华北秋季一次低槽冷锋积层混合云宏微物理特征与催化响应分析   总被引：2，自引：0，他引：2  

秦彦硕  蔡淼  刘世玺  蔡兆鑫  胡向峰  吕峰 《气象学报》2017,75(5):835-849

利用2013年10月13日机载粒子测量系统（PMS）在张家口涞源地区对积层混合云中上部进行的增雨探测数据,分析了云的垂直微物理结构、云区的可播性和作业前后液态云粒子、冰晶及降水粒子的微物理变化。结果表明,此次降水性积层混合云的垂直结构由冷、暖两层云配置,云层发展厚实,冷云区云粒子浓度平均为62 cm-3,液态水含量最大0.05 g/m3;2DC和2DP探测的冰晶及降水粒子平均浓度分别为1.9和2.2 L-1;暖云内云粒子数浓度集中在300 cm-3左右,液态水含量约0.1 g/m3。探测区域云粒子数浓度的水平分布不均匀。利用云内过冷水含量和冰晶浓度等参数判断,该降水性积层混合云的播撒作业层具有强可播性。对比作业前后云中粒子浓度及平均直径发现,云粒子在作业前时段内的平均浓度为31 cm-3,远高于作业后平均浓度（17.6 cm-3）;但平均直径变化不大。作业后冰晶粒子通过贝吉龙过程消耗过冷水长大,浓度由之前的0.86 L-1增至4.27 L-1,平均直径也增至550 μm。冰晶粒子逐渐长大形成降水,降水粒子浓度也相应有所升高,谱明显变宽。   相似文献   

水平角观测时竖轴倾斜引起误差的改正方法探讨     

胡特彧  杨松林  田爱军 《北京测绘》2008,(2):43-46

对于水平角观测时垂直轴倾斜带来的影响,一是采用测回间重新整平的方法来削弱;二是在有竖盘指标水准管的情况下,读取格值施加改正数的方法来削弱。但这两种方法的精度有限,且对于无竖盘指标水准管的仪器目前没有提出相应的解决方法,＂虚拟目标法＂可以有效地解决这个问题。  相似文献   

面积测算方法及精度分析     

卫建东 《测绘与空间地理信息》1999,22(4):42-43,45

面积测量有多种方法,采取何种方法取决于测区的环境条件、测量要求及仪器设备情况,不同的测量方法对面积的测量精度会产生不同的影响。本文在最后介绍了对某测区土地面积测量的情况。  相似文献   

南海季风爆发期间中尺度对流云带演变特征与持续性加强的机理研究   总被引：3，自引：1，他引：2  

李香淑  郭学良  付丹红 《大气科学》2011,35(2):259-271

南海季风爆发与随后爆发的东亚季风,与夏季东亚地区旱涝关系密切,而相伴的南海对流活动与季风爆发的维持和发展存在何种相互关系,是需要探究的.为此,利用热带测雨卫星(Tropical Rainfall Measuring Mission,TRMM)的雷达(Precipitation Radar,PR)、微波成像仪(TRMM ...  相似文献   

Synoptic Pattern and Severe Weather Associated with the Wide Convection over Southeast China During the Summer Monsoon Period          下载免费PDF全文

WANG Hui  LUO Yali  ZHANG Renhe 《Acta Meteorologica Sinica》2015,29(1):41-58

Based on the Tropical Rainfall Measuring Mission (TRMM) precipitation radar observations, wide con-vection (WC) is defi ned as contiguous convective echoes over 40 dBZ, accompanied with a near surface ...  相似文献   

A method to measure enforcement effort in shipping with incomplete information     

《Marine Policy》2015

Current methods in the shipping industry to evaluate performance do not account for differences in fleet profiles of registries such as age, size or ship type and not for bad luck. This can lead to unfair evaluation of enforcement efforts of the international standards. Furthermore, incentives to improve performance are concentrated on decreasing detentions rather than incidents. This article proposes a new method to a longstanding problem to evaluate performance that rectifies shortcomings of the method currently used. The proposed method measures the enforcement effort by means of proxy variables and introduces incentives for improvement that go beyond the currently used 'detention'. The aim is to provide a fair and transparent way. The proposed method is applied and results are compared with methods currently used to demonstrate how the rankings change. The method can be adapted to other areas of the shipping industry such as classification societies or ship management companies.  相似文献   

Complexity of seismic process; measuring and applications — A review     

T. Chelidze  T. Matcharashvili 《Tectonophysics》2007,431(1-4):49

Recent methods of analysis of so called disordered systems show that many objects and processes that earlier were considered as completely random reveal clear evidence of having some ordered structure in both time and space. These new methods (fractals, percolation, nonlinear dynamics and complexity theories) allow visualization and quantitative assessment of the level of complexity (orderliness) of these structures, using both theoretical models and experimental data. We consider sequentially some aspects of structural and evolutionary complexity of dynamics of seismic process and the technique of measuring this property.It is shown that the physical properties of geophysical medium are not always self-consistent and manifest fractal behavior on selected spatial and temporal scales. Mechanical percolation theory can be used for modeling geometry of fracture process. Namely, we consider fractal and connectivity aspects of delayed failure, including energy emission during fracturing. Special attention is paid to relating the intensity of geophysical anomalies to the strain in the framework of the pressure-induced anomalous strain-sensitivity (percolation) model, which explains naturally the observed heterogeneity of response of a geophysical media to the strain variation.Different methods of measuring the dynamic complexity of seismological time series are applied to magnitude and waiting time sequences of Caucasian earthquakes. The fractal (correlation) dimension d₂ of the latter is high (larger than 8), but the former one has as low dimension as 1.6–2.5, which makes waiting time sequences a promising tool for revealing precursory changes.The same nonlinear technique allow detecting significant changes in the seismic regime during external electromagnetic forcing by MHD pulses; similar tests on the laboratory scale show the possibility of triggering/controlling stick-slip process by relatively weak electromagnetic or mechanical forcing.Lastly, the predictive potential of complexity analysis of seismological time series is considered. For example, percolation model predicts the increase of the number of large events and the scatter of magnitudes of events, decrease of the magnitude-frequency relation slope and appearance of multifractality at approaching the final rupture.It seems that seismology can benefit from using the new techniques to cope with the complexity of earthquake machine; for example, the measures of complexity can be characteristic for a given region and change before strong earthquake.  相似文献   

