珠江三角洲中山横栏地区晚第四纪以来的沉积特征   总被引：1，自引：0，他引：1  

刘子宁 《华南地质与矿产》2015,(2)

中山横栏地区在珠江三角洲第四纪地层研究中具有代表性。本文通过对该地区第四纪Ⅳ01钻孔岩性、粒度及地球化学特征的综合研究,探讨珠江三角洲晚第四纪以来的沉积特征。结果表明,珠江三角洲晚第四纪沉积物自下而上包含三次沉积旋回:一次晚更新世海侵旋回和两次全新世的海侵旋回,其形成的下粗上细正向序列在进积型三角洲中具有一定的特殊性;在沉积学分析的基础上,结合粒度和微量元素B、Ba、Sr的指相特征,探讨珠江三角洲晚第四纪以来的海侵-海退旋回,揭示在中全新世中晚期(约5~2.5 ka BP)发生了海退过程,进一步印证中山横栏地区晚第四纪以来存在三次海侵事件的认识。  相似文献   

极端气温和极端降水复合事件的气候特征   总被引：1，自引：0，他引：1  

肖秀程  黄丹青  严佩文 《气象科学》2020,40(6):744-751

基于1961-2014年的中国台站资料,侧重探讨极端气温和极端降水复合事件的气候特征。结果表明,基于客观方法检测出四类极端复合事件：暖湿、暖干、冷湿和冷干。四类事件的频发区分别位于东北地区、华南地区、西藏及华南地区和长江以南及云贵高原一带。全国暖湿、暖干事件频数呈增加趋势,春夏季频发;冷湿事件频数在西藏东北一带呈增加趋势,而在长江流域呈减少趋势,夏秋冬季频发;冷干事件频数呈减少趋势,秋冬季频发。四类极端复合事件经验正交分解的时间序列主模态均表现为年代际信号。进一步分析四类复合事件与能源消费量的联系表明,极端湿事件与能源消费量呈正相关,而极端干事件则相反。  相似文献   

环渤海地区城市化对夏季极端暖夜的影响     

李庆祥  黄嘉佑 《气象学报》2013,71(4):668-676

城市化对人类生活息息相关的一些指标(如夏季极端暖夜等)的影响研究尚少.取环渤海地区气象观测站的夏季(6-8月)逐日最低气温资料(1958-2009年),使用广义极值(GEV)分布拟合夏季极端暖夜气温分布,并对拟合函数的3个分布特征参数的年际变化进行分析,根据特征参数变化特征进行城市化对极端暖夜的影响程度的分离.研究结果表明,环渤海地区,在极端暖夜气温分布的3个参数的年际变化中,以位置参数的代表性最好.在城市快速发展时期,城市偏高气温出现的可能性大,但极端气温变化幅度也较大.城市化对环渤海不同类型城市夏季极端暖夜气温的贡献均为上升作用,增温速度最大约为0.3℃/(10a).  相似文献   

Effects of Urbanization on Extreme Warmest Night Temperatures During Summer near Bohai   总被引：1，自引：0，他引：1  

LI Qingxiang  HUANG Jiayou 《Acta Meteorologica Sinica》2013,27(6):808-818

Many previous studies have focused on the impacts of urbanization on regional mean temperatures. Relatively few have analyzed changes in extreme temperatures. Here, we examine the impact of urbanization on extreme warmest night temperatures from 33 stations in the Bohai area between 1958 and 2009. We compute the Generalized Extreme Value（GEV） distribution of extreme warmest night temperatures and analyze long-term variations in its characteristic parameters. A new classification method based on the factor analysis of changes in extreme night temperatures is developed to detect the efects of urbanization in diferent cities. Of the three parameters that characterize the GEV distribution, the position parameter is the most representative of long-term changes in extreme warmest night temperatures. During the period of rapid urbanization（i.e., after 1978）, all three parameters of the GEV distribution are larger for the urban station group than for the reference station group, so are the magnitudes of their variations, and the urban areas have been experiencing higher extreme warmest night temperatures with larger variability. Diferent types of cities in the Bohai area have all experienced an urban heat island efect, with an average urbanization efect of approximately 0.3 per decade.  相似文献   

