More intensive summer tropical cyclone near 30°N of East Asia

The present study revealed that a climate regime shift occurred during the 1988–1991 period involving changes in tropical cyclone (TC) intensity (central pressure, maximum sustained wind speed) during the summer near 30°N in East Asia. Climatologically, TC intensity at 110°–125°E near 30°N (over Mainland China) is the weakest at that latitude while the strongest is found at 125°–130°E (over Korea). The TC intensity during the 1991–2015 (91–15) period had strengthened significantly compared to that of the 1965–1988 (65–88) period. The strengthening was due to a significantly lower frequency of TCs that passed through Mainland China during the 91–15 period. This lower frequency of was due to anomalous northeasterlies blown from the anomalous anticyclonic circulation located over continental East Asia and that had strengthened along the coast. Instead, TCs mainly followed a path from eastern regions in the subtropical western North Pacific to Korea and Japan via the East China Sea due to anomalous cyclonic circulations that had strengthened in the western North Pacific. In addition, low vertical wind shear had formed along the mid-latitude region in East Asia and along the main TC track in the 91–15 period, and most regions in the western North Pacific experienced a higher sea surface temperature state during the 91–15 period than in the previous period, indicating that a favorable environment had formed to maintain strong intensities of TCs at the mid–latitudes. The characteristics of TCs at the lower latitudes caused a strong TC intensity at the time of landfall in Korea and a gradual shifting trend of landing location from the western to southern coast in recent years.     

African Fire Cultures,Cattle Ranching,and Colonial Landscape Transformations in the Neotropics

Fire regimes emerge partly from human activities that reflect cultural‐ecological knowledge of the relationships among fire, vegetation, grazing, climate, and other variables, as well as social relations. More knowledge of such “fire cultures,” past and present, therefore remains necessary to better understand the causes and persistent consequences of landscape burning. In the neotropics, people have used fire for centuries to manage livestock pastures. Conventional wisdom has long posited that such practices derived solely from antecedent European and indigenous, Native American fire cultures. Analysis of accounts of rangeland burning from throughout the neotropics during colonial times, however, demonstrates that ranchers incorporated African fire cultures and that the timing of burning shifted from early during the dry season in the sixteenth century to late during the dry season by the nineteenth century.     

沱江流域水文对全球气候变化的响应

本文研究了全球气候变化对沱江流域水文的影响。根据流域水量平衡模型和未来气候情景对水量平衡各分量的可能变化进行了计算。结果表明;径流对气温变化不敏感,但对降水变化十分敏感;降水变化±１０％将引起径流量±３５％左右的变化;此外,径流年内分配亦发生了明显的变化。这将对沱江流域未来水资源计划与管理带来一定程度的影响。     

试论洞庭湖区近四十年来的水情变化

洞庭湖位于长江中游荆江以南和湘、资、沅、澧四水控制站以下的原理、湖泊水网区,天然湖泊面积２６９１ｋｍ＾２,洪道面积１４８１ｋｍ＾２。由于泥沙淤积、人类活动的影响,使湖区的水情发生了变化。通过对湖区主要水位控制站的水位流量关系的分析,得到了四十年水情变化的一些规律,供有关部门参考。     

Three-dimensional P-wave velocity structure in the upper crust beneath Kuju Volcano, central Kyushu, Japan

 Kuju Volcano lies near Aso Caldera at the center of Kyushu Island, western Japan. After a few hundred years of dormancy, a phreatic explosion accompanied by a small ash eruption occurred on 11 October 1995. This study was undertaken to determine the subsurface seismic velocity structure associated with the active magmatic regime in the Kuju volcanic region. The three-dimensional, upper crustal, P-wave velocity structure beneath Kuju Volcano was determined using methods for the simultaneous inversion of P-wave arrival times from local earthquakes in and around the Kuju volcanic region for velocities and hypocentral parameters. Results reveal two shallower low-velocity anomalies located in the northern and southern parts of Kuju Volcano, consistent with the presence of significant negative Bouguer gravity anomalies. In addition, a high-velocity anomaly is located approximately 5 km northwest of Mt. Kuju, one of the domes in Kuju Volcano. Beneath this high-velocity anomaly, a low-velocity anomaly is present. This velocity structure suggests a magmatic regime that has a lid consisting of cooled solid material overlying a chamber of partially molten material. Received: 23 September 1997 / Accepted: 20 June 1998     

数据处理组合方法在地下水动态预测中的应用

针对地下水水位变化复杂性,采用模拟生物有机体演化方式的数据处理组合方法,预测地下水水位动态变化特征。克服了常用数学方法和模型在预测复杂对象时精度低的缺点。该方法应用于地下水水位动态预测中,能很好地反映地下水的周期性动态变化特征,并具有较高的预测精度。     

黄河下游游荡段排沙比对水沙条件与断面形态的响应

提高黄河下游游荡段的输沙能力是河道治理的主要任务,而河道输沙效率（排沙比）受到来水来沙条件和河床边界条件的共同影响。本文基于1971—2016年花园口—高村河段（简称花高段）的实测水沙及地形资料,计算了花高段的平均河相系数及水沙条件（来沙系数和水流冲刷强度）,从汛期和场次洪水2个时间尺度,定量分析了排沙比与水沙条件及前一年汛后主槽形态之间的响应关系。分析结果表明：① 汛期和场次洪水排沙比与来沙系数呈负相关,与水流冲刷强度呈正相关,临界的汛期不淤来沙系数为0.012 kg?s/m ⁶,场次洪水排沙比与来沙系数及水量比的决定系数为0.76;② 游荡段排沙比与河相系数呈负相关,当河相系数大于15 /m ^0.5时,河段排沙比基本小于1;③ 以来沙系数与河相系数为自变量的汛期排沙比计算式的决定系数为0.82,计算精度较高,对于场次洪水排沙比而言,断面形态的影响权重大于来沙系数。这些排沙比计算公式能够反映游荡段的输沙特点,有助于定量掌握断面形态及水沙条件对河道输沙能力的影响。     

敏感型人工神经网络及其在水文预报中的应用

为充分挖掘资料信息、加快收敛速度,采用一种具有敏感功能的神经网络预报模型。该模型在构造时序样本时引入遗忘因子和期望因子,以体现对前期资料的遗忘和近期预测的期望。在权值调整过程中采用指数型能量函数,以加快网络的学习收敛速度。应用实例证明:该方法可以提高当前的预测精度,并避免网络学习过程中的振荡现象。     

广义Γ分布的特性和应用

介绍了广义Γ分布———对数Γ分布和指数Γ分布的一些特性和应用。通过变数的平移和倍比变换,建立起统计参数之间的关系,并可利用三参数分布的有关表格(如模比系数KP值表)和适线方法,应用于四参数分布的频率计算上,使计算简化。     

BP自组织神经网络在地下水动态分类中的应用

本文是根据国内外较为流行的BP自组织神经网络方法,与区域地下水动态成因及地下水观测井历时曲线形态相结合对哈尔滨市地下水的动态型进行定量分类:波动—水文型、上升—弱水文型、上升·下降—开采型、上升—开采型,并且定位在图上。此种分类更加直观地反映本区地下水在空间和时间的变化规律,并对本区地下水的水流模型参数分区具有参考价值。