高精度岩层应力仪探头安装在土层中的实验观测

高精度岩层应力仪的压磁探头在土层安装后，经８个多月的实验观测，对太原附近仅有的两次有感地震（ＭＬ３．５，ＭＬ４．２），仪器均有明显的前兆反映，出现了幅度达数十千帕的应力速率异常，并在震前成功地预报了这两次地震。     

全球地震活动性的统计分析

随着宇航事业的迅速发展,在地学中出现了对地球从整体上来进行研究的趋势,並把各种地球物理现象与宇宙中发生变动相联系。在地震学研究中,对全球地震活动性的研究亦是一个重要方面,它不仅有理论上意义,而且对一些地震带的地震趋势估计亦有重要作用,     

Significant enhancement in atmospheric biweekly disturbance over Northeast Asia during the recent warming hiatus

Based on daily 500-hPa geopotential height from ERA-Interim reanalysis data, this study analyzed the day-to-day circulation variance in cold season (October–March) by composite and correlation analysis. Two same-length time periods were compared, namely, the hiatus period (1999–2013) and the rapid warming period (1984–1998). Spectral analysis revealed that over the mid–high latitudes of the Northern Hemisphere, the most outstanding peak in the daily 500-hPa geopotential height variance was of quasi-biweekly timescale (about 10–20 days), accounting for about 32% of the total variance. During the warming hiatus, quasibiweekly disturbance (QBD) changed remarkably in Northeast Asia. On average, within the domain 42°–50 °N, 128°–142 °E, the QBD variance changed from 1860 m² in the rapid warming period to 2475 m² in the hiatus period, increasing by about 33% and statistically significant at the 95% confidence level. Lead–lag analysis showed that the QBD signal could be traced back by about 14 days, with an origin around the Ural Mountains. Then, the signal developed and propogated southeastward, with its location about 10 days prior to its peak in West Siberia, and about 6 days prior to its peak in the Sayan Mountains, and finally moving to Northeast Asia. By comparing the propagation process between the two periods, we found that the propagation paths were basically the same, but there were evident differences in the intensity of the signals. The intensification of QBD may have been related to the increased energy conversion from mean flow to QBD transients. The frequency of low-temperature extremes in negative QBD phases was much higher than under normal conditions or in positive phases. Associated with the enhanced QBD, the probability of extreme low temperature increased from 19% during the rapid warming period to 27% during the warming hiatus.     

西伯利亚高压的长期变化及全球变暖可能影响的研究

本文利用历史少平面气压资料建立了的百年来的西伯利亚高压强度指数。１９６０年代是近百年来西伯利来坟强度最强的一段时期１９８０年代后期到１９９０年代则是近百年来最弱的一段时期。４０年左右的年代际变化毕竟和西伯利亚高压强度能较好地解释近几十年来我国冬季气温变化的特征。近百年来西伯利亚高压的变化可能仍然以延寿自然变率为主,全球变暖的影响还较弱,但是,在全球持续变暖的背景下,西伯利亚高压的强度将会显著减弱,     

近百年中国华北农牧交错带与非洲Sahel 地区环境变化的比较分析

非洲Sahel 地区与中国华北农牧交错带在环境特征及演变过程中体现出许多相似之处, 存在明显内在联系。对两个地带近百年降水变化、植被覆盖、干旱事件和沙尘事件对比分析, 可以 对我国干旱/半干旱地区环境变化的相关科学问题有更好认识。两个地区年降水量序列的年代际 变化趋势有很大相似性。非洲Sahel 地区年降水量在1950s 以前存在明显的年际变化特征, 从 1960s 中期起主要以年代际变化为主; 其大部分地区植被覆盖表现为增长趋势; 降水量年代际变 化可能是影响该地区干旱的重要因素, 温度变化也可能存在作用; 该区沙尘暴频次年际、年代际 变化与降水量相应尺度变化有显著关系, 年均温变化和天气变率可能具有一定影响。华北农牧交 错带年降水量以年际变化为主要特征, 有明显低频波动; 该带偏北和偏东地区植被覆盖增长比较 显著, 南部部分地区植被覆盖呈下降趋势; 降水量年代际变化是影响该地区干旱的重要因素, 但 相同降水量可能引发不同程度的干旱; 该带春季沙尘暴频次与前冬温度变化及天气变率有密切 联系, 与春季降水量也有一定关系。     

