1637—1643年华北地区极端干旱事件中的粮食危机

粮食作为自然生态系统与社会经济系统的关联点,能够有效地揭示极端干旱事件对自然-经济-社会复合生态系统影响的过程和机理。以粮价异动为切入点,通过粮价通胀指数和“无透雨”的持续时间,分析农业旱情及其对粮食生产的影响,对1637—1643年华北地区极端干旱事件中的粮食安全进行深入剖析。结果显示:华北地区无透雨天数超过150 d,年降水量与5—9月降水量的距平值均≤-30%,水分异常短缺,土壤严重失墒,危及粮食生产安全。因此,降水量距平值≤-30%是华北地区粮食生产安全的临界阈值。此次极端干旱事件是历史同类事件之最,连续无透雨日数最长,地表径流枯竭记录最多,水资源的短缺导致伴生灾害相继发生,超过生态系统的忍耐极限,粮食生长期缩短,减产歉收,绝产绝收,粮食供给链条断裂。粮价通胀指数最低9.50,最高26.70;货币发行与粮食供给失衡,通货膨胀严重,粮价飞涨,市场倒闭,粮食安全体系崩塌,自然-经济-社会复合生态系统发生质变成为历史必然。     

ENVIRONMENTAL CHANGE AND ITS IMPACTS ON HUMAN SETTLF, MENT IN THE CHANGJIANG RIVER DELTA IN NEOLITHIC AGE

Dating data, altitude of Neolithic sites, climatic changes from sedimentary records and previous research results were collected and analyzed to detect possible connections between climatic changes and human activities in the Changjiang River Delta in the Neolithic Age. The results indicated that hydrological changes greatly impacted the human activities in the study region. Low-lying geomorphology made the floods and sea level changes become the important factors affecting human activities, especially the altitude change of human settlements. People usually moved to higher places during the periods characterized by high sea level and frequent floods to escape the negative influences from water body expansion, which resulted in cultural hiatus in certain profiles. However, some higher-altitude settlements were not the results of climatic changes but the results of social factors, such as religious ceremony and social status. Therefore, further research will be necessary for the degree and types of impacts of climatic changes on human activities in the study area at that time.     

极端气温和极端降水复合事件的气候特征

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。     

环渤海地区城市化对夏季极端暖夜的影响

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).     

Effects of Urbanization on Extreme Warmest Night Temperatures During Summer near Bohai

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.     

近50年来乌兰乌苏多种天气事件变化特征研究

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.     

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

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.     

Interannual and seasonal variation of the Huanghe (Yellow River) water discharge over the past 50 years: Connections to impacts from ENSO events and dams

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.     

脉冲型耀斑中阿尔芬波湍流加速3He和重离子机制探讨

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。