Variations of Precipitation Structure and Microwave Tbs During the Evolution of a Hailstorm from TRMM Observations     

HE Wenying  CHEN Hongbin 《Acta Meteorologica Sinica》2007,21(2):153-167

In this paper, a hailstorm occurring on 9 May 1999 in Huanghuai region was studied by using the combined data from the precipitation radar (PR), microwave image (TMI), and visible infrared scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite. According to the 3-orbit observations of 5-h duration from the TRMM satellite, the variation characteristics of the precipitation structures as well as cloud top temperature and microwave signals of the precipitating cloud were comprehensively analyzed during the evolution of hailstorm. The results show that the precipitation is obviously converted from early hail cloud with strong convection into the later storm cloud with weak convection. For hail cloud, there exists some strong convective cells, and the heavy solid precipitation is shown at the middle-top levels so that the contribution of rainfall amount above the freezing-layer to the column precipitation amount is rather larger than that within the melting-layer. However, for storm cloud, the convective cells are surrounded by the large area of stratiform precipitation, and the precipitation thickness gradually decreases, and the rainfall above the freezing-layer obviously reduces and the contribution of rainfall amount within the melting-layer rapidly increases. Therefore, the larger ratio of rainfall amount above the freezing layer to column precipitation amount is, the more convective the cloud is; reversely, the larger proportion of rainfall below the melting layer is, the more stable the stratiform cloud is. The different changing trends of microwave signals at different precipitation stages show that it is better to consider the structures and stages of precipitating cloud to choose the optimal microwave channels to retrieve surface rainfall.  相似文献   

利用西北印度洋船测数据评估基于卫星的海表面温度   总被引：1，自引：1，他引：0  

杨广  何海伦  王渊  韩喜球  王叶剑 《海洋学报(英文版)》2016,35(11):52-58

本文描述了一次夏季在西北印度洋进行的调查船水文测量,用船测数据评估卫星海面表温度,并寻找影响海表面温度误差的主要因素。我们考虑了两种卫星数据,第一种是微波遥感产品——热带降雨测量任务微波成像仪TMI数据,另外一种是融合了微波,红外线,以及少部分观测数据的融合数据产品——可处理海表温度和海冰分析OSTIA数据。结果表明融合数据的日平均海表面温度的平均误差和均方根误差都比微波遥感小。这一结果证明了融合红外线遥感,微波遥感以及观测数据来提高海表面温度数据质量的必要性。此外,我们分析了海表面温度误差与各项水文参数之间的相关关系,包括风速,大气温度,想对湿度,大气压力,能见度。结果表明风速与TMI海表面温度误差的相关系数最大。而大气温度是影响OSTIA海表面温度误差最重要的因素;与此同时,想对湿度与海表面温度误差的相关系数也很高。  相似文献   

Daytime precipitation identification scheme based on multiple cloud parameters retrieved from visible and infrared measurements     

XianTong Liu  Qi Liu  YunFei Fu  Rui Li 《中国科学:地球科学(英文版)》2014,57(9):2112-2124

Visible and infrared (VIR) measurements and the retrieved cloud parameters are commonly used in precipitation identification algorithms, since the VIR observations from satellites, especially geostationary satellites, have high spatial and temporal resolutions. Combined measurements from visible/infrared scanner (VIRS) and precipitation radar (PR) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite are analyzed, and three cloud parameters, i.e., cloud optical thickness (COT), effective radius (Re), and brightness temperature of VIRS channel 4 (BT4), are particularly considered to characterize the cloud status. By associating the information from VIRS-derived cloud parameters with those from precipitation detected by PR, we propose a new method for discriminating precipitation in daytime called Precipitation Identification Scheme from Cloud Parameters information (PISCP). It is essentially a lookup table (LUT) approach that is deduced from the optimal equitable threat score (ETS) statistics within 3-dimensional space of the chosen cloud parameters. South and East China is selected as a typical area representing land surface, and the East China Sea and Yellow Sea is selected as typical oceanic area to assess the performance of the new scheme. It is proved that PISCP performs well in discriminating precipitation over both land and oceanic areas. Especially, over ocean, precipitating clouds (PCs) and non-precipitating clouds (N-PCs) are well distinguished by PISCP, with the probability of detection (POD) near 0.80, the probability of false detection (POFD) about 0.07, and the ETS higher than 0.43. The overall spatial distribution of PCs fraction estimated by PISCP is consistent with that by PR, implying that the precipitation data produced by PISCP have great potentials in relevant applications where radar data are unavailable.  相似文献