A Comparative Study of Water Imagery in the Chinese Poem Happy Rain on a Spring Night and American Poem A Drop Fell on the Apple Tree

This essay directs at the water imagery of two poems Happy Rain on a Spring Night and A Drop Fell on the Apple Tree.Although living in different time and place, Chinese poet Du Fu and American poetess Emily Dickinson share some deep understanding of the water. This secret of water imagery is unveiled in this essay with the help of Archetypal Criticism, revealing its significance to the human beings as a race.

Rainfall Microphysical Properties of Landfalling Typhoon Yagi(201814)Based on the Observations of Micro Rain Radar and Cloud Radar in Shandong,China

The development and evolution of precipitation microphysical parameters and the vertical structure characteristics associated with Typhoon Yagi(201814)are analyzed in the city of Jinan,Shandong Province based primarily on the observations of a micro rain radar(MRR),a cloud radar,and a disdrometer.The precipitation process is further subdivided into four types:convective,stratiform,mixed,and light precipitation according to the ground disdrometer data,which is in agreement with the vertical profile of the radar reflectivity detected by the MRR.Vertical winds may be the main source of MRR retrieval error during convective precipitation.Convective precipitation has the shortest duration but makes the largest contribution to the cumulative precipitation.Collision-coalescence is the main microphysical process of stratiform precipitation and light precipitation below the bright band observed by the MRR.It is worth noting that as Typhoon Yagi(201814)transformed into an extratropical cyclone,its raindrop size distributions no longer had the characteristics of maritime precipitation,but become more typical of the characteristic of continental precipitation,which represents a very different raindrop size distribution from that which is normally observed in a landfalling typhoon.

青藏高原东南缘洱海流域人工增雨效果评估

采用区域回归数值模拟评价方案对2005—2020年洱海流域火箭人工增雨效果进行统计检验,得出洱海流域层云、混合云增雨效率分别为16.57%和20.09%。利用新一代天气雷达和激光雨滴谱仪对2020年1月31日层云降水和8月13日混合云降水进行增雨效果物理检验发现:作业后试验区层云目标云体雷达最大回波强度和平均垂直积分液态水含量(VIL)略有降低,回波顶高变化不大,混合云目标云体最大回波强度、平均VIL和回波顶高均出现跃增,两种类型增雨作业后地面降雨强度均显著增强。雨滴谱特征表明,试验区层云和混合云雨强和雨滴数浓度在作业后10~15 min开始增加,最大数浓度所在直径由0.437 mm增加到0.562 mm,雨滴谱的谱宽增加,峰型由单峰变为双峰结构。

Effects of Soil Compaction in the Fight against Unpaved Roads Degradation Due to Erosion Caused by Heavy Rain: Proposition of a Specific CBR Evaluation Model

Unpailt roads are generally subject to erosion, when they need to be bitumen, civil engineers need to know the geotechnical capabilities of the soil layers to be used as support, among these capabilities, for example, soil characteristics to withstand erosion. CBR has often been used to classify these soils according to their compaction. In this article, we propose a correlation between CBR and eroded soil mass through a simulator. Indeed, in this article we show that using a simulator, soils can be classified according to their ability to withstand water erosion, whether internal or external. Indeed it is shown that the mass of eroded soil is related to the compaction capacity of the soil just as the CBR also has. We study the effects and influence of soil compaction on the ability of an unpaved road to resist erosion caused by falling raindrops. To do this, lateritic soil is submitted to different compaction pressures. The compacted soil is then submitted to CBR test and rain fall through a mini rain simulator. Correlations between eroded soil masse and compaction pressure as well as CBR are derived. The study shows that the compaction reduces the erodibility and increases the bearing capacity of soil. The formula obtained is significant because we have a new way of evaluating soils in the laboratory.

Microphysical Processes of a Stratiform Precipitation Event over Eastern China:Analysis Using Micro Rain Radar data

Data collected using the micro rain radar(MRR) situated in Jinan city, eastern China, were used to explore the altitudinal and temporal evolution of rainfall microphysical characteristics, and to analyze the bright band(BB) characteristics and hydrometeor classification. Specifically, a low-intensity and stable stratiform precipitation event that occurred from 0000 to0550 UTC 15 February 2015 and featured a BB was studied. During this event, the rainfall intensity was less than 2 mm h-1 at a height of 300 m, which was above the radar site level, so the errors caused by the vertical air motion could be ignored.The freezing height from the radiosonde matched well with the top of the BB observed by the MRR. It was also found that the number of 0.5–1 mm diameter drops showed no noticeable variation below the BB. The maximum fall velocity and the maximum gradient fall velocity(GFV) of the raindrops appeared at the bottom of the BB. Meanwhile, a method that uses the GFV and reflectivity to identify the altitude and the thickness of the BB was established, with which the MRR can provide a reliable and real-time estimation of the 0?C isotherm. The droplet fall velocity was used to classify the types of snow crystals above the BB. In the first 20 min of the selected precipitation event, graupel prevailed above the BB; and at an altitude of2000 m, graupel also dominated in the first 250 min. After 150 min, the existence of graupel and dendritic crystals with water droplets above the BB was inferred.

