湿斜压热动力耦合强迫激发辐合增长和暴雨维持的一种机制

打破将散度演化分析局限于水平动力学框架内的传统认识思维,针对大气的斜压性与层结特征将对大气运动散度场演化产生显著影响的事实,从湿斜压原始方程出发,将大气的斜压热力作用通过热力学方程引入散度方程,在替换平衡近似（alternative balance）下,导出了显式包含湿非地转Q矢量与垂直风切变耦合强迫作用的新型散度方程.阐明了潮湿大气中非地转斜压强迫激发散度场演化的物理机制,为利用常规观测资料诊断散度场演化提供了一种有效的数学工具.通过对流层中低层气柱内总体辐合增长影响因子的分 关键词： 暴雨天气 散度演变 正压非平衡强迫 湿斜压热动力耦合强迫     

降雨对无线激光通信的影响

通过激光信号在雨介质中传输的实验发现,在大雨环境下,激光信号透射率要比在小雨或微雨的情况下大。这说明光信号在小雨时衰减较大,在大雨时衰减较小。这一现象与人们通常所认为的有所不同。针对降雨对激光信号的影响,根据Mie散射理论和Weibull雨滴尺寸分布模型,分析了不同尺寸的粒子对光的散射作用以及对衰减效率因子的影响,推导出单球粒子对光波的衰减公式,得到了衰减与降雨率的确定关系。通过数值计算发现,与小粒子相比大粒子的前向散射光强更大且更加集中;激光信号在雨介质中传输时,衰减系数在小雨时较大,中雨、大雨时较小,暴雨时不断增大。这一结果与实际情况较吻合,为激光在通信系统中的应用提供了一定的理论依据。     

浙江梅汛期分片暴雨前期气象因子场的相关分析

利用1990～1999年共10年浙江及其邻近地区梅汛期降水113个典型个例的多要素客观分析场和物理量诊断场与不同区域日降水量场分别进行相关分析,计算从过程发生前24 h到发生期间4个不同时刻的动力热力因子与分片日降水量之间的相关系数,重点揭示浙北梅汛期暴雨前期气象信号及其时间演变特征,并分析比较浙北与浙南区域暴雨前期信号的异同,为改进梅汛期暴雨分片预报提供物理依据.     

武汉地区雨强分维数随时间变化初探

对武汉大学电波综合观测站于１９９１年７月期间降雨自记纸曲线当积分时间为５ｍｉｎ时，用单变量雨强时间序列初步地研究了降雨这一大气过程中雨强分维数随时间变化特性．     

Differences in oxygen-18 and deuterium content of throughfall and rainfall during different flood events in a small headwater watershed

Inter-storm stable isotopic values of rainfall and throughfall for three flooding events were measured during the period of July to August 2011 to estimate their differences in a first-order chestnut watershed, Meilin, within the Taihu Lake basin. Comparison of δ²H and δ¹⁸O was conducted from four aspects: (1) sampling methods, (2) calculation methods, (3) stable isotopes and (4) flood events. Arithmetic and weighted incremental values of throughfall were generally lighter than those of rainfall. Isotopic composition of both incremental rainfall and throughfall exhibits marked temporal variation, particularly during large storm events; the former shows a higher variation than the latter. Differences of averaged precipitation and throughfall between storms were small, but individual storm variations were larger. Isotopic differences using different calculation methods are not significant; however, the differences resulting from sampling methods are of greater importance.     

Analysis of the relationship between total and effective rainfall by means of streamflow shot noise and rainfall stochastic models

Linking the results of two research topics on rainfall and streamflow stochastic models, the relationship between total and effective rainfall is studied here. The short time streamflow process is examined concerning the climatic and hydrogeological characters of the watershed, identifying four distinct components giving rise to runoff. In this way the watershed can be regarded as a four-component linear system, whose input is the effective rainfall. Finally, the streamflow model is used as an effective rainfall inverse estimator, allowing the analysis of the links between total and effective rainfall assuming a simple transformation law. The determination of this law is performed by applying a stochastic model, whose parameters are estimated on the companion series of recorded total rainfall and reconstructed effective rainfall. An application to a case study shows the effectiveness of the proposed approach.

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Sommario Raccordando i risultati di due ricerche sui modelli stocastici di pioggia e dei deflussi, vengono qui studiate le relazioni fra la pioggia totale e la pioggia efficace. I deflussi aggregati a breve scala temporale sono esaminati alla luce delle caratteristiche climatiche e idrogeologiche del bacino idrografico, identificando quanttro distinte componenti che danno origine al deflusso. II bacino idrografico viene così rappresentato da un sistema lineare a quattro componenti, il cui input è la pioggia efficace. Pertanto, il modello dei deflussi viene usato per effettuare la stima inversa delle piogge efficaci, consentendo lo studio delle relazioni fra le piogge totali ed efficaci ipotizzando una semplice legge di trasformazione. La determinazione di questa legge è effettuata applicando un modello stocastico, i cui parametri sono stimati sulle serie corrispondenti di pioggia totale registrata e di pioggia efficace ricostruita. Un'applicazione a un caso reale mostra l'efficacia dell'approccio proposto.

     

浙江省东阳市紫色土坡面土壤侵蚀和降雨因子关系的初步研究

紫色土分布区是我国南方水土流失区的重要组成部分。本文通过对东阳市紫色土坡面土壤侵蚀和降雨因子之间的相关分析,建立了利用降雨量和平均降雨强度对土壤流失量进行预测预报的回归方程,为紫色土地区土壤过度侵蚀的治理提供了定量方法,并为紫色土的综合开发利用提供了科学根据.     

降雨背景下诱骗态协议最优平均光子数的变色龙自适应策略

为了应对降雨给采用诱骗态协议的量子通信系统带来的突发性干扰,根据降雨分布模型和退极化信道的特性,本文提出了基于变色龙算法的每脉冲最优平均光子数自适应策略;建立了降雨强度、链路距离与最优平均光子数之间的自适应关系;并对采用变色龙算法前后,系统的性能参数进行了比较.仿真结果表明,当降雨强度J为30 mm/24 h、链路距离L为30 km时,通过采用变色龙算法,系统的安全密钥生成率由2×10~(-4)提高到3.5×10~(-4);当J为60 mm/24 h,L为20 km时,系统的信道生存函数值由0.52提高到0.63;当要求生存函数不低于0.5时,系统能够应对的最大雨强由62 mm/24 h提高到74 mm/24 h.因此,根据降雨强度和链路距离,通过变色龙算法自适应地调整系统发送端信号脉冲所含的平均光子数,可以提高量子通信系统在降雨背景下的有效性和可靠性.     

基于Fisher准则的两组判别分析方法在夏季降水预报中的应用

根据1959—2004年(12月到次年3月)逐月大气环流特征量资料,运用基于F isher准则的两组判别分析方法,预报安徽宣城夏季降水量.结果表明,历史拟合率高,在预报业务中具有实用价值.