北京地区“环流－降水－谷物”系统的短期振动研究

文章用因子分析方法提取北京地区小麦气象产量主要特征及代表序列，并对该序列和北京地面气象要素的关系用交叉谱进行研究。发现它们在前期秋冬季中的４－６年的周期振荡（中心周期为４．５年）中有显著的相关，当前期秋季和冬季的降水量和气温在振荡中处于正距平时，当年的气象产量为丰年，反之为欠年；进一步对该序列与大气环流的静力和动力物理量之间关系研究发现它们在同样的周期振荡中有十分强烈的表现，尤其表现在与动力物理量上。研究结果进一步证实“环流－降水－谷物”系统的存在，并揭示在短期气候振动（４－６年）上的规律性。     

试析刘宋统治区的气候波动与水旱灾害

刘宋时期虽然整体上属于历史气候变迁中的寒冷期,不过期间存在气温的波动。刘宋初年气温较低,元嘉中后期升至波峰,泰始年间降至波谷,刘宋末年气温再度升高。这种波动通过当时的各种气候资料表现出来,同时也反映在当时的水旱灾害发生特点上。一般在寒冷期,水灾发生的时间要晚,反之,则早。刘宋时期梅雨期到来的早晚和降水量的多少,受制于这种气候波动,同时也影响到当时水旱灾害的发生状况,是这种气温波动的集中表现。     

水位波动下的呼伦湖上覆水体与沉积物间隙水之间溶质的运移特征

为了探求内蒙古呼伦湖上覆水体和沉积物间隙水之间溶质运移机制,对呼伦湖的1个沉积物柱芯的间隙水、3个湖泊水体以及湖周边7个地下水体中的氯离子(Cl~-),氢、氧稳定同位素(δD和δ~(18)O)分别进行分析测试,并利用其示踪性对沉积物中溶质运移特征进行研究.结果显示,δD、δ~(18)O和Cl~-浓度在不同水体中的分布具有相似的分布规律,整体上从底部沉积物到上部湖水浓度分布呈现逐渐递减的抛物线趋势,在间隙水中最大值位于所取沉积物柱芯的最深处,Cl~-浓度为306 mg/L,δD和δ~(18)O分别为-58‰和-5.9‰;最小值位于沉积物柱芯上层,并与上覆水体中的值相似,Cl~-浓度为159 mg/L,δD和δ~(18)O分别为-66‰和-7.3‰.为了明确沉积物柱芯中间隙水的高浓度Cl~-和偏正δD、δ~(18)O的来源,比较不同水体的δ~(18)O-δD关系点分布,表明含有偏正值的δD、δ~(18)O和高浓度Cl~-的间隙水与上覆湖水关系密切,可能是由于低水位时期湖水与间隙水相互发生扩散作用而产生的结果.一维对流扩散迁移模型证实扩散作用是控制着沉积物间隙水中溶质浓度在垂向上分布的主要机制,同时湖水水位的变化会影响沉积物间隙水与上覆水体的扩散过程,特别是在水位上升期,富集在沉积物中的溶质可能成为湖水的重要物质来源,影响上覆水体的水质.因此,对于封闭湖泊水位的控制和管理不仅在维持湖泊水量方面有着直接的作用,同时在稳定湖泊水质条件上也有着重要的意义.     

Total solar eclipse effects on evapotranspiration captured by groundwater fluctuations in a Southern Appalachian fen

Solar eclipses provide opportunities to observe unusual natural phenomena. This paper presents data showing that diurnal groundwater fluctuations were briefly interrupted in a Southern Appalachian fen following a total solar eclipse on August 21, 2017. Groundwater levels, which were rapidly declining in the middle of a summer afternoon, nearly stabilized following totality. This anomaly in the water‐level record was caused by reduced evapotranspiration (ET). ET was significantly lower (36% ± 11%, p < 0.02) over a 45‐min time period following the eclipse when compared with other days within the study period, although the effects were short lived and did not have a significant impact on the daily total ET (p > 0.05). These findings may prompt evaluation of existing groundwater records along the path of totality from past eclipses or plan for studies ahead of future eclipses.     