The Clouds Microstructure and the Rain Stimulation by Acoustic Waves

A simplified model of clouds' microstructure dynamics under turbulent conditions is presented. The nature of rain stimulation by acoustic waves, based on the drops injection in the region of turbulent coagulation, is de-scribed. The conditions for effective rain stimulating are estimated.

Improving Radar Rainfall Estimation by Accounting for Microphysical Processes Using a Micro Rain Radar in West Africa

This study evaluates the improvement of the radar Quantitative Precipitation Estimation (QPE) by involving microphysical processes in the determination of Z-R algorithms. Within the framework of the AMMA campaign, measurements of an X-band radar (Xport), a vertical pointing Micro Rain Radar (MRR) to investigate microphysical processes and a dense network of rain gauges deployed in Northern Benin (West Africa) in 2006 and 2007 were used as support to establish such estimators and evaluate their performance compared to other estimators in the literature. By carefully considering and correcting MRR attenuation and calibration issues, the Z-R estimator developed with the contribution of microphysical processes and non-linear least-squares adjustment proves to be more efficient for quantitative rainfall estimation and produces the best statistic scores than other optimal Z-R algorithms in the literature. We also find that it gives results comparable to some polarimetric algorithms including microphysical information through DSD integrated parameter retrievals.

考虑滞后性的土-水特征曲线物理-统计模型研究

非饱和土的持水和渗透特性具有明显的滞后现象,即非饱和土的水力特性在脱湿过程与其在浸润过程会表现出明显的差异性。现有土-水特征曲线(SWCC)滞后模型多为经验模型,其结果在很大程度上依赖模型参数的选取。换言之,这些经验模型多为数学模型,模型参数缺失相应的实际物理意义。采用矩阵形式模拟修正毛细物理模型,通过数理统计的手段计算脱湿和浸润过程,土体中不同尺寸孔隙的水分含量,并累加各孔隙汇总的水分含量得到不同吸力状态土体的含水率。在计算浸润过程孔隙中水分含量时,深入分析留截空气、“墨水瓶”效应和“雨滴”效应对滞后现象的影响,并提出相应的计算公式。选取国内外SWCC脱湿与浸润的试验数据,和本文模型结果作对比。对比结果显示,物理-统计模型计算结果与试验数据吻合度较高,可作为预测SWCC滞后曲线行之有效的一种方法。

基于雨滴谱和雨量筒观测资料不同类型云降水对比分析

选取北海国家气候观象台2019年1—12月的雨滴谱和雨量筒资料,根据雨强划分降水类型,对比分析两种设备观测对流云和层状云降水的差异。结果表明:(1)两次降水过程均以“雨”和“阵雨”为主,由于仪器测量精度不同,雨滴谱和雨量筒观测到的降水量有所差别。(2)对于对流云和层状云降水,雨量筒与雨滴谱累积降水量绝对误差均小于20%,相关性系数均达到0.99;另外,对流云事件雨滴谱与雨量筒累积降水量平均值误差大于层状云事件的。(3)雨滴谱仪观测出现降雨时间早于雨量筒记录的,降雨结束时间则晚于雨量筒记录的。相比于层状云降水,对流云降水起始阶段雨量更大,降雨速度更快,雨滴谱仪和雨量筒记录到有降水现象的时间差更小。

偏振多普勒雷达定量测量降雨精度的改进

提高雷达估测降雨的精度一直都具有非常重要的实用意义,但是由于雨滴谱的地域差异性使得雷达测雨公式并不具有广泛的适用性。利用黑河流域遥感-地面观测同步试验(WATER项目)期间获得的大量不同类型降雨的雨滴谱资料,通过提取大量的雨滴直径D和对应的下落速度v,分析得到了它们之间的关系:v(D)=4.67D0.53。同时还得到了对应层状云和对流云雷达定量测量降雨的Z-R关系。利用滴谱数据计算得到对应X波段的双偏振雷达参数:差分反射率ZDR和差分传播相移常数KDP。并运用ZDR和KDP分别得到了适应层状云和对流云降雨的R(Z)、R(KDP)、R(Z,ZDR)和R(KDP,Z,ZDR)关系。通过降水过程获得的地面雨量筒数据和雷达实测数据,对各测雨方法进行了检验,发现组合参数的测雨公式能够很好地提高雷达测雨的精度。