近50年来乌兰乌苏多种天气事件变化特征研究     

王芳芳  吴燕锋  魏勇 《四川气象》2013,(4):42-48

利用乌兰乌苏镇1964～2012年的气象资料,选取逐年平均气温、极端最高气温、极端最低气温、大风、雷暴、沙尘暴、沙尘天气及大雾、轻雾天气出现的天数作为分析对象,运用3年移动平均法、回归分析法、非参数检验方法的Mann-Kendall趋势检验和突变检验法以及小波分析法,进行了多种天气事件的年纪变化趋势分析.结果表明：（1）大雾天气的发生日数呈增加趋势,沙尘天气、沙尘暴天气、轻雾天气、大风天气和雷暴天气的发生日数都呈减少趋势,其中大风天气发生日数减少趋势最为明显.（2）平均气温、年极端最高气温、年极端最低气温、大雾天气、轻雾天气、沙尘暴天气、雷暴天气和沙尘天气在研究时段都出现了突变,且平均气温、轻雾天气、沙尘天气和雷暴天气在突变之后不久都达到了极显著的上升或者下降变化趋势.（3）平均气温、年极端最低气温、年极端最高气温、大雾天气、雷暴天气和大风天气有明显的周期性,但是不同的气象要素周期性长短是不同的,沙尘、沙尘暴和轻雾天气则没有明显的周期性.  相似文献   

An investigation of sand–dust storm events and land surface characteristics in China using NOAA NDVI data     

Xingkui Xu  Jason K. Levy  Lin Zhaohui  Chen Hong 《Global and Planetary Change》2006,52(1-4):182

Observations from 560 weather stations in China show that sand–dust storms occur most frequently in April in north China. The region consists of Sub-dry Mid Temperate, Dry Mid Temperate, Sub-dry South Temperate and Dry South Temperate Zones and much of the land surface is desert or semi-desert: it is relatively dry with minimal rainfall and a high annual mean temperature. In most regions of China, the annual mean frequency of sand–dust events decreased sharply between 1980 and 1997 and then increased from 1997 to 2000. Statistical analyses demonstrate that the frequency of sand–dust storms correlates highly with wind speed, which in turn is strongly related to land surface features; on the other hand, a significant correlation between storm events and other atmospheric quantities such as precipitation and temperature was not observed. Accordingly, land surface cover characteristics (vegetation, snowfall and soil texture) may play a significant role in determining the occurrence of sand–dust storms in China. Analysis of Normalized Difference Vegetation Index derived from National Oceanic and Atmospheric Administration and Empirical Orthogonal Function show that since 1995 surface vegetation cover in large areas of Northern China has significantly deteriorated. Moreover, a high correlation is shown to exist among the annual occurrence of sand–dust storms, surface vegetation cover and snowfall. This suggests that the deterioration of surface vegetation cover may strongly influence the occurrence of sand–dust storms in China. Soils with coarse and medium textures are found to be more associated with sand–dust storms than other soils.  相似文献   

Interannual and seasonal variation of the Huanghe (Yellow River) water discharge over the past 50 years: Connections to impacts from ENSO events and dams   总被引：4，自引：2，他引：2  

Houjie Wang  Zuosheng Yang  Yoshiki Saito  J. Paul Liu  Xiaoxia Sun   《Global and Planetary Change》2006,50(3-4):212-225

