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Using IAP-AGCM, a model developed by the institute of atmospheric research, Academia Sinica,controlled numerital expertrients on SST and east Asian circulation have been performed and some conclusions have been reached as follows. The abnomality of subtropical high has a two-month remote lagging response to SSTA of the western tropical Pacific, the South China Sea and the Bay of Bengal. Theabnormality always appears in pair for the western Pacific subtrphal high and the eastern Pacific subtropical high, with the latter beginning earlier than the former. When the SST of the western trophal Pacific, South China Sea and Bay of Bengal anomalously decreases(increases), the subtropical high iskept anomalously more to the south(north),consistently so is the location at which two zonal geopotential waves meet in the subtropical western Pacific. Under the action of the SSTA above and when ablocking pattern over east Asia continent appears, the assembling location of the joinin8 waves for thewestern Pacific is closely related to that of the blocking high, which is especially important to consistentabnormality of the subtropical high. 相似文献
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Following climate change, changes in precipitation patterns and food security are major challenges faced by humans. However, research on how these changes in precipitation pattern impacts food supply is limited. This study aims to elucidate this impact and response mechanisms using precipitation data of a climate change-sensitive confluence zone of the southwest and southeast monsoons in Yunnan Province from 1988 to 2018. The results revealed that the precipitation pattern could be divided into three periods: abundant precipitation(Stage I, from 1988 to 2004), decreased precipitation(Stage II, from 2005 to 2015), and drought recovery(Stage III, from 2016 to 2018). Following the transition from Stage I to Stage II and from Stage II to Stage III, the area of precipitation changed significantly, accounting for 15.07%, 13.87%, and 16.53% of Yunnan's total area, for Stages I, II, and III, respectively. At the provincial level, a significant positive correlation was observed between precipitation and food production(r = 0.535, P 0.01), and the correlation coefficient between precipitation and grain yield was higher than that between precipitation and meat and milk production. Based on a precipitation–grain yield transect and breakpoint detection method, key precipitation thresholds affecting grain yield were estimated as 700 and 1500 mm, respectively; when precipitation was 700, 700–1500, and ≥1500 mm, the correlation coefficients between precipitation and grain yield were 0.448(P 0.01), 0.370(P 0.01), and –0.229(P 0.05), respectively. Based on the precipitation thresholds, Yunnan Province can be divided into precipitation surplus, precipitation equilibrium, and precipitation deficit regions, corresponding countermeasures to stabilize grain yield were proposed for each of these regions. The threshold effect of precipitation on grain yield is controlled by molecular-level water–crop mechanisms, in which reactive oxygen species, a by-product of plant aerobic metabolism, plays a key regulatory role. 相似文献
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泥石流沟道汇流对堆积危险范围影响的数值模拟研究 总被引：1，自引：0，他引：1
利用离散元法和图形处理器（GPU）并行计算手段建立泥石流运动堆积模型,以自然界沟道泥石流汇流后运动堆积特征及危险范围作为模拟参照,利用所构建的泥石流流通槽完成沟道泥石流不同交汇角汇流模拟试验和堆积危险范围预测,实现了泥石流沟道汇流的可视化模拟和数值模拟。试验结果表明,可视化模拟能够模拟出自然界中泥石流自流通区运动汇流后产生堆积的运动特征;数值模拟实现了锐角条件下仅考虑单因素即沟道交汇角对泥石流堆积危险范围影响的模拟试验。此外,利用GPU并行计算的优势可用于模拟大规模泥石流汇流现象,模型的可扩展性为泥石流汇流堆积危险范围分析向更为复杂的地理环境模拟奠定基础。 相似文献
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三江并流是反映地球演化主要阶段的杰出代表,区内保存着反映特提斯演化不同阶段和喜马拉雅期陆内造山阶段留下的丰富的地质遗迹,这些地质遗迹为解读三江并流地壳演化的历史提供了重要的依据.有关资料表明,三江并流是与青藏高原和横断山脉一起发育成长起来的,它们均经历了特提斯的演化,并且都是印度板块与欧亚板块强烈碰撞造山作用的产物.本文比较详细地介绍了横断山脉的形成演化过程及其与青藏高原形成演化之间的关系. 相似文献
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Gregory H. Sambrook Smith Andrew P. Nicholas James L. Best Jonathan M. Bull Simon J. Dixon Steven Goodbred Maminul H. Sarker Mark E. Vardy 《Sedimentology》2019,66(2):391-407