雨滴降落速度的数值模拟

通过对雨滴降落时空气阻力系数的拟合及修正，采用数值计算的四阶龙格—库塔（Ｒｕｎｇｅ—Ｋｕｔａ）法求解了雨滴降落运动微分方程。模拟的０．５～６ｍｍ直径雨滴极限降落速度与实测的雨滴降落速度基本一致。并分析给出了形式简单、便于应用的雨滴极限降落速度分段计算公式。

大雨环境下雨滴对线路电晕特性的影响

除了导线表面的状态和成分,导线附近大气状况也是引起导线电晕特性变化的重要因素。可听噪声、无线电干扰是反映电晕特性变化的重要参数。通过自制淋雨装置,在小型电晕笼中对单根LGJ-400/50型实际输电导线进行干燥和淋雨情况下的电晕实验,并利用无线电干扰接收机和声级计检测电晕放电情况。实验结果显示,同等电压下LGJ-400/50型导线在大雨状况下,可听噪声和无线电干扰值明显增加,在干燥时的电晕起始电压附近有最大差值;施加电压超过干燥时电晕起始电压后,随施加电压的增长,干燥和淋雨情况下的可听噪声和无线电干扰值差值均减小。

溅蚀研究进展

溅蚀是水蚀的初始阶段,是雨滴对地表击打直接作用的结果,是一个动能减少,地表土壤颗粒发生位移的过程。溅蚀主要发生在坡面产生径流之前和刚产生径流时,是水蚀的主要形式之一。国内外学者对溅蚀的影响因素的研究主要集中在降雨特征、土壤特性以及地形因素等方面,其中主要影响因子包括:坡度、降雨特征、植被覆盖和土层结构。溅蚀量随坡度的增大逐渐增多,但是坡度超过临界坡度时,随坡度增大而减小;随降雨强度和雨滴大小增大而增大;地表植被对降雨有直接的再分配的过程,主要表现为截流、透流和干流3方面,当地表覆盖物超过1cm时,溅蚀可以完全消失;不同级配的土壤颗粒抗溅蚀能力不同,粒径在0.15mm附近的颗粒最容易被溅蚀,溅蚀同时随着土壤结皮厚度增大,土壤抗溅蚀能力增强。然而目前国内外对溅蚀的研究主要是在实验室模拟条件下完成的,较少有野外实地的研究,更缺乏在实际农业生产条件下的研究。所以需要在前人的基础上结合我国有些地方坡耕地较多的情况,在不同作物、作物生产方式和土地耕作方式等条件下,探讨坡耕地溅蚀规律。

一次飑线过程的动力和微物理结构及滴谱变化对降水估测的影响研究

雨滴谱的变化和回波强度的垂直变化是影响雷达估测降水的重要原因。文章利用美国KOUN双线偏振雷达观测的一次飑线过程资料,用模糊逻辑的方法、β方法和约束条件下的Λ方法,分析了飑线过程降水粒子相态和雨区雨滴谱分布及其相态混合区冰雹融化过程,结合四维变分方法风场反演方法,研究了雨滴谱变化与飑线过程风场中尺度结构的关系,及其对双线偏振雷达不同估测降水方法的影响。结果表明:处在气旋中的飑线存在中低层辐合线,低层辐合带及强烈上升形成强回波,飑线后部的层状云中存在下沉气流,而飑线的前部存在下沉气流形成的边界层辐合线。飑线中对流单体组成的强回波带和后侧的层状云降水的雨滴谱分布有明显的变化,大雨滴区往往在飑线前部,在东南气流中新生的对流单体也常常有大雨滴区存在。ZH、ZDR随高度变化比较明显,而KDP基本不随高度变化,高度的选取对传统的Z-R关系方法、(ZH,ZDR)方法估测降水量影响很大,但KDP方法几乎不受高度变化的影响。本次过程雨滴谱变化非常明显,这对Z-R关系估测降水将产生重要影响,(ZH、ZDR)方法和KDP方法估测的降水比较接近,而Z-R关系方法在对流中心降水估测值偏大。小于30 dBz回波的KDP脉动很大,出现的不正常值对降水估测有一定影响,采用综合降水估测方法是必要的。

雨滴降落速度及终速公式

本文通过对雨滴降落过程中力学规律的分析,从理论上导出了雨滴降落任一高度时的速度计算公式,并进而导出了雨滴终速公式.本文提出了雨滴变形系数的概念,用于描述直径大于3.0mm的雨滴在降落过程中形状因子对其落速的影响.经收集到的前人试验资料的验证,所得公式计算精确度高,且公式形式简单,可用于确定降雨动能和设计人工模拟降雨装置等生产实践方面.

