南海夏季风强度潜在可预报性的年代际变化及可能原因

基于NCEP/NCAR再分析资料,利用信噪比(SNR)方法研究了南海夏季风强度潜在可预报性的年代际变化,结果表明:南海夏季风强度潜在可预报性在20世纪80年代出现了由潜在可预报性偏低位相向偏高位相的年代际转折。进一步的研究发现,南海夏季风强度潜在可预报性和东印度洋—西太平洋(EIOWP)的海表温度(SST)存在明显的正相关。当EIOWP区域SST年际变率较大时,对南海夏季风影响较强,使得南海夏季风的外部信号增强,从而提高了潜在可预报性;当EIOWP区域SST年际变率较小时,对南海夏季风影响较弱,南海夏季风的外部信号进而减弱,潜在可预报性降低。     

Predictability of Ensemble Forecasting Estimated Using the Kullback–Leibler Divergence in the Lorenz Model

A new method to quantify the predictability limit of ensemble forecasting is presented using the Kullback–Leibler(KL)divergence(also called the relative entropy), which provides a measure of the difference between the probability distributions of ensemble forecasts and local reference(true) states. The KL divergence is applicable to a non-normal distribution of ensemble forecasts, which is a substantial improvement over the previous method using the ensemble spread. An example from the three-variable Lorenz model illustrates the effectiveness of the KL divergence, which can effectively quantify the predictability limit of ensemble forecasting. On this basis, the KL divergence is used to investigate the dependence of the predictability limit of ensemble forecasting on the initial states and the magnitude of initial errors. The local predictability limit of ensemble forecasting varies considerably with the initial states, as well as with the magnitude of initial errors. Further research is needed to examine the real-world applications of the KL divergence in measuring the predictability of ensemble weather forecasts.     

瞬变天气涡旋对北大西洋涛动的增强效应

使用NCEP/NCAR再分析资料计算了冬季北大西洋瞬变涡旋活动强度与北大西洋涛动(NAO)逐日指数的时间序列,结果发现:当涡旋活动强度出现峰值后会伴随NAO模态增强现象;而随着NAO的增强,涡旋能量同落.为了判断是否涡流相互作用将天气尺度的能量转换为低频尺度的能量,使用瞬变涡度通量来研究涡度与能量的传输.通过分析瞬变涡...     

A hydrochemical framework and water quality assessment of river water in the upper reaches of the Huai River Basin, China

This study characterizes the major ion chemistry for river water in the upper reaches of Bengbu Sluice in the Huai River Basin in wet and dry seasons, and assessed the suitability of water quality for irrigation and human consumption. It is found that sodium and calcium are the dominant cations and bicarbonate is the dominant anion in most river water samples. River water in Zhoukou of the Ying River and Bozhou of the Guo River is characterized as a Na–Cl water type, whereas river water from the upper reaches and the lower reaches of the two cities is characterized as a Na-HCO₃ water type, which may be attributed by anthropogenic influences in these cities. The river water types vary from the upstream to the downstream of the Fuyang sluice, which indicates that the sluices play a critical role in determining the water type. The water chemistry of these rivers clearly shows that the second group of rivers is affected more severely by waste effluent than is the first group. Calculated values of sodium adsorption ratio, %Na, and residual sodium carbonate indicate that, in general, most of the river water is of acceptable irrigation quality. The river water in Zhoukou section of the Ying River and the Bozhou section of the Guo River cannot be used as drinking water; pollution control should be further improved and enhanced across the river.     

