中国短期气候变化的一个重要原因——青藏高原地表反射率的变化   总被引：5，自引：0，他引：5  

刘晓东  马柱国 《热带气象学报》1996,12(3):240-245

通过数值试验对高原地表反射率变化的气候效应进行了敏感性研究,同时对观测的近４０年中国区域气候变化趋势作了对比分析。结果表明,高原主体地表反射率增加是我国短期气候变化的重要控制因子之一,它能造成东亚夏季风和高原夏季风的显著减弱,使夏季我国东部季风区北方变暖,南方变冷,季风降水普遍减少。  相似文献   

Tripartite climate reversal in Central Europe 5600-5300 years ago     

Michel Magny  Urs Leuzinger  Jean Nicolas Haas 《Quaternary Research》2006,65(1):3-19

The history of variations in water level of Lake Constance, as reconstructed from sediment and pollen analysis of a sediment sequence from the archaeological site of Arbon-Bleiche 3, shows an abrupt rise in lake level dendrochronologically dated to 5375 yr ago (5320 yr relative to AD 1950). This event, paralleled by the destruction of the Neolithic village by fire, provoked the abandonment of this prehistoric lake-shore location established in the former shallow bay of Arbon-Bleiche, and was the last of a series of three episodes of successively higher lake level, the first occurring at 5600-5500 cal yr B.P. The dendrochronologically dated rise event was synchronous with an abrupt increase in atmospheric ¹⁴C. This supports the hypothesis of an abrupt climate change forced by varying solar activity. Moreover, the three successive episodes of higher lake level between 5600 and 5300 cal yr B.P. at Arbon-Bleiche 3 coincided with climatic cooling and/or changes in moisture conditions in various regions of both hemispheres. This period corresponds to the mid-Holocene climate transition (onset of the Neoglaciation) and suggests inter-hemispheric linkages for the climate variations recorded at Arbon-Bleiche 3. This mid-Holocene climate reversal may have resulted from complex interactions between changes in orbital forcing, ocean circulation and solar activity. Finally, despite different seasonal hydrological regimes, the similarities between lake-level records from Lake Constance and from Jurassian lakes over the mid-Holocene period point to time scale as a crucial factor in considering the possible impact of climate change on environments.  相似文献   

Présence d'une mangrove à Avicennia au Miocène moyen dans la région de Digne (Alpes-de-Haute-Provence,France) : implications stratigraphiques et paléoclimatiques     

Jean-Jacques Châteauneuf  Hugues Bauer  Isabelle Cojan 《Comptes Rendus Geoscience》2006,338(3):197-205

Avicennia pollen grains have been discovered in marine facies from the Middle Miocene deltaic series of Châteauredon (southeastern France). Based on the local stratigraphy, an age between 15.8 and 16.5 Ma is proposed for these grains. The age and the transgressive context of the Avicennia bearing-levels are in agreement with the maximum extension of the mangrove known in the western Mediterranean during interval N8–NN4 pro parte, in relation with the Langhian highstand. This mangrove occurrence at 42°N latitude during Middle Miocene is a more northern witness of the mangrove sites known in Languedoc and Provence areas. It also implies a lower climatic gradient than today. To cite this article: J.-J. Châteauneuf et al., C. R. Geoscience 338 (2006).  相似文献   

Relations between climatic variability and hydrologic time series from four alluvial basins across the southwestern United States   总被引：1，自引：3，他引：1  

R. T. Hanson  M. D. Dettinger  M. W. Newhouse 《Hydrogeology Journal》2006,14(7):1122-1146

Hydrologic time series of groundwater levels, streamflow, precipitation, and tree-ring indices from four alluvial basins in the southwestern United States were spectrally analyzed, and then frequency components were reconstructed to isolate variability due to climatic variations on four time scales. Reconstructed components (RCs), from each time series, were compared to climatic indices like the Pacific Decadal Oscillation (PDO), North American Monsoon (NAM), and El Niño-Southern Oscillation (ENSO), to reveal that as much as 80% of RC variation can be correlated with climate variations on corresponding time scales. In most cases, the hydrologic RCs lag behind the climate indices by 1–36 months. In all four basins, PDO-like components were the largest contributors to cyclic hydrologic variability. Generally, California time series have more variation associated with PDO and ENSO than the Arizona series, and Arizona basins have more variation associated with NAM. ENSO cycles were present in all four basins but were the largest relative contributors in southeastern Arizona. Groundwater levels show a wide range of climate responses that can be correlated from well to well in the various basins, with climate responses found in unconfined and confined aquifers from pumping centers to mountain fronts.  相似文献   

Impacts of Holocene climatic variations on alluvial fan activity below snowpatches in subarctic Québec     

Violaine Lafortune  Louise Filion  Bernard Htu 《Geomorphology》2006,76(3-4):375-391