两次降水过程的微降雨雷达探测精度分析

垂直指向微降雨雷达(MRR)能够测量从近地面至高空的雷达反射率因子和雨滴谱分布特征,对认识降水微物理结构,改进雷达定量降水估计精度有重要作用。为评估MRR探测的雨滴谱分布、降水和雷达回波精度,利用南京地区夏季观测的两次降水过程,将MRR与业务S波段天气雷达、二维视频雨滴谱仪、常规雨量筒观测进行层状云降水和对流性降水下的定量对比分析。结果表明,MRR垂直探测的雷达反射率因子与S波段雷达观测在中低层(<4 km)平均差异<1 dB,但高层(>4 km)出现显著低估,且该现象随降水强度增强更明显,这主要是雷达回波衰减导致。MRR在回波强度<35 dBz时对降水率的探测精度较高,但在>35 dBz时低估降水。其中,层状云降水的降水率比对流性降水更接近雨量筒观测。常规雨量筒对0.1 mm以下的降水无探测能力,而MRR探测敏感度较高,对于微弱降水率的估计效果也很好。由于MRR最大探测范围的限制,相对于2DVD而言,MRR探测的最大粒子直径低估、最小粒子浓度高估,但在中间段的探测效果和2DVD雨滴谱观测一致性较高。总体而言,MRR是一个有效的降水探测仪器,其探测结果在层状云降水过程中优于对流性降水过程。

人工模拟降雨技术研究综述

在开展雨水高效利用的试验研究中 ,用人工模拟降雨的方法 ,可以缩短试验周期 ,加速雨水入渗规律、土壤侵蚀规律的研究进程。可以通过控制试验条件 ,模拟不同环境 ,弥补在自然降雨条件下 ,因环境变化而无法得到试验期内计划的研究结果 ,或者进一步补充论证在自然降雨情况下得到的研究结果。介绍了在水土保持和降雨入渗研究中模拟降雨装置的研究概况 ,提出了简易模拟降雨装置的主要技术参数。

雨滴谱参数估计优化方案及其微物理资料检验

提出一种新的雨滴谱参数估计优化方案。其最大优点就是 :对于任意几束相邻的测雨雷达观测资料 ,从任意的雨滴谱模型 (如 Marshall- Palmer经验公式 )决定的积分雨参数之间的关系 (如 k- Z关系 )出发 ,利用雷达视反射率资料并借助雷达海平面或地表面回波信号 ,可以获取束向上的比较接近实际降雨场的雨滴谱 ;然后利用校正的雨滴谱参数决定的积分雨参数之间的关系 ,降雨量反演算法就可以提供较准确的降雨量分布。这个方案可行性被同区域机载 2 D-

耐淋雨试验系统的研制

对自行研制的耐淋雨试验系统进行了介绍。设备研制中对试验系统的试验台升降及旋转系统、降雨强度调节系统和控制系统进行了优化设计,同时根据环境试验要求,指出了该试验设备研制过程中所遇到的淋雨滴雨合一、受试面转换和温度调控等技术难点,并给出了解决途径。该试验系统研制成功,为考核装备的环境适应性和产品可靠性提供了科学的试验手段。

不同天气系统宁夏夏季降雨谱分布参量特征的观测研究

利用 1982— 1984年 6～ 9月份在 7个气象站 2 0 0次观测获取的 6 0 5 3份滴谱资料 ,分析了宁夏雨滴谱及有关物理量的特征。宁夏地区夏季降水平均雨滴空间浓度数为 2 85个·m-3 ,平均谱可以描述为N(Di) =2 0 9.2exp(- 2 .6 335Di)。文中给出了不同雨强下的平均谱分布及谱参数的演变和影响降水的 3种环流形势下的平均滴谱特征 ,还分别建立了雷达反射率因子Z与雨强、雨滴落地动能通量和雨水含量之间的相关关系。这些资料可用于雷达定量测定降水和区域降水量。