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51.
The temperature appeared rising trend during the 20th century in China's tropics.Two cooling stages and two warming stages in the process of climatic fluctuation can be recognized.After the 1980s the climate is the warmest which corresponds to the global change,but the warmest period is the 1940s in Kunming.The climate pattern mostly appears contemporaneity of warming and humidity,which is different from the situation of whole China.The natural disasters tend to be aggravated.The number of typhoons increased.Flood damages occurred frequently in the years of more typhoons.The number of droughts and cold damages increased.It was snowed in Guangzhou.There was frost in Haikou and Yaxian.Four years of heavy snow have been recorded in Kunming. 相似文献
52.
Rainfall thresholds for landsliding in the Himalayas of Nepal 总被引:5,自引:0,他引:5
Emmanuel J. Gabet Douglas W. Burbank Jaakko K. Putkonen Beth A. Pratt-Sitaula Tank Ojha 《Geomorphology》2004,63(3-4):131-143
Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to three orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 years of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure. 相似文献
53.
The present study aims the evaluation of bio-physical characteristics towards soil-water-vegetation stress and a rule is envisaged to assess the degree of temporal changes. The digital rule for assessment is initialized through the index of land Instability (ILI) where the variance indicates the temporal instability of the pixel i.e., smallest land unit. It is assumed that the biophysical characteristic of land is in command of land-dynamics where there is no change in Land Use/Land Cover (LU&LC). The intensity map on tendency of albedo (IALB) assesses the intensity of soil erosion and water stress whereas intensity map on tendency of NDVI (INDVI) appraises the stress on vegetation. The carry-out study covers a part of semiarid Western India. Primarily remote sensing technique, which carries the digital information of land temporally and spatially, is adopted in this paper. A part of the study area is represented using two sets of IRS 1A/1B LISS-I data of March with a decadal time domain (1989-1998) as a test area. It is assumed that the soil-water-vegetation stress is maximum during summer(March-April-May) in any tropical belt and decadal data will stretch the possibility of climate as well as man-made activity over the land. 相似文献
54.
1. IntroductionThe basic role of urban-rural boundary layer re-search is to study all kinds of physical process changesin the atmosphere boundary layer over urban and itssurrounding areas. Urban heat island (UHI) is a well-known feature of urban-rural climate. Attempts toincrease the understanding of the causes of the UHIand other urban-rural boundary layer phenomena haveused observational, theoretical and modelling methodssince long before. Seaman (1989) used a hydrostaticmodel, with real … 相似文献
55.
WU Yongfu & XU Jiyao Laboratory for Space Weather Center for Space Science Applied Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(10)
Gravity waves play a significant role in establishing the large-scale circulation and structure of the middle atmosphere. Through gravity wave saturation proc-esses, such motions are believed to cause turbulence, resulting in divergence of momentum flux and the diffusion of heat and constituents in the meso-sphere[1,2]. The mechanisms that contribute signifi-cantly to the gravity wave saturation are thought to be the dynamical and convective instabilities[3]. However, it is difficult to distin… 相似文献
56.
57.
临夏盆地13~4.4 Ma湖相沉积物颜色记录的气候变化探讨 总被引:18,自引:0,他引:18
利用高分辨率的代用资料来恢复古气候环境变化是当前过去全球变化研究的重要内容.通过对临夏盆地13~4.4 Ma时段稳定湖泊沉积物以10 cm间隔连续采得的2 060块样品进行颜色测定与分析,获得该时段湖相沉积物高分辨率颜色指标变化序列.通过沉积物颜色与成分分析,并与氯离子、CaCO3、风成石英砂含量和孢粉组合以及北太平洋ODP885/886孔的风成粉沙通量变化曲线对比,认为稳定湖相沉积物颜色指标是研究古气候变化的辅助性代用指标,并揭示了该地区在8 Ma和6.2 Ma左右存在两次重大的气候变干转型事件. 相似文献
58.
青藏高原东北部泥炭沉积粒度与元素记录的全新世千年尺度的气候变化 总被引:2,自引:0,他引:2
通过对青藏高原东北部共和盆地泥炭沉积的粒度与地球化学元素分析, 重建了区域全新世千年尺度的气候变化过程. 结果显示: 10.0~8.6 cal ka BP区域暖湿程度逐渐增加, 但在8.6~7.1 cal ka BP气候相对寒冷干燥, 7.1~3.8 cal ka BP 暖湿程度总体上为全新世最佳, 但也出现明显的气候波动, 3.8~0.5 cal ka BP气候向冷干方向发展, 0.5 cal ka BP以来气候又逐渐转向暖湿. 这一特征与中国东部季风区的气候变化有很好的一致性. 此外, 区域全新世气候变化过程中存在10次千年尺度的寒冷事件, 并与高原冰芯、 湖泊、 泥炭和风成沉积记录的古气候变化, 甚至与北半球高低纬度的气候变化都具有良好的可比性. 因此, 认为区域全新世气候变化具有"季风模式"与"千年尺度震荡"的双重特点. 相似文献
59.
柴达木盆地自然伽玛曲线与古里雅冰芯记录的末次间冰期以来气候环 … 总被引:1,自引:1,他引:1
采用柴达木盆地达参1井井自然伽玛(GR)曲线进行古气候反演,分析了GR曲线记录的末次间冰期以来的环境变迁过程,表明GR曲线忠实地记录了构造运动及气候变化的影响,与古里雅产,格陵兰冰芯所记录的气候事件均能均较好对应,表明柴达木盆地同时包含了高原隆升和全球性气候变化的信息,是反映古气候变化良好的信息载体之一,是反映内陆干旱盆地环境与气候变化良好的代用指标。 相似文献
60.
东南极Lambert冰川流域表面雪层中稳定同位素分布及近几十年来的气候变化(英) 总被引:7,自引:1,他引:7
The Lambert Glacier basin is one of particular regions in East Antarctica, because of its distinctive topography. During the repeat inland traverses carried out in recent several years, surface 2 m snow samples and shallow (10~27 m deep) cores were collected at several ten stations and at near ten stations, respectively. The stable isotopic ratios of these samples and cores were measured in order to investigate the relation of isotopes with temperature and to study the climatic change in recent decades over this area. The correlation between isotopic ratios and mean annual temperature gives that δ-temperature gradient is relatively close to that along a traverse route between Vostok and Mirnyy stations. The inconsistency of δ18O profiles of these cores makes it difficult to distinguish an overall trend of climatic change in past decades. After incorporating the result of snow accumulation variability and temperature record over 30 years at the coast station, it is believed that climate was in a little cooling and drying from 1950s to 1980s and has been in a warming period since then. 相似文献