The Huanghe, the second largest river in China, is now under great pressure as a water resource. Using datasets of river water discharge, water consumption and regional precipitation for the past 50 years, we elucidate some connections between decreasing water discharges, global El Niño/Southern Oscillation (ENSO) events and anthropogenic impacts in the drainage basin. Global ENSO events, which directly affected the regional precipitation in the river basin, resulted in approximately 51% decrease in river water discharge to the sea. The degree of anthropogenic impacts on river water discharge is now as great as that of natural influences, accelerating the water losses in the hydrological cycle. The large dams and reservoirs regulated the water discharge and reduced the peak flows by storing the water in the flood season and releasing it in the dry season as needed for agricultural irrigation. Thus, as a result, large dams and reservoirs have shifted the seasonal distribution patterns of water discharge and water consumption and finally resulted in rapidly increasing water consumption. Meanwhile, the annual distribution pattern of water consumption also changed under the regulation of dams and reservoirs, indicating that the people living in the river basin consume the water more and more to suit actual agricultural schedule rather than depending upon natural pattern of annual precipitation. The combination of the increasing water consumption facilitated by the dams and reservoirs and the decreasing precipitation closely associated with the global ENSO events over the past half century has resulted in water scarcity in this world-famous river, as well as in a number of subsequent serious results for the river, delta and coastal ocean.  相似文献   

脉冲型耀斑中阿尔芬波湍流加速3He和重离子机制探讨     

吴桂平  王德焴  许敖敖  唐玉华 《天文学报》2002,43(1):48-53

基于在^3He丰富事件中，高能^3He和重离子具有相似的幂律谱分布这一观测结果，通过数值求解Fokker-Planck方程，探讨经阿尔芬波湍动速后的离子分布随时间的演化特征。计算结果表明：加速源区的等离子体密度和阿尔芬波湍动能量密度对粒子能谱分布起主要作用，如果取加速源区等离子体密度n=(0.1-1)10^10cm^-3、磁场强度B=50-100Gs、湍动能量密度为0.4-2ergs cm^-3，则在1秒左右的时间内，湍动阿尔芬波能够将^3He和重离子加速到10MeV/nucleon量级，能谱指数为2.0-3.5。理论计算与观测结果基本一致。  相似文献   

Surface and deep water response to rapid climate changes at the Western Iberian Margin     

Joachim Schnfeld  Rainer Zahn  Lúcia de Abreu 《Global and Planetary Change》2003,36(4):237-264

Rapid climate changes at the onset of the last deglaciation and during Heinrich Event H4 were studied in detail at IMAGES cores MD95-2039 and MD95-2040 from the Western Iberian margin. A major reorganisation of surface water hydrography, benthic foraminiferal community structure, and deepwater isotopic composition commenced already 540 years before the Last Isotopic Maximum (LIM) at 17.43 cal. ka and within 670 years affected all environments. Changes were initiated by meltwater spill in the Nordic Seas and northern North Atlantic that commenced 100 years before concomitant changes were felt off western Iberia. Benthic foraminiferal associations record the drawdown of deepwater oxygenation during meltwater and subsequent Heinrich Events H1 and H4 with a bloom of dysoxic species. At a water depth of 3380 m, benthic oxygen isotopes depict the influence of brines from sea ice formation during ice-rafting pulses and meltwater spill. The brines conceivably were a source of ventilation and provided oxygen to the deeper water masses. Some if not most of the lower deep water came from the South Atlantic. Benthic foraminiferal assemblages display a multi-centennial, approximately 300-year periodicity of oxygen supply at 2470-m water depth. This pattern suggests a probable influence of atmospheric oscillations on the thermohaline convection with frequencies similar to Holocene climate variations. For Heinrich Events H1 and H4, response times of surface water properties off western Iberia to meltwater injection to the Nordic Seas were extremely short, in the range of a few decades only. The ensuing reduction of deepwater ventilation commenced within 500–600 years after the first onset of meltwater spill. These fast temporal responses lend credence to numerical simulations that indicate ocean–climate responses on similar and even faster time scales.  相似文献   

Source study of local coalfield events using the modal synthesis of shear and surface waves     

C. D. MacBeth  D. W. Redmayne 《Geophysical Journal International》1989,99(1):155-172

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