降雪回波的双偏振雷达云相态垂直特征分析

双偏振多普勒天气雷达为探测降雪回波提供了丰富信息,其中距离高度显示RHI(range height indicator)垂直特征有助于识别降水云体相态分布的精细结构。以2018年1月3～5日南京信息工程大学C波段双偏振雷达RHI扫描的暴雪回波为例,结合探空资料进行物理量诊断,研究暴雪回波偏振参量和非偏振参量的相态分布垂直特征及其与大气风温湿结构的关系。结果表明:暴雪回波中,雷达高带或淞附效应存在于6 km高度附近,温度在-12～-15℃,含有湿雪和冰晶粒子;2 km高度附近的差分反射率因子强回波带为增温增湿的层云,层云之上的热力不稳定易促进对流抬升,揭示了冬季降雪具有高架对流的特点。研究结果有益于深入认识降雪在垂直方向上的精细结构及云微物理机制,提高降雪的预测能力。     

毫米波测云雷达在晴雨观测中的初步应用

利用平和县气象观测站2018年8～11月地面观测资料,结合毫米波测云雷达的观测结果,初步分析了回波强度、云含水量和云场分布在晴雨观测中的应用。结果表明,晴天回波强度在-39.3～-5.3dBz,云含水量0.1g/m~3,以层云和层积云为主。多云和阴天回波强度增大,回波中心达-5.3～17.3dBz,云含水量1.0～2.0g/m~3,以层云、雨层云和层积云为主。雨天回波强度17.3～27.8dBz,呈片状分布,云含水量1.5～2.5g/m~3,积雨云深厚且覆盖全天空,回波强度和云含水量中心出现时间与地面降水时段相吻合。     

福州市冰雹的时空分布及雷达参数统计分析

利用福州市1987-2016年冰雹灾害资料,统计分析得到福州地区冰雹的时空分布特征。同时对相对应的新一代天气雷达资料物理量进行统计分析,初步得到福州地区冰雹单体雷达预报指标为:回波强度达到60d Bz以上(3-7月),VIL值跃增至41 kg/m~2(3月)、44kg/m~2(4月)、57 kg/m~2(5月和7月),强回波核高度达到4.8km(3月)、5.4km(4月)、5.8km(5月)、5.2km(7月),单体高度达到8km以上。     

福州地区X波段相控阵雷达与S波段机械雷达回波数据对比分析

为验证福州地区X波段相控阵雷达系统和雷达回波数据的可靠性,检验其探测性能,以2022年4月27日福州地区强降水过程为例,利用直接对比法分析了X波段相控阵雷达与S波段机械雷达回波数据。结果表明,X波段相控阵雷达回波反射率清晰细腻,雷达回波的结构分布较为均匀,可以观测更加细微的回波特征,空间分辨率明显高于S波段机械雷达,更有利于突发强对流致灾天气系统的预警预报。在强降水天气过程中,小时累计降雨量预测S波段机械雷达算法占优势,定量降水估计产品X波段相控阵雷达算法占优势。     

飞机测风资料在大气边界层研究中的应用

利用飞机和风廓线雷达2009年8月至2010年6月的连续观测资料, 讨论上海地区飞机测风资料在大气边界层风场研究中的适用性, 探究造成飞机资料偏差的可能原因并给出初步的修正方法。结果表明: 与风廓线雷达观测结果相比, 飞机观测得到的水平风速偏小, 这主要与仪器系统偏差有关; 在300 m高度以下, 1500 m高度以上, 以及气温低于-8℃, 风速小于1 m/s的低温小风情况下, 飞机观测得到水平风速的差异显著增大, 在这些条件下飞机对大气风场的探测具有局限性。用修正后的风速资料分析上海地区低层大气的风场结构, 得到的结果符合风场的一般变化规律。     

