal area is characterized by shallow open wells, which are particularly sensitive to pollution and eutrophication. Stable water isotopes ((18)O and deuterium) were used for the first time in this region to determine the isotopic characteristics of the different waters. There is a clear seasonal difference in the isotopic ratios and d-excess values between the summer and winter monsoon periods, with a predominance of lighter isotopes in the latter period. No significant variations in isotopic ratios were observed in relation to altitude because of the possible role of mist formation at high altitude. Greater d-excess values were observed in the west-flowing streams than in rivers flowing east on account of the moist westerly oceanic winds and water vapour recycling.  相似文献   

13.
Geological and geochemical events were elucidated in by using U series nuclides in combination with chemical leaching technique. Two examples were examined: (1) in the apatite-bearing sediment column samples U(VI) is moving, while U(IV) in the samples is almost retained, and (2) the redistribution of U occurred along the column under the monsoon climate. On the other hand, U in the conglomerate sample is divided into 5 categories by the leaching technique, which are related with exchangeable, carbonate, iron oxide, organic/sulfide and silicate components, respectively. Uranium is shown to be abundant in the carbonate and iron rich fractions of conglomerate sediment. Appropriate models are proposed in each case study.  相似文献   

14.
树轮具有记录气候信息丰富、连续性强、分辨率高以及定年精确等优势,然而在实际研究中却少有人注意到,树轮的同位素研究在气候与环境变化研究领域中的应用前景更是有待大力开发。以树轮同位素在气候研究的典型应用举例,旨在唤起大家对树轮研究应用的重视,以期在环境与气候的研究领域中找到新的突破口,取得重大科研成果。  相似文献   

15.
This paper discusses how natural climate changes may have influenced anthropological development. The main characteristics of solar variablity are reviewed: (1) as measured in detail over recent decades by instruments on-board artificial satellites; (2) as recorded in historical documents on the time-scale of centuries; and (3) as inferred on millennial time-scales from archived records of the cosmogenically generated isotopes 14C and 10Be. The older, proxy data comprise temperature changes reconstructed from tree ring studies and environmental changes deduced from multi-disciplinary studies of lake sediments. The effects of changes in ocean circulation and the sporadic influence of volcanic activity are also considered briefly.  相似文献   

16.
Constructed wetland employs vegetation as a natural medium to remove pollutants from wastewater for this treatment. It is eco-friendly, sustainable, economical, low maintenance, low running cost, and easy to use. This has prompted several studies to investigate its performance in treating pollutants from the conventional to emerging contaminants category, including pharmaceutical compounds. However, there is still a lack of work on the impact of monsoons on the removal efficiency of pharmaceutically active compounds from wastewater. This study evaluated constructed wetland performance during the premonsoon, monsoon, and post-monsoon seasons. A pilot-scale constructed wetland setup was established to conduct this study. The target compound included paracetamol, ibuprofen, carbamazepine, lorazepam, ciprofloxacin, sulfamethoxazole, and Fluvastatin. In the constructed wetland, for paracetamol and ibuprofen, NSAIDs concentration was observed to be 1503–6307 ngL?1 and 564–808 ngL?1. The concentrations of antibiotics, sulfamethoxazole, and ciprofloxacin were 16532–21635 ngL?1 and 734–1178 ngL?1, respectively. The carbamazepine, lorazepam, and Lutvastatin concentration range was 616–906 ngL?1, 2742–3775 ngL?1, and 694–2068 ngL?1, respectively. The hazard quotient approach was adopted to evaluate potential environmental risk from target compounds. The increase of paracetamol 33 %, ibuprofen 94 %, ciprofloxacin 242 %, Sulfamethoxazole 64 %, and carbamazepine 77 % validated the study hypothesis. However, a decrease of 15 % lorazepam and 43 % Fluvastatin inferred that dilution was inversely proportional to the removal of these compounds. The seasonal removal efficiency was in order pre-monsoon < post-monsoon < monsoon. Hospital wastewater had HQ values of 90, 100, and 130 for premonsoon, monsoon, and post-monsoon, respectively. After treatment from the constructed wetland, the wastewater effluent had reduced HQ value to 53, 35, and 70 for premonsoon, monsoon, and post-monsoon periods respectively. The HQ values were further reduced in tubesettler to 22, 11, and 28. Ciprofloxacin posed no significant risk. However, sulfamethoxazole posed a high risk during premonsoon, monsoon, and post-monsoon season. Further works are required to analyze the removal mechanism through plant uptake, sediment bed, and biodegradation for a different season or climatic condition to present the real-time performance of constructed wetlands for treating wastewater loaded with pharmaceutical compounds.  相似文献   

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