VARIABILITY IN THE WESTERN PACIFIC SUBTROPICAL HIGH AND ITS RELATIONSHIP WITH SEA TEMPERATURE VARIATION CONSIDERING THE BACKGROUND OF CLIMATE WARMING OVER THE PAST 60 YEARS

By adopting characteristic index data for the Western Pacific Subtropical High (WPSH) from the National Climate Center of China, U.S. National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, and the National Oceanic and Atmospheric Administration (NOAA) sea surface temperature (SST) data, we studied the WPSH variability considering the background of climate warming by using a Gaussian filter, moving averages, correlation analysis, and synthetic analysis. Our results show that with climate warming over the past 60 years, significant changes in the WPSH include its enlarged area, strengthened intensity, westward extended ridge point and southward expanded southern boundary, as well as enhanced interannual fluctuations in all these indices. The western ridge point of the WPSH consistently varies with temperature changes in the Northern Hemisphere, but the location of the ridgeline varies independently. The intensity and area of the WPSH were both significantly increased in the late 1980s. Specifically, the western ridge point started to significantly extend westward in the early 1990s, and the associated interannual variability had a significant increase in the late 1990s; in addition, the ridgeline was swaying along the north-south-north direction, and the corresponding variability was also greatly enhanced in the late 1990s. With climate warming, the SST increase becomes more weakly correlated with the WPSH intensity enhancement but more strongly correlated with the westward extension of the ridge point in the equatorial central and eastern Pacific Ocean in winter, corresponding to an expanding WPSH in space. In the northern Pacific in winter, the SST decrease has a weaker correlation with the southerly location of the ridgeline but also a stronger correlation with the westward extension of the ridge point. In the tropical western Pacific in winter, the correlations of the SST decrease with the WPSH intensity enhancement, and the westward extension of the ridge point is strengthened. These observations can be explained by strengthened Hadley circulations, the dominant effects of the southward shift, and additional effects of the weakened ascending branch of the Walker circulation during warm climatological periods, which consequently lead to strengthened intensities, increased areas, and southward expansions of the WPSH in summer.     

灰色自记忆模型的高层建筑物沉降分析

针对GM(1,1)模型对非线性数据的沉降趋势及其波动特征无法进行准确地预测,而灰色残差模型和灰色马尔科夫模型又无法解决这个问题,提出了灰色自记忆预测模型。该模型利用了自记忆原理考虑过去和现在对未来的影响的记忆性特点,克服了GM(1,1)模型对初值比较敏感、预测精度低等局限性,提高了对波动性数据的预测能力。通过实例验证表明了灰色自记忆模型的可靠性和可行性。     

东北地区资源型城市经济转型发展波动特征与影响因素——基于面板数据模型的分析

借助H-P滤波和面板数据回归模型分析2000~2014年东北资源型城市转型以来经济发展的趋势特征和影响因素。结果表明：① 东北资源型城市经济总量保持上升趋势,但存在明显的周期性波动,与国家振兴老工业基地政策和城市产业结构调整历程相吻合;② 第三产业发展和市场化进程对经济增长的促进作用逐渐增强,而技术进步、对外开放程度等因素作用强度仍然较弱;③ 东北资源型城市转型发展可划分为试验阶段、全面启动阶段和深化阶段,经济转型深化过程中应加强实践探索,激励体制机制创新,构建有利于衡量测度的指标体系。     

逆延华南气温序列方法的探讨

本文用香港１８８４－１９８３年逐年１月平均气温代表冬温，把它的年际变化时间序列作为原样本进行了谱分析，从中提取有代表性的周期波，用谱波分析和方差分析法，对选出来的周期波延，迭加，拟合成新的冬温时间序列。用地方志的冻灾史料进行了检验，结果９５％以上的冻灾年与新序列的冷冬年对应；冬季应温多出现连续性冷冬年，史料和新序列也有很好的一致性。     

EFFECT OF DUNE MIGRATION ON SCOUR AT BRIDGE PIERS

This paper examines the effect of dune migration on local scour around bridge piers. Experiments show that local scour depths fluctuate in response to the translation of dunes past the scour hole. The scour depths measured in a model study conducted in live-bed conditions contain both scour due to the pier and that due to dunes. The con' tribution from scour due to the dunes may form a significant fraction of the total scour depth measured in model investigations. Therefore, it is imperative to separate these two components of scour for analysis and comparison. The study proposes that an equilibrium or time-average scour depth normalized using pier diameter be used for analysis, and the contribution from dunes to the total scour depth be added independently. Dune size, in the absence of field or measured data, may be estimated using published predictive curves. Comparisons between computed and measured scour depths show a good correlation, and 90% of all the data tested fall within a scatter of 15%.