北半球春季植被NDVI对温度变化响应的区域差异

利用1982年到2000年的探路者NDVI资料，采用奇异值分解分析方法，研究北半球春季NDVI对温度变化响应的空间差异，前7对模态对总的协方差平方的解释率高达91％以上，反映出NDVI和气温的相关性非常高，第一对模态解释率达42．6％，显示北半球最显著的NDVI响应中心在西西伯利亚，其次是北美大陆，中心在其中东部，第三对及以后的模态反映的是次一次的空间特征，分析表明这些NDVI一温度的耦合模态受大尺度的大气环流系统的显著影响，9个重要的大气环流指标能解释整个北半球NDVI方差的55．6％，其中对欧洲、北美东南部，北美西北部，亚洲高纬以及东亚地区的影响最突出，因此，研究未来植被生态系统对全球变化响应的区域特征时，必须要考虑到这些环流系统的可能变化及其影响。     

近百年中国年气温序列的建立

该文根据气温观测,并利用敦德及古里雅冰芯资料及有关史料、树木年轮资料,得到了东北、华北、华东、华南、台湾、华中、西南、西北、新疆、西藏10个区1880～1996年的年平均气温序列。然后根据每个区的面积加权平均得到代表中国的气温序列。根据这个序列,1880～1996年增温为0.44℃/100a,显著高于过去对中国气候变暖的估计值0.09℃/100a。这主要是因为新计算的中国气温包括了我国西部地区,而那里在上世纪末到本世纪初气温显著偏低。另外本世纪90年代的迅速增暖也加强了这个趋势。     

Extreme drought event of 2009/2010 over southwestern China

The extreme drought of 2009/2010 over southwestern China is the driest event with the lowest percentage rainfall anomaly and the longest non-rain days during winter season (October–February) in the past 50?years, and also the severest one with the lowest percentage rainfall anomaly at the same period since 1880. The drought domain is characterized with anomalous warming and drying in the mid-lower troposphere as well as an evident anomalous subsidence. The favorable circulation anomalies for this drought are associated with the following two factors. One is the strongest negative-phase Arctic Oscillation during 2009/2010 winter that accompanies with a weakened Middle East Jet Stream (MEJS), the cyclonic anomaly over Arabian Sea (AS), the anticyclonic anomaly over Tibet and the cyclonic anomaly over Lake Baikal. The weakened MEJS, the AS cyclonic anomaly and the Tibet anticyclonic anomaly weaken the Southern Branch Trough (SBT) that directly decreases the moisture transport toward the southwestern China; the cyclonic anomaly over the Lake Baikal causes a deepened and westward shifted East Asian Major Trough (EAT) so that dry cold air behind the EAT easily invades down to southwestern China. The AS cyclonic anomaly favors the westward extension of Western Pacific Subtropical High (WPSH). The westward extension of WPSH is also associated with the second factor that is the El Nino Modoki event during 2009/2010 autumn–winter. The intensification and westward extension of WPSH enhance the local subsidence, weaken the SBT and exacerbate this drought.     

A preliminary study on the relationship between Arctic Oscillation and daily SLP variance in the Northern Hemisphere during wintertime

In the present study, the authors investigated the relationship between the Arctic Oscillation (AO) and the high-frequency variability of daily sea level pressures in the Northern Hemisphere in winter (November through March), using NCEP/NCAR reanalysis datasets for the time period of 1948/49-2000/01.High-frequency signals are defined as those with timescales shorter than three weeks and measured in terms of variance, for each winter for each grid. The correlations between monthly mean AO index and high-frequency variance are conducted. A predominant feature is that several regional centers with high correlation show up in the middle to high latitudes. Significant areas include mid- to high-latitude Asia centered at Siberia, northern Europe and the middle-latitude North Atlantic east of northern Africa. Theirs trong correlations can also be confirmed by the singular value decomposition analysis of covariance between mean SLP and high-frequency variance. This indicates that the relationship of AO with daily Sea Level Pressure (SLP) is confined to some specific regions in association with the inherent atmospheric dynamics. In middle-latitude Asia, there is a significant (at the 95% level) trend of variance of-2.26% (10yr)^-1. Another region that displays a strong trend is the northwestern Pacific with a significant rate of change of 0.80% (10 yr)^-1. If the winter of 1948/49, an apparent outlier, is excluded, a steady linear trend of 1.51% (10 yr)^-1 shows up in northern Europe. The variance probability density functions (PDFs) are found to change in association with different AO phases. The changes corresponding to high and low AO phases, however, are asymmetric in these regions. Some regions such as northern Europe display much stronger changes in high AO years, whereas some other regions such as Siberia show a stronger connection to low AO conditions. These features are supported by ECMWF reanalysis data. However, the dynamical mechanisms involved in the AO-high frequency SLP variance connection have not been well understood,and this needs further study.