Channel confluences are key nodes within large river networks, and yet surprisingly little is known about their spatial and temporal evolution. Moreover, because confluences are associated with vertical scour that typically extends to several times the mean channel depth, the deposits associated with such scours should have a high preservation potential within the rock record. Paradoxically, such scours are rarely observed, and their preservation and sedimentological interpretation are poorly understood. The present study details results from a physically‐based morphodynamic model that is applied to simulate the evolution and alluvial architecture of large river junctions. Boundary conditions within the model were defined to approximate the junction of the Ganges and Jamuna rivers, Bangladesh, with the model output being supplemented by geophysical datasets collected at this junction. The numerical simulations reveal several distinct styles of sedimentary fill that are related to the morphodynamic behaviour of bars, confluence scour downstream of braid bars, bend scour and major junction scour. Comparison with existing, largely qualitative, conceptual models reveals that none of these can be applied simply, although elements of each are evident in the deposits generated by the numerical simulation and observed in the geophysical data. The characteristics of the simulated scour deposits are found to vary according to the degree of reworking caused by channel migration, a factor not considered adequately in current conceptual models of confluence sedimentology. The alluvial architecture of major junction scours is thus characterized by the prevalence of erosion surfaces in conjunction with the thickest depositional sets. Confluence scour downstream of braid bar and bend scour sites may preserve some large individual sets, but these locations are typically characterized by lower average set thickness compared to major junction scour and by a lack of large‐scale erosional surfaces. Areas of deposition not related to any of the specific scour types highlighted above record the thinnest depositional sets. This variety in the alluvial architecture of scours may go some way towards explaining the paradox of ancient junction scours, that while abundant large scours are likely in the rock record, they have been reported rarely. The present results outline the likely range of confluence sedimentology and will serve as a new tool for recognizing and interpreting these deposits in the ancient fluvial record. 相似文献
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In this paper,the evolutions of flow pattern and sediment transportation at a 90° open-channel confluence with different discharge ratios (q*) of the tributary flow to the total flow were studied.The e... 相似文献
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Hydrological processes of glacier and snow melting and runoff in the Urumqi River source region,eastern Tianshan Mountains,China 总被引：1，自引：0，他引：1
Hydrological processes were compared, with and without the influence of precipitation on discharge, to identify the differences between glacierized and non-glacierized catchments in the Urumqi River source region, on the northern slope of the eastern Tianshan Mountains, during the melting season (May-September) in 2011. The study was based on hydrological data observed at 10-min intervals, meteorological data observed at 15-min intervals, and glacier melting and snow observations from the Empty Cirque, Zongkong, and Urumqi Glacier No.1 gauging stations. The results indicated that the discharge differed markedly among the three gauging stations. The daily discharge was more than the nightly discharge at the Glacier No.1 gauging station, which contrasted with the patterns observed at the Zongkong and Empty Cirque gauging stations. There was a clear daily variation in the discharge at the three gauging stations, with differences in the magnitude and duration of the peak discharge. When precipitation was not considered, the time-lags between the maximum discharge and the highest temperature were 1-3 h, 10-16 h, and 5-11 h at the Glacier No.1, Empty Cirque, and Zongkong gauging stations, respectively. When precipitation was taken into consideration, the corresponding time-lags were 0-1 h, 13 h, and 6-7 h, respectively. Therefore, the duration from the generation of discharge to confluence was the shortest in the glacierized catchment and the longest in the catchment where was mainly covered by snow. It was also shown that the hydrological process from the generation of discharge to confluence shortened when precipitation was considered. The factors influencing changes in the discharge among the three gauging stations were different. For Glacier No.1 station, the discharge was mainly controlled by heat conditions in the glacierized region, and the discharge displayed an accelerated growth when the temperature exceeded 5°C in the melt season. It was found that the englacial and subglacial drainage channel of Glacier No.1 had become simpler during the past 20 years. Its weaker retardance and storage of glacier melting water resulted in rapid discharge confluence. It was also shown that the discharge curve and the time-lag between the maximum discharge and the highest temperature could be used to reveal the evolution of the drainage system and the process of glacier and snow melting at different levels of glacier coverage. 相似文献
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