In the Lake Guillaume-Delisle area of subarctic Québec, storm-generated alluvial fans have been active sporadically throughout the Holocene. In this study, we propose that the persistence of late-lying snowpatches in fan catchments during Holocene cold episodes promoted alluvial fan activity by lowering the precipitation threshold required to trigger a torrential event. This hypothesis was tested by characterizing the depositional processes responsible for alluvial fan formation below snowpatches, and by reconstructing the Holocene alluvial fan activity. Stratigraphic and sedimentary analyses conducted on seven alluvial fans revealed that they were deposited by torrential activity leading to waterlaid, transient, or hyperconcentrated deposition. The chronology of the storm-generated alluvial fans — based on 22 radiocarbon dates — indicates that torrential activity was enhanced during the cooler Late Holocene (i.e., after ca. 3500 cal. yr BP). Snowier winters and cooler summers were beneficial to nival activity, allowing the persistence of larger snowpatches throughout the summer and fall seasons. Rainfall-induced thaw of such snowpatches during rainstorm events is inferred to have contributed to alluvial fan activity by increasing water availability. Three peaks of alluvial activity occurred during the Late Holocene (2950–2750, 1900–1400, and 800–300 cal. yr BP) and are indicative of increased storminess resulting in higher fan activity. Increased fan activity during cooler episodes was concurrent with increased runoff activity in the immediate pronival area. This stresses the importance of nivation below snowpatches and pinpoints the role of nivation in enhancing geomorphological activity during period of cooler and more humid climate in subarctic environments.  相似文献   

On global forces of nature driving the Earth’s climate. Are humans involved?     

L. F. Khilyuk  G. V. Chilingar 《Environmental Geology》2006,50(6):899-910

The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.  相似文献   

时间序列转折突变点检测的线性函数方法   总被引：6，自引：2，他引：6  

曹杰  陶云  田永丽 《高原气象》2002,21(5):518-521

根据转折突变的定义，在引入线性半截多项式的前提下，提出检测时间序列转折突变点的一种新方法。此方法不仅能找出时间序列中存在的多个转折突变点，而且使得检测到的突变点通过统计显著性检验。应用此方法对北半球1851—1990年年平均气温距平及其11年滑动平均序列，1901—1999年昆明5月降水及其11年滑动平均的降水序列分别进行了检测。发现北半球年平均气温距平在1879、1889、1939和1973年附近出现了年际转折突变，在1878、1888和1941年以及1972年出现了年代际尺度的转折突变；昆明5月雨量不存在年际转折突变点，但昆明5月雨量在1918、1966以及1978年附近出现了年代际尺度转折突变。  相似文献   

青藏高原冬季平均温度、湿度气候特征的REOF分析   总被引：14，自引：2，他引：14       下载免费PDF全文

牛涛  陈隆勋  王文 《应用气象学报》2002,13(5):560-570

通过对青藏高原123个测站, 1961~1998年冬季 (12月至翌年2月) 平均温度、相对湿度资料做气候特征分析, 得到32°~33°N附近地区可能是高原南北温湿变化的分水岭, 以北主要受干冷空气影响, 以南主要受暖湿空气影响。用方差极大正交旋转EOF (即REOF) 方法对以上资料进行分析, 可以将青藏高原温度、相对湿度进行分型、分区, 并对各区的温度、相对湿度特征进行分析。结果表明, 近40年来, 各区的温度总趋势是在波动中逐步升高的。增温时段主要出现在1978~1981年及1983年至今。1983年开始的增温, 是近40年来最强的一次, 增温幅度大且持续时间长, 但从90年代开始增温幅度及范围出现波动。从温度线性倾向来看, 东部高原增温幅度从南到北存在“大—小—大”的现象。高原大部分地区湿度变化总趋势是在波动中逐步增湿的, 但高原北界以变干为主。从80年代后期至今高原进入显著增湿阶段, 但从90年代中后期开始增湿幅度及范围出现波动。从湿度线性倾向来看东部高原增湿幅度从南到北存在逐步减小现象, 甚至祁连山地区出现变干现象。  相似文献   

晚更新世以来青海北部的人类活动与湖泊演变          下载免费PDF全文

周笃珺  马海州  P.J.Brantingham  谭红兵 《盐湖研究》2003,11(2):8-13

作为高海拔生态环境的青海北部是青藏高原的重要组成部分。晚更新世晚期以来 ,青海北部气候环境一直处于冷暖、干湿波动过程之中 ,湖泊水域也发生了相应的扩张和收缩 ,成为高原人类迁移和发展的自然背景。约 3 0kaB .P .,在晚期智人出现和迁徙的关键时期 ,青海北部开始有了最早的人类活动 ;更新世末—全新世初 ,气候转暖 ,古人类再次来到青海北部 ;进入全新世中期 ,气候暖湿 ,湖水位回升 ,细石器技术变得十分普通 ,青海北部的人类活动渐趋频繁。  相似文献   

利用NOAA AVHRR数据研究北半球雪盖气候学特征   总被引：2，自引：0，他引：2  

杨向东 《国土资源遥感》2003,14(1):16-19

利用NOAA卫星图像,研究了北半球、欧亚、北美和青藏高原雪盖气候学特征及其变化趋势.指出北半球、欧亚和北美雪盖气候变化趋势基本一致,年均雪盖面积在1987年前后明显下降; 而青藏高原雪盖面积在1984年后明显下降,说明青藏高原雪盖的年际变化与北半球及欧亚、北美不完全一致.  相似文献