青藏高原东北部两次大到暴雨雷达和云图对比分析

利用常规观测、NCEP/NCAR1°×1°再分析、自动站、西宁多普勒雷达、卫星云图及TBB资料,对2015年6月19~20日(简称"6.19")和2015年8月1-3日(简称"8.1")发生在青海省东部的两次区域性大到暴雨天气从环流背景场、雷达回波、卫星云图及TBB进行对比分析,结果表明:(1)两次过程都是在有利的大尺度环流背景下发生,地面有冷空气从河西走廊扩散南下,伴有辐合线.(2)"6.19"是混合云系造成,水汽图像上表现为白亮、密实的区域,TBB-33℃,"8.1"为结构紧密、呈椭圆形的中尺度对流云团,TBB-73℃.(3)"6.19"为混合型降水回波,"8.1"为"S"型回波,强度达到55dBZ,强中心高度15km,形成"列车效应",0℃层高度偏高,有逆风区存在,"S"型气旋性的辐合等典型的强降水单体回波的特征,VIL经历了两次爆发式的增长及突然降低的现象.     

双发双收双偏振天气雷达信噪比改善方法研究

针对双偏振天气雷达在同时发射同时接收体制下,存在信噪比损失3 d B的现象,分析了信噪比损失对雷达回波产品显示的影响,并详细介绍了一种在信号处理器中对水平和垂直通道内的I/Q回波信号进行相干叠加,改善雷达回波信噪比的方法。理论分析和计算表明,该方法可以提高雷达信噪比2~3 d B;观测结果证实,该方法可以增强双偏振天气雷达对弱信号的探测能力。     

基于龙岩市新一代天气雷达资料的冰雹识别与预警

利用福建省龙岩市2001~2013年41次冰雹过程的新一代天气雷达资料,对冰雹和雷雨大风、短时强降水,以及冰雹自身过程发展阶段和成熟阶段的雷达数据进行了对比分析,结果表明,三体散射、V型缺口、钩状回波等是冰雹特有的雷达反射率回波的形态特征;回波强度、强回波核高度、回波顶高和VIL可用于判断冰雹,其阈值分别为60d Bz、5.3km、8km和30kg/m~2。冰雹的雷达强回波核(≥60d Bz)高度都在零度层以上,冰雹的45d Bz雷达回波伸展高度绝大多数在-20℃层以上。根据以上特征判据和阈值,对龙岩2014—2015年35次强对流天气(其中有8次出现冰雹)进行预报试验,预报10次冰雹,其中8次预报正确,2次空报,没有漏报。该文还分析了冰雹直径与雷达回波形态特征和数据的关系,发现如果出现三体散射、V型缺口、钩状回波特征,冰雹直径普遍≥2cm,VIL密度大于2.9,冰雹直径≥2cm,冰雹直径与风暴顶辐散、弱回波区伸展高度等没有明显相关关系。     

基于激光雷达数据对混合层高度与细颗粒物浓度关系的研究

利用微脉冲激光雷达观测资料, 运用人工辅助算法, 获得2016―2019年白天混合层高度(MLH), 并分析其变化特征及其与空气污染物PM_2.5浓度的关系。结果表明, 混合层高度表现出明显的季节变化和日变化, 春季高度明显大于其他季节, 最大值均发生在 5月。混合层高度在08:00―15:00 BJT的变化趋势与PM_2.5浓度负相关。线性拟合结果表明, 当考虑风速的影响时, 通风指数与 PM_2.5具有更强的负相关关系; 当考虑风向的影响时, 西南风情况下, 混合层高度与PM_2.5具有更强的负相关关系。对天气分型后, 每个天气类型的PM_2.5浓度与混合层高度的相关性更加显著。     

基于气象条件的大气混合层高度模型研究

根据2011-2013年重庆市沙坪坝地区的常规气象数据,运用MATLAB软件分析近3年大气混合层高度mm变化和特征,且与气象参数的相关性;结果表明:每天在8∶00-19∶00,大气混合层高度与太阳辐射强度、温度、风速呈正相关性;与气压、相对湿度呈负相关性,与露点温度的相关性不明显;而在20∶00-7∶00,大气混合层高度与太阳辐射强度和风速呈正相关,与其他参数的相关性不明显;同时,通过气象数据建立重庆市大气混合层高度的预测模型,并验证其准确性。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that