Relationships between the Extratropical ENSO Precursor and Leading Modes of Atmospheric Variability in the Southern Hemisphere

Previous studies suggest that the atmospheric precursor of El Ni ?no–Southern Oscillation(ENSO) in the extratropical Southern Hemisphere(SH) might trigger a quadrapole sea surface temperature anomaly(SSTA) in the South Pacific and subsequently influence the following ENSO. Such a quadrapole SSTA is referred to as the South Pacific quadrapole(SPQ).The present study investigated the relationships between the atmospheric precursor signal of ENSO and leading modes of atmospheric variability in the extratropical SH [including the SH annular mode(SAM), the first Pacific–South America(PSA1) mode, and the second Pacific–South America(PSA2) mode]. The results showed that the atmospheric precursor signal in the extratropical SH basically exhibits a barotropic wavenumber-3 structure over the South Pacific and is significantly correlated with the SAM and the PSA2 mode during austral summer. Nevertheless, only the PSA2 mode was found to be a precursor for the following ENSO. It leads the SPQ-like SSTA by around one month, while the SAM and the PSA1 mode do not show any obvious linkage with either ENSO or the SPQ. This suggests that the PSA2 mode may provide a bridge between the preceding circulation anomalies over the extratropical SH and the following ENSO through the SPQ-like SSTA.     

Lorenz系统误差方程的吸引子特性研究

将Lorenz方程及其导出的误差方程作为联立方程(即全误差方程)来研究误差的性质,结果表明联立方程可以变换为一个特殊的算子方程,误差轨线将收敛于一个有限的区域;此外联立方程对应的流的散度为负值,因此其在相空间中的体积不断收缩,最终趋向一个低纬曲面;联立方程的这两个性质使得Lorenz系统中初始误差不会无限放大,而是趋于一个吸引子.误差在吸引子上的概率分布是确定的,因此平均的绝对误差趋于常数,这个结果可以用来解释小初始误差经过一段时间的发展之后,趋向饱和的现象.利用稳定性分析方法研究了误差吸引中心的位置和个数,并使用数值试验进行了验证,结果显示误差吸引子的结构与解的吸引子位置、数量和结构均有不同.最后本研究将针对Lorenz方程的误差联立方程方法拓展到一般的常微分动力系统,展示了对一般误差方程的特征矩阵进行分析,研究其特征行列式性质的方法,得到了一般误差系统中稳定点和平衡态性质与原动力系统的稳定点和平衡态性质的关系,这些结果对于认识误差系统长期的动力学行为和性质是有意义的.     

基于多元线性回归模型的冻土强度影响因素 显著性分析

为定量分析土质、含水率、温度和应变速率等因素对冻土强度的影响,本文根据公开发表的试验数据,应用多元线性回归模型对冻土强度影响因素进行了显著性分析。分析结果表明,在仅考虑线性影响条件下,温度和土性是影响冻土强度的主要因素,影响强度分别为0.632和0.193,含水率对冻土强度也有显著性影响,影响强度为-0.577。为探明各影响因素对冻土强度的非线性作用,在保留强度Taylor展开二次项的条件下,通过变量代换,将非线性项进行线性化,并利用多元线性回归模型进行了进一步分析。分析结果表明含水率与温度对冻土强度的影响包含线性、非线性和交叉影响项三项,应变率对冻土强度的影响仅包含非线性和交叉影响项。各因素对冻土强度的影响程度可用偏回归系数定量描述。     

内蒙古二连盆地阿特巴音敖包地区eU、eTh、K等天然放射性水平调查评价

为了对内蒙古二连盆地阿特巴音敖包调查区铀成矿潜力做出评价,通过对其天然放射性水平测量数据的统计分析、参数构建等手段,多维度探索了铀(eU)、钍(eTh)、钾(K)元素含量及γ照射量率在空间上的分布规律及其变化趋势。结合区域地质资料对古铀含量、活化铀量、铀迁移富集指数、地化活动性指数等新构建参数特征进行了综合解释,成功预测了调查区铀成矿有利地段,经钻探查证,发现了良好的铀矿化信息。     

Joint impact of North Pacific Victoria mode and South Pacific Quadrapole mode on Pacific ITCZ summer precipitation

Climate Dynamics - This study investigates the joint impact of the boreal late winter–early spring North Pacific Victoria mode (VM) and South Pacific Quadrapole (SPQ) mode on the following...